Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hart, W. S. Articles by Oviatt, C. G. Search for Related Content GeoRef GeoRef Citation

The ⁸⁷Sr/⁸⁶Sr ratios of lacustrine carbonates and lake-level history of the Bonneville paleolake system

William S. Hart¹, Jay Quade^,1, David B. Madsen^,2, Darrell S. Kaufman^,3 and Charles G. Oviatt^,4

¹ The Desert Laboratory and Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA
² Environmental Sciences, Utah Geological Survey, Salt Lake City, Utah 84114-6100, USA
³ Department of Geology, Northern Arizona University, Flagstaff, Arizona 86011-4099, USA
⁴ Department of Geology, Kansas State University, Manhattan, Kansas 66506-3201, USA

Lakes in the Bonneville basin have fluctuated dramatically in response to changes in rainfall, temperature, and drainage diversion during the Quaternary. We analyzed tufas and shells from shorelines of known ages in order to develop a relation between ⁸⁷Sr/⁸⁶Sr ratio of carbonates and lake level, which then can be used as a basis for constraining lake level from similar analyses on carbonates in cores. Carbonates from the late Quaternary shorelines yield the following average ⁸⁷Sr/⁸⁶Sr ratios: 0.71173 for the Stansbury shoreline (22–20 ¹⁴C ka; 1350 m), 0.71153 for the Bonneville shoreline (15.5–14.5 ¹⁴C ka; 1550 m), 0.71175 for the Provo shoreline (14.4–14.0 ¹⁴C ka; 1450 m), 0.71244 for the Gilbert shoreline (10.3–10.9 ¹⁴C ka; 1300 m), and 0.71469 for the modern Great Salt Lake (1280 m). These analyses show that the ⁸⁷Sr/⁸⁶Sr ratio of lacustrine carbonates changes substantially at low- to mid-lake levels but is invariant at mid- to high-lake levels.

Sr-isotope mixing models of Great Salt Lake and the Bonneville paleolake system were constructed to explain these variations in ⁸⁷Sr/⁸⁶Sr ratios with change in lake level. Our model of the Bonneville system produced a ⁸⁷Sr/⁸⁶Sr ratio of 0.71193, very close to the observed ratios from high-shoreline tufa and shell. The model verifies that the integration of the southern Sevier and Beaver rivers with the Bear and others rivers in the north is responsible for the lower ⁸⁷Sr/⁸⁶Sr ratios in Lake Bonneville compared to the modern Great Salt Lake. We also modeled the ⁸⁷Sr/⁸⁶Sr ratio of Lake Bonneville with the upper Bear River diverted into the Snake River basin and obtained an ⁸⁷Sr/⁸⁶Sr ratio of 0.71414. Coincidentally, this ratio is close to the observed ratio for Great Salt Lake of 0.71469. This means that ⁸⁷Sr/⁸⁶Sr ratios of >0.714 for carbonate can be produced by climatically induced low-lake conditions or by diversion of the upper Bear River out of the Bonneville basin. This model result also demonstrates that the upper Bear River had to be flowing into the Bonneville basin during highstands of other late Quaternary lake cycles: carbonates from the Little Valley (130–160 ka) and Cutler Dam (59 ± 5 ka) lake cycles returned ⁸⁷Sr/⁸⁶Sr ratios of 0.71166 and 0.71207, respectively, and are too low to be produced by a lake without the upper Bear River input.

Key Words: Bonneville • Pleistocene • carbonates • strontium • lake

This article has been cited by other articles:

				S. J. Davis, H. T. Mix, B. A. Wiegand, A. R. Carroll, and C. P. Chamberlain Synorogenic evolution of large-scale drainage patterns: Isotope paleohydrology of sequential Laramide basins Am J Sci, September 1, 2009; 309(7): 549 - 602. [Abstract] [Full Text] [PDF]