Some aspects of the Krol formation of the Himalaya,India

The Lower Krol sediments consist of intercalations of dolomite with shales in the marginal areas (Solan and Nainital), while limestones are interbedded with marls in the central part of the basin (Massoorie). The Upper Krols are largely composed of dolomites with subordinate limestones and shales.The non-carbonate detrital fraction is dominated by quartz with minor amounts of orthoclase, microcline and plagioclase feldspars. Illite and chlorite constitute the dominant clay minerals, lesser amounts of corrensite and kaolinite are sometimes present. An eastward increase in illite and decrease in chlorite has been ascribed to the supply and distribution of the terrigenum.Zirconium, rubidium, strontium, zinc, nickel and manganese were determined by X-ray fluorescence. Early diagenetic dolomites contain Sr, Zn, Ni and Mn in trace amounts, while the late diagenetic dolomites are characterized by an absence of these elements. The posttectonic dolomites are unusually rich in iron, manganese and sometimes in zinc.Authigenic formation of alkali feldspars, chlorite, illite, quartz and pyrite is not uncommon. The feldspars appear to have formed at early and late diagenetic stages. Potash feldspars dominate over albite in association with dolomite, whereas albite tends to be more common in the limestones.The Krol sedimentation seems to have started in a shallow coastal lagoon behind a barrier beach, upwards changing into tidal-flat deposits.