ROLE OF NEOTECTONICS AND CLIMATE IN DEVELOPMENT OF THE HOLOCENE GEOMORPHOLOGY AND SOILS OF THE GANGETIC PLAINS BETWEEN THE RAMGANGA AND RAPTI RIVERS

Fifteen soil-geomorphic units have been delineated from the Gangetic P lains between the Ramganga and Rapti rivers. They were identified by r emote sensing and field checks. On the basis of degree of profile deve lopment, their soils are grouped into five members (QGH1 to QGH5, QGH5 being the oldest) of a soil chrono-association. Tentative ages assign ed to QGH1 to QGH5 are < 500, > 500, > 2500, 8000 and 13,500 yr B.P., respectively. From the early Holocene to about 6500 yr B.P. a cold, ar id to semi-arid climiate prevailed and pedogenic calcrete developed ov er large areas in the Gangetic Plains. Later, a warm and humid climate and improved drainage resulted in complete removal of calcrete from s oil profiles in some areas or its dissolution and re-precipitation in lower horizons in other areas. Neotectonics seems to have played a sig nificant role in the evolution of the geomorphology and soils of the a rea. It determined areas of active sedimentation, pedogenesis and eros ion (in upland regions). It led to tilting and sagging of large blocks resulting in shifting and increase in sinuosity of the rivers. Tecton ic slopes/faults determined the courses of large rivers.