Holocene moisture variations in western arid central Asia inferred from loess records from NE Iran

Holocene variations in precipitation in central and eastern arid central Asia (ACA) have been widelyinvestigated, but the pattern in western ACA remains unclear. We present records of the stable carbonisotope composition of bulk organic matter (δ۱۳Corg), magnetic parameters, and sediment color, from fiveloess-paleosol sequences in NE Iran, in western ACA, with the aim of reconstructing Holoceneprecipitation. The Yellibadragh (YE) section (the thickest among the five sequences) was selected for OSLdating of the coarse-grained quartz (۶۳-۹۰ μm) fraction, and its δ۱۳Corg record was used to quantitativelyreconstruct mean annual precipitation (MAP). The record indicates a dry early Holocene (~۱۱.۸-۷.۴ ka),with nearly constant MAP (~۹۳ mm), followed by a wetting trend from the mid-Holocene (~۷.۴ ka)onwards, with the wettest period in the late Holocene (~۴.۰-۰.۰ ka, ~۳۹۰ mm). The stratigraphicobservations and environmental proxies support the reconstruction. The other loess profiles showstratigraphic features and trends of environmental proxies which are similar to those of the YE profile. Adry early Holocene and wetting trend since the mid-Holocene, with the wettest climate in the late Holocenein NE Iran, are both consistent with records from sand dunes and lake sediments from adjacent areas, andwith loess records from central and eastern ACA. Comparison with loess records from monsoonal Asiasupports the interpretation of a “westerlies-dominated climatic regime” (WDCR) which was proposedmainly on the basis of lake sediment records from the region. Changes in solar insolation may have beenresponsible for the persistent wetting trend during the Holocene in western ACA.

Keywords:

Iranian loess-paleosol sequence , Holocene , Precipitation trend , western ACA