Abstract

Two extensive exposures of tillite of probable Lower Carboniferous age occur on Highway 37 between Bharmaur and Tissa, Himachal Pradesh. One lies eight kilometres south of the village of Kalhal, the other five kilometres west of Durgatti (Fig. 1). The two sections lie some fifty kilometres apart along the strike and are between three areas where tillites have previously been recognized, namely, Salt Range, Kashmir and Simla.

Lithology and texture

The tillites in both localities occur within a succession ascribed by McMahon (1883) to the Silurian System. Both comprise grey phyllites containing cobbles, pebbles and sand size grains. The larger clasts are completely surrounded by the matrix Plate 1 and their concentration varies from beds with only one or two cobbles and/or pebbles per square metre, to beds which resemble a polymict conglomerate. The larger fragments are angular to sub-rounded but intense, penetrative deformation has considerably modified original shapes. The tillites are strongly schistose and usually bedding cannot be distinguished. In more conglomeratic horizons, however, bedding is reflected by changes in the concentration of fragments. The clasts are of pure white quartzite, buff limestone and grey phyllite. No igneous or strongly metamorphosed rocks occur.

The ill-sorted nature of the deposits is confirmed in thin section where the matrix consists of single crystal fragments of quartz, calcite and occasional feldspar set in finer mica, quartz, calcite and opaque ore. Recrystallization of mica and ore has occurred and quartz frequently exhibits syntaxial growth rims.

In both localities the tillites are associated with

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