Since the beginning of the Neolithic Era ca. 9500 years before present (y BP), some of the first and most outstanding human civilizations rose across the Fertile Crescent, an area extending between the northern Persian Gulf and the eastern and southeastern Mediterranean Sea. Evidence is mounting from paleoclimate reconstructions that human societies have been impacted by abrupt climate change on the scale of decades to centuries throughout the Holocene, the current period of interglaciation that began ~11,700 y BP. Few high-resolution studies, however, have been conducted in the interior of West Asia that document climate variability at decadal to centennial timescales, which are most relevant to the flourishing and diminishing of human societies.
With extensive involvement and contributions from two undergradate and one graduate students, we developed high-resolution records of changes in atmospheric dust input and paleo-environmental conditions based on inorganic and organic geochemical data from two ombrotrophic (rain fed) peat mires in NW Iran that encompass the last 13000 y BP.

In the longest record from the Neor peat mire (37°57'37"N, 48°33'19"E), down-core variations in major and trace elements, organic carbon accumulation, stable carbon isotope values, organic biomarker abundances and compound-specific hydrogen isotope values for leaf wax compounds suggest that dry and dusty conditions prevailed prior to the Holocene followed by a wet and low dust period during the early Holocene (~11000-6000 y BP). In contrast, higher dust and lower moisture availability were dominant during middle to late Holocene (6000 y BP-present). Geochemical fingerprinting of dust particles with radiogenic Sr-Nd-Hf isotopic composition and rare
earth element anomalies indicated changes in the sources of dust to the study area prior to and during the Holocene. Time-series analysis of aeolian input revealed periodicities at 540, 1050 and 2940 years that correspond with solar variability and internal climate feedbacks. Transitions in major Mesopotamian and Persian civilizations, including the collapse of the Akkadian empire at 4,200 y BP, Ur III empire at 3,955 yr BP, the Elam empire at 2,500 y BP and the Achaemenids around 2,280 y BP overlap with major dust events (dryer periods) from this study.

As the Mediterranean climate of northwest Iran is influenced by mid-latitude Westerlies and the winter expansion of the Siberian Anticyclone, preservation of organic matter within the crater peat of Almalou (37°39′55″N, 46°37′55″E) recorded changes in atmospheric deposition and paleo-environmental conditions during the last 2400 years. We studied a high-resolution multi-proxy record of climate variability from a 3-m peat core recovered from the crater peat. Down-core X-ray fluorescence measurements of selected lithogenic and redox-sensitive elements revealed several periods of elevated
abundances that we interpret to correspond with enhanced atmospheric dust
deposition. These intervals of high atmospheric dust coincide with historical records of drought and famine in Iran since 2000 BP. Wavelet analysis conducted on selected lithogenic elements for the first 1500 years revealed a major periodicity around 261 y., which may be related to the De Vries (~210 y) and 520-year solar cycles through internal climate feedbacks. When compared with a pollen record of anthropogenic herbs from the same crater peat, stable carbon isotopes and lithogenic elements from our study indicate that contributions from anthropogenic plant species, which provide a measure of ancient agricultural activities in the region, increased during times of low
atmospheric dust (wetter periods) and were coincident with shifts in the values of bulk stable carbon isotopes.

We performed climate modeling experiments to examine the role of solar forc...

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