Lateglacial and Holocene variation in aeolian sediment flux over the northeastern Tibetan Plateau recorded by laminated sediments of a saline meromictic lake

The dD of closed-basin tropical lakes such as Wandakara reflects the hydrologic balance of the lake, with drier conditions causing isotopically enriched lake water due to both the amount effect on precipitation and kinetic fractionation during evaporation from the lake surface, which favors the retention of deuterium relative to hydrogen in the lake water (Craig, 1961).

Short-chain (C16?C18) fatty acids in lake sediments are derived primarily from aquatic sources (Eglinton and Hamilton, 1967; Huang et al., 2002), and the principal control on their ?D is the ?D of lake water (Huang et al., 2002, 2004). ... "The ?D of closed-basin tropical lakes such as Wandakara reflects the hydrologic balance of the lake, with drier conditions causing isotopically enriched lake water due to both the amount effect on precipitation and kinetic fractionation during evaporation from the lake surface, which favors the retention of deuterium relative to hydrogen in the lake water (Craig, 1961). "

The shift toward grassland at AD 1000 must therefore have influenced the ?DC30 record due to biosynthetic fractionation differences between trees and grasses (Hou et al., 2007). Indeed, the enormous amplitude of shifts in ?DC30 relative to ?DC16 likely results from the replacement of forest with C4 grasslands during wet periods?a process driven by humans rather than by climate. The amplified ?DC30 response occurs because of a combination of the amount effect during wet periods and stronger isotopic fractionation by grasses relative to trees, both of which favor isotopically depleted ?DC30 (Hou et al., 2008).

The ?D of long-chain, terrestrially derived fatty acids is controlled by the ?D of the water used by plants, transpiration from leaf surfaces, and kinetic fractionation during biosynthesis (Hou et al., 2008; Sessions et al., 1999).  ... "Thus, although the first-order control on leaf wax ?D in the tropics is the ?D of meteoric waters, interactions between climate and vegetation suggest the potential for complex, non-linear responses of leaf wax ?D to rainfall variability."