Paleoclimate reconstruction from lake sediments in central and eastern Iran
Final Report Abstract
Within this one-year study a coring campaign was conducted to the Sistan Oasis, East Iran, at the boundary to Afghanistan. The ephemeral Hamoun (Lake) Pouzak was cored and a number of water samples from the deltaic branches of the River Helmand, various irrigation channels, wells, natural springs, and artificial water reservoirs were collected. Because of a general absence of datable organic and shell material the radiocarbon chronology is based on determination of the sedimentation rate using bulk carbonate samples – with only two exceptions. The obtained sedimentation rate from bulk-carbonate samples, however, fits the rate suggested by the only two non-bulk samples. This confirms a continuous sedimentation sequence over the last 13 000 years. Abrupt changes in sedimentary Ca and K content – as determined by XRF scanning – were observed for two time intervals at ~ 4000 years ago and ~ 1500 years ago. The early Holocene interval appears to have been drought dominated, in agreement with the paleolimnologic record in Western Iran. The accuracy of the chronology is currently insufficiently constrained, however, and does not allow the precise comparison of climatic events with the regional database available. As such, the observed 4000 BP drought only tentatively suggests a climatic reason for the abandonment of the early Bronze Age city of Sharh-e-Souhkteh at that time. An additional but unexpected result was obtained in the field of stable isotope hydrology, where we were able to systematically describe the evaporative evolution of 17-O-excess in residual water bodies in dependence of relative air humidity for the first time.
Publications
- 17-O-excess in evaporated desert waters and vapor from evaporation experiments. Abstract H14-1464, 2013 Fall Meeting, AGU, San Francisco, Calif., 9-13 Dec.
Surma J., Assonov S.S., Staubwasser M.
