An Outline of the Stratigraphy and Structure of the Southern Part of Pithoragarh District, Uttar Pradesh

Three stratigraphical formations have been recognized in the southern part of the frontier district of Pithoragarh. (i) The Calc Zone, (consisting of dolomitic and cherty limestones, slates, stromatolite-limestone and magnesite beds), has been compared with the Deoban Limestone, Shali Series and the Naldera-Kakarhatti-Limestone of the Simla Series. On the basis of the contained Collenia, the position of this Calc Zone could be fixed anywhere between late Precambrian and Cambrian. (ii) The Quartzite Zone, (composed of phyllites, quartzites, conglomerates and sericite quartzites with associated chlorite schists and amphibolites) is correlated with the Nagthat (= Jaunsar) series. (iii) The crystalline Zone of Askot (consisting of ortho- and para-gneisses and schists) is correlated with the Chandpur (= Daling-Darjeeling) series.

The sedimentary zone, occupying a vast tectonic window between the crystalline zones to the north and south corresponds to the Krol nappe, or its eastern analogue, the Nawakot nappe. The whole sedimentary pile represents the lower limb of a mighty recumbent anticlinal fold, thrust from north to south; the minimum distance of translation is about 115 miles. The thrust-bound Crystalline Zone of Askot and the Crystalline Zone of Lohaghat to the south represent two detached outliers of a single thrust sheet corresponding to the Garhwal nappe, or its eastern equivalent, the Kathmandu Nappe. The width of thrusting of the crystallines is approximately 106 miles.