排序方式: 共有21条查询结果,搜索用时 0 毫秒
21.
William Berelson Frank Corsetti Brad Johnson Toan Vo Chris Der 《Journal of Paleolimnology》2009,42(1):25-36
Closed-basin alkaline lakes record climate change particularly well because they generally contain a sedimentary record that
is high in carbonate mineral content from which climate proxies can be determined. Various approaches are used to estimate
paleo-lake level and volume (δ18O, dating of “shoreline” tufas, biotic proxies, etc.), yet all carry certain caveats that limit their usefulness. Ultimately,
the relationship between the chemistry of the lake, the volume of the lake, and the response of the proxy will determine how
well a proxy serves a paleolimnologic purpose. Here, we discuss the use of carbonate-associated sulfate (CAS), the sulfate
contained within the lattice of carbonate minerals that precipitate in lake water, as a proxy for lake water chemistry and
by extension, lake volume. Walker Lake, an alkaline closed-basin lake in western Nevada, has experienced a well-documented
lake-level decline since 1880 and provides a test case for CAS as a lake-level proxy. By extracting the CAS from sedimentary
carbonate and tufas that have been age dated, we can relate these values to lake sulfate content based on historical or other
proxy data. We confirm that CAS tracks lake sulfate. Our study of sedimentary carbonates demonstrates that CAS is a linear
function of lake sulfate through a range of 10–25 mM, which corresponds to a change in lake level of 30 m. As confirmation
of the CAS technique, we analyzed a stromatolitic tufa dated using AMS 14C. The CAS trend in the stromatolite suggested that it grew during a lake-level decline, a result consistent with other proxy
data. Finally, laboratory experiments were conducted that demonstrate CAS is monotonically correlated with sulfate concentration
and that precipitation kinetics are not likely a major control on CAS in alkaline lakes, but that ionic strength of the solution
exerts a strong control on CAS. 相似文献