40th Annual GeoDaze
March 29-31, 2012
GeoDaze 2012 Committees Co-­Chairs Kendra Murray and Sarah Truebe Fundraising Kat Compton and Liz Balgord Correspondence Clare Tochilin and Kate Metcalf Registration Mallory Morell and Molly Dendas Treasurer Outreach Jamie Worthington Mariel Schottenfeld and Brandon Bishop Audio/Video Adam Hudson and Drew Laskowski Publications Slideshow Sarah Dasher and Kate Metcalf Caitlin Orem and Clare Tochilin Webmaster Awards Rachel Murray Esther Posner and Shaunna Morrison Refreshments and Party Field Trip Nate Evenson and Jamie Ryan Matt Dettinger, Drew Laskowski and Kevin Ward P a g e | 2 Thank you to the following organizations and individuals, whose generous contributions made GeoDaze 2012 possible. Brittoil Company LLC Balfour Holdings, Inc. GeoMark Research, Ltd. Golden Software Inc. Individuals Gerard Beaudoin Thomas Biggs Elwood Brooks Carlotta Chernoff Anthony and Nancy Ann Ching Jean Cline Gary Colgan Adam Csank and Stephanie McAfee Raj and Cynthia Daniel John and Wilhelmina Dreier Gregg Garfin Terrence M. Gerlach Julia B. Gordon Christopher Greenhoot James Hardy James Hays John Hoelle Gary and Yvonne Huckleberry Richard D. Jones Susan Kidwell Charles Kluth Peter Kresan Robert B. Laughon John Matis Edgar and Deborah McCullough Leslie D. McFadden Norm Meader Keith Meldahl J. Dale and Audrey R. Nations Mary Kay O'Rourke Maxine W. Peirce Barbara Bohn and Robert Peterson Sarah Lynn Peyton Richard Pfirman Bernard W. Pipkin Randall and Virginia Richardson Miles G. Shaw Louis H. Taylor Herbert and Diane Welhener Donald Witter Donations received after March 21 will be acknowledged on-­line at http://earth.geo.arizona.edu/geodaze/12/sponsors.html P a g e | 3 Table of Contents GeoDaze 2012 Committee 2 GeoDaze 2012 Benefactors 3 Welcome 5 Schedule of Events 6 Thursday, March 29 6 Friday, March 30 9 Abstracts 14 Maps and Directions 70 Field Trip Guide 72 Download a complete version of the GeoDaze 2012 Program with Abstracts: http://earth.geo.arizona.edu/geodaze/12/schedule.html P a g e | 4 Welcome Welcome to GeoDaze 2012, the 40th Annual Geosciences Symposium! GeoDaze is run by the graduate students in the Department of Geosciences of the University of Arizona and funded by the generosity of private donations. For four decades, GeoDaze has given students an invaluable opportunity to share their research with a broad audience and receive feedback from faculty, industry and government representatives, and their peers. We would like to extend an especially warm welcome to all the UA Geosciences Alumni who are joining us for this special anniversary year. We are proud to offer a pURJUDPDWWKLV\HDU¶V*HR'D]HIHDWXULQJSUHVHQWDWLRQVWKDW
showcase the diverse research interests of earth science graduate and undergraduate students at the University of Arizona. GeoDaze student presentations will occur on Thursday, March 29th and Friday, March 30th, and cover a wide variety of topics, including: economic geology, structural geology, seismology, geodesy, planetary geology, paleoclimatology, diffusion in minerals, geomorphology, archaeological geology, geochemistry, geochronology, and tectonics. The 40th annual GeoDaze is a part of EarthWeek 2012, and thereby one of five jointly-­held symposia hosted by the departments in the School of Earth and Environmental Sciences (SEES). We highly encourage you to consult the EarthWeek program and attend sessions and keynote presentations KRVWHGE\RWKHUGHSDUWPHQWVQRWHWKDW(DUWK:HHNEHJLQVRQ:HGQHVGD\0DUFKWK'RQ¶WPLVVWKH
EarthWeek Plenary Session on Thursday at 2:30pm, where one top graduate student from each department will present their research on Climate in the Southwest. )RU WKLV \HDU¶V *HR'D]H NH\QRWH SUHVHQWDWLRQ ZH DUH GHOLJKWHG WR ZHOFRPH 'U .DWKDULQH
Huntington. Dr. Huntington is an Assistant Professor in the Department of Earth and Space Sciences at the University of Washington. Her research focuses on the evolution of mountain systems and landscapes, and the interactions between the deformational, thermal, climatic, and surface processes that shape them. Dr. Huntington will speak at 3:30pm on Friday, March 30th. Her talk is entitled From Paleoclimate to Plateau Uplift: Clumped Isotopes in Terrestrial Carbonate. The afternoon of Friday, March 30th we will announce the student awards, have a special retrospective on the last 40 years of UA Geosciences, and²of course²view the (in)famous annual GeoDaze slide show. Friday evening, everyone is invited to attend the annual GeoDaze party, which will be hosted by Dr. Jon Pelletier and his family at their home. On Saturday morning, we will depart for the Whetstone Mountains on a field trip to Kartchner Caverns State Park. In honor of the 40th anniversary, we will not only be touring the caverns and hiking that afternoon, but also²for those who choose to stay²camping overnight, having dinner together, exploring the night sky by telescope, and hiking the JHRORJ\K\GURORJ\JHRPRUSKRORJ\RIWKH6DQ3HGUR9DOOH\OHGE\'U%RE&DVVDYDQW.DUWFKQHU¶V&DYH
Resources Manager and the Science & Research Director of the Arizona State Parks. The 40th annual GeoDaze adventure departs from the loading dock on the North side of the Gould-­Simpson Building at 10:00am. GeoDaze is an important tradition for our department, and we would like to thank everyone who has contributed to making it a success. GeoDaze would not be possible without the 40 years of hard work and dedication of the faculty, students and staff in the Department of Geosciences and WKH JHQHURXV ILQDQFLDO VXSSRUW RI WKH GHSDUWPHQW¶V DOXPQL IULHQGV DQG FRUSRUDWH VSRQVRUV
Particular thanks go out to those who donated especially in honor of the 40th anniversary. We are honored to be part of such a wonderful community of people who engage in and support geoscience UHVHDUFK7KDQN\RXIRUDWWHQGLQJWKLV\HDU¶V*HR'D]H6\PSRVLXPDQGZHKRSHWRVHH\RXLQWKH
years (and decades!) to come! Kendra Murray & Sarah Truebe Co-­Chairs, 2012 GeoDaze Symposium P a g e | 5 Thursday, March 29, 2012 8:00 Coffee 8:15 Welcome from Dr. Karl Flessa, Geosciences Department Head 8:30-­9:15 Geophysics I 8:30 Teleseismic Study of the Subducting Slab and Forearc in the Maule Aftershock Rupture Zone Mallory Morell, Susan L. Beck, Steve Roecker, Anne Meltzer, and Ray Russo 8:45 Shear-­Wave Velocity Structure of the Central Andean (13ºS ± 23ºS) Upper Lithosphere as Determined Using Ambient Noise Tomography: Implications for Crustal Deformation History Kevin M. Ward, Ryan C. Porter, Susan L. Beck, George Zandt, Lara S. Wagner, Estela Minaya, and Hernando Tavera 9:00 EBSD-­Based Calculations of Seismic Velocities of Eclogites from the HP-­UHP Western Gneiss Region, Norway James R. Worthington and Bradley R. Hacker 9:15-­10:00 Geomorphology 9:15 Regional Frequency-­Magnitude-­Area Relationships for Precipitation and River Discharges Derived from Next-­Generation Radar (NEXRAD) Caitlin A. Orem and Jon D. Pelletier 9:30 Can the River Reach the Sea? Re-­Connecting the Colorado River and the Gulf of California Hector A. Zamora and Karl W. Flessa 9:45 Recurring Slope Linae on Mars: Updated Global Survey Results Lujendra Ohja, Alfred McEwen, Colind Dundas, Sarah Mattson, Shane Byrne, Ethan Schaefer and Marian Masse P a g e | 6 10:00-­10:15 Coffee Break 10:15-­11:30 Paleoclimate and Climate Dynamics 10:15 Long-­Term Climate Cycles and Seasonal Precipitation Balance in Arizona: Evidence from a Speleothem Oxygen Isotope Record Rachel Murray, Julia Cole, and Sarah Truebe 10:30 Modern Permafrost Degradation Contributes to Lake Size Increase in Tibet Alyssa Abbey, Adam M Hudson, and Paul Kapp 10:45 A Paleohydrologic Model of Baqan Tso, Tibet Based on Lake Shorelines Tyler Huth and Jay Quade 11:00 A 1.2 Ma Paleoecological Record from Ostracodes, Charcoal and other Paleoclimate Indicators from Lake Malawi, East Africa Margaret Blome and Andrew S. Cohen 11:15 7URSLFDO&OLPDWH7UHQGV,QIHUUHGIURP&RUDOį18O: A Comparison of CMIP-­5 Forward-­Model Results with Paleoclimatic Observations Diane Thompson, M.N. Evans, J.E. Cole, T.R. Ault, and J. Emile-­Geay 11:30 GeoDaze Anniversary Lecture: Volcanic v. Anthropogenic Carbon Dioxide Terrence Gerlach, (student presenter at the inaugural GeoDaze) 12:00-­1:00 Lunch 1:00-­2:00 Posters P a g e | 7 Paleoclimate and Climate Dynamics 28. How Important is Isotopic Equilibrium for Paleoclimate Records from Caves? A Case Study from Southern Arizona Sarah Truebe, Julia Cole, Heidi Barnett, Gideon Henderson, Jennifer Wagner, and Stephan 29.Sedimentological Interpretation and Analysis of Littoral Surface Sediments: Southern Lake Malawi Matthew J. Lopez, Margaret Whiting Blome, and Andrew S. Cohen 30. Orbital Forcing of Asian Monsoon Rainfall Based on 10Be in Chinese Loess Lara Y. White, J. Warren Beck, A. J. Timothy Jull, Li Cheng, Weijian Zhou 31.Seasonal Anomalies in the Sea Ice Concentration and Thickness in the Ross Sea and Their Correlation to the Southern Annular Mode Kiley Yeakel, Paul Goodman, and Joellen Russell 32. A Study Of The Causes Of The Decline In Fish Catch At Lake Tanganyika Elizabeth Gergurich and Andrew Cohen Hlohowskyj 33. Southwest Climate in the Common Era Chelsea Powers, Cody Routson, and Jonathan Overpeck Paleobiology and Taphonomy 34. Does Size Matter?: A Comparison of Body Size with Length of Hinge Teeth in Lentidium mediterraneum Rachel C. Feuerbach 35. Taphonomic Variation between Different System Tracts in the Paleo-­
environment of the Po Valley, Italy Muhammad Ikhwan Mahmood P a g e | 8 36. Assessment of Anthropogenic Impact on Crassostrea Virginica Reefs in Southeastern North Carolina Using Live-­Dead Analysis Leanndra Romero, Gregory P. Dietl, Patricia H. Kelley, Jessica G Lambert, and Christy C. Visaggi Science and Society 37. Digging for the Next Generation of Geologists: The Effectiveness of Saturday Science Academy Elysse N. Hernandez, Philip J. Stokes, Jenelle Zumbusch, Karl W. Flessa, Manny Leon, Sarah Truebe, Kendra Murray, and Nicole Conway Friday, March 30, 2011 8:00 Coffee Scientific Program 8:15-­9:30 Economic Geology 8:15 Characterization and Correlation of Skarn Mineralization and Protoliths, Resolution Porphyry Copper Deposit, Superior District, Arizona Michael J. McCarrel 8:30 Alteration and Veining in the Pinto Valley Porphyry Copper Deposit, Globe-­Miami District, Arizona Logan Hill 8:45 The Anatomy of an IOCG Vein System;; Massive Blob or Complex Structure? Insights from the Iron Queen Deposit, Southern Palen Mountains (SPM), Riverside County, CA James D. Girardi 9:00 Association of Non-­Ore Alteration with Ore Redistribution and Reworking at the Fungurume Sediment-­Hosted Cu-­Co Deposits P a g e | 9 Isabel Fay 9:15 Observations of NaCa, Ca, and K-­Ca Alteration at Multiple Scales in the Battle Mountain District, Nevada Caleb A. King 9:30-­10:15 Diffusion in Minerals 9:30 Development of a Radiation Damage and Annealing Model for the Zircon (U-­Th)/He Thermochronometer William Guenthner, Peter Reiners, Richard Ketcham, and Lutz Nasdala 9:45 Numerical Models of Garnet-­Whole Rock Isochron Development: Consequences of Differential Diffusion for Lu-­Hf Geochronology Elias Bloch, Jibamitra Ganguly, and Richard Hervig 10:00 Planetary Applications of Cation Diffusion in Mantle Minerals Esther S. Posner, Jibamitra Ganguly, Elias Bloch, Richard Hervig, and Robert G. Erdmann 10:15-­10:30 Coffee Break 10:30-­12:00 Geophysics II 10:30 Determining Fault Relationships and Timing Related to Continental Rifting Using 3D Reflection Data, Offshore Guinea, West Africa Russ Edge and Noah McDougall 10:45 Regional Investigation of Cretaceous, Offshore Guinea Rifting Structures ± Fracture Zones and Related Volcanism Noah J. McDougall and Russ D. Edge 11:00 Interpretation of Conical Structures in the West-­African Guinea Plateau Using 3D Seismic Reflection Data Melissa M. McMillan and James Broermann 11:15 Andes Retroarc Decollement Parameter Estimation From the Puna Andes GPS Network P a g e | 10 Katrina Gressett and Rick Bennett 11:30 Investigating Crustal Rheology through GPS Coordinate Time Series Analysis following Two Large Earthquakes within the Southern San Andreas Fault System Joshua Spinler and Richard Bennett 11:45 Global Positioning System Study of Western Eurasia Plate Rigidity Goran Buble and Richard A. Bennett 12:00 Lunch 1:00-­2:15 Posters Geochemistry and Tectonics 1. Determining Fluid Source for Pumpkin Hollow, an Iron-­Oxide-­Copper-­
Gold (IOCG) Deposit in Yerington, Nevada Simone Runyon 2. A Trace Element Record of Lake Level Rise and Evaporative Solute Concentration in Lake Bonneville, 26-­18 ka Nathan S. Evenson, Peter Reiners, Jay Quade, and David McGee 3. Observing Copper Ore Deposits, Slag and Metal Samples for Arsenic Content During the Late Sican Culture in Northern Peru Meri Hembree 4. Temporal and Spatial Variability in the Geochemistry of the CoAxial Segment of the Juan de Fuca Ridge and its Mantle Sources Cody-­John Davis, Matthew C. Smith, Michael R. Perfit, and George D. Kamenov 5. A Comparative Study of Shocked Mafic Minerals by Use of Raman Spectroscopy Amber L. Keske, Esther S. Posner, Robert T. Downs, and Hexiong Yang 6. ,QVLJKWVLQWRWKH&U\VWDO&KHPLVWU\RIWKH(DUWK¶V7UDQVLWLRQ=RQH P a g e | 11 Esther S. Posner, Heixong Yang, Jürgen Konzett, Robert T. Downs, and Daniel J. Frost 7. Influence of Thick-­ And Thin-­Skinned Deformation and Inversion Of Cretaceous Rift Structures on the Timing of Exhumation and Amount of Shortening in the Eastern Cordillera Thrust Belt, Northwest Argentina Cullen Kortyna 8. Apatite (U-­Th)/He Date Dispersion Due to Secondary Grain Boundary Phases: An Example from the Henry Mountains, Utah Kendra E. Murray, Devon A Orme, and Peter W Reiners 9. Basin Evolution and Exhumation of the Xigaze Forearc, Southern Tibet: Insight from Field Stratigraphy and Thermochronology Devon Anne Orme and Barbara Carrapa Geophysics 10. Geodetic and Seismic Reflection Data Constraints on Active Southern Basin and Range Extension, SE Arizona James Broermann, Rick Bennett, and Roy A Johnson 11. Assessing Apparent Differences Between Geodetic and Paleoseismic Slip-­Rates in Panama Kat Compton, J.C. Spinler and R.A. Bennett 12. Data Mining for Teleseismic Tomography in the Central Andes Alissa Scire, C. Berk Biryol, George Zandt, and Susan Beck 2:15-­2:30 Coffee Break 2:30 ± 3:30 Tectonics and Geochemistry 2:30 Erosional History of Glacially Derived Sediments in Prydz Bay, East Antarctica from Single Grain Triple-­Dating Clare Tochilin, Peter W. Reiners, Stuart N. Thomson, and George E. Gehrels P a g e | 12 2:45 Orogen-­Scale Sediment Dispersal Pathways in the Cordilleran Retroarc Foreland Basin System of North America Andrew K. Laskowski 3:00 Paleoelevation Estimate of the Oligo-­Miocene Gangrinboche Conglomerate, South-­Central Tibet, and What it Means for Tibetan Plateau Evolution Matthew Dettinger, Jay Quade, Ross Waldrip, and Kate Metcalf 3:15 Provenance, Paleoaltimetry, and Tectonic Significance of the Liuqu Conglomerate, Southern Tibet Ryan J. Leary, Jay Quade, and Peter G. DeCelles 3:30 40 Years of Daze, A GeoDaze Retrospective Karl Flessa 3:35 Keynote Address From Paleoclimate to Plateau Uplift: Clumped Isotopes in Terrestrial Carbonate Dr. Kate Huntington, Univ. of Washington 4:30-­5:00 Slideshow 5:00 Awards and Closing Remarks P a g e | 13 DATA MINING FOR TELESEISMIC TOMOGRAPHY IN THE CENTRAL ANDES Alissa Scire1, C. Berk Biryol1, George Zandt1, and Susan Beck1 1
Department of Geosciences, The University of Arizona The central Andes are characterized by along-­strike variations in magmatism, upper crustal shortening, crustal thickness, and lithospheric structure. Higher resolution regional-­scale tomographic imaging of the upper mantle, including the subducting slab and the underlying mantle, is required to better understand the relationship between large-­scale structural variations and mountain building processes. Multiple temporary seismic networks composed of both broadband and short period stations have been deployed in the central Andes between ~16 to 26°S. The goal of this project is to integrate data from individual seismic networks in the study region between 1994 and 2008 into a single database and, using modern teleseismic tomography methods, study upper mantle variations. P-­wave arrivals for teleseismic events between 30° and 90° are picked in three frequency bands (0.2 to 0.8 Hz, 0.1 to 0.4 Hz, and 0.04 to 0.16 Hz) for the broadband stations and in one frequency band (0.5 to 1.5 Hz) for the short period stations using a multi-­channel cross-­correlation algorithm. Results from finite frequency tomography clearly show a trench-­parallel fast anomaly which migrates to the east with increasing depth and appears to correspond to the steeply dipping subducting slab. At shallower depths, the slab anomaly shows large variations in amplitude, making identifying the slab at these depths difficult. Slab recovery tests indicate that resolution in the area of the subducting slab is sufficient to recover the slab-­related fast anomaly. Therefore the cause of the observed amplitude variations is uncertain, but does not appear to be a result of uneven data distribution. P a g e | 14 MODERN PERMAFROST DEGRADATION CONTRIBUTES TO LAKE SIZE INCREASE IN TIBET Alyssa Abbey1, Adam M Hudson1, and Paul Kapp1 1
Department of Geosciences, University of Arizona The Qinghai-­Tibetan Plateau is covered by thousands of lakes ranging in size from a few square kilometers to a few thousand square kilometers. Many of the lakes are located in internally drained basins, and lake area can be used as a direct indicator of the hydrologic budget within the basin. Eight internally drained lakes were chosen to represent four regions on the plateau (NE, NW, SE, and SW);; half were in basins fed by glacial runoff and half in basins without modern glaciers. For each lake, classification mapping was GRQH XVLQJ $UF*,6 DQG /DQGVDW LPDJHV IURP WKH ¶V WR SUHVHnt. Changes in lake size were measured using area calculations based on extracting the pixel number that made up the lake in each image. A constructed time series showed that between 1972 and 1997 lake level decreased slightly or had no change. From 1998 to present all lakes show an increasing trend in size. Precipitation in each region is not changing significantly and although glacier melt may be contributing to this increase in lake size in glaciated watersheds, this is not the case for non-­glaciated watersheds. We suggest permafrost degradation is the dominant factor contributing to this increasing trend. The plateau is almost entirely covered in frozen ground, which has been degrading over the past 50 years as the average annual ground temperatures have been rising. We propose that the frozen water in the soil has been melting and feeding the growth of the lakes on the plateau. P a g e | 15 A COMPARATIVE STUDY OF SHOCKED MAFIC MINERALS BY USE OF RAMAN SPECTROSCOPY Amber L. Keske1, Esther S. Posner1, Robert T. Downs1, and Hexiong Yang1 1
Department of Geosciences, University of Arizona Raman analysis of shocked minerals, such as silica and feldspar, has revealed that shocked minerals exhibit broader Raman peaks than those of their corresponding unshocked minerals (Velde, 1985;; Gucsik, 2003). Shock effects in mafic minerals, however, remain poorly understood. To address this problem, we are conducting a study using Raman spectroscopy and x-­ray diffraction to analyze shocked mafic minerals, with a particular focus on pyroxenes, from gabbroic impactites obtained from five different confirmed meteorite impact sites. We present preliminary results of Raman peak broadening and crystallographic effects of shock metamorphism in pyroxenes as compared to unshocked pyroxenes. P a g e | 16 OROGEN-­SCALE SEDIMENT DISPERSAL PATHWAYS IN THE CORDILLERAN RETROARC FORELAND BASIN SYSTEM OF NORTH AMERICA Andrew K. Laskowski1 1
Department of Geosciences, University of Arizona The Cordilleran retroarc thrust belt and foreland basin system consolidated in Late Jurassic time in response to North Atlantic spreading and coeval subduction of oceanic plates under the western margin of North America. Over the next ~100 My, contractional deformation within the Cordilleran orogenic wedge drove flexural subsidence and foreland basin sedimentation within North America's immense Western Interior Basin. 68 published and 29 new detrital zircon samples from the foreland basin system of southwestern Canada and the western United States were compiled to investigate provenance, thrust belt exhumation, and arc magmatism during the construction of the Cordilleran system. This dataset, which consists of 8,939 U-­Pb spot analyses on detrital zircon grains, defines a comprehensive age spectrum for foreland basin strata. These data were interpreted within the context of new detrital zircon age spectra from the North American Miogeocline (Gehrels and Pecha, in press) to reveal long-­
lived, south to north axial transport of foreland basin sediments during the Late Jurassic and Cretaceous. P a g e | 17 REGIONAL FREQUENCY-­MAGNITUDE-­AREA RELATIONSHIPS FOR PRECIPITATION AND RIVER DISCHARGES DERIVED FROM NEXT-­GENERATION RADAR (NEXRAD) Caitlin A. Orem1 and Jon D. Pelletier1 1
Department of Geosciences, University of Arizona Flood-­envelope curves delineate the upper boundary of flood discharges for a given drainage basin area. The usefulness of flood-­
envelope curves is limited by the absence of recurrence interval information. In this study, Stage-­III NEXRAD (Next-­Generation Radar) precipitation datasets for the Colorado River Basin (CRB) are used to calculate precipitation and flood discharges of 10, 50, 100, and 500-­
year recurrence intervals for southeastern Arizona and the upper and lower CRB regions. Recurrence intervals are calculated from a frequency-­magnitude distribution of precipitation as a function of drainage basin area and storm duration. This study also provides insight into the controls on the characteristic concave-­down shape of the flood envelope curves. To test possible controls, flood discharges are calculating using two techniques: a technique that includes geomorphic dispersion, and a technique that includes geomorphic and hydrodynamic dispersion. Results show that flood and precipitation discharges increase with increasing recurrence interval. In general, precipitation and flood discharges of 10 and 50-­year recurrence intervals were higher in the lower CRB than the upper CRB, but 100 and 500 year recurrence intervals were higher in the upper CRB regions than the lower CRB. Also, precipitation and flood discharges of different recurrence intervals were more similar in the lower CRB region than the upper CRB region. Precipitation discharges for all regions and recurrence intervals are power-­law functions of drainage area with an exponent of approximately 0.7. Results from this study suggest that the concave-­down shape of the flood-­envelope curve is primarily due to geomorphic dispersion. P a g e | 18 OBSERVATIONS OF NACA, CA, AND K-­CA ALTERATION AT MULTIPLE SCALES IN THE BATTLE MOUNTAIN DISTRICT, NEVADA Caleb A. King1 1
Department of Geosciences, University of Arizona Mapping results throughout the Battle Mountain District, Nevada indicate widespread NaCa, Ca, and K-­Ca alteration. These alteration types can be associated with both porphyry and IOCG systems, but their genetic relationships in this case are unclear. Detailed mapping at the Elder Creek porphyry system and reconnaissance work at other porphyry systems in the district at many scales, allows the comparison of these alteration types to gain perspective into their origins and relationships to ore forming processes. At the thin section and hand sample scale, mineral associations and assemblages are observed. Petrography, whole rock data, staining, and microprobe analyses indicate the systematic exchange of materials between the host rocks and circulating fluids represented by these alteration types. Reconnaissance work at the deposit scale shows the distribution of alteration types enabling a comparison of different intrusive centers and associated alteration types. At the district scale we can combine the smaller-­scale observations and comparisons to address broader questions involving the processes of fluid circulation, regional structure and potentially climate. Documentation of the types and distribution of hydrothermal alteration in the porphyry-­related systems of the Battle Mountain District provides context for a regional synthesis of these types of alteration. These data combined with radiometric dating are essential for understanding the environment of ore formation, fluid compositions, the origins of the fluids and ultimately the time-­space evolution of the district. Are magmatic or basinal fluids responsible for these types of alteration? P a g e | 19 SOUTHWEST CLIMATE IN THE COMMON ERA Chelsea Powers1, Cody Routson1, and Jonathan Overpeck1 1
University of Arizona, Department of Geoscience Mountainous environments are important sources of water as well as many other natural resources in the Southwest. Recent changes in temperature, precipitation, and dustiness are having a dramatic impact on precipitation and snow cover duration in these sensitive regions. Here we use lake sediments and tree-­rings in the south San Juan Mountains to generate long records of dustiness, runoff, and drought. Grain size and X-­ray-­fluorescence analysis suggests recent dustiness is anomalous with respect to the last 500 years, and that increased GXVWLQHVV OLNHO\ DFFRPSDQLHG ZLGHVSUHDG PHGLHYDO DULGLW\ í-­1300 CE). Furthermore an earlier interYDO VSDQQLQJ í-­200 CE may also have been anomalously dusty. A 2000 yearlong Bristlecone pine drought record also suggests medieval times were indeed dry in the San Juan Mountains and at least part of the earlier dusty period (1-­400 CE) was punctuated by anomalous aridity, which corroborates well with gridded tree-­ring reconstructed drought. Much work remains to fully understand these new records, including constraining age uncertainty and fine-­tuning our fingerprinting of dust, but already these records provide intriguing insights into past Southwest climate P a g e | 20 EROSIONAL HISTORY OF GLACIALLY DERIVED SEDIMENTS IN PRYDZ BAY, EAST ANTARCTICA FROM SINGLE GRAIN TRIPLE-­DATING Clare Tochilin1, Peter W. Reiners1, Stuart N. Thomson1, and George E. Gehrels1 1
Department of Geosciences, The University of Arizona Little is known about the tectonic and erosional history of East Antarctica since the onset of the East Antarctic Ice Sheet (EAIS) at 34 Ma. To better constrain the subglacial erosional record, we have analyzed glacially derived sediments deposited from the Oligocene through Quaternary in Prydz Bay on the eastern margin of the continent, as these sediments contain geo-­ and thermochronologic records of their bedrock source areas. The Prydz Bay region contains the largest ice stream in Antarctica, draining ~20% of the EAIS. A triple-­dating approach was applied in the analysis of these sediments, involving U-­
Pb, fission track, and (U-­Th)/He dating of single apatite and zircon grains to measure a range of crystallization and cooling ages. Apatite U-­Pb analyses of grains spanning the entire sampled stratigraphy yield ages of ~500 Ma, indicating that much of this area experienced Pan-­African metamorphism to temperatures greater than 500°C. Zircon U-­Pb ages are also characterized by a dominant ~500 Ma signature. Mean apatite fission track ages show a decreasing trend from the early Oligocene through late Miocene samples (the dominant age peak decreasing from ~280 to ~170 Ma), and remain young and relatively constant (~160 Ma) from the Pliocene until Quaternary. Apatite He ages in late Miocene samples show a larger spread of young ages, ranging from ~30-­160 Ma. These results indicate that most erosional activity associated with glacial incision affected East Antarctica between the early Oligocene and late Miocene. This is consistent with models of the EAIS that show that it transitioned to less erosive cold-­based conditions following the middle Miocene climatic optimum. P a g e | 21 TEMPORAL AND SPATIAL VARIABILITY IN THE GEOCHEMISTRY OF THE COAXIAL SEGMENT OF THE JUAN DE FUCA RIDGE AND ITS MANTLE SOURCES Cody-­John Davis1, Matthew C. Smith2, Michael R. Perfit2, and George D. Kamenov2 1
Department of Geosciences, The University of Arizona 2
Geological Sciences, University of Florida Trace element and isotopic (Sr, Nd, Pb) geochemical analyses of recent and historic lavas from three eruptive sites of the CoAxial Segment of the Juan de Fuca Ridge (JdFR) have provided improved understanding of spatial/temporal chemical variability in lavas, and further insight into JdFR magmatic processes. Modeling of major and trace element abundances suggest intraflow chemical variation within CoAxial lavas is largely due to shallow-­
level fractional crystallization, however a single fractional crystallization model cannot account for all interflow chemical variation. Specifically, elemental and isotopic abundances require different parental magmas for each of the three CoAxial Segment lava flows ± indicating very short-­term changes or heterogeneity in the chemistry of the mantle source region. This is noticeably GHPRQVWUDWHG E\ WKH ¶V )ORZ 6LWH ZKRVH SDUHQWDO PDJPD OLNHO\
formed at higher pressures and with smaller degrees of melting than magmas that erupted just over a decade later. A comparative analysis of CoAxial Segment lavas with lavas from nearby seamounts and ridge segments show that much, though not all, of the data conforms to binary mixing arrays. This suggests parental lavas from this region of the JdFR can be formed from variable amounts of mixing of two or more distinct end-­member mantle sources. In addition to one or more depleted mantle (DM) sources, regional isotopic data also likely support a high U/Pb (HIMU?) source component. Strong correlations exist between long-­lived radiogenic isotopes and ratios of highly incompatible elements for most lavas, indicating that mantle heterogeneities sampled are ancient. However, in some cases elemental data is decoupled from the radiogenic isotope data, suggesting more recent depletion events. P a g e | 22 INFLUENCE OF THICK-­ AND THIN-­SKINNED DEFORMATION AND INVERSION OF CRETACEOUS RIFT STRUCTURES ON THE TIMING OF EXHUMATION AND AMOUNT OF SHORTENING IN THE EASTERN CORDILLERA THRUST BELT, NORTHWEST ARGENTINA Cullen Kortyna1 1
Department of Geosciences, The University of Arizona The Eastern Cordillera of northwest Argentina exhibits a transition in structural style between thick-­ and thin-­skinned features. Traditionally, foreland structural geometries are correlated with the orientation of the subducting Nazca Plate. Whereas thin-­skinned deformation to the north is attributed to simple VKHDUDQGQRUPDOVXEGXFWLRQÛDQGWKLFN-­skinned deformation to the south is associated with pure shear and flat slab subduction, deformation in the Salta Rift region is likely controlled by inversion of inherited Cretaceous rift structures. South of Salta, in the UDQJHV VXUURXQGLQJ WKH &DOFKDTXt DQG /HUPD 9DOOH\V EHWZHHQ aÛ-­Û6
DQGaÛ-­Û:WKHWKUXVWEHOWLVFKDUDFWHUL]HGE\VWHHSZHVW-­verging, N-­S trending reverse faults juxtaposing Precambrian-­Cambrian basement rocks on Mesozoic-­Cenozoic syn-­to-­post-­rift and foreland basin deposits. Geologic mapping, structural data and stratigraphic relationships confirm that these reverse faults are primarily reactivated extensional faults of the Cretaceous Salta rift, a complex of extensional basins beneath the modern foreland basin, and that the rift geometry provides a major control on fold and fault geometries in the area. Mio-­Pliocene deformation is characterized by thrust kinematics with E-­W to NW-­SE shortening, perpendicular to major Andean structures, whereas Plio-­Quaternary deformation is characterized by strike-­slip kinematics with NE-­SW shortening. Current balanced cross sections predict that the foreland has been shortened 25%. Detrital apatite (U-­Th)/He ages document sequential propagation of exhumation (and inferred deformation) from ~14 to 3 Ma and quasi-­uniform rates of propagation through the whole region regardless of structural style;; however, some authors argue for erratic, out-­of-­sequence deformation based on sediment architecture and facies associations. P a g e | 23 TREE-­RING INSIGHT ON SUMMER MONSOON PALEOCLIMATE IN THE SOUTHWESTERN U.S. Daniel Griffin1, Connie A. Woodhouse2, David M. Meko1, Christopher L. Castro3, Holly L. Faulstich1, and Carlos Carrillo3 1
Laboratory of Tree-­Ring Research, The University of Arizona School of Geography and Development, The University of Arizona 3
Department of Atmospheric Sciences, The University of Arizona 2
Southwestern North America is characterized by a dual-­season hydroclimate regime. Cool-­season frontal storms are the primary contributor to surface water supplies;; however, the highly variable VXPPHU PRQVRRQ LV D FULWLFDO VRXUFH RI PRLVWXUH IRU WKH UHJLRQ¶V
social and environmental systems. As southwestern resource managers begin adapting to 21st century climate changes, understanding the nature of long-­term monsoon variability is more important than ever. This was the motivation for developing a dense network of tree-­ring FKURQRORJLHV IURP ZLGWK PHDVXUHPHQWV RI ³HDUO\ZRRG´ DQG ³ODWHZRRG´
the light-­ and dark-­colored sub-­annual components of conifer growth rings that respectively form in spring and summer. Our recently minted database of earlywood and latewood chronologies from over 50 sites across the southwestern U.S. offers a QRYHO PHDQV IRU HYDOXDWLQJ WKH UHJLRQ¶V GXDO-­season hydroclimatic history. Targeting the Arizona-­Sonora sub-­region of the North American monsoon, we developed high-­quality reconstructions of cool-­ and warm-­season precipitation that extend from 1539-­2008. The monsoon (June-­August) precipitation reconstruction points to a period of dry summers in the late 19th century that was more persistent than any during the instrumental era. Comparison with the complimentary reconstruction of winter-­spring precipitation (October-­April) indicates that persistent monsoon drought often coincided with cool-­
season drought periods, including the 16th century Megadrought, the 17th century Puebloan drought, and the ongoing 21st century drought. This research offers paleoclimatic perspective on the current drought and underscores the importance of precipitation seasonality in the Southwest. The new reconstruction establishes an accurate, precisely-­dated geochronology for comparison with other monsoon climate proxy records and provides an estimate of long-­term monsoon variability for comparison with regional climate model output. P a g e | 24 BASIN EVOLUTION AND EXHUMATION OF THE XIGAZE FOREARC, SOUTHERN TIBET: INSIGHT FROM FIELD STRATIGRAPHY AND THERMOCHRONOLOGY Devon Anne Orme1 and Barbara Carrapa1 1
Department of Geosciences, University of Arizona In southern Tibet, the Cretaceous-­Eocene Xigaze forearc is a crucial data archive for understanding the evolution of the Indo-­Asia continental margin. Contrasting ideas exist on the pre-­collisional paleogeography of Asia and India and on the timing of collision. Some propose that Asian crust was thick and high pre-­collision and that collision occurred in the early Cenozoic (Rhormann et al., 2011) whereas others suggest uplift in the late-­Cenozoic and that collision occurred in the mid-­Cenozoic (Aitchison et al., 2007). This research addresses these discrepancies through the application of sedimentology, stratigraphy and detrital thermochronology to Xigaze forearc strata. Investigation of a previously unexplored sequence of the Xigaze forearc reveals good exposures of Cretaceous-­Cenozoic strata. Presently, 2.5 km of late Cretaceous strata consisting of 1.3 km of distal turbidite deposits and turbidite channel conglomerates, and 1.2 km of estuarine and marginal marine facies have been measured. In order to determine the timing and rates of basin exhumation, we have utilized detrital thermochronology (i.e. zircon(U-­Th)/He dating) coupled with U-­Pb geochronology. To date, results from U-­Pb detrital zircon geochronology indicate that the primary source of forearc detritus is the Gangdese Magmatic Arc, which is active ~150-­70 Ma. Double-­Dated (U-­Th/He and U-­Pb) zircon crystals suggest basin exhumation between 30-­10 Ma. This younger age corresponds to independently determined ages for movement along the basin bounding Great Counter Thrust (GCT). Therefore, we postulate that this fault was the primary mechanism for exhuming the forearc. The application of detrital thermochronology coupled with U-­
Pb geochronology is the first study of its kind and provides critical constraints on the timing of forearc exhumation. P a g e | 25 7URSLFDO&OLPDWH7UHQGV,QIHUUHGIURP&RUDOį18O: A Comparison of CMIP-­
5 Forward-­Model Results with Paleoclimatic Observations Diane Thompson1, M.N. Evans2, J.E. Cole1, T.R. Ault3, and J. Emile-­Geay4, 1
Department of Geosciences, University of Arizona 2
Department of Geology and Earth System Science Interdisciplinary Center, University of Maryland 3
National Center for Atmospheric Research 4
Department of Earth Sciences, University of Southern California The response of the tropical Pacific Ocean to anthropogenic climate change remains highly uncertain, in part because of the disagreement among 20th-­century trends derived from observations and coupled general circulation models (CGCMs). We use a model of reef FRUDO R[\JHQ LVRWRSLF FRPSRVLWLRQ į18O) to compare the observational FRUDOQHWZRUNZLWKV\QWKHWLFFRUDOVµSVHXGRFRUDOV¶PRGHOHGIURP&*&0
sea-­surface temperature (SST) and sea-­surface salinity (SSS). When driven with historical data, we found that a linear temperature and VDOLQLW\ GULYHQ PRGHO IRU į18Ocoral was able to capture the spatial and temporal pattern of ENSO and the linear trend observed in 23 Indo-­
Pacific coral records between 1958 and 1990. However, none of the pseudocoral networks obtained from a subset of 20th-­century AR4 CGCM runs reproduced the magnitude of the secular trend, the change in mean state, or the change in ENSO-­related variance observed in the coral network from 1890 to 1990 (Thompson et al., 2011). Differences between corals and AR4 CGCM simulated pseudocorals may result from uncertainties in the observed coral network or linear bivariate coral model, undersensitivity of AR4 CGCMs to radiative forcing during the 20th century, and/or biases in the simulated AR4 CGCM SSS fields. Here we apply the same approach to an extended temperature and salinity reanalysis product (SODA v2.2.4, 1871-­2008), a long CGCM control run, and CMIP-­5 simulations to further address 20th-­century tropical climate trends and assess remaining uncertainties in both the proxies and models. We explore whether model improvements in the tropical Pacific have led to a stronger agreement between simulated and observed tropical climate trends. P a g e | 26 NUMERICAL MODELS OF GARNET-­WHOLE ROCK ISOCHRON DEVELOPMENT: CONSEQUENCES OF DIFFERENTIAL DIFFUSION FOR LU-­HF GEOCHRONOLOGY Elias Bloch1, Jibamitra Ganguly1, and Richard Hervig2 1
2
Department of Geosciences, University of Arizona School of Earth and Space Exploration, Arizona State University Because garnet preferentially fractionates the parent nuclides of both the Lu-­Hf and Sm-­Nd decay systems, garnet-­whole rock isochrons are widely used for Lu-­Hf and Sm-­Nd geochronology. The Lu-­Hf system is particularly appealing because 176Lu has a much smaller decay constant than 147Sm, and because it is less susceptible to contamination from inclusions [1], [2];; however, the high charge of Hf causes it to diffuse much more slowly than Lu, a problem which is avoided when utilizing the Sm-­Nd decay system owing to the essentially identical diffusion properties of Sm and Nd [3]. An additional complexity arises because the slow diffusivity of Hf makes it extremely unlikely that Hf is homogenized in most garnets. Thus, one of the fundamental assumptions made in all existing analytical formulations for closure temperature is not satisfied [4], [5]. In order to address this problem, we have constructed a model which couples numerical simulations of garnet growth and isotope diffusion with analytical solutions for element fractionation and radioactive decay. This model indicates that diffusive modification can cause Lu-­
Hf ages to pre-­date peak metamorphism, or even garnet nucleation, while Sm-­Nd ages date either cooling or peak metamorphism. References: [1] Scherer et al. (2000) GCA 64, 3413-­3432 [2] Kohn (2009) GCA 73, 170-­182 [3] Ganguly et al. (1998) Science 281, 805-­807 [4] Dodson (1973) Cont. to Min. and Pet. V. 40, No. 3, 259-­274 [5] Ganguly and Tirone (1999) EPSL 170, 131-­140 P a g e | 27 A STUDY OF THE CAUSES OF THE DECLINE IN FISH CATCH AT LAKE TANGANYIKA Elizabeth Gergurich1 and Andrew Cohen1 1
Department of Geosciences, University of Arizona Lake Tanganyika, located in the East African Rift valley, is a meromictic lake whose productivity relies on the internal loading of nutrient rich anoxic deep waters back into the surface waters. This mixing facilitates phytoplankton and zooplankton growth, which in turn SURYLGH WKH EDVLV IRU WKH ODNH¶V SHlagic fishery. Trends towards higher global air temperatures over the last 100 years are reflected LQWKHZDUPLQJRI/DNH7DQJDQ\LND¶VVXUIDFHZDWHUWHPSHUDWXUHDQGKDYH
resulted in increased stratification, decreased mixing of the water column and lowered primary productivity. Fish fossil abundance from short cores can potentially reveal how such changes have impacted the ODNH¶V ILVK DEXQGDQFH GXULQJ SHULRGV RI ODNH ZDUPLQJ VLQFH ZH PLJKW
expect warming and fish abundance to be inversely correlated. Fossil fish bone and scale counts per dry gram of sediment were performed for the basal 33 cm of lake core LT-­98-­7M located in the isolated Lubulungu River delta off the Mahale Mountains. Correlating this core data to the Pb-­210 dates from a previously studied core collected at a similar depth ~4km from the 7M core site suggest peak fish fossil assemblage intervals at depths of 50cm-­47cm (~1396-­1418 AD), 42cm(~1462 AD), 40cm-­35cm(~1476-­1513AD) and 30cm-­23cm (~1549-­
1600AD). Preliminary data shows a weak correlation between fish fossil assemblage peaks and low lake surface temperature. Further study of the fossil assemblage trends in the top 20cm will aid in the determination of the effects of the increase in global temperature and fishing practices on the pelagic fish populations of Lake Tanganyika. P a g e | 28 DIGGING FOR THE NEXT GENERATION OF GEOLOGISTS: THE EFFECTIVENESS OF SATURDAY SCIENCE ACADEMY Elysse N. Hernandez1, Philip J. Stokes1, Jenelle Zumbusch2, Karl W. Flessa1, Manny Leon3, Sarah Truebe1, Kendra Murray1, and Nicole Conway1 1
Department of Geosciences, University of Arizona 2
3
American Institutes for Research Arizona Mathematics, Engineering, Science Achievement Saturday Science Academy (SSA) is an academic outreach event held each year at the University of Arizona. With a variety of hands-­on educational activities and demonstrations, SSA has attracted hundreds of participants over the past two years. The target audience of SSA is local middle and high school students from underrepresented minority groups who attend schools that do not emphasize geosciences in their curriculum. Hispanic and Native American students typically comprise the majority of participants in SSA. SSA is supported by the Department of Geosciences at the University of Arizona, The Arizona Mathematics Engineering Science Achievement (MESA), and The Southern Arizona Geosciences Union for Academics, Research and Outreach (SAGUARO). To better understand the effect of SSA on local students, evaluation surveys were administered to participants at the 2009, 2010 and 2011 SSA events. Fossils and other prizes were used as incentives to encourage students to complete the surveys. In 2011, 112 surveys were collected from participants both before and after SSA. Program effectiveness was asseVVHG WKURXJK FRPSDULVRQV RI SDUWLFLSDQW¶V SUH-­
and post-­SSA responses. Preliminary results suggest that SSA is effective in improving the perception of geosciences amongst both ZKLWH DQG PLQRULW\ VWXGHQW JURXSV \HW WKHUH DUH GLIIHUHQFHV LQ 66$¶V
effectiveness in reaching each group. Such differences can be seen WKURXJK WKH UHVSRQVHV WR WKH VWDWHPHQW µ*HRVFLHQFHV DUH LQWHUHVWLQJ¶
where Hispanic students largely agree with the statement, while Native American students largely disagree with it. P a g e | 29 PLANETARY APPLICATIONS OF CATION DIFFUSION IN MANTLE MINERALS Esther S. Posner1, Jibamitra Ganguly1, Elias Bloch1, Richard Hervig2, and Robert G. Erdmann3, 1
2
3
Department of Geosciences, University of Arizona School of Earth & Space Exploration, Arizona State University Department of Materials Science and Engineering, University of Arizona Diffusion kinetic data are essential for modeling the timing of events and processes that took place during the earliest stages of solar system formation (e.g. chondrule and planetesimal formation, accretion rate, and core formation) by determining the closure temperature of short-­lived decay systems, such as 53Mn-­53Cr and 182Hf-­
182W with half-­lives of 3.7 and 8.9 million years, respectively. We have experimentally determined the diffusivity Cr in spinel as a function of temperature, pressure, and oxygen fugacity, and W in diopside as a function of temperature and crystallographic orientation. When coupled with isotopic measurements of planetary materials, these data provide critical parameters on the modeling and interpretation of important early-­stage planetary processes. W diffusion in silicates is of particular interest for the modeling of the timing of planetary accretion and core formation due to the strong metal-­silicate fractionation of lithophile 182Hf from siderophile 182W. Excess 182W in the silicate mantles of differentiated bodies has traditionally been thought to indicate early differentiation (<60 my) (Jacobsen 2005). The extent to which W would have fractionated into the core, however, depends on the time scale of diffusive transport of W from the silicate into the core-­forming melt. Compositional zoning in minerals is also a common relict of chemical disequilibrium that occurs during petrogenesis, metamorphism, and exhumation. The high preference of Cr to occupy the spinel octahedral site within ultrabasic mineral assemblages make Cr diffusion in spinel an important tracer of thermal histories experienced by mantle xenoliths and meteorite parent bodies. P a g e | 30 INSIGHTS INTO THE CRYSTAL CHEMISTRY OF THE EARTH¶S TRANSITION ZONE Esther S. Posner1, Heixong Yang1, Jürgen Konzett2, Robert T. Downs1, and Daniel J. Frost3, 1
2
Department of Geosciences, University of Arizona Institut für Mineralogie und Petrographie, Universität Innsbruck 3
Bayerisches Geoinstitut, Universität Bayreuth Silicon is four-­coordinated in the Earth's crust and upper mantle and six-­FRRUGLQDWHG LQ WKH ORZHU PDQWOH ,Q WKH (DUWK¶V WUDQVLWLRQ
zone (between depths of 410 -­ 670 km), minerals are found to contain both IVSi and VISi. Phase transitions that involve a change in the Si coordination may affect many important physical and chemical properties of materials, such as density, bulk moduli, and elasticity, which, when coupled with seismic observations, can provide vital information on the complex constituents of the Earth's mantle. Clinopyroxenes, one of the major rock-­forming minerals of the Earth's upper mantle, were long assumed to contain IVSi only. Studies of pyroxenes synthesized at high temperatures and pressures, however, have revealed their capacity to accommodate both IVSi and VISi (Angel et al. 1988;; Yang et al., 2009), pointing to their possible stabilities at higher pressures. To gain more insights into the systematics on the crystal chemistry and stability field of pyroxenes with VISi, we conducted a structure refinement of a high-­pressure synthetic clinopyroxene that crystallized in P2/n with 0.40 VISi atoms per formula unit (apfu). Previous studies revealed that a phase transition from disordered C2/c to ordered P2/n occurs between 0.33-­
0.45 VISi afpu. Our results further narrow the range to 0.33-­0.40 VISi apfu. The foremost implications of this study include that (1) portions of the Earth's upper mantle may contain a greater ratio of Na/Al than previously inferred from xenolith chemistry, and (2) clinopyroxenes may be one of potential candidates as a silica-­rich phase in the Earth's mantle. P a g e | 31 GLOBAL POSITIONING SYSTEM STUDY OF WESTERN EURASIA PLATE RIGIDITY Goran Buble1 and Richard A. Bennett1 1
Department of Geosciences, University of Arizona We analyze continuous GPS data collected over the last 21 years at stations distributed broadly throught the interior of the Eurasian plate. We estimate crustal velocities at 250 locations relative to the ITRF05 reference frame. For all sites, velocity estimate uncertainty is less than 0.6 mm/yr. We used the velocities to test whether the motion of western Eurasia may be described as a single rigid plate. Depending on the sites we choose to estimate the Euler pole, the rigid plate model fits site velocities with a root mean square scatter of 0.3-­0.4 mm/yr, however residual velocities exhibit statistically significant systematic trends. Tests for differential motion between eastern and western Eurasia across the Rhine Graben reveal E-­W convergent motion of ~0.5 mm/yr generally orthogonal to the strike of the graben. Far field convergent motion, interpreted in light of structural geologic and focal mechanism evidence for near axis extensional tectonics, may be associated with downwelling mantle lithosphere. Tests for differential motion across the Pyrenees reveal motion of the Iberian peninsula relative to the remainder of western Eurasia at rates in the range of ~0.0 ± 0.1 to 0.2 ± 0.1 mm/yr, varying significantly across short distance due to the proximity of the inferred Iberia-­western Eurasia Euler pole. Spatial variation in the predicted style of deformation are in partial agreement with earthquake slip vectors from the Pyrenees region and may correlate with upper mantle heterogeneity imaged by other recent studies. P a g e | 32 CAN THE RIVER REACH THE SEA? RE-­CONNECTING THE COLORADO RIVER AND THE GULF OF CALIFORNIA Hector A. Zamora1 and Karl W. Flessa1 1
Department of Geosciences, University of Arizona River-­sea connectivity is essential for restoring ecosystem services in the Colorado River Delta (CRD) by sustaining biodiversity and for providing brackish-­water nursery grounds for both commercially important and endangered marine species. I used 20 years of Landsat 5 TM scenes from the CRD and remote sensing software to assess river-­sea connectivity and geomorphic processes after 50 years of extensive KXPDQ PDQLSXODWLRQ RI WKH &RORUDGR 5LYHU 7KH ULYHU¶V UHOLFW FKDQQHO
is obstructed by an accumulation of sediments deposited during flood tides;; ebb flows are not strong enough to keep the channel open. Tides at the mouth of the river reach 10 m in amplitude and can extend into the former channel. Satellite images and tide charts show that the river reaches the sea or the sea reaches the river about 10-­15 days per year. As part of a bi-­national effort by U.S. and Mexican research institutions to restore the CRD, I seek to understand sedimentation processes in the area in order to maximize the potential of the remaining wetland habitats. Active management ±both dredging and water allocations-­ is required to reconnect the remaining riparian wetlands in the Colorado River to the Gulf of California. An ongoing 210Pb geochronology study calibrated with anthropogenic-­derived markers will quantify sedimentation rates. Evidence derived from sediment core analysis, satellite data, and a topological survey suggest sedimentation rates of 10-­20 cm per year in the remnant channel, indicating the need for dredging once every 5-­10 years to maintain this connectivity. P a g e | 33 ASSOCIATION OF NON-­ORE ALTERATION WITH ORE REDISTRIBUTION AND REWORKING AT THE FUNGURUME SEDIMENT-­HOSTED CU-­CO DEPOSITS Isabel Fay1 1
Department of Geosciences, University of Arizona The Neoproterozoic strata of the Fungurume district, D.R. Congo, host large, high-­grade Cu-­Co deposits altered by three to four generations of dolomite alternating with two of silica. This study was undertaken to determine whether these alteration episodes affected ore distribution or merely reworked ore mineralogy. Petrographic, cathodoluminescence, and SEM examination were used to assess the distribution of trace metals in different alteration minerals to determine if their corresponding alteration episodes affected ore mineralogy or distribution. Results show that early alteration involved only ore reworking, whereas later supergene alteration both reworked metals into different minerals and redistributed them across the deposits. Early reworking without redistribution is shown by overgrowth or inclusion of original sulfides by later sulfides contemporaneous with the penultimate dolomite generation. These dolomites are devoid of Cu, Co, and related metals. The last dolomites, by contrast, contain trace to ore-­grade Co. Their elevated Co and association with a supergene Cu mineral suite show that the fluid that precipitated them participated in ore reworking. Their distribution pattern differs from the distribution of the ore sulfides, indicating that ore was redistributed as well as reworked in the last alteration episode. These results illustrate how the role and importance of alteration in ore distribution and mineralogy varies over time. At Fungurume, early ore reworking was succeeded by ore reworking and redistribution. These processes, traceable by petrographic and geochemical analyses, combined to create the modern ore mineralogy and occurrence patterns of the deposits. P a g e | 34 GEODETIC AND SEISMIC REFLECTION DATA CONSTRAINTS ON ACTIVE SOUTHERN BASIN AND RANGE EXTENSION, SE ARIZONA James Broermann1, Rick Bennett1, and Roy A Johnson1 1
Department of Geosciences, University of Arizona The southern Basin and Range is thought to be extending at low rates of strain although little is known about how this strain is distributed. The North Swisshelm normal fault (NSF), which strikes NW and dips NE, is located at the northern end of the Swisshelm Mountains in southeastern Arizona and is thought to have had one or more surface-­rupturing earthquakes in the Quaternary. Recent earthquakes of magnitude 2.6 (1/7/2008) and 0.9 (12/25/2007), located using data from Earthscope's Transportable Array, are in close proximity to the NSF and suggest it is in an actively deforming region. As part of an Earthscope project, we recently installed 16 geodetic stations located in the southern Basin and Range and on the Colorado Plateau. Initial coordinate time series from GPS data collected at the sites in Arizona suggest the data quality is similar to that of Plate Boundary Observatory GPS data. As the total time of data collection increases, improved estimates of location, velocities and possible locations of strain partitioning are expected in the area of the network, including southeastern Arizona where the NSF is located. Industry 2D seismic reflection data in the area of the NSF show reflections dipping to the NE away from the NSF within a time interval of 0.5-­1.0 s that provide information about the depositional history near the NSF. Seismically locating the top of the NSF hanging wall block can provide an estimate of total fault motion with a possible time constraint on fault initiation after mid-­Tertiary eruption of the Chiricahua volcanics. P a g e | 35 THE ANATOMY OF AN IOCG VEIN SYSTEM;; MASSIVE BLOB OR COMPLEX STRUCTURE? INSIGHTS FROM THE IRON QUEEN DEPOSIT, SOUTHERN PALEN MOUNTAINS (SPM), RIVERSIDE COUNTY, CA James D. Giradi1 1
Department of Geosciences, University of Arizona Iron oxide-­rich hydrothermal systems with accessory or elevated levels of Cu, Au, Ag, U, and LREE (a.k.a. IOCG¶VDVVRFLDWHGZLWKWKH
Jurassic arc of southwest North America are an important facet of Cordilleran metallogenic evolution. Unfortunately, these systems are rarely well-­GHVFULEHG DQG FRPPRQO\ RYHUVLPSOLILHG DV ³PDVVLYH´ LURQ
oxide bodies, providing little useful context for interpreting how they formed. Our ability to understand IOCG formation in this region can be greatly enhanced using fundamental field observations. Bench mapping of magnetite-­apatite(-­actinolite-­titanite) veins at the Iron Queen prospect in the SPM reveals that the deposit is not massive, but consists of sheeted 0.1-­1 m+ thick veins that are complexly cross-­cutting, re-­opening, and brecciating each other. The deposit is crosscut by quartz, calcite, epidote, chlorite, and actinolite veins, and cemented breccias. Vertically, the system pinches out into a narrow diffuse vein zone, and transitions laterally into a magnetite crackle breccia. The deposit is located in a fault zone, and surrounded by intense Na-­Ca alteration, dated at 161±3 Ma, hosted in dioritic and andesitic rocks. Observations from the SPM support the involvement of an external brine fluid in the formation of iron oxide-­rich veins at the Iron Queen prospect. Recognition of such a fluid has significant implications for explaining regional alteration patterns and mechanisms for transport and precipitation of Fe, and other metals, in IOCG vein systems like the Iron Queen prospect. The SPM vein systems share similarities of intense regional Na-­Ca alteration and complex vein mineralogy/morphology with other well-­documented IOCG vein systems in the region and worldwide. P a g e | 36 EBSD-­BASED CALCULATIONS OF SEISMIC VELOCITIES OF ECLOGITES FROM THE HP-­UHP WESTERN GNEISS REGION, NORWAY James R. Worthington1 and Bradley R. Hacker2 1
2
Department of Geosciences, University of Arizona Department of Earth Science, University of California, Santa Barbara Seismic velocities were calculated for eleven eclogites from the Western Gneiss Region, Norway, based on electron backscatter diffraction (EBSD). The P-­wave velocities are 8.0±8.5 km/s and the S-­
wave velocities are 4.5± NPV 3RLVVRQ¶V UDWLR LV ±0.26. All the eclogites are relatively isotropic, with the higher anisotropies (3±4%) in micaceous samples. Peridotite is more anisotropic, which may be a useful means of distinguishing peridotite from eclogite. P a g e | 37 INVESTIGATING CRUSTAL RHEOLOGY THROUGH GPS COORDINATE TIME SERIES ANALYSIS FOLLOWING TWO LARGE EARTHQUAKES WITHIN THE SOUTHERN SAN ANDREAS FAULT SYSTEM Joshua Spinler1 and Richard Bennett1 1
Department of Geosciences, University of Arizona We present crustal motion measurements from an analysis of continuous GPS (CGPS) data for southern California and northern Baja California, Mexico. The 2010 April 4 Mw7.2 El Mayor-­Cucapah (EMC) earthquake in northern Baja California, Mexico, is the largest event to occur along the southern San Andreas fault system since the 1999 October 16 Mw7.1 Hector Mine (HM) earthquake, located in the Mojave Desert. We analyzed the CGPS data from 10 sites located within 250 km of both the EMC and HM earthquakes for the time period 1993-­2011.5 using the GAMIT/GLOBK software, determining coordinate time series relative to a stable North America reference frame. We then applied a constrained random search algorithm minimizing the misfit to the individual site coordinate positions to determine the parameters of our kinematic model. We estimate interseismic velocity, annual and semi-­annual perturbations to the interseismic velocity, coseismic offsets and postseismic deformation following the EMC and HM events, and the characteristic exponential decay time for each event at each individual site. The mean of the estimates for exponential decay time for the EMC event is ~480 days and ~725 days for the HM event. Typical uncertainty estimates for the exponential decay times range from 10 to 150 days, while the variability in the decay time estimates is greater between individual sites. We investigate different layered viscoelastic models to reconcile the differences in exponential decay times between the individual sites, where the distance from the event is important in understanding which layers the data is sampling. P a g e | 38 ASSESSING APPARENT DIFFERENCES BETWEEN GEODETIC AND PALEOSEISMIC SLIP-­RATES IN PANAMA Kat Compton1, J.C. Spinler1 and R.A. Bennett1 1
Department of Geosciences, University of Arizona Recently identified active strike-­slip faulting along the Pedro Miguel-­Limon and Rio Gatun faults in central Panama indicates appreciable internal deformation of the Panama Isthmus. Understanding the histories and current behavior of these faults is important for hazards assessments, which may have important implications for Panama Canal operations. Constructing a simple elastic block model constrained by crustal velocities derived from a 5-­station continuous GPS (CGPS) network across these active structures, we estimate fault slip rates for the Rio Gatun (0.8±0.5 mm/yr) and Limon-­Pedro Miguel (0.6±0.5 mm/yr) fault zones. These slip rates differ significantly from the 3-­7 mm/year rates inferred from paleoseismology. In an effort to reconcile this difference, we employ the elastic layer over viscoelastic half-­space model of Savage and Prescott (1978) to account for the response of the lower crust and upper mantle to past earthquakes. We use this viscoelastic coupling model, historical earthquake data, and paleoseismic slip rate estimates to explore the range of crustal and upper mantle rheologies and earthquake recurrence intervals consistent with the data and test whether viscoelastic processes may explain the apparent discrepancy between paleoseismic and CGPS-­based elastic block models. P a g e | 39 ANDES RETROARC DECOLLEMENT PARAMETER ESTIMATION FROM THE PUNA ANDES GPS NETWORK Katrina Gressett1 and Rick Bennett1 1
Department of Geosciences, University of Arizona Crustal shortening in the central Andes retroarc in northwest Argentina is thought to be accommodated by a series of steep back arc thrust faults all interconnected to one governing decollement. Although balanced cross sections can often provide estimates for the amount of shortening, this is not always possible in certain orogenic belts. Independent measurements of modern day shortening rate, such as geodetic data, provide direct measurement of active tectonic processes in retroarc thrust belts. Such measurements may be used to model the amount and rate of shortening, infer decollement parameters such as dip angle and down dip locking width. Such parameters could provide useful constraints on models for orogenic wedge mass and force balance, flexural wave migration in the foreland basin, and other retroarc processes. In March 2009, we constructed a 5 station continuous GPS network across the Andes retroarc and onto the Puna plateau of northwest Argentina. Data from this network have been analyzed for the time period of March 2009 through March 2011. Preliminary estimates of crustal motion relative to the South American reference frame show our network moving to the northeast at a rate of ~5.67±.02 mm/yr on the Puna Plateau with rates decreasing sharply near the thrust front. To explain this trend, we constructed a model using a dislocation source embedded in a homogeneous elastic half-­space. Using this model we estimate that the decollement has a dip of 20°, a slip rate of ~6 mm/yr, is locked at a depth of 12 km, and surfaces ~30 km east of the Lomas de Olmeda Range in Northwest Argentina. P a g e | 40 APATITE (U-­TH)/HE DATE DISPERSION DUE TO SECONDARY GRAIN BOUNDARY PHASES: AN EXAMPLE FROM THE HENRY MOUNTAINS, UTAH Kendra E. Murray1, Devon A Orme1, and Peter W Reiners1 1
Department of Geosciences, The University of Arizona Non-­analytical sources of variation in apatite (U-­Th)/He (AHe) dates include effects of variable radiation damage, crystal size, and parent zonation. A more insidious and potentially widespread source of date dispersion is U-­Th located outside but within ~15-­20 microns of dated apatites. The presence of extragranular U-­Th-­bearing phases can make He dates too old or too young, depending on 1) when it forms, UHODWLYH WR WKH JUDLQ¶V FRROLQJ GDWH ZKHWKHU LW LV UHFRYHUHG DQG
analyzed with the grain, and 3) the relative U-­Th content of the apatite and extragranular phase. Here we document the presence and effects of external secondary phases on AHe dates from the Henry Mountains, Utah, where magmas intruded sedimentary rocks at 26-­28 Ma. We present a model that predicts how such U-­Th-­rich external phases would affect a measured AHe date, in order to diagnose the significant date dispersions in these samples. Apatites from sedimentary rocks surrounding the igneous laccoliths have positive date-­effective uranium ([eU]) correlations consistent with residence at ~1.5-­km depths from ~27 to less than 5 Ma, when they were exhumed rapidly to near-­surface temperatures. In contrast, AHe dates from igneous samples have no correlation with [eU] despite a date dispersion of similar magnitude. Apatite separates from one igneous sample have delicate Fe-­rich phases coating the outside of most grains. Geochemical analyses of the external phase suggest that it has concentrations of U and Th up to an order of magnitude greater than that the apatites. If this is a common secondary phase in these rocks it could be the primary source of the observed date dispersion. P a g e | 41 SHEAR-­WAVE VELOCITY STRUCTURE OF THE CENTRAL ANDEAN (13ºS ± 23ºS) UPPER LITHOSPHERE AS DETERMINED USING AMBIENT NOISE TOMOGRAPHY: IMPLICATIONS FOR CRUSTAL DEFORMATION HISTORY Kevin M. Ward1, Ryan C. Porter1, Susan L. Beck1, George Zandt1, Lara S. Wagner2, Estela Minaya3, and Hernando Tavera4 1
2
Department of Geosciences, The University of Arizona Department of Geological Sciences, University of North Carolina, Chapel Hill 3
El Observatorio San Calixto, La Paz, Bolivia 4
Instituto Geofísico del Perú, Lima, Peru A striking correlation is observed between the location of the Bolivian orocline and the widest section of the Central Andes with active deformation over 800 km inboard from the trench. Total shortening estimates are highest (~326 km) in the area of the orocline (20ºS) and lessen to ~126 km north of the orocline in southern Peru (12-­14ºS). Several structural cross-­sections have been published but remain constrained mostly by the surface geology. We image the shear-­
wave velocity of the central Andean upper lithosphere and combine this data with the surface geology to better constrain lithospheric evolution of the northern central Andean plateau. We use data from ~80 broadband seismometers currently deployed in southern Peru, Bolivia, and northern Chile to resolve the seismic structure of the upper lithosphere of the Central Andes (13ºS ± 23ºS). We use the relativity new method of Ambient Noise Tomography to approximate the Rayleigh wave response of the Earth structure between station pairs. We then invert for the shear-­wave velocity structure and observe the following (1) a strong correlation between a shallow (~5 km) low velocity zone spatial associated with the Altiplano, (2) an intermediate depth (~15-­25 km) high velocity body located spatially underneath lake Titicaca and expanding horizontally to the southwest, and (3) a transition along-­strike in mid-­crustal structure from the northern Altiplano to north of Lake Titicaca (14ºS). P a g e | 42 SEASONAL ANOMALIES IN THE SEA ICE CONCENTRATION AND THICKNESS IN THE ROSS SEA AND THEIR CORRELATION TO THE SOUTHERN ANNULAR MODE Kiley Yeakel , Paul Goodman2, and Joellen Russell2 1
1
Chemical and Environmental Engineering, The University of Arizona 2
Department of Geosciences, The University of Arizona Global warming has had significant impact on the seasonal pack ice thickness and concentration in Antarctica. While the Weddell Sea has become warmer over the past few decades, the more southern Ross Sea has experienced more intensified seasons. In the Ross Sea summers have become warmer and conversely winters have become colder resulting in dramatic changes in pack ice formation and duration. To understand the drivers behind these intensified seasons, anomalies in sea ice concentration and thickness in the Ross Sea are correlated to anomalies in surface temperature, winds and the Southern Annular Mode. It is hypothesized that the Southern Annular Mode is strongly correlated with seasonal variations in ice cover. In addition, it is expected that stratification in the Ross Sea will become seasonal due to anthropogenic emissions;; the implications of increased seasonality for pack ice formation will be addressed. P a g e | 43 ORBITAL FORCING OF ASIAN MONSOON RAINFALL BASED ON 10BE IN CHINESE LOESS Lara Y. White1, J. Warren Beck2, A. J. Timothy Jull1,2, Li Cheng2, Weijian Zhou3 1
2
Department of Geosciences, The University of Arizona NSF-­Arizona Accelerator Mass Spectrometry Laboratory, The University of Arizona 3
State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences The main goal of this work is to generate quantitative paleorainfall reconstructions from loess profiles collected from Baoji, Shaanxi, China. These records will provide a quantitative measure of the strength of the Asian Monsoon that can be compared with existing climate models. The periods of focus here are 80-­145kaBP (Eemian) and 340-­420kaBP (Marine Isotope Stage 11) to observe the interglacial behavior of the Asian Monsoon during times of high and low precessional insolation forcing and determine the better analog for modern climate. In the Eemian, monsoon intensity appears to have been strongly influenced by insolation forcing at precessional periods as a result of high eccentricity, and in MIS11 low eccentricity reduced precessional forcing of climate. A paleoprecipitation record of Asian Monsoon intensity can be obtained from 10Be in sediments on the Chinese Loess Plateau. The cosmogenic radionuclide 10Be is produced by cosmic-­ray spallation in (DUWK¶V DWPRVSKHUH and has a half-­life of 1.38x106years. Its production rate is regulated by the geomagnetic field intensity and its atmospheric fallout rate varies locally with rainfall rate. After accounting for 10Be in remobilized dust and converting 10Be to a flux using the accumulation rate, the variations in 10Be flux due to the geomagnetic field signal can be removed to give only the variations due to precipitation. These variations can be converted from fluxes to quantitative (mm/yr) estimates of precipitation with the relationship between 7Be in modern precipitation and the tropospheric 10
Be/7Be ratio. P a g e | 44 ASSESSMENT OF ANTHROPOGENIC IMPACT ON CRASSOSTREA VIRGINICA REEFS IN SOUTHEASTERN NORTH CAROLINA USING LIVE-­DEAD ANALYSIS Leanndra Romero1, Gregory P. Dietl2, Patricia H. Kelley3, Jessica G Lambert2, and Christy C. Visaggi4 1
Department of Geosciences, The University of Arizona 2
Paleontological Research Institution 3
Department of Geography and Geology, University of North Carolina Wilmington 4
Biology and Marine Biology, University of North Carolina Wilmington Along the southeastern North Carolina coast, Crassostrea virginica reefs are an ecologically and economically important component of the estuarine ecosystem. Discordance between the taxonomic composition of dead and live assemblages of mollusks has been suggested to indicate recent anthropogenic change (Kidwell 2009). Previously, Lambert et al. (2009) conducted live-­dead analyses to determine the magnitude of anthropogenic impact at three replicate sites on oyster reefs at five locations near Wilmington, NC: Howe Creek, Pages Creek, Hewletts Creek and Masonboro Island 1 and 2. They XVHG .LGZHOO¶V OLYH-­dead method to assess the fidelity of the dead assemblages of mollusks (taken from the top 30cm of the oyster reef matrix) to the living community in terms of rank order abundance and species richness. In this study, we resampled the same reefs as Lambert et al. (2009) to a greater depth (60cm). Comparisons were made between the dead assemblage at 30-­60cm and the live assemblage (0-­30cm) using 6SHDUPDQ¶V UKR DQG WKH &KDR-­Jaccard test. Preliminary results from Howe Creek Sites 2 and 3 suggest concordance between the live and dead DVVHPEODJH 6SHDUPDQ¶V UKR-­values calculated for Howe Creek Site 2 and 3 were 0.691 and 0.461. The Chao-­Jaccard values calculated for Howe Creek Site 2 and 3 were 0.956 and 0.928. Radiocarbon dates were taken from Howe Creek Site 2 (50-­55cm) and 3 (45-­55cm) at two sigma. Howe Creek Site 2 was dated at 1390AD-­1643AD. Howe Creek Site 3 was dated at 1394-­1647. Radiocarbon dates on these two sites indicate that deeper layers are much older than any modern impacts. P a g e | 45 ALTERATION AND VEINING IN THE PINTO VALLEY PORPHYRY COPPER DEPOSIT, GLOBE-­MIAMI DISTRICT, ARIZONA Logan Hill1 1
Department of Geosciences, The University of Arizona The Pinto Valley deposit is located in the Globe-­Miami copper district of southern Arizona. The district is part of the Laramide porphyry copper cluster of southwestern North America. Most of the deposits in the district, including Pinto Valley, are associated spatially and temporally with the Shultze Granite pluton (~61 Ma), which intrudes Precambrian basement and Paleozoic sediments. The district was thoroughly dismembered by Tertiary extension, which sliced the original porphyry systems into a series of porphyry pieces scattered across the area in a number of fault blocks. Systematic logging of vein mineralogy, abundance, and timing has provided a better spatial understanding of the orebody, as well as the temporal evolution of the hydrothermal system. Ongoing petrographic and Electron Microprobe analyses will allow for a better understanding of alteration mineralogy in the deposit. This can help us further understand the evolution of Pinto Valley and which part of the porphyry system it represents. This will provide one guide toward the causative porphyry stock, and perhaps other pieces of this dismembered porphyry system. P a g e | 46 RECURRING SLOPE LINEAE ON MARS: UPDATED GLOBAR SURVEY RESULTS Lujendra Ojha1, Alfred McEwen1, Colin Dundas2, Sarah Mattson1, Shane Byrne1, Ethan Schaefer1, and Marian Masse1 1
Lunar and Planetry Laboratory, The University of Arizona 2
United States Geological Survey, Flagstaff, Arizona Recurring Slope Lineae (RSL) are dark, narrow features which extend downslope on steep (>20°), equator-­facing, mid-­latitude rocky slopes of Mars [1]. They are observed to form and grow during multiple warm seasons, and fade in cold seasons. Prior to this investigation, RSL had been confimed from repeat coverage at only 7 locations ranging in latitude from 48S to 32S. Likely RSL (evidence of fading in cold seasons, but not yet observed to recur in multiple Mars years) were observed at 12 locations in the mid-­latitudes. Candidate mid-­latitude RSL (CMR), ³ZKLFK KDYH PRUSKRORJ\ DQG JHRORJLFDO VHWWLQJ RI 56/ EXW ZLWK QR
UHSHDW LPDJLQJ RU ZLWKRXW DSSDUHQW FKDQJHV´ ZHUH LQYHVWLJDWHG LQ ORFDWLRQV &DQGLGDWH HTXDWRULDO 56/ &(5 DUH PXFK OLNH &05 ³EXW
changes between images are observed and seasonalit\ LV XQFOHDU´ ZHUH
investigated at 8 locations in the equatorial region. Intensive monitoring of confirmed RSL sites was conducted in the most recent southern-­hemisphere late spring to early fall, and we attempted to confirm additional candidates. We present results from our preliminary seach for RSL over all latitudes of Mars in images acquired during 2011 by the High Resolution Imaging Science Experiment (HiRISE) onboard the Mars Reconnaissance Orbiter (MRO). Summaries of updated thermal data, geographical distribution, slope profile and other attributes (albedo, elevation, thermal inertia etc) are also presented. P a g e | 47 TELESEISMIC STUDY OF THE SUBDUCTING SLAB AND FOREARC IN THE MAULE AFTERSHOCK RUPTURE ZONE Mallory Morell1, Susan L. Beck1, Steve Roecker2, Anne Meltzer3, and Ray Russo4 1
2
Department of Geosciences, The University of Arizona Earth and Environmental Sciences, Rensselaer Polytechnic Institute 3
4
Earth and Environmental Sciences , Lehigh University Department of Geological Sciences, University of Florida Rupturing ~600 km of the plate boundary, the 2010 Mw=8.8 Maule megathrust earthquake that occurred off the coast of Chile is one of the largest ever to be recorded. This segment of the Nazca-­South America plate boundary is an ideal region to investigate the processes related to the structure of the down-­dip edge of the seismogenic zone, forearc wedge and subducting slab. Immediately after the Maule earthquake, Chilean seismologists were joined by international teams from France, Germany, Great Britain, and the United States to install an array of seismic stations between 33°-­38.5°S, from the coast to the foothills of the Andes to produce the International Maule Aftershock Deployment (IMAD) data set. The deployments lasted from March-­
December 2010 in order to capture and study the aftershocks in and around the rupture zone, and to better understand crustal and mantle wedge structure. We calculated receiver functions (RFs) from P and PP phases and made Common Conversion Point stacks to image the structures in the slab and forearc wedge down to a depth of 100 km. We have identified the oceanic slab Moho on several E-­W and N-­S profiles at 40 to 80 km depth beneath the array and several discontinuities above the slab in the forearc. We also used older data to extend our transect E-­W across the arc, a first at this latitude. P a g e | 48 A 1.2 MA PALEOECOLOGICAL RECORD FROM OSTRACODES, CHARCOAL AND OTHER PALEOCLIMATE INDICATORS FROM LAKE MALAWI, EAST AFRICA Margaret Blome1 and Andrew S. Cohen1 1
Department of Geosciences, University of Arizona Drill core MAL05-­1B is the longest (380m) continuous lacustrine record of climate and limnologic change for the African southern subtropics. We have sampled the core every 16cm (intra-­sample time average of ~32 years, inter-­sample time step of ~505 years) for coarse residue analyses of biological/sedimentological indicators of lake level and redox. For ostracodes we collected taxonomic data at the generic level, as well as ostracode abundance and taphonomic condition. Two sections of core have been analyzed thus far (79-­164 and 231-­
381 mblf). The ostracode assemblage data for the older section suggest a transition from a relatively diverse saline/alkaline assemblage at the base, to a Cypridopsis-­rich assemblage above 272m (~870 ka), indicative of somewhat deeper water conditions. These conclusions are supported by other indicators in the core record: from ~338±347 mblf (~1.08 ± 1.11 Ma) there are abundant littoral indicators such as ooids, rounded and sorted quartz sand, framboidal pyrite and authigenic siderite (where co-­occurring, indicative of anoxic marsh conditions), and the ostracode genera Limnocythere and Ilyocypris;; all indicating an extremely shallow lake environment (and in the case of Ilyocypris probably indicative of nearby deltaic inputs). This interpretation is supported by the pollen data over the same interval, suggesting an arid watershed at this time. In contrast, the younger section (138-­
434ka) transitions repeatedly from a deep water environment with abundant chaoborids, to intervals with a diverse assemblage of Limnocythere, Cypridopsis, and Candonopsis suggesting shallower (not marshy or deltaic) conditions. P a g e | 49 PALEOELEVATION ESTIMATE OF THE OLIGO-­MIOCENE GANGRINBOCHE CONGLOMERATE, SOUTH-­
CENTRAL TIBET, AND WHAT IT MEANS FOR TIBETAN PLATEAU EVOLUTION Matthew Dettinger , Jay Quade , Ross Waldrip1, and Kate Metcalf1 1
1
1
Department of Geosciences, University of Arizona The tectonic history of the suture zone between the Indian and Asian plates is key to understanding the greater convergence history and the evolution of the tallest mountains and the largest plateau on Earth. An Oligo-­Miocene 2-­4 km-­thick package of conglomerates, fluvial sandstones, paleosols, and lacustrine facies crops out nearly continuously for ~1300 km along the suture zone and is known collectively as the Gangrinboche, or Kailas, conglomerates. My work concentrated on stable isotope paleoelevation estimates derived from pedogenic carbonate nodules, calcite-­rich fluvial sandstone concretions, and limestone clasts pulled from the conglomerate. The OLPHVWRQH FODVWV SURGXFH į2 DQG į& YDOXHV WKDW DUH UHDVRQDEOH IRU
marine values. The soil and fluvial carbonates, however, are much PRUH QHJDWLYH LQ ERWK į2 DQG į& YDOXHV 7KLV Vuggests there has been little/no widespread diagenetic alteration and that the values for the pedogenic/fluvial carbonates are primary. Furthermore, the į2 YDOXHV RI VRLO DQG IOXYLDO FDUERQDWH DYHUDJH -­Å 93'% ZKLFK
at reasonable Earth-­surface temperatures, reconstruct parent water ZLWKį2FRPSRVLWLRQVIURPa-­16 to -­Å9602:7KHVHFRPSRVLWLRQV
are close to, or even more negative, than modern meteoric water in south-­central Tibet. The only effective way to deplete meteoric water in this situation is a large orographic barrier. And so the stable isotope results from the suture zone suggest that not only were the Himalaya high by ~25 Ma, but that the Tibetan Plateau was also a massive topographic feature, blocking the enriched moisture crossing the Asian continent. P a g e | 50 SEDIMENTOLOGICAL INTERPRETATION AND ANALYSIS OF LITTORAL SURFACE SEDIMENTS: SOUTHERN LAKE MALAWI Matthew J. Lopez1, Margaret Whiting Blome1, and Andrew S. Cohen1 1
Department of Geosciences, University of Arizona We have analyzed surface (upper 2cm of lake-­bottom sediment) sediment samples from Lake Malawi. The samples were collected in the field March 2010, on the southern shores of Lake Malawi, using a Ponar grab sampler and by hand (SCUBA). Samples were taken along number of transects perpendicular to the shoreline in order to maximize change in depth over a shorter horizontal distance. Depth, surface water temperature, pH values, and sample description were taken at each site;; bottom water temperature and dissolved oxygen content were measured at sites < 20m deep. We are using both wet-­sieving and Mastersizer laser particle size analysis methods to conduct grain-­size analyses, separating the sediment samples into percentages of >2mm, 2mm-­63um, and <63um fractions (sand sized and greater, silt, and clay). Sediment samples are also being characterized by Loss On Ignition (LOI) methods to quantify total organic and inorganic carbon. The grain size and LOI data, along with ostracode assemblage data, will be used to better interpret paleolake core records for limnological variables that are not directly observable in MAL 1B drill core samples. Preliminary LOI data shows a potential positive correlation between the percentage of silt and the amount of organic carbon. P a g e | 51 INTERPRETATION OF CONICAL STRUCTURES IN THE WEST-­AFRICAN GUINEA PLATEAU USING 3D SEISMIC REFLECTION DATA Melissa M. McMillan1 and James Broermann1 1
Department of Geosciences, The University of Arizona The formation and geomorphology of the West-­African Guinea Plateau is a product of Jurassic rifting that created the northern Mid-­Atlantic Ridge and Cretaceous transform deformation that separated Africa from South America in the equatorial Atlantic. Syn-­ and post-­
rift magmatic activity in this region has produced several volcanic events, creating large seamount chains such as the Sierra Leone Rise, the Canary and Cape Verde Islands, and volcanic structures on the Guinea Plateau. Seismic investigation of the south-­central Guinea Plateau has led to the identification of several cone-­shaped anomalies interpreted to be hydrothermal features or volcanic intrusions that were emplaced in a post-­rift tectonic environment. Normal faults observed near the anomalies displace Cretaceous sediments, often terminate at depth into the conical structures, and are interpreted to be related to magmatic or hydrothermal activity. Inferences for the timing of these features are consistent with seamounts local to the Guinea Plateau that have dated formation ages of late Paleocene to early Eocene. The source of such recent magmatic activity in this region is largely unknown, but some have suggested that pre-­existing Cretaceous fracture zones have provided conduits for plume material remaining in the upper mantle. The complex distribution of volcanic activity in the region is difficult to explain via a local hot-­spot-­
related source. However, the observations could be explained by a major regional-­scale plume under West Africa from which melt was emplaced at fault intersections or through other suitable conduits. P a g e | 52 OBSERVING COPPER ORE DEPOSITS, SLAG AND METAL SAMPLES FOR ARSENIC CONTENT DURING THE LATE SICAN CULTURE IN NORTHERN PERU Meri Hembree1 1
Department of Geosciences, The University of Arizona Metallurgists of the Late Sican culture (900-­1150 AD) produced copper metals by smelting batches of granulated copper ore with blow pipes and charcoal in small furnaces which were dug in the ground. A number of these furnaces have been discovered. During recent archeological release in the Ynalche Valley. These have recovered furnaces, slag and are the objects of this study. This study consists of analyzing the structure and composition of copper ores deposits, slag and copper metal samples for arsenic content during the Late Sican culture in Northern Peru. It is not known how the copper-­arsenide metal composition was obtained or created by the Sican during their abundant productions, did the copper ores initially contain the arsenic mineral or did arsenic minerals become added during the smelting of the ores? The methods used include petrographic examination of the thin section of ores and slag. Metallographic study of raw and forged metal, and bulk chemical analysis of slag P a g e | 53 CHARACTERIZATION AND CORRELATION OF SKARN MINERALIZATION AND PROTOLITHS, RESOLUTION PORPHYRY COPPER DEPOSIT, SUPERIOR DISTRICT, ARIZONA Michael J. McCarrel1 1
Department of Geosciences, The University of Arizona Resolution, a deeply buried, high grade porphyry copper deposit, which formed at ~64 Ma, is currently undergoing development. Carbonate rocks that have been hydrothermally altered to skarn, host VRPH RI 5HVROXWLRQ¶V KLJKHVW FRSSHU JUDGHV ,Q WKLV VWXG\ WKUHH
carbonate stratigraphic units, Proterozoic Mescal Limestone, Paleozoic Martin and Escabrosa Limestones, were tracked through the deposit by logging core from less altered to more altered equivalents. Garnets in Cu bearing skarns, like Resolution, are predominantly of the andradite variety. Unexpectedly, analyses have also revealed a small population of grossular garnets, Gr(95-­100)Ad(0-­4)Sp(0-­5). Calc-­silicate minerals, particularly garnets, commonly exhibit compositional zoning on various scales within skarn deposits. At Resolution the zoning is principally evident on the microscopic scale. Electron microprobe analyses have yielded individual grains of skarn garnet varying from Ad96 to Ad62. Three broad alteration types were observed in carbonate rocks at Resolution: anhydrous skarn, hydrous skarn, and skarn-­destructive alteration. The anhydrous assemblages (quartz + garnet + pyroxene ± idocrase ± epidote) formed synchronously with the potassic alteration of igneous rocks, and are commonly overprinted by subsequent alteration. Hydrous skarn assemblages, synchronous with sericitic alteration (chlorite + amphibole + calcite + clay ± pyrite ± chalcopyrite), are widespread. Skarn-­destructive assemblages (quartz + pyrite + chalcopyrite ± magnetite), occur in restricted zones contemporaneously with advanced argillic alteration. Skarn alteration and mineralization at Resolution, particularly hydrous skarn, is noteworthy, as it is a principal copper host within this world class deposit. Resolution Copper Mining LLC and Science Foundation Arizona are gratefully acknowledged for financial support. P a g e | 54 TAPHONOMIC VARIATION BETWEEN DIFFERENT SYSTEM TRACTS IN THE PALEO-­ENVIRONMENT OF THE PO VALLEY, ITALY Muhammad Ikhwan Mahmood1 1
Department of Geosciences, The University of Arizona Taphonomy, which is a measure of the degradation of a fossil, can be used to interpret paleo-­environmental conditions. Specimens from different systems tracts were analysed in order to determine the influence the sedimentological environment has on preservation potential. Core samples were taken from the Po Plains in the northeast of Italy. This basin is a thick, Plio-­Quarternary marginal marine sequence. In early Pleistocene, the basin was entirely marine and is followed by mixed tererstrial and marine sequences in middle Pleistocene through Holocene. The bivalve Lentidium mediterraneum as recognized by its hinge teeth structure was collected by wet sieving of core samples. 30 specimens were randomly selected from samples within the two environments;; an early Holocene transgressive systems tract (TST) and a later Holocene highstand systems tract (HST). The specimens were qualitatively scored by rank with 3 as the most damaged, and 0 for pristine using the following taphonomic categories;; encrusting, articulation, fragmentation, predation, edge modification, bioerosion and glossiness for internal and external valve surfaces. Scores will be statistically analysed to compare their distributions using Microsoft Excel and PAST Version 2.14. The higher damage scores for these categories predicts how a particular environment effects the taphonomy and preservation of these fossils. The results from across systems tracts in the same locality give us a temporal perspective on taphonomy that can be applied to help our understanding of preservation in modern environments. P a g e | 55 MANAGEMENT AND VISUALIZATION OF FOSSIL RODENT MIDDEN DATA IN AN INTEGRATED PALEOBIOLOGICAL DATABASE Nadine L. Warneke1, Julio L. Betancourt1,2, Kate A. Rylander2, and Owen K. Davis1 1
Department of Geosciences, The University of Arizona 2
USGS Databases are critical infrastructure for paleobiological research, and have diverse and important applications. The NEOTOMA Database is an NSF-­funded online, integrated, and international data management system for paleobiological information spanning the last 5 million years, including late Quaternary fossil rodent middens. Middens are preserved in arid and semi-­arid regions worldwide and contain well-­preserved plant and animal remains. Several thousand middens have been analyzed to reconstruct the vegetation history of the North and South American deserts over the last 50,000 years. Over a hundred midden series across the two continents track persistence and species turnovers in response to changing atmospheric CO2 levels, temperature and precipitation. The midden record has provided broad coverage with highly resolved spatial and temporal accuracy, leading to important ecological insights about plant migration, species coexistence, community disassembly and assembly, and ecophysiological responses to variations in temperature and atmospheric CO2 levels. We have integrated plant macrofossil and pollen data from a 30,000-­year midden series recently collected and analyzed from City of Rocks (CIRO) National Reserve in south-­central Idaho to demonstrate the various data entry and graphical interface features of TILIA, the excel-­based, spreadsheet program used to enter metadata and abundance data into NEOTOMA. Graphics will be customized to highlight vegetation change at CIRO, including recent colonization and expansion of two dominant woodland elements in the Great Basin, Utah juniper (Juniperus osteosperma) and single-­needle pinyon (Pinus monophylla). We will generate two sets of graphics, one for publication of results in Quaternary Research and the other for a fact sheet to inform visitors at CIRO. P a g e | 56 A TRACE ELEMENT RECORD OF LAKE LEVEL RISE AND EVAPORATIVE SOLUTE CONCENTRATION IN LAKE BONNEVILLE, 26-­18 KA Nathan S. Evenson1, Peter Reiners1, Jay Quade1, and David McGee2 1
2
Department of Geosciences, University of Arizona Department of Geology and Geophysics, University of Minnesota Concentrations of trace elements in authigenic calcium carbonate precipitated from Lake Bonneville waters form coherent trends that reflect the filling and evaporative concentration of dissolved species in the hydrologically closed Bonneville Basin between 26-­18 ka. I use ICP-­MS analysis of aragonite and calcite from a sample that formed as a massive wall coating in Cathedral Cave, located in the lower portions of the basin. Element concentrations range from ppb to ppm levels. Using 13 U/Th ages determined on the sample, I construct age-­
concentration series for each element. Comparisons of these concentration time series data with stable isotope compositions determined from the same sample suggest that trace elements reflect major events in the lake history. High concentrations of nearly all elements in the oldest samples reflect the flooding of the cave in the HDUO\ SRUWLRQV RI WKH ODNH¶V 6WDQVEXU\ SKDVH 7KURXJK 6WDQVEXU\ WLPH
(26-­23 ka), comparisons of d18O values with element concentrations suggest that most elements, particularly LREE, are directly correlated with the P/E ratio within the basin. This relationship is particularly clear in the elemental series during the H2 Heinrich event. During the 23-­22 ka transition from Stansbury lake levels to the Bonneville highstand, the relationship between d18O and element concentration shifts, such that after 22 ka, Mg, Rb, REE, and other elements display an inverse correlation with basin P/E ratio. Coincidence of large spikes in Na concentration with lake level regressions in the stratigraphic record suggests that Na may provide a sensitive record of lake level changes. P a g e | 57 GREENHOUSE EFFECT CONCEPT INVENTORY IN GEOSCIENCES MEGA-­COURSE Nicole Santangelo1, Gina Brissenden2, Ed Prather2, Jeff Eckenrode2, Phil Stokes1, and Jessica Kapp1 1
2
Department of Geosciences, The University of Arizona Center for Astronomy Education, Steward Observatory, The University of Arizona We present the results of a study on the teaching and learning of the naturally occurring greenhouse effect as taught in a general education, non-­science major, introductory geosciences mega-­course using the Greenhouse Effect Lecture Tutorial (GELT) as a major component to instruction beyond the lecture. In Fall 2011, 570 students enrolled in this mega-­course taught at the University of Arizona²a 4-­year, public, research intensive institution²completed the Greenhouse Effect Concept Inventory (GECI) before and after instruction. The GECI contains 20 conceptual questions designed to assess the understanding of the greenhouse effect and its connection to global warming. In addition, there are 6 demographic questions that provide a framework to establish a relationship between demographic characteristics and student responses. With nearly an even gender distribution (56% female and 46% male), the class was comprised of 60% freshmen and 29% sophomore students. Furthermore, 88% of the students were non-­science majors. The average GECI score received prior to instruction was 23%. To evaluate the gain in student understanding of the greenhouse effect, a normalized gain score was calculated to be 0.41. Our findings are consistent with the validation study of the Greenhouse Effect Lecture, showing that the use of the GELT improves student learning over lecture alone. The GECI and the GELT were developed at the University of Arizona as one of the first Astronomy Education Research PhD's awarded in the US (to John Keller in collaboration with the UofA Lunar and Planetary Laboratory and the UofA Center for Astronomy Education). P a g e | 58 REGIONAL INVESTIGATION OF CRETACEOUS, OFFSHORE GUINEA RIFTING STRUCTURES ± FRACTURE ZONES AND RELATED VOLCANISM Noah J. McDougall1 and Russ D. Edge1 1
Department of Geosciences, The University of Arizona Offshore Guinea is a relatively unexplored, but tectonically intriguing area of the western margin of Africa. The subsurface is riddled with rift-­related structures from the Jurassic separation of North America and Africa, which formed the North Atlantic basin, followed by Cretaceous separation with South America to form the South Atlantic basin. In addition, this region shows complex episodes of volcanic extrusion and intrusion that are coeval with, and post-­date, rifting. Over the past several years, Hyperdynamics, Inc. acquired high-­quality, 2D and 3D seismic reflection data, along with magnetic and gravity data, in the area;; the University of Arizona is collaborating with Hyperdynamics to evaluate volcanic and tectonic features in the offshore Guinea region. Two, large, 3D seismic surveys span the edge of the offshore Guinea Plateau and the present continental shelf and slope which formed with the separation of Africa and South America. The larger southeast, 3D survey area contains a major growth fault with approximately four kilometers of displacement, capped by an Albian (98 Ma) erosional surface. This growth fault may be associated with a once-­transtensional transform fault and fracture zone valley. Prominent magnetic anomalies spatially correlate with the growth fault and other geologic features in the 3D seismic data, such as an interpreted volcanic "bulge" and younger, now-­buried, subaerial volcanic field. The magnetic anomalies extend far beyond the bounds of the 3D seismic surveys, possibly allowing a more regional interpretation of crustal structures related to rifting. Determining the geologic history and detailed geometry of offshore *XLQHD¶V FRPSOH[ ULIW-­transform structures will further understanding of rifting processes and evolution of continental rift margins. P a g e | 59 TROUBLESHOOTING THE PIPELINE: DEVELOPING A CRITICAL INCIDENT TAXONOMY FOR MINORITY AND NON-­MINORITY STUDENT PATHWAYS INTO THE GEOSCIENCES Philip J. Stokes1, Karl W. Flessa1, Roger Levine2, and Kristin L. Gunckel3 1
Department of Geosciences, University of Arizona 2
Independent Consultant 3
Department of Teaching, Learning & Sociocultural Studies, University of Arizona Within the STEM (science, technology, engineering, and math) fields, the geosciences are among the least diverse in terms of racial and ethnic representation at the college and professional levels. Hispanic students, in particular, have yet to bridge the gaping disparity with non-­minority students enrolled in the geosciences. A better understanding of the early stages of the geosciences pipeline is vital in order for the major to provide a sustainable supply of future geoscientists. This research uses the critical incident technique (CIT) to identify specific behaviors that students report were causally responsible for their choice (or rejection) of a geosciences major. Despite being a natural science with frequent exposure in the media, popular culture, and science fiction literature, many neutral to negative perceptions exist about the geosciences. Using over 500 critical incidents from student interviews, a preliminary set of LQGLYLGXDO DQG RUJDQL]DWLRQDO H[SHULHQFHV ZKLFK LQIOXHQFH VWXGHQWV¶
pursuit of degrees in the geosciences was identified. Using the CIT, this set of experiences was systematically organized into a taxonomy to enable comparisons of their prevalence in minority and non-­minority students. Based on an initial sample of 20 students, several trends emerged from the data. Familial factors and experiences involving mentors and advisors were two of the most commonly reported incidents. Additionally, Hispanic students, compared to non-­Hispanic students, reported a disproportionate number of familial factors involved in their decision to major in geoscience. Finally, when assessing the outcomes of all incidents, Hispanic students reported substantially more negative outcomes than non-­Hispanic students. P a g e | 60 DOES SIZE MATTER?: A COMPARISON OF BODY SIZE WITH LENGTH OF HINGE TEETH IN LENTIDIUM MEDITERRANEUM Rachel C. Feuerbach1 1
Department of Geosciences, University of Arizona The purpose of this study is to analyze body size of the bivalve species Lentidium mediterraneum to determine whether sequence stratigraphic parameters have an influence. In order to do this, a metric for determining body size from bivalve hinge teeth was developed. Length of hinge teeth and overall body size was measured to determine the correlation which was then used to assess whether body size ratios change through environment and different time periods. Bivalve specimens were obtained from a series of dated sediment cores from the Po Plains of Italy, representing two transgressive/regressive cycles from the Upper Pleistocene and Holocene periods. Samples from the sediment cores were sieved to remove clay and mud, leaving behind a total of 70,000 mollusks shells, representing 129 genera and 241 species. A binocular scope with an eyepiece graticule, calibrated with a metric ruler, was used to measure more than 30 specimens. Anterior-­posterior lengths and widths of specimens from several different layers were measured and analyzed using Excel and PAST Ver. 2.14. Major axis regression was conducted to determine whether species size correlates with hinge teeth length and the averages and standard deviations between sample layers were compared to determine how body size changed across time periods and environments. This project is part of an overall effort to determine how patterns in fossils can be applied to geology;; a process called stratigraphic paleobiology. This knowledge will allow sequence stratigraphic parameters to be predicted in other study areas using similar species. P a g e | 61 LONG-­TERM CLIMATE CYCLES AND SEASONAL PRECIPITATION BALANCE IN ARIZONA: EVIDENCE FROM A SPELEOTHEM OXYGEN ISOTOPE RECORD Rachel Murray1, Julia Cole1, and Sarah Truebe1 1
Department of Geosciences, University of Arizona During the Pleistocene and Holocene, large-­scale climate changes correlate closely with Milankovitch cycles -­ long-­term, periodic changes in the HDUWK¶V RUELWDO SDUDPHWHUV WKDW FRQWURO WKH VHDVRQDO
GLVWULEXWLRQ RI VRODU HQHUJ\ LQVRODWLRQ RYHU WKH HDUWK¶V VXUIDFH
Milankovitch cycles are believed to set the timing of glacial (cool) and interglacial (warm) periods on a global scale through a number of dynamic interactions, however the influence of orbital parameters on precipitation amount and seasonality of precipitation in the Southwest LV QRW ZHOO NQRZQ ,Q $UL]RQD WKH R[\JHQ LVRWRSH UDWLR į2 RI
summer precipitation is distinct from that of winter precipitation, VXFKWKDWWKHDQQXDOPHDQį2YDOXHRISUHFLSLWDWLRQFDQWHOOXVWKH
relative amount of precipitation in the two seasons. This allows us to explore past variations in the seasonality of precipitation through WKH DQDO\VLV RI į2 UHFRUGV SUHVHUYHG LQ VSHOHRWKHPV -­ cave formations of calcium carbonate such as stalagmites. We present a VSHOHRWKHP į2 UHFRUG IURP &DYe of the Bells, Arizona, and compare climatic conditions between the last and current interglacial (warm) periods, known as the Eemian and the Holocene, respectively. During ERWKWLPHSHULRGVWKHWUHQGLQį2YDOXHVFRUUHODWHVZLWKWKHWUHQG
in summer insolation associated with the Milankovitch cycles, suggesting that orbital parameters influence the seasonality of precipitation in the region. P a g e | 62 DETERMINING FAULT RELATIONSHIPS AND TIMING RELATED TO CONTINENTAL RIFTING USING 3D REFLECTION DATA, OFFSHORE GUINEA, WEST AFRICA Russ Edge1 and Noah McDougall1 1
Department of Geosciences, University of Arizona Recently acquired 3D seismic reflection data from offshore Guinea, provides an unprecedented look at the structural relationships of this complex rifted margin in the central Atlantic. The 3D reflection data, which were collected both on the continental shelf and within the deeper marine basin, provide excellent resolution of a major listric normal fault that defines the extent of a broader deformation zone. In its hanging wall, this normal fault has 3 -­ 4 km thick, Lower Cretaceous growth strata, confined in age by the stratigraphically lower Aptian unconformity (110 Ma) and the higher Albian unconformity (98 Ma). Current research has been focused to 1) further constraint of the slip rate on the listric fault and relating it to the larger regional tectonic framework, and 2) determine where transform-­related strike-­slip motion has been accommodated. Interpretation of age constraints is based on the presence of onlapping growth strata and North Atlantic sea-­level curves, allowing estimates of slip rate on the listric fault. Such estimates provide better understanding of the IDXOW¶V WLPLQJ DQG UROH LQ ODUJHU-­scale continental rifting and continent-­margin development. In addition, a major change in strike orientation along the fault creates no apparent confining-­ or releasing-­bend deformation in hanging-­wall strata, suggesting that minimal strike-­slip movement has been associated with it. This relation raises the question of where such accommodation has taken place. Our current hypothesis is that this strike-­slip motion is associated with deeper crustal structures not imaged in the exploration seismic dataset. Continuing interpretation of these passive-­margin structures, with analysis of apparent strain partitioning, will permit greater understanding of offshore Guinean rifting. P a g e | 63 PROVENANCE, PALEOALTIMETRY, AND TECTONIC SIGNIFICANCE OF THE LIUQU CONGLOMERATE, SOUTHERN TIBET Ryan J. Leary1, Jay Quade1, and Peter G. DeCelles1 1
Department of Geosciences, University of Arizona Although the history of the India-­Asia collision is fundamental for understanding intercontinental collision in general, its timing and nature remain topics of heated debate. The record of this event is preserved in Cenozoic sedimentary basins along the Indus-­Yarlung Suture Zone in southern Tibet. Here, I present preliminary data on the age, provenance, and paleoelevation of the Liuqu Conglomerate, a Paleogene terrestrial unit exposed within this suture zone. Paleocurrent analysis indicates that this sediment was shed northward. However, detrital U-­Pb zircon age spectra and clast counts indicate that the Liuqu Conglomerate contains both Asian and Indian detritus. Mixed provenance shows that this unit was deposited after the onset of continental collision. Weathered paleosols and carbon isotopic composition of soil carbonates suggest that the Liuqu Conglomerate was deposited in a warm, low elevation environment much different than its modern setting. Although the age of the Liuqu Conglomerate remains poorly constrained, more accurate dating of this unit will likely provide a minimum age for Indo-­Asian collision as well as a maximum age for uplift of the Indus-­Yarlung Suture Zone. P a g e | 64 OROGRAPHY, AND MODES OF VARIABILITY IN SOUTH AMERICAN PRECIPITATION Sarah Dasher1, J. Russell1, C. Castro, and P. Goodman1 1
Department of Geosciences, University of Arizona The Andes form a topographic wall between one of Earth's wettest climates (the Amazon) and one of its driest (the Atacama). In the northern Andes, predominantly easterly winds from the Atlantic bring orographically focused precipitation to Andes' eastern flanks, contributing to hyperarid conditions on the western side. By contrast, westerly winds prevail in the southern Andes, where most precipitation occurs near the coast. We examine 30 years of high-­resolution satellite and ground-­based precipitation data to identify the primary modes of variability in South American precipitation over time. We then compare these modes against high-­resolution elevation models, to assess the relative contribution of orography to rainfall patterns in South America. P a g e | 65 HOW IMPORTANT IS ISOTOPIC EQUILIBRIUM FOR PALEOCLIMATE RECORDS FROM CAVES? A CASE STUDY FROM SOUTHERN ARIZONA Sarah Truebe1, Julia Cole1, Heidi Barnett2, Gideon Henderson3, Jennifer Wagner1, and Stephan Hlohowskyj1 1
Department of Geosciences, The University of Arizona 2
3
Ventana Medical Systems, Inc. Department of Earth Sciences, Oxford University Cave speleothems provide an excellent, high-­resolution, absolutely dated method to explore past monsoon variations in the Southwest. Here we present two speleothem records (0-­7000 years before present (yr BP), and 6500-­3500 yr BP) from Cave of the Bells, Arizona, which we couple with 7 years of dripwater monitoring and 2 years of calcite monitoring to aid in interpretation. These two climate records are highly correlated within age model error and indicate a greater contribution of monsoonal moisture to the cave system in the middle Holocene, likely a response to the increased seasonality of radiation at that time. Both also indicate significant multidecadal-­ to century-­scale variability in moisture. But disagreement between carbon isotope records, along with monitoring data, suggest that modern calcite is not precipitating in isotopic equilibrium. The coupled monitoring and paleoclimate studies from Cave of the Bells suggest that isotopic equilibrium may not be necessary for speleothem calcite oxygen isotopic composition to record a climate history. However, our results indicate that using carbon isotopic data for paleoenvironmental reconstruction requires detailed understanding of the cave system. We compare these carbon and oxygen isotopic records to a 0-­4000 yr BP record from nearby Fort Huachuca Cave to rule out site-­specific effects on isotopic variability. The remarkable consistency of longer-­term climate patterns between stalagmites in southern Arizona suggests that speleothem oxygen isotope records provide useful archives of surface hydroclimate, even at sites where there is demonstrable disequilibrium. P a g e | 66 DETERMINING FLUID SOURCE FOR PUMPKIN HOLLOW, AN IRON-­OXIDE-­COPPER-­GOLD (IOCG) DEPOSIT IN YERINGTON, NEVADA Simone Runyon1 1
Department of Geosciences, The University of Arizona The Jurassic Pumpkin Hollow (PH) iron-­oxide-­copper-­gold (IOCG) deposit in the Yerington District of western Nevada is composed of six copper-­magnetite skarn ore bodies. As with most other IOCG deposits worldwide, it is not clear whether metals were brought to PH by non-­
magmatic fluids or by fluids derived from local porphyry bodies associated with the Yerington batholith. This study addresses that issue using petrographic and electron probe micro-­anayzer (EPMA) data to investigate the spatial relationship between Cu mineralization and local magmatic intrusions. If fluids that exsolved from the porphyry bodies created the PH ore bodies, ore distribution will correlate with the occurrences of the porphyry bodies, with the highest metal grades closest to the intrusions. If this correlation is not observed, the possibility that surface brines transported the PH metals will be further investigated using fluid inclusion thermometry and chemistry. High homogenization temperatures and low Cl indicate contributions from magmatic fluid. Adversely, low homogenization temperatures and high Cl indicate contributions from surface-­derived fluids. This detailed study of ore grade distribution and fluid inclusion chemistry will help constrain the origins not only of PH, but also of other IOCG deposits worldwide. P a g e | 67 A PALEOHYDROLOGIC MODEL OF BAQAN TSO, TIBET BASED ON LAKE SHORELINES Tyler Huth1 and Jay Quade1 1
Deparment of Geosciences, University of Arizona As the Asian 0RQVRRQDIIHFWVRYHUKDOIRIWKH(DUWK¶VSRSXODWLRQ
it is important to understand past variations in its intensity during warmer global climate when attempting to make predictions about how it will vary over the next century. While warming is expected to occur over much of Asia during the next century, modeling efforts inadequately represent the Tibetan Plateau. Much of the difficulty here is attributed to a lack of instrumental and paleoclimate observations. Previous studies of the area attempted to use lake cores as records of monsoon intensity, but can only provide qualitative estimates of monsoon strength. Recent workers at Ngangla Ring Tso (NRT), a closed, glaciated basin in western Tibet, used paleolake shorelines to reconstruct Holocene monsoon intensity (Hudson and Quade, in prep). Although the chronology is constrained by discrete, discontinuous shorelines, it shows connections to millennial-­scale oscillations in other comparably resolved indicators of the paleomonsoon like Chinese cave and deep-­sea records. However, modeling the NRT basin and acquiring paleoprecipitation estimates is difficult because the basin is glaciated. Baqan Tso is a nearby closed but non-­glaciated basin that provides an excellent opportunity to independently verify the NRT chronology and quantify monsoon intensity. Stable isotope data show modern Baqan Tso is comparable to other lakes in Tibet. We expect Baqan Tso to have a negligible reservoir effect and provide a robust shoreline chronology. These favorable attributes will allow us to model Baqan Tso (after Kutzbach 1980) and generate quantitative estimates of monsoon intensity for the Holocene that other records are unable to provide. P a g e | 68 DEVELOPMENT OF A RADIATION DAMAGE AND ANNEALING MODEL FOR THE ZIRCON (U-­TH)/HE THERMOCHRONOMETER William Guenthner1, Peter Reiners1, Richard Ketcham2, and Lutz Nasdala3 1
Department of Geosciences, University of Arizona 2
3
Jackson School of Geosciences, University of Texas Institute for Mineralogy and Crystallography, University of Vienna Zircon (U-­Th)/He (ZHe) thermochronometry is widely used but lacks D SURSHU FDOLEUDWLRQ RI WKH V\VWHP¶V NLQHWLF SDUDPHWHUV 'LIIXVLRQ
studies have shown that He diffusion in zircon is anisotropic, and that radiation damage has a large effect on He diffusivity. Furthermore, in many cases single-­grain zircon He dates from single samples show either positive or negative (and sometimes both) correlations between date and effective uranium (eU) concentration. If these are due to radiation damage they may yield useful time-­
temperature information. Parameterization of the damage-­diffusivity relationship is required, however, for such correlations to be properly interpreted. We conducted step-­heating experiments on pairs of crystallographically oriented slabs of zircons with damage ranging IURP ( WR ( ĮJ 'LIIXVLYLWLHV IRU HDFK SDLU H[KLELW
anisotropy, although these differences are minimal compared with differences caused by varying amounts of radiation damage. We define the following relationship between He diffusion (at any T) and UDGLDWLRQ GDPDJH %HWZHHQ a DQG ( ĮJ GLIIXVLYLW\ GHFUHDVHV E\
nearly three orders of magnitude. Diffusivity then remains roughly FRQVWDQW ZLWK LQFUHDVLQJ GDPDJH XQWLO a( ĮJ DW ZKLFK SRLQW LW
increases again by ~10 orders of magnitude. We fit this relationship with a model that describes the tortuosity of diffusion pathways as increasing with damage, which causes decreases in He diffusivity at low damage amounts. Increasing diffusivity at high damage amounts results from damage zone interconnection and consequential shrinking of the effective diffusion domain size. Linking this parameterization to one describing damage annealing, we can model the coevolution of damage, He diffusivity, and ZHe dates. This generates positive or negative correlations depending on the extent of damage at the time of partial resetting. P a g e | 69 Student Union Memorial Center -­ Level 3 Directions: From Speedway Blvd., turn south on N. Park Ave and west on E. 2nd St. Complimentary parking is available 0.1 miles west on E. 2nd Street in the Main Gate Garage. North Grand Ballroom (Talks) Catalina and Rincon Rooms (Posters) Diamond Atrium (Registration Desk) P a g e | 70 Grant Rd
Sabino Canyon Rd
4231 N. Bidahochi Drive (Home of Jon Pelletier and family)
7 PM Dinner and drinks, live music to follow
Bear Canyon Rd
GeoDaze Party
Park Ave
Tanque Verde Rd
I-10
2 mi
UA
1. Head north on Park Ave (or any other major N-S street
in the area) until its junction with Grant Road
2. Turn right (east) on Grant Road and follow it until
its junction with E Tanque Verde Road
3. Turn left onto E Tanque Verde Road and follow it to
the east over the Tanque Verde Creek Wash, until its
junction with N Bear Canyon Road
4. Turn left (north) onto N Bear Canyon Road and follow
it north for approximately 1.7 miles, until its junction
with E Kayenta Drive
5. Turn right (east) onto E Kayenta Drive
6. Take the first left onto N Bidahochi Drive. Find a
parking spot along N Bidahochi Drive.
On-street parking is allowed in this neighborhood, but be
courteous!
N Harrison Rd
Directions
1000 ft
Inset
Saturday, March 31 to Sunday, April 1: Field Trip Saturday, March 31, 2012 9:30AM ± Gather at the loading dock (NW corner of Gould-­Simpson Building) 10:00AM ± Shuttles depart for Kartchner Caverns State Park. 12:00PM ± Lunch (provided) at the Discovery Center (NE corner of main parking lot). You must arrive by noon to secure a place on the tour. 1:45-­3:15PM ± *XLGHGFDYHWRXUVRIWKH5RWXQGDDQG³%LJ´5RRPV 4:30 PM ± Shuttle back to Tucson for those not camping. 3:30-­5:30PM ± Free time for hiking/exhibits/gift shop/wildlife viewing/staking out a campsite claim. We have reserved Campsites 18-­23. 5:30PM ± Dinner and beverages (provided) at the campsite. 7:00PM ± Dark sky talk and telescope viewing (flashlights required!) led by Scott Kardel, Public Affairs Director, International Dark-­Sky Assoc. 10:00PM ± Campsite quiet hours begin. Sunday, April 1, 2012 7:00AM ± Breakfast (provided) at the campsite. 7:45 AM ± Geomorphology hike led by Bob Casavant, Manager, Science & Research / Natural Resources, Arizona State Parks. 9:30AM ± Depart for Tucson. Cave Tour and other Information For detailed information about parking and other facilities, please see the Kartchner Caverns SP website: http://azstateparks.com/parks/kaca/facilities.html We have reserved room for each attendee to attend one of the two guided cave tours. Please consult the information below to decide which tour you P a g e | 72 would prefer. Tour spaces will be allocated on a first-­come, first-­serve basis. 6LJQXSVKHHWVZLOOEHSDVVHGDURXQGGXULQJ6DWXUGD\¶VOXQFK General Tour Information A trained guide leads all tours. No self-­guided tours are available. No items (bags, purses, packs, bottled water, etc) are allowed into the cave while on tour;; however lockers are available at the park to store these items. The cave has an average temperature of 72° Fahrenheit (22° Celsius) and 99% humidity year-­round, so it will feel very warm and steamy. Most areas are dimly lit and some passages may pass through narrow or enclosed areas. This may be difficult for persons with mobility, respiratory or claustrophobia issues. The following are NOT permitted on Cave Tours: x
x
x
x
x
x
x
Purses, handbags, backpacks, fanny packs, baby backpacks or other bags/items. Binoculars or flashlights. Photography or video equipment (to include phones, other electronic recording devices and tripods). Food, gum, tobacco products and drinks (including bottled water). Strollers, walkers, crutches. Touching or damaging formations (punishable by law). Littering or tossing coins. Please plan to leave all items in your vehicle or in the lockers located on the rear patio of the Discover Center. Heavy clothing will not be necessary in the warm, humid cave. A coat or jacket appropriate to the outside weather is all that you will want to bring with you on tour. Rotunda/Throne Tour Length: ½ mile. Time: 1½ hours. This tour has been open since 1999! It is half of a mile in length and takes approximately an hour and a half to complete, 50 minutes of which is underground. Discover the role that water plays in creating the caverns. You will see the discoverers' original trail, 45,000-­year-­old bat guano, delicate IRUPDWLRQVDQG³.XEOD.KDQ´WKHODUJHVWFROXPQIRUPDWLRQLQ$UL]RQD Big Room Tour Length: ½ mile. Time: 1¾ hours. This tour is currently open and will remain open until April 15, 2012. It will re-­open Oct. 15, 2012. The cave is closed Dec. 25. This tour has been open since 2003. It is half of a mile long and takes an hour and 45 minutes to complete, one hour of which is underground. The Kartchner Cavern story is about amazing discoveries past, present and future. Marvel at the many strange and colorful formations. Learn about the cave IDXQDERWKOLYLQJDQGDQFLHQW([SHULHQFHWKHZRQGHURIWKHFDYH¶VGLVFRYHU\
P a g e | 73 Legend
®
(520) 586-4100
P.O. Box 1849, Benson, AZ 85602
Mountain
Viewpoint (.5 mi.)
Foothills Loop Trail (2.5 mi.
)
Gatehouse
Ramada/Picnic
Discovery Center
Campground
%DW&DYH&DIé
Showers
Parking Area
Dump Station
Rest Rooms
Scenic Overlook
Amphitheater
%HQFK
Telephone
& Ben
(9 mi.) son
Map not to scale
Please Recycle
Please Stay on Trails
Coronado National Forest
+LNLQJRIIWUDLOVLVSURKLELWHG
Milepost 298
Bridge (No
Pedestrians)
Water
Tank Upper
Volunteer
Village
sh
i Wa
an
uind
G
Discovery
Center
Ranger Residences
Emergencies Only
‡%DW&DYH&DIé
‡Gift Shop
‡+XPPLQJELUG*DUGHQ
‡Theater
Cave
Unit
Office
Park
Entrance
ing
RV Park
Guindani
Trailhead
Gatehouse
Sierra
V
(19 mi.ista
)
Maintenance
Lower
Volunteer
Village
Maintenance
Entrance