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

David P. Bouchard, Darrell S Kaufman, Amy Hochberg, Jay Quade

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

The Bear River, the largest river in the Great Basin, was diverted from its former course to the Pacific Ocean into the Bonneville Basin by Quaternary basalt flows that form the northern rim of Thatcher Basin, Idaho. Reconstructing the history of the river's diversion is important to understanding the aquatic biogeography of the Bonneville Basin and the climatological implications of its lake-level fluctuations. This study employs strontium (Sr) isotopes in lacustrine mollusc fossils as a tracer of Bear River water that entered Lake Thatcher, a small lake into which the redirected river flowed en route to the Bonneville Basin. The 87Sr/86Sr composition and Sr concentration of modem rivers were measured to construct a mixing model for Lake Thatcher water. The low 87Sr/86Sr ratio of the Bear River and its large discharge assures that the presence or absence of its flow into Lake Thatcher is readily detectable. Temporal control is provided by amino acid geochronology on lacustrine molluscs and calibrated using tephrochronology and 14C dating. 87Sr/86Sr ratios of six fossil molluscs from the oldest exposed Quaternary deposits in Thatcher Basin (lower Main Canyon Formation, MCF) indicate that, during the early Quaternary (>620 ka), the basin was occupied by shallow, locally fed lakes. A single shell from the base of the upper MCF, together with sedimentological evidence, suggests that the Bear River may have been diverted into Thatcher Basin by ~140 ka. 87Sr/86Sr ratios in eight younger shells from the upper MCF indicate that the Bear River was not present in the basin between ~140 and ~80 ka. By 50 ± 10 ka, however, it was tributary to Lake Thatcher. A simple hydrologic model shows that, if not for drainage through Oneida Narrows, Thatcher Basin would fill to its highest shoreline under present climate, even without the input of the Bear River. It is not clear when the lava flows that form the northern divide had been built high enough to allow Lake Thatcher to spill over its former southern divide into the Bonneville Basin, but it was probably by ~100 ka. At that time, headward incision of Oneida Narrows was underway. By ~20 ka, the incision of the narrows was complete and Lake Bonneville had backed up into Thatcher Basin.

Original languageEnglish (US)
Pages (from-to)95-114
Number of pages20
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume141
Issue number1-2
DOIs
StatePublished - Aug 1998
Externally publishedYes

Fingerprint

Ursidae
bear
amino acid composition
fossils
amino acid
fossil
basins
rivers
history
basin
river
lakes
lake
canyons
mollusc
canyon
molluscs
shell (molluscs)
strontium
lava

Keywords

  • Amino acid
  • Geochronology
  • Lake Bonneville
  • Pluvial lake
  • Sr isotopes

ASJC Scopus subject areas

  • Palaeontology

Cite this

@article{307b1ece70d343cb9075af6c6d8f523b,
title = "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",
abstract = "The Bear River, the largest river in the Great Basin, was diverted from its former course to the Pacific Ocean into the Bonneville Basin by Quaternary basalt flows that form the northern rim of Thatcher Basin, Idaho. Reconstructing the history of the river's diversion is important to understanding the aquatic biogeography of the Bonneville Basin and the climatological implications of its lake-level fluctuations. This study employs strontium (Sr) isotopes in lacustrine mollusc fossils as a tracer of Bear River water that entered Lake Thatcher, a small lake into which the redirected river flowed en route to the Bonneville Basin. The 87Sr/86Sr composition and Sr concentration of modem rivers were measured to construct a mixing model for Lake Thatcher water. The low 87Sr/86Sr ratio of the Bear River and its large discharge assures that the presence or absence of its flow into Lake Thatcher is readily detectable. Temporal control is provided by amino acid geochronology on lacustrine molluscs and calibrated using tephrochronology and 14C dating. 87Sr/86Sr ratios of six fossil molluscs from the oldest exposed Quaternary deposits in Thatcher Basin (lower Main Canyon Formation, MCF) indicate that, during the early Quaternary (>620 ka), the basin was occupied by shallow, locally fed lakes. A single shell from the base of the upper MCF, together with sedimentological evidence, suggests that the Bear River may have been diverted into Thatcher Basin by ~140 ka. 87Sr/86Sr ratios in eight younger shells from the upper MCF indicate that the Bear River was not present in the basin between ~140 and ~80 ka. By 50 ± 10 ka, however, it was tributary to Lake Thatcher. A simple hydrologic model shows that, if not for drainage through Oneida Narrows, Thatcher Basin would fill to its highest shoreline under present climate, even without the input of the Bear River. It is not clear when the lava flows that form the northern divide had been built high enough to allow Lake Thatcher to spill over its former southern divide into the Bonneville Basin, but it was probably by ~100 ka. At that time, headward incision of Oneida Narrows was underway. By ~20 ka, the incision of the narrows was complete and Lake Bonneville had backed up into Thatcher Basin.",
keywords = "Amino acid, Geochronology, Lake Bonneville, Pluvial lake, Sr isotopes",
author = "Bouchard, {David P.} and Kaufman, {Darrell S} and Amy Hochberg and Jay Quade",
year = "1998",
month = "8",
doi = "10.1016/S0031-0182(98)00005-4",
language = "English (US)",
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TY - JOUR

T1 - Quaternary history of the Thatcher Basin, Idaho, reconstructed from the 87Sr/86Sr and amino acid composition of lacustrine fossils

T2 - Implications for the diversion of the Bear River into the Bonneville Basin

AU - Bouchard, David P.

AU - Kaufman, Darrell S

AU - Hochberg, Amy

AU - Quade, Jay

PY - 1998/8

Y1 - 1998/8

N2 - The Bear River, the largest river in the Great Basin, was diverted from its former course to the Pacific Ocean into the Bonneville Basin by Quaternary basalt flows that form the northern rim of Thatcher Basin, Idaho. Reconstructing the history of the river's diversion is important to understanding the aquatic biogeography of the Bonneville Basin and the climatological implications of its lake-level fluctuations. This study employs strontium (Sr) isotopes in lacustrine mollusc fossils as a tracer of Bear River water that entered Lake Thatcher, a small lake into which the redirected river flowed en route to the Bonneville Basin. The 87Sr/86Sr composition and Sr concentration of modem rivers were measured to construct a mixing model for Lake Thatcher water. The low 87Sr/86Sr ratio of the Bear River and its large discharge assures that the presence or absence of its flow into Lake Thatcher is readily detectable. Temporal control is provided by amino acid geochronology on lacustrine molluscs and calibrated using tephrochronology and 14C dating. 87Sr/86Sr ratios of six fossil molluscs from the oldest exposed Quaternary deposits in Thatcher Basin (lower Main Canyon Formation, MCF) indicate that, during the early Quaternary (>620 ka), the basin was occupied by shallow, locally fed lakes. A single shell from the base of the upper MCF, together with sedimentological evidence, suggests that the Bear River may have been diverted into Thatcher Basin by ~140 ka. 87Sr/86Sr ratios in eight younger shells from the upper MCF indicate that the Bear River was not present in the basin between ~140 and ~80 ka. By 50 ± 10 ka, however, it was tributary to Lake Thatcher. A simple hydrologic model shows that, if not for drainage through Oneida Narrows, Thatcher Basin would fill to its highest shoreline under present climate, even without the input of the Bear River. It is not clear when the lava flows that form the northern divide had been built high enough to allow Lake Thatcher to spill over its former southern divide into the Bonneville Basin, but it was probably by ~100 ka. At that time, headward incision of Oneida Narrows was underway. By ~20 ka, the incision of the narrows was complete and Lake Bonneville had backed up into Thatcher Basin.

AB - The Bear River, the largest river in the Great Basin, was diverted from its former course to the Pacific Ocean into the Bonneville Basin by Quaternary basalt flows that form the northern rim of Thatcher Basin, Idaho. Reconstructing the history of the river's diversion is important to understanding the aquatic biogeography of the Bonneville Basin and the climatological implications of its lake-level fluctuations. This study employs strontium (Sr) isotopes in lacustrine mollusc fossils as a tracer of Bear River water that entered Lake Thatcher, a small lake into which the redirected river flowed en route to the Bonneville Basin. The 87Sr/86Sr composition and Sr concentration of modem rivers were measured to construct a mixing model for Lake Thatcher water. The low 87Sr/86Sr ratio of the Bear River and its large discharge assures that the presence or absence of its flow into Lake Thatcher is readily detectable. Temporal control is provided by amino acid geochronology on lacustrine molluscs and calibrated using tephrochronology and 14C dating. 87Sr/86Sr ratios of six fossil molluscs from the oldest exposed Quaternary deposits in Thatcher Basin (lower Main Canyon Formation, MCF) indicate that, during the early Quaternary (>620 ka), the basin was occupied by shallow, locally fed lakes. A single shell from the base of the upper MCF, together with sedimentological evidence, suggests that the Bear River may have been diverted into Thatcher Basin by ~140 ka. 87Sr/86Sr ratios in eight younger shells from the upper MCF indicate that the Bear River was not present in the basin between ~140 and ~80 ka. By 50 ± 10 ka, however, it was tributary to Lake Thatcher. A simple hydrologic model shows that, if not for drainage through Oneida Narrows, Thatcher Basin would fill to its highest shoreline under present climate, even without the input of the Bear River. It is not clear when the lava flows that form the northern divide had been built high enough to allow Lake Thatcher to spill over its former southern divide into the Bonneville Basin, but it was probably by ~100 ka. At that time, headward incision of Oneida Narrows was underway. By ~20 ka, the incision of the narrows was complete and Lake Bonneville had backed up into Thatcher Basin.

KW - Amino acid

KW - Geochronology

KW - Lake Bonneville

KW - Pluvial lake

KW - Sr isotopes

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