On the problem of the horizontal heterogeneity of the earth's crust and uppermost mantle in southern Eurasia

Abstract

An analysis of the geological structure and history of development of the Himalayas points to the conclusion that prior to the Neogene most of that territory was part of the epi-Proterozoic Indian Platform; it was reworked only in the epoch of Neogene-Quaternary activation of tectonic movements. It was precisely during this period that the mountain ridge of the Himalayas formed. Only the narrow northern zone — the Himalayas of Tibet — which is composed of marine deposits of all systems of the Paleozoic and Mesozoic groups possibly did not develop on the platform with the Precambrian basement. Most likely, it is a near-fault folded zone that arose on the site of a near-fault trough, which already in the Cambrian Period had formed along the northern boundary of the Indian Platform. The Cenozoic geosynclinal structures located to the west and east of the Himalayas are fundamentally different in structure and history of development. This is clearly evident from an analysis of geological and geophysical data. These differences may be traced far back into geological history and are related to processes which took place and are now taking place at considerable depths, some of which are far below the bottom of the earth's crust. The western Cenozoids are part of the Laurasian segment, the eastern Cenozoids, part of the Pacific Ocean segment of the earth. Obviously, one must speak of a large horizontal heterogeneity of the earth's crust and the uppermost mantle within the limits of the territory described above. The Himalayas — this northern boundary zone of the Indian Platform which was elevated only in very recent times — represents a natural border between the Mediterranean and Pacific Ocean folded zones.