Biogenic Silica Measurements in Cores Collected from Bear Lake, Utah and Idaho

The overall goal of our research on Bear Lake is to create records of past
climate change for the region, including changes in precipitation (rain and
snow) patterns during the last 10,000 years and longer. As part of the project,
we are attempting to determine how the size of Bear Lake has varied in the past
in order to assess the possibility of future flooding and drought. We also seek
to understand human influences on sediment deposition, chemistry, and life in
the lake.

Evidence of past conditions comes from sediments deposited in the lake, so
reconstructions of past conditions require accurate dating of the sediments.
The study includes the upper Bear River watershed as well as Bear Lake. The
Bear River is the largest river in the Great Basin and the source of the
majority of water flowing into the Great Salt Lake. In this region, wet periods
may produce flooding along the course of the Bear River and around Great Salt
Lake, while dry periods, or droughts, may affect water availability for
ecosystems, as well as for agricultural, industrial, and residential use.

Diatoms are one of the most sensitive indicators of environments in many lakes.
In addition to species compositions and abundances (Moser and Kimball, 2005),
total diatom productivity commonly varies considerably with changes in
limnological conditions. Biogenic silica preserved in sediments is an index of
total diatom productivity and, thus, is an indirect proxy for paleolimnology
(for example, Colman and others, 1995; Johnson and others, 2001). In this
paper, we present the results of biogenic silica analyses of two cores taken in
Bear Lake, Utah, and discuss preliminary paleolimnologic conclusions based on
these data.

[Summary provided by the USGS.]