Factors controlling the oxygen isotopic composition of lacustrine authigenic carbonates in Western China: implications for paleoclimate reconstructions.

ABSTRACT: In the carbonate-water system, at equilibrium, the oxygen isotopic composition of carbonate is dependent not only on the temperature but also on the isotopic composition of host water in which the carbonate is formed. In this study, lake surface sediment and water samples were collected from 33 terminal lakes in Western China to evaluate controls on the oxygen isotopic composition of lacustrine authigenic carbonates (?¹⁸O_carb) and its spatial distribution. Our results show that water oxygen isotopic composition (?¹⁸O_water) rather than lake summer water temperature (T_water), is the main determinant of ?¹⁸O_carb, irrespective of whether oxygen isotope equilibrium is achieved. There are significant linear correlations between ?¹⁸O_carb and elevation, as well as that between ?¹⁸O_carb and latitude for lakes located on the Tibetan Plateau. In Western China, the spatial distribution of ?¹⁸O_carb is consistent with that of ?¹⁸O_water, and is ultimately controlled by the isotopic composition of local precipitation (?¹⁸O_{precipitation}) that depends on the source of water vapor. Therefore, changes in ?¹⁸O_carb can be predominantly interpreted as variations of ?¹⁸O_water, which in turn represent changes in ?¹⁸O_{precipitation} for paleoclimate reconstructions in this region, and may be relevant to studies of other areas.

SUBMITTER: Li H 

PROVIDER: S-EPMC7529879 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature