Distribution of Glycerol Dialkyl Glycerol Tetraethers (GDGTs) in Carbonate-Type and Sulfate-Type Lacustrine Sediments: Insight into the Influence of Ionic Composition on GDGTs

Abstract

The distribution of glycerol dialkyl glycerol tetraethers (GDGTs) in carbonate-type and sulfate-type saline lacustrine sediments from the Ordos Plateau in China is investigated to explore the influence of ionic composition on GDGTs. In general, they are relatively small (1.2–6.0 km2 surface area) and shallow ponds (0.05–0.2 m water depth) and even seasonally dry lakes. The results reveal that the concentration of GDGTs has a good positive correlation with the (nCO32− + nHCO3−)/total ions, and the concentration of GDGTs in carbonate-type lake sediments is significantly higher than that in sulfate-type lake sediments. Most GDGT-based indices show no significant differences, and the distributions of GDGTs are similar in the two types of saline lake sediments. The lack of a positive correlation between the content of clay minerals and the concentration of GDGTs may imply that the ability of clay minerals to carry terrigenous organic matter is very limited in arid climates. The branched GDGTS (brGDGTs) in the two saline lake sediments may mainly come from in situ biological production and have low terrestrial inputs. The different weathering level of feldspar minerals in the two types of saline lakes results in the difference in organic matter content, which ultimately affects the concentration of GDGTs.

Keywords

• carbonate-type saline lake
• sulfate-type saline lake
• ionic composition
• GDGTs
• reconstructed temperature