Late cenozoic lacustrine and climatic environments at Tule Lake, northern Great Basin, USA
- Geological Survey, Denver, CO (United States)
Cores of lake sediment to a depth of 334 m in the town of Tulelake, northern California, document the late Cenozic paleolimnologic and paleoclimatic history of the northwestern Great Basin. Lacustrine diatoms are abundant throughout the record documenting a nearly continuous paleolimnologic history of the Tule Lake basin. Except for a drier (and cooler?) interval recorded by Fragilaria species about 2.4 Ma, the Pliocene is characterized by a dominance of planktonic Aulacoseira solida implying a warm monomictic lake under a climatic regime of low seasonality. Much of the Pleistocene is dominated by Stephanodiscus and Fragilaria species suggesting a cooler, drier, and highly variable climate. Benthic diatoms typical of alkaline-enriched saline waters commonly appear after 1.0 Ma, and tephrochronology indicates slow deposition and possible hiatuses between about 0.6 and 0.2 Ma. The chronology of even-numbered oxygen isotope stages approximately matches fluctuations in the abundance of Fragilaria since 800 ka indicating that glacial periods were drier environments at Tule Lake. Glacial and interglacial environments since 150 ka were distinct from, and more variable than, those occurring earlier. The last full glacial period was very dry, but shortly Tule Lake became a deep, cool lacustrine system indicating a substantial increase in precipitation. Aulacoseira ambigua characterized the latest glacial and Holocene record of Tule Lake, indicating that warmer and wetter climates began about 15 ka. Diatom concentration fluctuates at 41000 year intervals between 3.0 and 2.5 Ma and at approximately 100000 year intervals after 1.0 Ma. In the late Pliocene and early Pleistocene, Aulacoseira solida percentages wax and wane in an approximately 400000 year cycle. The possible response of Tule Lake diatom communities to orbitally-induced insolation cycles underscores the importance of this record for the study of late Cenozoic paleoclimate change. 41 refs., 8 figs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 181948
- Journal Information:
- Climate Dynamics, Journal Name: Climate Dynamics Journal Issue: 3-4 Vol. 6; ISSN 0930-7575; ISSN CLDYEM
- Country of Publication:
- United States
- Language:
- English
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