Geologic Field Trips to the Basin and Range, Rocky Mountains, Snake River Plain, and Terranes of the U.S. Cordillera (GSA Field Guide 21)

230 Pages·2011·44.77 MB·English

by  Jeffrey Lee

s
N / Borah Peak Chicken-out
Ridge
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Geologic Field Trips to the Basin and Range, Rocky Mountains,
Snake River Plain, and Terranes of the U.S. Cordillera
edited by
Jeffrey Lee
Department of Geological Sciences
400 E. University Way
Central Washington University
Ellensburg, Washington 98926
USA
James P. Evans
Department of Geology
Utah State University
4505 Old Main Hill
Logan, Utah 84322-4505
USA
Field Guide 21
3300 Penrose Place, P.O. Box 9140 Boulder, Colorado 80301-9140, USA
2011
Copyright © 2011, The Geological Society of America (GSA), Inc. All rights reserved. GSA grants
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Printed in U.S.A.
Cataloging-in-Publication Data for this volume is available from the Library of Congress.
Cover: Cedar Creek and Borah Peak horst. Borah Peak fault scarp is plain at the base of the mountains.
Cedar Creek contains multiple generations of late Pleistocene moraines, cut by the Borah Peak fault. See
Figure 18 in Chapter 5 (P.K. Link and M.K.V. Hodges, The Neogene drainage history of south-central
Idaho, p. 103–123).
10 9 8 7 6 5 4 3 2 1
Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .v
1. New investigations of Pleistocene glacial and pluvial records in northeastern Nevada . . . . . . . . .1
Jeffrey S. Munroe and Benjamin J.C. Laabs
2. Timing, distribution, amount, and style of Cenozoic extension in the northern Great Basin . . . .27
Christopher D. Henry, Allen J. McGrew, Joseph P. Colgan, Arthur W. Snoke, and
Matthew E. Brueseke
3. Tectonomagmatic evolution of distinct arc terranes in the Blue Mountains Province, Oregon
and Idaho . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
C.J. Northrup, M. Schmitz, G. Kurz, and K. Tumpane
4. Neogene drainage development of Marsh and Portneuf valleys, eastern Idaho . . . . . . . . . . . . . .89
Glenn D. Thackray, David W. Rodgers, and Andrew Drabick
5. The Neogene drainage history of south-central Idaho . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103
Paul K. Link and Mary K.V. Hodges
6. Paleontology and stratigraphy of middle Eocene rock units in the Bridger and Uinta Basins,
Wyoming and Utah . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
Paul C. Murphey, K.E. Beth Townsend, Anthony R. Friscia, and Emmett Evanoff
7. Middle Cryogenian (“Sturtian”) Pocatello Formation: Field relations on Oxford Mountain and
the Portneuf area, southeast Idaho . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167
Joshua A. Keeley and Paul K. Link
8. New descriptions of the cap dolostone and associated strata, Neoproterozoic Pocatello Formation,
southeastern Idaho, USA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183
Carol M. Dehler, Kathleen Anderson, and Robin Nagy
9. Reinterpreted history of latest Pleistocene Lake Bonneville: Geologic setting of threshold failure,
Bonneville flood, deltas of the Bear River, and outlets for two Provo shorelines, southeastern
Idaho, USA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195
Susanne U. Janecke and Robert Q. Oaks Jr.
iii

Preface
The geologic record preserved within the Rocky Mountain and Cordilleran regions spans nearly all of
Earth’s time. The combination of the long geologic record and stunning scenery has attracted geologists
for two centuries. Past and ongoing geologic research in this region has resulted in a wealth of signifi cant
observations and paradigm shifts in interpretations. This fi eld trip guide, compiled for the 2011 joint meet-
ing of the GSA Rocky Mountain and Cordilleran Sections, provides a small and succulent appetizer to the
full menu of remarkable geology of the Rocky Mountain and Cordillera regions. Field trips presented in this
volume span geologic topics from Neoproterozoic deposits, late Paleozoic–early Mesozoic terrane accretion,
Eocene mammals and climate, Eocene to middle Miocene extension, late Miocene and younger basin and
river system evolution, and Pleistocene glaciers and pluvial lakes.
In chapter one, Munroe and Laabs’ fi eld trip examines latest Pleistocene to Holocene mountain glacial
and pluvial lake deposits in the East Humboldt and Ruby Mountains, northeastern Nevada, and implica-
tions for temperature and precipitation changes during this time period. Henry et al.’s fi eld trip, in chapter
two, highlights geologic fi eld relations, quantitative metamorphic petrology, and extensive geochronology
that indicate a contrast in the timing of mid-crustal versus supracrustal extension in the East Humboldt and
Ruby Mountains area, northeastern Nevada. In chapter three, Northrup and colleagues discuss new mapping,
geochronology, and geochemistry data that bear on the tectonic evolution and pre-accretion history of the
Wallowa and Olds Ferry terranes of the Blue Mountains Province, Oregon and Idaho. Thackray et al., in
chapter four, investigate the basin evolution of Marsh and Portneuf valleys, Idaho. The focus of this trip is to
examine the basin’s complex record of drainage capture, faulting, volcanism, and the Bonneville Flood. In
chapter fi ve, a companion paper to Thackray et al., Link and Hodges summarize detrital-zircon geochronol-
ogy from two large river systems—the Big Lost and Wood rivers—on the north side of the Snake River Plain
that shed light on the course of these rivers during the past 10 m.y. and the location of the paleo-continental
divide. Murphey et al.’s fi eld trip, described in chapter six, centers on a 10-m.y.-long biotic, environmental,
and climate history recorded in Eocene sediments of the Green River and Uinta basins, Utah. The next two
chapters are for a trip focusing on the Neoproterozoic Pocatello Formation, Idaho. Keeley and Link, in chap-
ter 7, examine the diamictite stratigraphy and discuss U-Pb zircon ages from these deposits in the Oxford
Mountain and Portneuf area. In chapter eight, Dehler et al. investigate the stratigraphy and sedimentary facies
of deposits that overlie diamictites in the Fort Hall Mine area south of Portneuf Narrows. In chapter nine,
Janecke and Oaks highlight geologic, geomorphic, and geophysical data that document the southward shift
of the Lake Bonneville outlet.
Thanks to the authors for agreeing to lead a fi eld trip, to reviewers for their thoughtful and helpful
reviews, and the GSA publications staff for their time and effort in compiling this volume.
Jeffrey Lee
James Evans
v

The Geological Society of America
Field Guide 21
2011
New investigations of Pleistocene glacial and pluvial records in
northeastern Nevada
Jeffrey S. Munroe
Geology Department, Middlebury College, Middlebury, Vermont 05753, USA
Benjamin J.C. Laabs
Department of Geological Sciences, State University of New York–Geneseo, Geneseo, New York 14454, USA
ABSTRACT
The Great Basin of the western United States offers tremendous potential for
exploring the response of mountain glaciers and lowland lakes to climate changes
during the Last Glacial Maximum (LGM, MIS-2, ca. 22–18 ka B.P.) and subsequent
glacial-interglacial transition. The combination of well-distributed alpine moraine
records and pluvial lake deposits offers an unparalleled opportunity to develop a
more precise understanding of temperature and precipitation changes during the lat-
est Pleistocene and into the Holocene. This fi eld trip provides an overview of recent
and ongoing work illuminating aspects of the glacial and pluvial history of northeast-
ern Nevada from the LGM to the present. The route of this trip involves three full
days of stops separated by two nights in Elko, Nevada. The fi rst day focuses on glacial
deposits at the type locality for the LGM Angel Lake Glaciation on the eastern side of
the East Humboldt Range. The second day explores the geomorphic record of pluvial
Lakes Franklin and Clover on the east side of the Ruby–East Humboldt Mountains
and describes recent efforts to develop a chronology for the late Pleistocene regression
of these lakes. The fi nal day again focuses on glacial geology, starting with the type
locality of the pre-LGM Lamoille Glaciation on the west side of the Ruby Mountains,
and ending with several stops along the scenic drive up Lamoille Canyon.
INTRODUCTION 2001; Blackwelder, 1934). For instance, the Sierra Nevada, which
form the western border of the Great Basin, were extensively gla-
The Great Basin of the western United States offers tremen- ciated and were one of the fi rst locations in which cosmogenic
dous potential for exploring the response of mountain glaciers surface-exposure dating was employed to develop a moraine
and lakes to climate changes during the Last Glacial Maximum chronology (Phillips et al., 1996). At the eastern border of the
(LGM) and subsequent glacial-interglacial transition (GIT). Great Basin, a detailed chronology of latest Pleistocene glacia-
Despite the modern arid climate and hot summer temperatures, tion has been developed for the Wasatch Mountains (Madsen and
numerous mountain ranges in the region contain evidence of for- Currey, 1979; Lips et al., 2005; Laabs et al., 2007) and glacial
mer glaciers (Blackwelder, 1931; Sharp, 1938; Osborn and Bevis, records there have been used in numerical m odeling e xercises
Munroe, J.S., and Laabs, B.J.C., 2011, New investigations of Pleistocene glacial and pluvial records in northeastern Nevada, in Lee, J., and Evans, J.P., eds., Geo-
logic Field Trips to the Basin and Range, Rocky Mountains, Snake River Plain, and Terranes of the U.S. Cordillera: Geological Society of America Field Guide
21, p. 1–25, doi: 10.1130/2011.0021(01). For permission to copy, contact [email protected]. ©2011 The Geological Society of America. All rights reserved.
1
2 Munroe and Laabs
to yield paleoclimatic inferences (Plummer and Phillips, 2003; three full days of stops separated by two nights in Elko, Nevada
Laabs et al., 2006). Yet in contrast to these well-s tudied ranges (Fig. 1). Latitude and longitude coordinates are given for each
at the margins, little is known about the timing of late Pleisto- stop (WGS-84) in the following descriptions as an aid to future
cene glacier fl uctuations in the interior ranges of the Great Basin, users of this guide. The fi rst day of the trip focuses on glacial
an area covering more than 500,000 km2. The largest glaciers deposits at the type locality for the LGM Angel Lake Glaciation
between the Wasatch and Sierra Nevada were located in the East on the eastern side of the East Humboldt Range. From Logan, we
Humboldt and Ruby Mountains of northeastern Nevada where will drive west across the Bonneville Basin in northwestern Utah
moraines document the LGM and multiple glacial stillstands dur- into Nevada. After reaching I-80, we will continue west over
ing the last GIT (Laabs and Munroe, 2008). Indeed, the last glaci- Pequop Summit, across the Independence Valley, and over Moor
ation in the Great Basin was designated the “Angel Lake Glacia- Summit to the town of Wells. Exiting the highway at Wells, we
tion” after well-preserved glacial deposits in the East Humboldt will follow a winding road up to the valley of Angel Creek and
Range (Sharp, 1938). Three pluvial lakes were also present near spend the afternoon visiting three closely spaced stops (Fig. 2).
the East Humboldt and Ruby Mountains during the Angel Lake After a night in Elko, Nevada, the second day of the trip
Glaciation: Lakes Franklin, Clover, and Waring. Although these explores the geomorphic record of pluvial Lakes Franklin and
lakes were small compared with the better-known Lakes Lahon- Clover on the east side of the Ruby–East Humboldt Mountains
tan and Bonneville, their deposits are easily recognized and (Fig. 2). The Franklin Valley is home to the Ruby Lake National
mapped, allowing their former extents to be delineated (Reheis, Wildlife Refuge, and we will start our day with an overview of
1999). The combination of well-d istributed alpine moraine the Refuge provided by staff of the U.S. Fish and Wildlife Ser-
records and pluvial lake deposits offers an unparalleled oppor- vice. We will then work our way northward from the southern
tunity to develop a more precise understanding of temperature end of the Franklin Valley, stopping to examine localities where
and precipitation changes during the latest Pleistocene and into the late Pleistocene highstand and other water planes are well
the Holocene. expressed. We will also discuss new geochronologic constraints
on some of these deposits. In mid-afternoon, we will exit the
TRIP OVERVIEW north end of the former Lake Franklin basin and cross the divide
to the Clover Valley that hosted pluvial Lake Clover during the
This fi eld trip provides an overview of recent and ongoing late Pleistocene. Our two fi nal stops will provide an overview
work illuminating aspects of the glacial and pluvial history of of the Lake Clover geomorphic record, including a spectacular
northeastern Nevada from the Last Glacial Maximum (MIS-2, series of beach ridges that have been dated by optically stimu-
ca. 22–18 ka B.P.) to the present. The route of this trip involves lated luminescence (OSL) and 14C.
Figure 1. Route of the fi eld trip from Logan, Utah (UT), to northeast Nevada (NV). F—Lake Franklin; C—Lake Clover; W—Lake
Waring. Lower right inset shows location of fi gure in western United States. Shaded box outlines the location of Figure 2.
Pleistocene glacial and pluvial records in northeastern Nevada 3
The fi nal day will again focus on glacial geology, starting PHYSICAL SETTING
with the type locality of the pre-LGM Lamoille Glaciation on the
west side of the Ruby Mountains (Fig. 2). Deposits at the mouth Northeastern Nevada is the heart of the Great Basin and fea-
of Lamoille Canyon have been assumed to represent an advance tures classic Basin and Range topography. The relative lowland of
during MIS-6, and we will discuss efforts to date these landforms the Bonneville Basin, formerly inundated by pluvial Lake Bonn-
with cosmogenic 10Be surface-exposure dating. We will also eville, ends abruptly at the Utah-Nevada state line, where the
hike southward along the range front to Seitz Canyon to visit a landscape takes on an increasingly corrugated appearance moving
spectacularly preserved series of Lamoille and Angel Lake–age westward from the border. Long, linear valleys separated by rug-
moraines that have been the focus of a concerted 10Be dating ged north-south–oriented mountain ranges characterize the area of
effort. Our fi nal stops will be along the scenic drive up Lamoille this fi eld trip. Moving westward from the state line along I-80, one
Canyon, a deep U-shaped valley considered the “Yosemite of sequentially crosses the Toano Range at Silverzone Pass (1815
Nevada.” We will discuss the geomorphology of the valley, the m), the Goshute Valley formerly occupied by pluvial Lake War-
distribution of glacial deposits within it, and efforts to identify the ing, the Pequop Mountains at Pequop Summit (2124 m), the Inde-
moraine from the LGM (i.e., the Angel Lake equivalent moraine pendence Valley, Moor Summit (1882 m), and the Clover Valley
in Lamoille Canyon). After lunch at the head of Lamoille Can- before arriving at the highest mountains in the region, the Ruby–
yon, we will drive northward along the western slope of the East Humboldt Range. These mountains extend for ~130 km
Ruby–East Humboldt Mountains to reach I-80 and retrace our with an orientation of north-northeast to south-southwest. Summit
route back to Logan. elevations range up to 3471 m at Ruby Dome.
Figure 2. Detail map of fi eld trip stops. Dotted line shows alternate route over Harrison Pass on Day 2. See text
for details.