Quaternary International ( IF 2.003 ) Pub Date : 2020-10-16 , DOI: 10.1016/j.quaint.2020.10.036 H. Wani; Bilal A. Sunu; Meenal Mishra; Imran Khan
The Himalayan-Tibetan orogen has a great influence on regional and global atmospheric circulation and, hence, it is important for understanding the dynamics of global environmental change. The Kashmir valley, located in the northwestern Himalaya, provides a unique sequence of continuous sedimentary records of unconsolidated sediments of more than a km thickness, dated back to 4 Ma. There are number of studies which suggest episodic and widespread cold conditions, including glaciations, within the Kashmir valley during the Plio-Pleistocene. In order to test the hypothesis of the glacial input into the Kashmir basin, scanning electron microscopy (SEM) was applied to analyze quartz grains of Karewa deposits stratigraphically for the evidence of their sedimentary history. The microtextures indicate the dominant presence of sustained high stress fractures on the quartz grains with little effect of weathering and dissolution from 4 to 2.1 Ma and from 1.6 to 0.4 Ma. The quartz grains are also angular and of high relief. All these features suggest that these sediments are primarily transported by glaciers and melt water streams. However, the samples ranging in age from 2.1 to 1.7 show a mixed signal (glacial and fluvial) with a dominance of fluvial signal. This transition is attributed to the source area change from Himalayan range (NE) to Pir Panjal range (SW) because of the uplift along the Main Boundary Thrust (MBT). Furthermore, we report the first occurrence of a till deposit within the lower part (Dubjan Member 4–3.5 Ma) of the Karewa Group of the Kashmir basin which points to ice advancement in the northwestern Himalaya during the mid-Pliocene. Since, the till occurs in the upper part of the Dubjan Member, therefore, the timing of this glaciation can be restricted to be between 3.7 and 3.5 Ma. Hence, matches well with the mid-Pliocene glaciation that occurred in the Tibetan Plateau (∼3.6 Ma) and other parts of the Northern Hemisphere (3.5 Ma).