T51 Lakes Past, Present, and Future—Archives of Climate Variability, Paleoenvironment, Geohazards, and Economic Resources II

Sunday, 9 October 2022
1:30 PM - 5:30 PM
607

CLIMATIC AND ENVIRONMENTAL FACTORS GOVERNING ALKENONE DISTRIBUTIONS AND UNSATURATION INDICES IN LACUSTRINE SEDIMENTS

Paper number: T51-13
Program: Technical Sessions
Time: 4:20 PM – 4:35 PM

Authors

Abstract

Sedimentary alkenones reflect survival of intact biosynthetic products derived from a few haptophyte species defined as three phylotypes, Groups I, II, and III, that are associated with freshwater environments, saline or alkaline settings, and marine systems, respectively [1]. Subclades of Group II haptophytes have also been proposed [2], while both the timing of divergence of phylotypes I, II, and III are poorly defined [1,2,3]. Complexities in the origins of lacustrine alkenones parallel the proliferation of reports affirming their prevalence in diverse lake environments and expanding their geographical range, predominantly in the northern hemisphere [4]. The capability of alkenone unsaturation indices to record lake temperatures has also been proven, albeit typically restricted to localized settings [5]. However, alkenone distributions can also reflect temporal changes in contributions from Group I versus Group II phylotypes associated with fluctuations in salinity [6]. They may also derive from a Group II subclade favored during warmer seasons that doesn’t produce alkatetraenones [7]. Thus, alkenone compositions in lacustrine sediments can record fluctuations in haptophyte populations associated with changes in salinity or alkalinity rather than temperature [8], which may govern stratigraphic variations in unsaturation indices for lakes experiencing climatic shifts from warm/dry to cold/wet conditions [9]. A global compilation of alkenones in lake sediments [4] reveals expansive ranges for unsaturation indices in saline/alkaline systems from arid regions, likely reflecting variations in strains of alkenone-producing haptophytes in response to hydrological changes associated with alternating wetter/drier cycles driven by climate.

[1] Theroux et al. (2010) doi:10.1002/lno.11311; [2] Wang et al. (2021) doi:10.1038/s41467-020-20187-z; [3] Richter et al. (2019) doi:10.1111/gbi.12330; [4] Brassell et al. (2022) doi:10.1016/j.orggeochem.2022.104437; [5] Toney et al. (2010) doi:10.1016/j.gca.2009.11.021; [6] Liu et al. (2008) doi:10.1016/j.gca.2007.11.016; [7] Yao et al. (2022) doi:10.1016/j.gca.2021.11.001; [8] Randlett et al. (2014) doi:10.1002/2016GC006621; [9] He et al. (2021) doi:10.1016/j.apgeochem.2021.105105

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-379161

© Copyright 2022 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.