MELTWATER CONTRIBUTION OF GLACIERS
IN THE UINTA AND WASATCH MOUNTAINS
TO PLUVIAL LAKE BONNEVILLE, UTAH, U.S.A
KRUEGER, Charles R., Department of Geosciences, Idaho State University,
921 South 8th Avenue, STOP 8072, Pocatello, ID 83209, kruechar@isu.edu,
LAABS, Benjamin J.C., Department of Geological Sciences, State University of
New York at Geneseo, 234 ISC, 1 College Circle, Geneseo, NY 14454, and
LEGGETT, Andrea, Geology, Kansas State University, 108 Thompson Hall,
Manhattan, KS 66506
The watershed of Lake Bonneville, the largest of the Pleistocene paleolakes in
the Great Basin, featured numerous glaciers in five mountain ranges in northern
Utah. Recent updates to the Pleistocene glacial chronology of the Wasatch and
western Uinta Mountains, which hosted the largest glaciers in the watershed,
indicate that the timing of local glacier maxima closely coincided with the
highstand of Lake Bonneville. However, the lake apparently maintained a positive
hydrologic budget until after glaciers in these two ranges began retreating at 17
to 15 ka BP, despite widespread evidence of warming and drying of regional
climate at this time. We estimate the contribution of melting glaciers in the
Wasatch and western Uinta Mountains to the hydrologic budget of Lake
Bonneville by simulating the known maximum ice extent in its drainage basin.
Areal extents of mountain glaciers in the Wasatch and western Uinta Mountains
that contributed meltwater to Lake Bonneville are determined from available
mapping data and interpretations of 7.5-minute topographic maps, Google Earth
images, and aerial photographs. Maximum ice extents in these areas are
simulated by a two-dimensional mass/energy balance and ice flow model (of
Plummer and Phillips, 2003). Results of modeling experiments indicate that the
volume of ice in the Wasatch and Uinta Mountains is ca. 243 km 3, less than three
percent of the total volume of Lake Bonneville (ca. 9,500 km3). These findings
indicate that the melting of glaciers in the Wasatch and western Uinta Mountains
was a small component of the hydrologic budget of Lake Bonneville during the
late Pleistocene and that the relatively late highstands of the lake were more
likely sustained by a regional increase in effective precipitation. [Plummer, M.A.,
Phillips, F.M., 2003. A 2-D numerical model of snow/ice energy balance and ice
flow for paleoclimatic interpretation of glacial geomorphic features. Quaternary
Science Reviews 22, 1389–1406].
TESTING AND REFINING THE TIMING OF
HYDROLOGIC EVOLUTION DURING THE
LATEST PLEISTOCENE REGRESSIVE PHASE
OF LAKE BONNEVILLE
SPENCER, Joel Q.G.1, OVIATT, Charles1, PATHAK, Manas2, FAN, Yuxin3, and
LEGGETT, Andrea1, (1) Geology, Kansas State University, 108 Thompson Hall,
Manhattan, KS 66506-3201, joelspen@ksu.edu, (2) Geology, Indian School of
Mines, Dhanbad, 826004, India, (3) MOE Key Laboratory of Western China's
Environmental Systems, Lanzhou University, Lanzhou, 730000, China
Lacustrine, fluvial, and wetland landforms present in the now desertified regions
of Dugway Proving Ground (DPG) and the Sevier Desert (SD) in western Utah,
record a fascinating history of falling lake level, river development, and
establishment of wetland habitats in the Lake Bonneville basin between ~14-8 ka
ago. This was not only a time of rapid climate change but also of human
occupation into suitable habitats made available by decline of the large lake.
Using optically stimulated luminescence (OSL) dating methods we are
determining depositional ages for sediment samples from bar features (reworked
deltaic sands), braided fluvial channels, and topographically inverted fluvial
channels collected from DPG during prior fieldwork. These data will be compared
to existing chronological evidence from DPG and SD to test and refine the timing
of changes in the geologic environment during this stage of Lake Bonneville
regression. Accurate assessment of the timing of the hydrological and
geomorphological changes taking place during the late regressive phase of Lake
Bonneville will help determine the relative importance of environmental change
compared with groundwater discharge thought to accompany falling lake levels.
PLUVIAL LAKES IN THE WESTERN U.S.—A
VIEW FROM THE OUTCROP
REHEIS, Marith, U.S. Geological Survey, Box 25046, MS 980, Denver Federal
Center, Denver, CO 80225, mreheis@usgs.gov
Huge strides have been made during the last 40 years in deciphering the
geologic and climatic records of Pleistocene pluvial lakes in the western U.S.
using cores from extant lakes and from desiccated lakes such as Lake Bonneville
and Owens (dry) Lake. Sedimentology, stable isotopes, pollen and other
microfossils, and physical properties from cores provide proxies for changes in
lake level, water temperature and chemistry, and ecological conditions in the
surrounding landscape. Commonly, such core data do not directly record lake
level or reveal geologic factors that may confound interpretations of proxy data,
and most core records do not extend beyond the last ~40 kyr. In contrast,
outcrop studies of incised basin fill provide much longer lake histories, indicate
absolute lake level, and yield clues to geologic events such as earthquakes,
floods, or drainage-basin changes that can clarify interpretations of lake sediment
and stratigraphy.
Notable advances made using outcrop studies include recognition of: (1) many
pre-late Pleistocene lakes in the western Great Basin that were significantly
larger and record wetter conditions than the youngest lakes; (2) drainage-basin
changes caused by tectonic or volcanic damming, in some cases triggering lake
overflow or catastrophic floods and altering the depositional setting of previously
deep-water locations; (3) complex relations among basins and subbasins
controlled by changing threshold altitudes; and (4) rapid lake-level fluctuations in
dated records. Combined outcrop and core data from Lake Manix yield a 500-kyr
lacustrine history indicating persistent lakes during both glacial and interglacial
periods, and recognition of significant change in depositional setting of the core
by a drainage integration event. Outcrop studies should be coupled with core
data to provide the most comprehensive understanding of lake records of
environmental change.
IDENTIFYING SUITABLE TERRESTRIAL
ANALOGS OF MARS SHOREZONE FEATURES:
PLANETARY EXPLORATION GUIDELINES
JEWELL, Paul1, CHAN, Marjorie1, NICOLL, Kathleen2, PARKER, Timothy3,
OKUBO, Chris H.4, KOMATSU, Goro5, ORMO, Jens6, and BARKER, Donald7, (1)
Dept. of Geology and Geophysics, Univ. of Utah, 115 S. 1460 E. Rm 383 FASB,
Salt Lake City, UT 84112, paul.jewell@utah.edu, (2) University of Utah, 260
South Central Campus Dr, Salt Lake City, UT 84105, (3) Jet Propulsion
Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena,
CA 91109, (4) Astrogeology Science Center, US Geological Survey, 2255 North
Gemini Road, Flagstaff, AZ 86001, (5) Irsps, Univ. G.d'Annunzio, Viale Pindaro,
42, 65127, Pescara, Italy, (6) Centro de Astrobiologia, Torrejon de Ardoz, 28850,
Spain, (7) Earth and Atmospheric Sciences, University of Houston, 312 Science
& Research Building 1, Rm. 312, Houston, TX 77204
The nature or even the past existence of a large water body on Mars has been
the subject of intense controversy and is a driving force behind selection of future
exploration sites on the Red Planet. Whatever the nature of Martian oceans or
lakes, they were almost certainly subjected to physical forcings and climate with
no direct analog in Earth’s geologic history. Nevertheless, any large body of
water that remains in the same place for an extended period of time invariably
leaves a physical record of its presence at the water-atmosphere interface. In the
case of oceans and large lake shorezones on Earth this record includes
shorelines, strandlines, beach ridges, and other physical manifestations.
Recognition of these features depends on their geomorphic expression (length,
relation to surrounding topography) and sedimentary character (textures,
structures, or chemical deposits such as tufa).
For many years to come, recognition of possible shorezone features on Mars
must rely on remote sensing instruments that in turn will be a function of the
spatial resolution and spectral capabilities of these instruments and relating the
resulting images to Earth analogs. Unfortunately, a large percentage of
appropriate shorezone Earth analogs are (1) too subtle or small to be detected
by currently deployed Martian instrumentation or (2) distinguished by vegetation
patterns which in turn are a function of the sedimentary characteristics of the
substrate and thus are not appropriate analogs for the modern surface of Mars.
Appropriate Earth analogs for Martian shorelines must necessarily be restricted
to a narrow suite of shoreline features. Specific examples from ice age water
bodies Lake Bonneville, Lake Agassiz, Baltic Ice Lake and the modern Great
Lakes provide guidelines for recognizing shorezone features on Mars and should
guide the search for paleo-oceans and paleo-lakes on the Red Planet.