Early Pleistocene climate in western arid central Asia inferred from loess-palaeosol sequences.

Xin Wang,Mehdi Taheri,Fahu Chen,Farhad Khormali,Guzel Danukalova,Haitao Wei

doi:10.1038/srep20560

Abstract

Arid central Asia (ACA) is one of the most arid regions in the mid-latitudes and one of the main potential dust sources for the northern hemisphere. The lack of in situ early Pleistocene loess/dust records from ACA hinders our comprehensive understanding of the spatio-temporal record of aeolian loess accumulation and long term climatic changes in Asia as a whole. Here, we report the results of sedimentological, chronological and climatic studies of early Pleistocene loess-palaeosol sequences (LPS) from the northeastern Iranian Golestan Province (NIGP) in the western part of ACA. Our results reveal that: 1) Accumulation of loess on the NIGP commenced at ~2.4–1.8 Ma, making it the oldest loess known so far in western ACA; 2) the climate during the early Pleistocene in the NIGP was semi-arid, but wetter, warmer, and less windy than during the late Pleistocene and present interglacial; 3) orbital-scale palaeoclimatic changes in ACA during the early Pleistoceneare in-phase with those of monsoonal Asia, a relationship which was probably related to the growth and decay of northern hemisphere ice sheets.

Highlights

Occurred during glacials, and warmer and wetter climates during interglacials, in monsoonal Asia during the Pleistocene[10,12,16], and that this relationship was triggered mainly by the Northern Hemisphere glaciations via their impact on the EASM10,17,18
The work carried out so far raises the following questions: Are there any older loess deposits in ACA than have heretofore been discovered? What is the spatial distribution of the lower Pleistocene loess in ACA? What are the characteristics of the early Pleistocene climate in ACA and how they did they vary on an orbital time scale? What is the relationship of climatic changes in the region during the Pleistocene with those of monsoonal Asia?
Sedimentological evidence confirms that the widespread red-coloured sediments underlying the upper Pleistocene loess in the NIGP are aeolian in origin

Summary

Introduction

Occurred during glacials, and warmer and wetter climates during interglacials, in monsoonal Asia during the Pleistocene[10,12,16], and that this relationship was triggered mainly by the Northern Hemisphere glaciations via their impact on the EASM10,17,18. The relationship between loess accumulation and long-term climatic history in ACA remains unclear, largely due to the lack of known LPS in this remote region. Most loess records reported from ACA cover a time span from the middle-late Pleistocene to the present[20,21,22,23,24]. What is the spatial distribution of the lower Pleistocene loess in ACA? What is the relationship of climatic changes in the region during the Pleistocene with those of monsoonal Asia?. We attempt to address these questions via an analysis of the stratigraphy, origin, chronology, and palaeoclimatic proxies of the red-coloured sediments underlying middle-to-upper Pleistocene loess successions in the NIGP (Fig. 1b) (see SI text for more detailed information on the geological setting)

Methods

Results

Conclusion