A study finds stalagmite evidence in Iran of a significant increase in dust, implying regional aridity, concurrent with the decline of the Mesopotamian Akkadian Empire around 4,200 years ago. Several civilizations, including the Akkadian Empire, display significant transformations around 4,200 years ago, suggesting a possible general climate event around that time, although the nature and source of such an event are unclear. Stacy A. Carolin and colleagues studied a stalagmite from Gol-e-Zard cave in northern Iran. Geochemical analysis revealed two events of increased magnesium/calcium ratios, slow stalagmite growth, and increased stable oxygen isotope ratios. The authors report that the events began at around 4,510 and 4,260 years ago. Oxygen isotopes suggest a period of drying, and the increased magnesium/calcium ratios suggest enhanced dust activity, suggestive of relatively arid climate conditions in Mesopotamia. The onset of the climate events appears to have been sudden, suggesting that climate conditions passed a threshold of aridity. According to the authors, the second event coincides with the abandonment of North Mesopotamian settlements, suggesting societal impacts of changing climates as well as the region's capacity to experience sudden century-scale dry events.
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Article #18-08103: "Precise timing of abrupt increase in dust activity in the Middle East coincident with 4.2 ka social change," by Stacy A. Carolin et al .
MEDIA CONTACT: Stacy A. Carolin, University of Oxford, UNITED KINGDOM; e-mail: stacy.carolin@earth.ox.ac.uk
Proceedings of the National Academy of Sciences