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Chapter 05
Geological Studies
In the north, where the conglomerates overlap the Kailash granite, the regional dip is about 10° to the south. Southwards this dip diminishes to about 2-3° (Fig. 99). The almost horizontal layers can be followed southwards until the thrust of the Himalayan Flysch is reached. Here one is struck by the sudden upturning of the horizontal conglomerate beds into an over turned position. This fact is very well visible in the field (Ph. 29, 30). Approaching the thrust, some of the smaller intercalated sandstones gradually show intense disharmonic folding, while the conglomerates are still undisturbed (Fig. 100). Only very near the thrust is some secondary folding visible within the conglomerate layers.
The distribution and size of the conglomerates and sandstones clearly indicate that the conglomerates have been deposited from north to the south, and originated north of the Kailash granite. The acid volcanic components are a rock type unknown in the south, but are similar to some volcanic rocks collected by Sven Hedin north of the Trans-Himalayas and described by Hennig (1916). Nothing is known of the lateral extension of the Kailash conglomerates except that they seem to continue eastwards along the Trans-Himalayan foothills, while their westwards extension seems limited.
The age of the conglomerates is still questionable. They are certainly younger than the Kailash granite, and the latter, as we will see, could be correlated with the Cretaceous Kyi-Chu granite of Lhasa (Hayden, 1907). They are older than the thrust of the Himalayan Flysch and most likely should be placed between the Eocene and the Miocene.
Kailash Granite
The Kailash conglomerate transgresses with a normal stratigraphical contact over the Kailash granite, which rises northwards from underneath the conglomerate forms a wild granite landscape north of the Kailash Mountain. The granite, with its sharp peaks, has a strong irregular cleavage, and produces coarse scree. It is generally rather fresh up to the transgression of the conglomerates. In the Kailash region the granite is completely massive, but further to the north it seems to become somewhat gneissified. The main rock type is hornblende - biotite granite, medium-grained with alkali feldspars not exceeding 2 cm. These are mostly microcline while the plagioclase is oligoclase to and esine. Most interesting are the hornblendes, with sievelike relics of augite (Ph. 32). The latter have a uniform extinction and seem to have been the primary constituent. Sphene is frequently associated with the hornblende. These facts are important for the correlation of the granites. They frequently contain more basic inclusions of a hornblende- dioritic composition. Here again the hornblende is characterized by augite inclusions. A few tourmaline aplites cut through the granite, but other dykes are absent or rare. Practically nothing is known so far about the extension of the Kailash granite. From the few samples collected by Sven Hedin north of the Kailash region, the Kailash granite seems to change into liparite and dacites. The latter are very wide spread and intrude Middle Cretaceous Orbitolina limestones (Hennig, 1916). Westwards, along the foothills of the Trans-Himalayas, granite has been recorded again by Sven Hedin at Gartok-determined by Hennig as a biotite - hornblende granite which seems quite similar to the Kailash granite. There too, dacitic lavas seem to occur further to the north. Another granite occurrence similar to the Kailash granite
197
Central Himalayan Geological Observations
