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Imperial Gazetteer of India, v. 19, p. 142.

142 NORTH-WEST FRONTIER PROVINCE success for building and ornamental purposes. The prevailing strike direction of the slates is east-north-east to west-south-west. The slate zone is bounded on the south by a sinuous line of faulting with over- thrust, from near the axis of the Cherat hills to the Jhelum near its junction with the Kunhar river. South and south-east of the great fault line (as well as in the form of outliers in parts of the slate zone) comes a great set of younger forma- tions, stretching in gentle undulations right through the rest of Hazara and Peshawar, and the whole of Kohat, Bannu, and Dera Ismail Khan. These younger formations are mainly higher Mesozoic, Tertiary, and post-Tertiary, but they also include limited outcrops and sub-zones of infra-Trigs (Devonian?), Permian, and Trias. With these younger formations begin much irregularity and sinuous winding of the strike, which coincides with the direction of the bare rock ridges, and also with what may most aptly be called the curling crests of the rock waves and undulations. These, by means of devious S-shaped curves, settle down to a north and south strike in Dera Ismail Khan District at the foot of the Sulaiman range. The curved direction of the crests of the folds expresses the buckling caused by the meeting along this portion of the earth's surface of the Himalayan, Hindu Kush, and other more western systems of crust movement, setting in from three sides against the old and rigid gneissic rocks of Peninsular India. The so-called infra-Trigs of Hazara-which consists of abasal con- glomerate followed by purple sandstones, shales, and 2,000 feet of dolomitic limestone, quite unfossiliferous, and coming beneath the Trigs-has only a restricted occurrence near Abbottabad at the base of the outliers of younger rocks. Its age may be Devonian', and it is not known elsewhere. Carboniferous strata are not certainly known in this Province. The Permo-Carboniferous formation exposed in strips along the axes of folds in the Sheikh Budin and Khisor ranges 2 consists of a glacial boulder-bed with striated and faceted blocks at the base, followed by 500 feet of magnesian and white limestone with sandstones and earthy beds, containing Productus, Spirfer, Bellerophon, corals, &c. In Hazara the Permo-Carboniferous may be represented by a felsite and hematitic breccia, found unconformably overlying the infra-Trigs (Devonian?). The Sheikh Budin and Khisor ranges also expose a continuous section, without any physical break, up through the Trigs, containing Ceratites, and corresponding with the Trias of the Salt Range of the Punjab. In Hazara the Trias, represented by a massive dark-grey limestone containing Megalodon and Dicerocardium, and resembling 1 Lieutenant-General McMahon, Geological Magazine, vol. ix, pp. 3-8 and 49-58, 1902; also vol. x, p. 52, 1903. 2 .al. B. Wynne, Memoirs, Geological Survey of India, vol. xvii, article 2.