211 / 2019-06-20 10:23:30

Aeolian accumulation: An alternative origin of laterite on the Deccan Plateau, India

geochemistry; grain size; basalt; red clay; weathering

Laterite is ubiquitous in India and has been extensively studied. However, it is still controversial with respect to its origin, definition, classification, and implications in paleoclimate, tectonic history and topography evolution. Of those, the origin of laterite, either in situ weathering of protoliths or weathering of allochthonous input, is the most critical to address. The ca. 25-m-thick laterite (duricrust) capping the Deccan Plateau is conventionally hypothesized to derive from in situ weathering of the topmost basalt. However, this thick laterite lacks upward progressive weathering which is characteristic of lateritic profile. Instead, it displays: 1) homogeneity in weathering intensity through the duricrust; 2) a clear unconformable contact of laterite with red clay, which together suggests that this thick laterite is genetically unrelated to in situ weathering of the topmost basalt. Lines of evidence in mineralogy, granularity, and geochemistry proved the disconnection between this laterite and basalt, and in contrast, indicated its correlation to aeolian accumulation. In this study the laterite together with the red clay was proposed to derive from aeolian dust accumulation and weathering since 65 Ma within context of Indian plate drifting across the equator from southern to northern hemisphere.