Mid to late Holocene Indian monsoon variability, aridification and civilization changes in the Deccan Plateau, India

Climate change has been a key driver throughout human history and has frequently been associated with the rise and fall of civilizations. Holocene settlement changes or population displacements were almost always preceded by changes in climate. A high-resolution sedimentary record from the western Bay of Bengal offers insights to centennial-scale mid- to late-Holocene Indian summer monsoon (ISM) variability and its role in the decline of chalcolithic human settlements on India's Deccan Plateau. Increased erosion in the Indian peninsula during the mid- to late-Holocene, due to aridification and agricultural expansion, is evidenced by higher sedimentation, more magnetic mineral content, coarser magnetic grain size, and increased sand content. The results from mineral magnetic and textural analyses reveal centennial-scale abrupt weak ISM during the Bond events in the core monsoon zone of India. The Deccan Chalcolithic civilizations flourished between ∼4.0–3.0 ka BP owing to the favorable climatic conditions, but most of the settlements were deserted after ∼3.0 ka BP. We argue that the abrupt weakening of ISM during Bond event 2 (∼3.1–2.8 ka BP) caused this collapse of Deccan Chalcolithic. The results from this study together with the published records of number of settlements and summed radiocarbon dates suggest a climate-culture link in the Deccan Plateau. The weak ISM periods in this study are coherent with the records of total solar irradiance and the percentage of hematite-stained grains from the North Atlantic and suggest solar control on these abrupt climatic events.