II.—Additional Note on the Correlation of the Rocks associated with the Devonian Limestones of the Hindu Khoosh

Extract

Since the publication of the joint paper by Mr. W. H. Hudleston and myself on “Fossils from the Hindu Khoosh,” in which the Devonian age of well-preserved fossils found in the limestone member of a series in Chitral was demonstrated, my attention has been called by Mr. T. H. Holland to the fact that the series in Chitral agrees very closely with the rocks known to the Geological Survey of India as the infra-Trias, and described, for the last time, in Hazara by Mr. C. S. Middlemiss.

The Chitral series consists of three principal formations:— (1) A lower bed of conglomerate with rounded to subangular pebbles, varying greatly in size up to 3¼ inches in diameter, lying in an indurated, fine-grained matrix of slaty grit or arenaceous mudstone. The pebbles consist of limestone, slates, sandstones, and quartzites, with rounded, white quartz-pebbles, which recall the ‘eggs’ of the Blaini conglomerate of the Simla area. (2) A middle band described by my son, who made a hurried visit to the place, as red sandstone; and (3) an upper bed of grey, dark-blue, and creamcoloured fossiliferous limestone.

In Hazara the system of rocks known to the Geological Survey as the infra-Trias, on account of its position unconformably below the Trias, consists in the same way of a lower conglomerate, a middle sandstone series, and an upper limestone formation. These rocks, originally referred to by Wynne and Waagen, were described in fuller detail by Middlemiss in 1896.

According to Middlemiss, the conglomerate is composed of sub-angular pebbles of slates and quartzites, usually of about the size of a cricket ball, but varying from mere pebbles to larger lumps, and set in a fine purple sandy clay or shale.