Geochemistry and Clay Mineralogy of Weathering and Soil Profiles, Malappuram District, Northern Kerala, India: Its Implications on Paleoclimate

Abstract

The present investigation chiefly concerns with the geochemical and clay mineralogical studies on two weathering and soil profiles at Pathirappadam and Ernadampadam in Nilambur valley, Malappuram district, Kerala. We attempt to understand the mobility of elements, weathering paths, and the common weathering products of gneissic rocks weathering on the western flanks of the Western Ghats. Our results indicate the depletion of Na, K, Ca, Mg and enrichment of Al and Fe with respect to the upper continental crust in both the profiles. The X-ray diffraction study reveals that kaolinite is the dominant clay mineral present in all the samples with minor amounts of gibbsite and goethite. Both the profiles possess two distinct horizons namely upper eluvial zone and the lower Illuvial zone as inferred from dominance of iron oxides in the upper zone and enrichment of aluminosilicates as well as predominance of kaolinite in the lower zone of the profiles. The above findings suggest that the study area is experiencing intense chemical weathering without much change in the geological, geomorphological setups and climatic conditions. The wide spread occurrence of laterite in this region, higher CIA value of the samples and abundance of kaolinite indicates that the study area was experiencing extreme weathering underwet and humid tropical climatic conditions with mean annual precipitation of above 200 cm for a quite long time.