Characteristics of the paleosol at the Archean - Proterozoic contact in the Aravalli Craton, NW India and paleoclimatic implications
Final Report Abstract
In the region of Udaipur, Rajasthan the Archean - Proterozoic interface represents a largescale folded surface related to the regional-scale F2 folding and is exposed on both, eastern and western flanks of the synclinorium. Paleosol occurrences on both the limbs of this structure imply an originally continuous paleoweathering horizon and not individual pockets of paleosol as seen today. Complete sections are recognized in the eastern side of Udaipur valley while in the western flank the contact is heavily sheared and Archean basement and Proterozoic units are interfingering at a small- scale. The complete section along the eastern side represents an ancient lateritic weathering profile with an iron-depleted pallid lower zone (lithomarge) and an iron-enriched upper zone (mottled zone to ferricrete). Original kaolinite in the saprolite and pallid zone has been transformed to kyanite during metamorphism and subsequently to white mica during retrograde overprint, while Fe-rich clay and goethite were probably the primary minerals for the chloritoid and hematite which now constitute the upper zone. We rank the Udaipur paleosols as best-preserved and most complete Archean-Paleoproterozoic paleosol sections in India. Their timing of formation can be deduced by the stratigraphic position only. The weathering interval is defined by the stabilization of the craton at ~ 2.5 Ga and deposition of rift-related sequences of the Aravalli basin (Delwara formation) at ~ 2.15 Ga.
Publications
-
(2008). Paleosol at the Archean-Proterozoic contact in NW India revised – evidence for oxidizing conditions during paleo-weathering? J. Earth System Science, 117, 201-210
Pandit, M.K., de Wall, H. & Chauhan, N. K.
