Late Pleistocene to early Holocene lake level and paleoclimate insights from Stansbury Island, Bonneville basin, Utah

a r t i c l e i n f o Keywords: Great Basin Lake Bonneville Great Salt Lake Stansbury Island Stansbury shoreline Stansbury oscillation Stansbury Gulch Paleolake chronology Paleoclimate Multiple proxy This paper reports on recent multiproxy research conducted to determine the chronology of lake-level fluctuations recorded in sediments from a natural exposure at a classic Bonneville basin site. Grain size, carbonate percentage, magnetic susceptibility, amount of charcoal, and diatom community composition data were collected from the 16 lacustrine units that compose the 122 cm stratigraphic column in Stansbury Gulch. Trends observed in the measured proxies reveal several significant changes in lake level, and thereby effective moisture, over the approximately 14,500 yr time span represented by the sediments. Results (1) verify the effectiveness of the multiproxy approach in Bonneville basin studies, which has been underutilized in this region, (2) reaffirm the double nature of Lake Bonneville's Stansbury oscillation, (3) suggest a previously undocumented post-Gilbert highstand of Great Salt Lake, and (4) identify possible teleconnec-tions between climate events in the Bonneville basin and events in the North Atlantic at about 20,500 and 7500 14 C yr BP. The Bonneville lake basin of northwestern Utah, northeastern Nevada, and southeastern Idaho has been recognized as an important source of paleoenvironmental data for more than 135 yr because of widespread sedimentary and geomorphic evidence of late Pleistocene Lake Bonneville and its Holocene successor, Great Salt Lake (Sack, 1989) (Fig. 1). With a maximum depth of 372 m and area of 50,000 km 2 (Gilbert, 1890), Lake Bonneville was the largest of the scores of paleolakes that existed and fluctuated in subbasins of the Great Basin from about 30,000 to 12,000 14 C yr BP. Because it was a closed-basin lake for most of its existence, Lake Bonneville responded sensitively to climate change through oscillations in water level and area, as has A thorough understanding of the record of climate change stored in the sediments of Lake Bonneville and Great Salt Lake is essential for accurately reconstructing the regional paleoenvironment and for predicting how Great Salt Lake and other large, climatically sensitive lake systems will be affected by future climate change. The general chronology of Lake Bonneville and Great Salt Lake is well established (Fig. 2). According to previous work, Lake Bonneville originated sometime after 30,000 14 C yr BP (Oviatt et al., 1992). 14 C yr BP it underwent its protracted, transgressive phase, …