Abstract
Branched GDGTs in soils taken from the watershed of Lake Biwa and in sediment core (BIW07-6) retrieved from the lake were analyzed. The dependency of CBT and MBT on pH and mean annual air temperature (MAAT) in our sample set is different from that in global set of soil samples. This difference suggests that some local factor(s) is(are) crucial in the relationship between MBT/CBT and pH/MAAT. The branched GDGT distributions of the surface sediment of BIW07-6 were remarkably different from those of soils, which suggests that branched GDGTs of the sediment were not derived from the watershed soils, but were most likely produced in the lake. CBT-pH supports that branched GDGTs in the sediment were produced in the bottom water and/or the sediment. The variation of estimated paleotemperatures in core BIW07-06 is in harmony with pollen records in nearby cores, suggesting that MBT/CBT index is useful for paleotemperature estimate.
