Publication Date

2017-12-15

Availability

Embargoed

Embargo Period

2019-12-15

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Marine Geology and Geophysics (Marine)

Date of Defense

2016-12-08

First Committee Member

Ali Pourmand

Second Committee Member

Larrt C. Peterson

Third Committee Member

Elizabeth A. Canuel

Fourth Committee Member

Peter K. Swart

Fifth Committee Member

Amy C. Clemen

Abstract

The regional climate over West Asia, extending between Iran and the Arabian Peninsula to the eastern Mediterranean Sea, is governed by interactions between three major synoptic systems; mid-latitude Westerlies, the Siberian Anticyclone and the Indian Ocean Summer Monsoon. In recent years, a number of paleoclimate studies have drawn potential links between episodes of abrupt climate change during the Holocene, and the rise and fall of human civilizations across the “Fertile Crescent” (also known as the Cradle of Civilization) of West Asia. The paucity of high-resolution palaeoclimate data from the “Cradle of Civilization” in West Asia, however, has limited our ability to evaluate the potential role of Holocene climate variability on early societies. The current research is the first study which presents a high-resolution, multi-proxy reconstruction of aeolian input and palaeoenvironmental conditions based on records of ombrotrophic (rain fed) peat and from Neor Lake and sediment record from hypersaline Urmia Lake in Northwest Iran. Multi-proxy record from Neor peat record suggest dry and dusty conditions prevailed during the Younger Dryas, and a substantial increase in atmospheric dust loading and decrease in moisture availability occurred between the early and late Holocene. This result further supported by palaeohydrological reconstructions and multi-proxy record from Urmia Lake, which suggest wet condition prevailed during the early Holocene and drier condition with increased aeolian input was dominated during mid- to late Holocene. Variations in radiogenic Sr-Nd-Hf isotopic composition and REE anomalies in samples from Neor peat core indicate dust particles deposited during the low-flux, early Holocene period (11,700-6,000 yr BP) is distinctly different from times of high dust fluxes during the Younger Dryas and the mid-late Holocene (6,000-present). This indicates that the composition of mineral dust deposited at the study site changed as a function of prevailing atmospheric circulation regimes and land exposure. Simulations of atmospheric circulation over the region show the Northern Hemisphere Summer Westerly Jet was displaced poleward across the study area during the early Holocene when solar insolation was higher. This shift, coupled with lower dust emissions simulated based on greening of the Afro-Asian Dust Belt during the early Holocene likely led to potential sources in Central Asia dominating dust export to West Asia during this period, in contrast to the dominant western and southwest Asian and Eastern African sources that prevail during the modern period. Time-series analysis of aeolian input to NE Iran reveals periodicities that correspond with solar variability and internal climate feedbacks identified in other records of Holocene climate change from the northern hemisphere. Paleoclimate reconstructions from Neor and Lake Urmia suggest an atmospheric teleconnection existed between North Atlantic climate and West Asia during the last glacial termination and the Holocene. Transitions in major Mesopotamian and Persian civilizations, including the collapse of the Akkadian empire, the fall of the Ur III Empire, the fall of Elam Empire and the demise of the Achaemenids overlap with major climate events from this study.

Keywords

Holocene Climate; West Asia; Iran; Urmia Lake; Dust Sr-Hf-Nd isotopes; Peat; Paleoclimate

Available for download on Sunday, December 15, 2019

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