Himalayan Geology Research Articles

Contributions to geodynamic research in the Himalaya

Parts of Tethyan and the Higher Himalaya in Ladakh, Kumaun, Garhwal, Arunachal Pradesh and adjoining areas have been investigated by the Wadia Institute of Himalayan Geology. A summary of the geological work carried out in the last five years is presented.

The western border of the Indian plate: implications for Himalayan geology

The study of regions situated beyond the western margin of the present-day Indian plate (Afghanistan principally) point to the following facts: 1. (1) During the Late Precambrian—Early Paleozoic, stratigraphical continuity existed between western and central Iran, Central Afghanistan, Salt Range and western Pakistan. 2. (2) During the Paleozoic a similar epicontinental cover existed in central Afghanistan, Kashmir and Tibet, with Gondwana tillites and associated cold fauna, such as in India (Umaria); however, a so-called Hercynian zone exists also in northern Iran—Hindu Kush and northern Pamir: it exibits a Middle Paleozoic unconformity (Upper DevonianCarboniferous) on metamorphic Early Paleozoic. 3. (3) The end of the Paleozoic, is marked by: a fracturation of the basement of the Hercynian zone, with powerful volcanic eruptions at the northern part of Hindu Kush, Kashmir (Panjal trap) and also Nepal (Nar valley) the formation of a geosynclinal zone at the southern part of Hercynian zone (Turkman, Penjaw). 4. (4) During the Jurassic: the geosynclinal evolution of the Turkman—Penjaw furrow accelerated, with the accumulation of flysch, radiolarites, ophiolites, olistolites and incipient HP metamorphism. A general subduction took place followed by a Neocimmerian orogenic phase with overthrusting of the central Afghanistan ranges on the scar of the geosynclinal furrows. 5. (5) During the Cretaceous: the geosynclinal evolution ended: Lower Cretaceous lies unconformably on the folded Jurassic flysch. In eastern Afghanistan and northern Pakistan, during the Middle (?) or Upper Cretaceous, a new geosynclinal zone was created. 6. (6) During the Cenozoic, central Afghanistan was emerged; northwards, sedimentary basins were created along the Herat fault, with volcanic and magmatic activity. A southeastern geosynclinal furrow evolved with accumulation of flysch, ophiolites and finally molasse deposits (Katawas—Soleimans). Its western border began overthrusting, but this movement changed into a left lateral fault i.e., the presentday Chaman Arghandeh fault. Conclusion: Two major phases of dislocation took place during the geological history of Gondwana: the first one began during the Permian and ended in the Jurassic; the second one began during the Cretaceous and is still active. The important Eocimmerian orogenic phenomena, existing in the Central Afghanistan and northern Pakistan, took place at the edge of a Gondwana continental fragment, which was larger than the presentday Indian plate. Coeval phenomena may exist in the Himalayan region and perhaps in one of the ophiolitic sutures of Tibet.

Stratigraphic and structural evolution of the Kumaon Lesser Himalaya

Six years of geological investigations comprising studies of sedimentology, geomorphology, photo-interpretation and field checks carried out by a team of 6–8 geologists have led to a reappraisal of Lesser Himalayan geology. The Algonkian and Early Palaeozoic basin derived its sediments from the south. The Caledonian orogeny had a limited effect, the Himalayan basin was sliced into two parts by a central NW-SE trending arch which became a source of sediments during the later Palaeozoic and Mesozoic evolution. The Damta group of turbidites are of Algonkian-Cambrian age; they serve as a “supra-basement” over the whole region and may have partly been taken up in the later metamorphism of the central zone of the Himalaya. Facies changes between the Deoban-Shali carbonate sequence and the Chandpur-Basantpur black shales and shales are worked out. During the Mesozoic and Tertiary, facies changes are controlled by old arches and fundamental lines of weakness which can be recognized even in the present seismic and geomorphological evolution. The Blaini boulder beds, extensively quoted in literature as tillites and used as “fool-proof” marker beds are shown to be a slumped series at the base of the Krol foredeep sequence. The Krol belt rocks are autochthonous and find an extension across the Tehri-Meenus high in the Kophara black shale series that wedge out towards the north. The occurrence of the Eocene nummulitics is two-fold: 1. (a) in concordance with the Jurassic rocks, this position occurs in quiet synclinal areas; 2. (b) in discordance over all the earlier deposited series, this position occurs over the arches witnessing late Mesozoic erosion. Reversal of metamorphism and production of gravity slides is a logical result in the evolution of the basin.

Problems in Himalayan geology

The Central Crystalline Axis of the Great Himalaya holds clues to the solution of many problems dealing with the crystallines, metamorphics and geological contrasts encountered in the areas to the north and south of the Axis. The problems discussed include criteria for deciphering the stratigraphy in the Himalayan zone to the south of the Crystalline Axis, age of Jutogh and Chail groups, their relationship with each other and with the Crystalline Axis, nature of the Simla Slates, Jaunsar, Blaini, Infra-Krol, and Krol formations, unfossiliferous nature of the Palaeozoic and Mesozoic sediments, relationship between the Lower, Middle and Upper Tertiaries and the age, presence and absence, and also the cause of metamorphism. It has been found that high grade metamorphism is not a Tertiary phenomenon. Very low grade metamorphism in the sedimentaries and the absence of plutonic intrusives from the Palaeozoic, Mesozoic and Tertiary sedimentary rocks indicate that magmatism, regional metamorphism and orogeny are not always mutually associated in space and time. Orogenic and epeirogenic episodes other than Cretaceous-Tertiary hold clues to many problems of Himalayan Geology.

Palaeozoic Biostratigraphy of the Tethys Himalaya in North-Eastern Kumaun

NEW fossil finds in the Kali and Kuti valleys in north-eastern Kumaun Himalaya considerably elucidate the problems of the biostratigraphic subdivision of the Palaeozoic succession and tectonic history of the Tethys Himalaya. Northern Kumaun was explored by Griesbach1–2 in the 1890s and Heim and Gansser3 made this region a classical area for the study of the Tethys Zone of the Himalaya through their monumental work in the 1930s. Although mostly conforming to the general structural picture of the entire Tethys Himalaya, the area showed certain biostratigraphic features that did not agree well with the wide regional stratigraphy and tectonic history as inscribed in the lithological successions in Spiti to the north-west and in West Nepal to the south-east. To study afresh the peculiarities of the Kumaun Tethys Himalaya, an expedition was sponsored and organized by the Wadia Institute of Himalayan Geology in August and September, 1971. Many significant facts have emerged from this short expedition. The new scheme of stratigraphy—with its implication on the tectonic history—accords very well with that established in the Dhaulagiri-Nilgiri region in western Nepal4,5. The highlights of the result of the investigation are as follows.

V.—The Gneissose Rocks of the Himalaya

It had not been my intention to publish anything on this subject at present, as I have in preparation a review of the present state of our knowledge of Himalayan geology; but as Col. McMahon has started the subject, and his paper is not exhaustive, I trust the following outline of that part which relates to the gneissose rocks may prove of interest.