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Sudden desiccation of Lake Gosiute at ∼49 Ma: A downstream record of heart
mountain faulting?
Article in The Mountain Geologist · January 2007
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Sudden Desiccation of Lake Gosiute at ~49 Ma:
A Downstream Record of Heart Mountain Faulting?1
MERIDITH K. RHODES2
DAVID H. MALONE3
ALAN R. CARROLL2
ELLIOT M. SMITH2
1. Manuscript received June 27, 2006; Accepted November 28, 2006
2. Department of Geology and Geophysics, University of Wisconsin, 1215 West Dayton Street, Madison, Wisconsin 53706, USA
3. Department of Geography-Geology, Illinois State University, Normal, IL 61790-4400, USA
ABSTRACT
Mudcracks originally more than 2 m deep are directly superimposed on profundal lacustrine mudstone of the lower LaClede Bed of the Green River Formation in the Washakie Basin, recording sudden
and intense desiccation of Eocene Lake Gosiute. We propose that this desiccation was caused by a giant
rockslide/debris avalanche that blocked a major southward-flowing river to Lake Gosiute in response to
the catastrophic emplacement of the upper plate of the Heart Mountain Detachment (HMD). In the
Washakie Basin, dolomitic mudstone, siltstone, and sandstone (known as the “buff marker bed”) were
deposited above the mudcrack horizon. These fluvial deposits mark the first appearance of volcaniclastic
sediments in the Washakie Basin, and together with overlying lacustrine mudstone record the reestablishment of regional drainages after the debris avalanche. Sudden desiccation of Lake Gosiute contradicts
models that require slow emplacement of the upper plate of the HMD and highlights the importance of
lacustrine strata as archives of continental tectonics.
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
DEER CREEK MEMBER OF THE WAPITI
FORMATION, HEART MOUNTAIN
FAULTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
THE “BUFF MARKER” . . . . . . . . . . . . . . . . . . . . . . . . 2
DISCUSSION AND CONCLUSIONS . . . . . . . . . . . . 6
ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . 8
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Introduction
Stanley, 1980), or volcanic activity (Bouchard et al., 1998;
Waythomas, 2001). It is generally believed that tectonic
influences on lacustrine sedimentation tend to act relatively
slowly, whereas higher-frequency changes are usually
attributed to periodic climate variability. It is important to
consider that sudden tectonic events might also be capable
of producing abrupt stratal discontinuities.
The Heart Mountain Detachment (HMD) has been one
of the most enigmatic and controversial features in North
American structural geology for much of the last century
It is becoming increasingly apparent that the tectonic
and magmatic history of lake basins exerts a first-order
control on the character of their deposits (Carroll and
Bohacs, 1999). Major changes in lacustrine sedimentary
facies associations may be induced by subtle structural
influences on regional drainage organization (e.g.,
Kowalewska and Cohen, 1998; Sáez et al., 1999; Pietras et
al., 2003), by basin and uplift stability (e.g., Surdam and
The Mountain Geologist, Vol. 44, No. 1 (January 2007), p 1-10
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Meridith K. Rhodes, David H. Malone, Alan R. Carroll, and Elliot M. Smith
(for a summary of previous work see Hauge, 1993). It is an
important part of an ongoing debate over the mechanics of
low-angle faulting and large-scale landsliding (Hauge,
1993). Several aspects of the HMD are in dispute, the most
notable of which is the rate at which the upper plate was
emplaced (Defrates et al., 2006, Aharonov and Anders
2006, Beutner and Gerbi, 2005, Craddock et al. 2000).
Emplacement was contemporaneous with widespread
igneous activity within the 18,000 km2 Absaroka Volcanic
Province (Smedes and Prostka, 1972; Sundell, 1990; Fig. 1)
that occurred during the Early and Middle Eocene (~53-46
million years ago; Torres and Gingerich, 1983; Sundell,
1990; Hiza, 1999). Pierce (1987) argued for catastrophic
emplacement as numerous independently moving upper
plate sliding blocks. In this “tectonic denudation” model,
overlying and adjacent Eocene volcanic rocks were interpreted to largely post date faulting. Malone (1995, 1996,
1997) also argued for rapid emplacement, but interpreted
Eocene volcanic rocks in the distal areas of the HMD as a
gigantic debris avalanche derived from the gravitational
failure of a pre-existing volcanic edifice. In contrast, Hauge
(1985, 1990) envisioned a single, continuous allochthon
that gradually extended by normal faulting over a period of
one million years, synchronously with Eocene volcanism.
The Laney Member of the Green River Formation was
deposited in Eocene Lake Gosiute, which was located several hundred kilometers to the south. Lake Gosiute most
likely received waters from the area of the HMD (Surdam
and Stanley, 1980; Lillegraven and Ostresh, 1988), and was
therefore ideally situated to record the effects of emplacement of the detachment on regional drainage patterns. The
deposits of the Green River Formation provide a higherresolution record than is available in the area of the HMD,
and recent advances in age-dating of interbedded tephras
allow the timing of upstream events to be determined at a
high level of precision and accuracy (Smith et al., 2003).
Conversely, recognition of the downstream effects of the
HMD on sedimentation in the Green River Formation
would greatly expand our general understanding of the
genesis of lacustrine stratigraphic sequences. In this paper,
we propose a causal relationship between the emplacement of the upper plate of the HMD as a rockslide/debris
avalanche, and the occurrence of a major desiccation surface overlain by volcanic rich fluvial-lacustrine deposits
within the Laney Member of the Green River Formation.
sand-sized volcaniclastic material. The areal extent and volume of the proximal facies of the DCM are ~450 km2 and
~100 km3, respectively. The general characteristics of the
DCM were introduced by Malone (1995) and described in
detail by Malone (1996, 1997), who interpreted it to be the
deposit of a large debris avalanche formed by the collapse
of a large stratovolcano within the Absaroka Range during
the early middle Eocene. Malone (2000) broadened the
interpretation of the DCM to include spatially and temporally associated allochthonous Paleozoic rocks in the distal
areas of the HMD. This interpretation is akin to the
emplacement model for the HMD upper plate advanced by
Beutner and Gerbi (2005), where carbonate and volcanic
rocks in all areas of the HMD were emplaced catastrophically together as part of a large rockslide/debris avalanche.
The DCM/HMD was emplaced into the adjacent
Absaroka and Bighorn Basins upon an Eocene paleotopography with at least 300 m of relief (Fig. 2; Malone, 1996).
Locally, the DCM is overlain by a stratified succession of
light colored, epiclastic volcanic sediments. This succession
consists of alternating beds of mudstone, sandstone, conglomerate, and tuff, and ranges in thickness from 0-150 m.
It is thickest where it fills topographic lows on the underlying DCM. These rocks are structurally, texturally, and compositionally different from overlying Wapiti Formation
rocks and have a general appearance that is similar to preDCM Wapiti and Aycross Formation lithologies present further to the south (Love, 1939; Bown, 1982; Malone, 1997;
Sundell, 1990). The overlying Wapiti Formation rocks consist of massive, dark-colored breccias and lava flows that
mark the onset of renewed proximal volcanic activity in
this part of the Absaroka Range (Fig. 2).
The “Buff Marker”
The Laney Member of the Green River Formation (Fig.
1) records the final saline to freshwater stage of Eocene
Lake Gosiute (Bradley, 1964; Roehler, 1993). The lower
LaClede Bed of the Laney Member is characterized by
repeated, 1-3 m facies successions of stromatolite, laminated organic-rich carbonate mudstone (oil shale), and
dolomitic mudstone. These successions are commonly
interpreted to represent episodes of relatively rapid deepening of Lake Gosiute, followed by more gradual shallowing (e.g., Surdam and Stanley, 1980; Rhodes et al., 2002).
Cm- to dm-scale mudcracks are commonly found with the
uppermost parts of each succession, and are interpreted to
result from relatively minor fluctuations in lake level that
occurred during a more gradual overall regression. However, a single, unique horizon of much larger mucracks
also occurs with the lower LaClede bed, and is directly
overlain by a regionally-correlative interval of lighter-colored strata that has been informally named the “buff
Deer Creek Member of the Wapiti Formation,
Heart Mountain Faulting
The Deer Creek Member (DCM) of the Wapiti Formation
consists of blocks (individually as large as several km2 in
area) of vent-medial-facies lava flows, breccia, and sandstone, all within a thin, heterogeneous matrix of boulder to
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SUDDEN DESICCATION
OF
LAKE GOSIUTE
AT
~49 MA: A DOWNSTREAM RECORD
OF
HEART MOUNTAIN FAULTING
Figure 1. Regional geologic map with Eocene
paleocurrent patterns, present known extent
of the Deer Creek Member, approximate
location of the paleovalley shown in Figure 2,
outline of Eocene Lake Gosiute, and the field
localities for buff marker correlation. It is
important to note that many of the details of
this Eocene drainage network are buried by
younger volcanic rocks or have been
removed by erosion.
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Meridith K. Rhodes, David H. Malone, Alan R. Carroll, and Elliot M. Smith
Figure 2. The Deer Creek Member (DCM) of the Wapiti Formation along the North Fork of the Shoshone River valley. West is to the left. The
west edge of the Eocene paleo-surface is marked with an arrow. Also shown are: Kc = Cody Shale, Twl = Willwood Formation; Twd = Deer
Creek Member of Wapiti Formation; Mm = allocthonous block of Madison limestone within the Heart Mountain allocthon; Twus = ‘upper
stratified’ post Deer Creek epiclastic volcanic sediments; Twlb = lower breccias of Wapiti Formation; Twj = Jim Mountain Member of
Wapiti Formation; Twub = upper breccias of the Wapiti Formation.
Figure 3. Stratigraphic correlation of the buff marker and surrounding strata along the Delaney and Kinney Rims in the Washakie
Basin.
The Rocky Mountain Association of Geologists
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SUDDEN DESICCATION
OF
LAKE GOSIUTE
AT
~49 MA: A DOWNSTREAM RECORD
OF
HEART MOUNTAIN FAULTING
Figure 4. Photomosaic of the section at Sand Butte illustrating the lower LaClede, desiccated surface, buff marker, oil shale interval, and
upper LaClede beds.
Figure 5. Mudcrack at the base of the buff marker bed at Sand
Butte.
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Meridith K. Rhodes, David H. Malone, Alan R. Carroll, and Elliot M. Smith
Figure 6. Faunal and radioisotopic constraints on the ages of the Deer Creek Member and the buff marker (see text for complete explanation and references).
marker” (term coined by Roehler, 1973). The mudcracks
extend ~2 m downward into laminated, profundal lacustrine mudstone; their original uncompacted depth may
therefore have been considerable greater (Figs. 3-5). At the
Laney and Kinney Rims (Washakie Basin) the cracks are
generally spaced 15 to 20 m apart and are filled with
dolomitic and volcaniclastic silt, fine-grained sand, and
intraclasts. The mudcrack horizon can be traced laterally
for ~100 km. Similar giant desiccation cracks have been
documented within modern playas of the Great Basin
(Neal et al., 1968) and the Black Rock and Smoke Creek
Deserts (Willden and Mabey, 1961). We interpret this horizon to record a period of sudden and profound desiccation of Lake Gosiute that was anomalous and apparently
unique in this stratigraphic succession.
The buff marker interval is roughly 12.5 m thick at its
best exposure in the Trail Dugway section, where the
coarsening-and-thickening to fining-and-thinning upward
bed sets are composed of dolomite, silt to medium-grained
micaceous sand, and volcaniclastic detritus interbedded
with mudstone (Fig. 3). Lacustrine facies in the lower
Laclede Bed immediately above the buff marker are similar
to those below, consisting of ~1.5 m of laminated mudstone, followed by two more complete successions of stromatolite, laminated mudstone, and massive mudstone. The
overlying upper LaClede Bed consists of an additional 3050 m of relatively massive mudstone and is itself overlain
by deltaic volcaniclastic strata of the Sand Butte Bed
(Roehler, 1973).
Middle Eocene. Early rivers flowing across the present Wind
River Range and adjacent areas carried arkosic detritus that
was deposited as southward-prograding deltas of the Farson
Sandstone (Roehler, 1993; Pietras et al., 2003). Beginning in
the early Bridgerian, Absaroka-derived alluvial volcaniclastic
sediments entered the northwest corner of the basin and
were deposited as part of the Wasatch (Cathedral Bluffs
Member), Bridger and Washakie Formations (West, 1973;
Steidtmann and Middleton, 1991). North-to-south sediment
dispersal is recorded by southeast-directed paleocurrents,
and by clasts of andesite and distinctive “Pinyon-type”
quartzite that were sourced from north of the Wind River
and Gros Ventre-Teton uplifts (Kistner, 1973; West, 1973).
Similar detritus also filled the Wind River Basin starting in
the Lostcabinian (Keefer, 1957; Winterfield, 1990). Lake
Gosiute was eventually infilled by southeast-prograding
volcaniclastic deltas, which subsequently spilled further
south in the Piceance Creek Basin (Surdam and Stanley,
1980; Johnson, 1981; Stucky et al., 1996). Given the predominance of such drainage patterns, any major landscape
modifications that took place north of the greater Green
River Basin would have impacted Lake Gosiute. Large
debris-flow avalanches have been shown to be especially
effective at altering lake basin hydrology, due to the immediate and catastrophic blockage of stream channels (e.g.,
Reneau and Dethier, 1996; Waythomas, 2001).
Emplacement of the DCM and deposition of the buff
marker appear to have been synchronous events, within
the limits of current chronostratigraphic resolution. However, due to uncertainties in regional biostratigraphic, magnetostratigraphic, and radioisotopic data and in the
timescale itself, it is difficult to exclude a difference in timing on the order of ~0.5 my. The primary basis for correlation is mammalian biostratigraphy (Fig. 6). North American
Land Mammal (NALMA) faunal zones in the Willwood and
Discussion and Conclusions
Major drainage systems entered the greater Green River
Basin from the north throughout much of the Early to
The Rocky Mountain Association of Geologists
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SUDDEN DESICCATION
OF
LAKE GOSIUTE
AT
pre-DCM Wapiti Formations place a lower age limit for the
DCM in the Br1a faunal zone (Torres 1985; Gunnell et al.,
1992). Fossils from the Br1b zone have been reported from
the lower part of the DCM at the Shoshone River (Torres
1985). However, this occurrence may be problematic if the
DCM originated as a catastrophic debris avalanche as postulated. Stratified nonmarine deposits overlying the DCM
contain fossils of the Br2 zone, confirming that the DCM
most likely does fall within the Br1b zone. No vertebrate
collections have been reported from the buff marker or
the enclosing Laney Member, so direct faunal comparison
with the DCM is impossible. Br1a fauna occur in the
Cathedral Bluffs Tongue below the Laney Member at
South Pass (Clyde et al., 2001; Gunnell and Bartels, 2001).
We infer that the lower contact of the Laney is nearly
isochronous across the greater Green River Basin due to
rapid expansion of Lake Gosiute, and that the age of the
Laney/Cathedral Bluffs contact is therefore the same in the
Washakie Basin as it is at South Pass. However, the upper
contact of the Laney Member with the Bridger Formation
is strongly diachronous due to basinward progradation of
overlying alluvial facies. We therefore infer that the buff
marker correlates with the Bridger Formation at South
Pass, which contains fossils of the Br1b faunal zone
(Clyde et al., 2001; Gunnell and Bartels, 2001). Fossils of
the Br3 zone occur above the Laney Member in the
Washakie Formation (McCarroll et al., 1996), providing an
additional age constraint.
Radioisotopic studies using 40Ar/39Ar offer an alternative
means of establishing the age relationship between the
DCM and buff marker, but also introduce new ambiguities.
Smith et al. (2003) reported ages that constrain the buff
marker between 49.70 ± 0.18 and 48.94 ± 0.18 Ma, based
on analysis of multigrain sanidine aggregates (Fig. 6, all
ages reported with 2s intercalibration uncertainties relative
to 28.34 Ma for TCs). Smith et al. (in prep) also obtained
an age of 48.60 ± 0.44 Ma for a tuff near the top of the
Bridger Formation at Continental Peak, which is consistent
with correlation of the buff marker with part of the Bridger
Formation and faunal zone Br1b. In contrast, ages between
49.78 ± 0.19 and 48.37 ± 0.15 Ma for lava flows that overlie
the DCM reported by Feely and Cosca (2003; recalculated
to the same standards used by Smith et al., 2003), would
make the DCM older than the buff marker. However,
because these lava flows sit above Br2 strata that overlie
the DCM, these ages conflict biostratigraphically with those
of Smith et al.(in prep) (Fig. 6). The ages reported by Feely
and Cosca (2003) were obtained from basalt groundmass
and plagioclase, both of which typically have low K concentrations, and are more prone to alteration and recoil
effects than sanidine, and may thus contain undetected
errors. Such systemic problems may be the cause for stratigraphically out-of-sequence ages for some of the lava
flows sampled by Feeley and Cosca. In contrast, the ages
~49 MA: A DOWNSTREAM RECORD
OF
HEART MOUNTAIN FAULTING
for Green River Formation tuffs were obtained from unaltered mineral phases with higher K concentrations and all
fall within the correct stratigraphic sequence. Further work
is needed to resolve the apparent inconsistencies between
these ages.
We propose that catastrophic emplacement of the DCM
debris avalanche was responsible for the sudden desiccation of Lake Gosiute, due to infill of topographic lows and
diversion of streams that had previously carried water
southward from the Absaroka volcanic province. The DCM
may in fact have blocked waters derived from as far away
as southwest Montana, based on the recent identification
of two major southeast-directly Eocene paleovalleys there
(Janecke et al., 2000). Diversion of drainage away from the
greater Green River Basin shifted the overall hydrologic
balance of Lake Gosiute toward evaporation, causing the
lake to dry up, groundwater levels to drop, and giant mudcracks to form. Shortly thereafter, southward flow was
restored either by overtopping of the debris avalanche
dam and breaching by outlet streams, headward erosion,
or both. The buff marker records the rapid influx of alluvial fine-grained dolomitic, volcanic, and siliciclastic detritus into Lake Gosiute as regional drainage was
reestablished. We infer that the dolomite was derived from
reworking of efflourescent crusts formed above the water
table on the exposed lake plain, as proposed by Wolfbauer
and Surdam (1974). The siliciclastic detritus, compositionally similar to volcaniclastic material contained within the
Wapiti, Aycross, and Bridger Formations, marks the first
known influx of such detritus into the eastern greater
Green River Basin. Micaceous sand in the buff marker may
also have been derived in part from metamorphic rocks
exposed in surrounding basement uplifts. Lake Gosiute
expanded, lake level rose, and shorelines transgressed
back toward the basin margins. The oil shale bed that
immediately overlies the buff marker records the return of
deep lacustrine conditions.
The above scenario is most consistent with catastrophic
emplacement of an intact upper plate of the HMD (e.g.
Defrates et al. 2006, Aharonov and Anders, 2006, Beutner
and Gerbi, 2005, Craddock et al., 2000). The actual time
required to form the giant mudcracks and buff marker bed
is unknown, but based on comparison with modern analogues a period of years to centuries seems most likely
(c.f., Willden and Mabey, 1961; Neal et al., 1968; Reneau
and Dethier, 1996; Waythomas, 2001). In contrast, the postmovement volcanism envisioned in the “tectonic denudation” model might be expected to more gradually modify
the pre-existing topography, and thus would have produced less sudden drainage modifications. Although we
favor the debris-avalanche model for the DCM, any model
involving catastrophic emplacement of such a large feature
as the HMD (e.g. Defrates et al. 2006, Aharonov and
Anders, 2006, Beutner and Gerbi, 2005 ) would be
7
The Rocky Mountain Association of Geologists
Meridith K. Rhodes, David H. Malone, Alan R. Carroll, and Elliot M. Smith
expected to profoundly alter regional topography and
drainage networks and thus leave a significant record in
downstream lakes.
The proposal that this event caused dessication of Lake
Gosiute lends itself to a number of additional tests. First,
more work is needed to examine evidence for preemplacement topography in areas affected by the upper
plate of the HMD, specifically to look for infill of paleovalleys. Evidence for paleovalleys should also be sought to
the northwest of the Green River basin. Second, stratigraphic investigation of units overlying the distal HMD
rocks should be focused on evidence for debris-dammed
lakes or deposits from outburst floods resulting from
debris-dam breaching. Third, emplacement of the upper
plate of the HMD may also have influenced drainage into
the Bighorn and Wind River basins, so evidence of significant hydrologic changes may also be present there. Finally,
additional work is needed to better resolve the age relationships between HMD emplacement and enclosing sedimentary rocks.
The broader implication of this study for lacustrine
sequence stratigraphy is that regional tectonic and magmatic events may profoundly alter the character of downstream lake deposits over the relatively short timescales
normally associated with climate change. These observations indicate that relatively random events of large magnitude may exert a disproportionate influence on the
deposition and preservation of lacustrine facies, as has
been previously proposed for other depositional settings
(e.g., Dott, 1983). The results of this study also demonstrate that lacustrine strata can provide an important and
unique perspective on the tectonic evolution of the continents that so far has been underutilized.
Bouchard, D.P., D.S. Kaufman, A. Hochberg, and J. Quade, 1998,
Quaternary history of the Thatcher Basin, Idaho, reconstructed
from the 87Sr/86Sr and amino acid composition of lacustrine
fossils: implications for the diversion of the Bear River into the
Bonneville Basin, Palaeogeography, Palaeoecology, Palaeoclimatology, v. 141, p. 95-114.
Bown, T.M., 1982, Geology, paleontology, and correlation of
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Carroll, A.R., and K.M. Bohacs, 1999, Stratigraphic classification of
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Clyde, W.C., N.D. Sheldon, P.L. Koch, G.F. Gunnell, and W.S. Bartels, 2001, Linking the Wasatchian/ Bridgerian boundary to the
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Craddock, J.P., K.J. Neilsen, and D.H. Malone, 2000, Calcite Twinning Strain Constraints on the Hearth Mountain Detachment
Emplacement Rates and Kinematics: Journal of Structural Geology, v. 22 p. 983-991.
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of magmatism at Sunlight volcano, Absaroka volcanic
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Gunnell, G.F., and W.S. Bartels, 2001, Basin margins, biodiversity,
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Wapiti Valley faunas, early and middle Eocene fossil vertebrates from the North Fork Shoshone River Valley, Park
County, Wyoming, Cont. from the Museum of Paleontology,
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Hauge, T.A, 1985, Gravity-spreading origin of the Heart Mountain
Allochthon, northwestern Wyoming: GSA Bulletin, v. 96, p.
1440-1456.
Hauge, T.A., 1990, Kinematic model of a continuous Heart Mountain allochthon: GSABulletin, v. 102, p. 1174-1188.
Hauge, T.A., 1993, The Heart Mountain detachment, northwestern
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Acknowledgements
Financial support was provided by Conoco Inc. and
Texaco Inc. and by grants from the American Association
of Petroleum Geologists, J. David Love Wyoming Field
Geology Fellowship, the Morgridge Distinguished Graduate
Fellowship, and the Department of Geology and Geophysics at the University of Wisconsin – Madison, and the
Graduate School of the University of Wisconsin.
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OF
LAKE GOSIUTE
AT
~49 MA: A DOWNSTREAM RECORD
OF
HEART MOUNTAIN FAULTING
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9
The Rocky Mountain Association of Geologists
Meridith K. Rhodes, David H. Malone, Alan R. Carroll, and Elliot M. Smith
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THE AUTHORS
MEREDITH RHODES
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ALAN CARROLL
MEREDITH RHODES began her
career in the geosciences at the
State University of New York College at Geneseo where she
received her B.S. in geology,
focusing on micropaleontology.
She went on to earn her M.Sc.
and Ph.D. from the University of
Wisconsin, Madison studying
lacustrine stratigraphy and strontium isotope geochemistry. She
currently works as a geologist in
deepwater Gulf of Mexico exploration for BP in Houston, TX.
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DAVID MALONE
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MICHAEL SMITH
DAVID MALONE is professor and
chair of the Department of Geography-Geology at the University
of Wisconsin. His research specialties are in structural geology
and stratigraphy. He has studied
various aspects of the Heart
Mountain Detachment for the
past fifteen years. He holds a BS
from Illinois State University, and
an M.Sc. and Ph.D. from the University of Wisconsin, Madison.
The Rocky Mountain Association of Geologists
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ALAN CARROLL is a professor at the
University of Wisconsin, Madison,
who conducts research on sedimentary basins and ancient lakes in the
western U.S., China, Argentina, and
Indonesia. He holds a B.S. from
Carleton College, an M.Sc. from the
University of Michigan, and a Ph.D.
from Stanford University.
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10
MICHAEL SMITH is a visiting assistant
professor at the University of Montana. His research interests are in
the geochrolonogy of sedimentary
basins, lacustrine basin analysis,
and rates of continental uplift,
denudation, and sedimentation. He
holds a B.S. from Carleton College,
and an M.Sc. and Ph.D. from the
University of Wisconsin.