Palynological evidence for vegetation cycles in a 1.5 million year pollen record from the Great Salt Lake, Utah, USA

Pollen analysis of the mid-lake Indian Cove well in the Great Salt Lake, collected by Amoco Production Co., provides a 1.5 Ma record of climatic change, correlative with the deep-sea oxygen isotope record. Chronologic control for Indian Cove is provided by the Lava Creek B (0.60 Ma), Bishop (0.76 Ma), and Huckleberry Ridge (2.06 Ma) volcanic ashes. The processing of close-interval (3 m, ca. 8 ka) samples is complete for the upper 628 m (1.5 Ma) of the Indian Cove well. During the last 750 ka, interglacial-glacial cycles are expressed as the ratio of Juniperus + Ambrosia + Sarcobatus (interglacial) vs. Picea, Abies, and Pseudotsuga (glacial). Correlating the peak abundances of this ratio with the odd-numbered oxygen isotope stages has refined the time control provided by three volcanic tephra. The average Pleistocene sedimentation rate is 0.39 m ka(-1) (Huckleberry Ridge. 2057 ka, 797 m). Based on the refined time scale, resulting from correlation with the marine chronology, sedimentation reached maximum values during isotope stages 11-9, and was slow between stages 13 and 11 and stages 9-7. Development of the Bonneville Pluvial cycles, from 759 to 600 ka, is recorded by changes in wetland and aquatic palynomorphs. Increased pollen concentration above 150 m (310 ka) may result from the diversion of the Bear River into the Great Salt Lake Basin. (C) 1998 Elsevier Science B.V.