Date of Award

Spring 5-1-1985

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geography, Geology, and Anthropology

First Advisor

John E. Oliver

Second Advisor

Donald W. Ash

Third Advisor

Walter Sullins

Abstract

Geomorphic history of the study area, which is located in the northwestern Himalaya, is intimately related to the complex geologic and tectonic history of the Himalaya. The Himalayan orogeny started near the CretaceousTertiary boundary when the Indian and Eurasian plates collided. Northern ranges were raised first and the uplift of the southern ranges followed. In the study area, the Pir Panjal was uplifted in the Miocene and the Dhaula Dhar in the Pliocene. It is shown in this research that the pre-Pleistocene history of the study area (the Ravi River basin) is very intimately related to the Himalayan orogeny and its various phases. Pleistocene and Holocene history is related to, in addition to the uplift still going on, the occurence of glacial and interglacial ages. The terraces in the study area are the result of the aggradational and degradational events accompanying these ages. After the uplift of the Pir Panjal in the Miocene, the northern section of the Ravi River basin was established as the streams flowing on the south slopes of the Pir Panjal. In the Pliocene the uplift of the Dhaula Dhar to the south led to the establishment of the Ravi River and the southern section of its basin as the streams flowing on the north slopes of the Dhaula Dhar. The Dhaula Dhar uplift axis plunges northwestward, and because of this the Ravi River takes a sharp rectangular bend in the western part of iv the basin. This bend provided favorable configuration for a river capture. The main stream was captured by one headward eroding tributary located on the inside of the bend. The river terraces found in the study area are a result of climatic changes during the Pleistocene and the Holocene. During the Pleistocene, when the discharges in the streams were small, leading to their inability to transport the load supplied, deposition took place. These deposits in the Ravi River valley are glacial, glaciofluvial, and fluvial in nature. Two heterogenous and unstratified bouldery deposits are associated with glacial and proglacial depositional environments. Sandwiched between these two bouldery deposits is a thick sequence of stratified fluvial sediments. During the Holocene increased stream discharges, isostatic rebound after glacial unloading and continuous uplift of the study area led to accelerated downcutting. Simultaneous downcutting and lateral swinging of the Ravi River led to the formation of unpaired terraces.

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