River response to Quaternary climatic fluctuations: evidence from the Son and Belan valleys, north-central India

The last glacial period was cold and dry in peninsular India. In north-central India, the interval from 39 +/- 9 to 16 +/- 3 ka was associated with widespread and prolonged aggradation in the Son and Belan valleys. The aggradation ended with sustained vertical incision after 16 +/- 3 ka and reflects a return to warmer, wetter conditions. In this region, it would appear that terminal Pleistocene to Holocene river incision was broadly synchronous with a strong summer monsoon regime and higher levels of river discharge and the preceding river aggradation with lower discharge and a weaker or more variable summer monsoon regime. Two older phases of prolonged aggradation followed by vertical incision are evident in the Son and Belan valleys before similar to 39 ka. One of these phases is centred towards 73 +/- 4 ka when ash from the Toba mega-eruption in Sumatra was deposited across peninsular India. The following phase of aggradation has yielded infrared stimulated luminescence ages of 58 +/- 6 and 45 +/- 12 ka. The youngest phase of aggradation began towards similar to 5.5 ka and seems to mark a return to a weaker summer monsoon regime. (c) 2006 Elsevier Ltd. All rights reserved.