Abstract
Sedimentary magnetic records of shelf region contains complex environmental evolution information, necessitating records from various global regions to accurately interpret its significance. A sediment core (SSD-39/GC-01) retrieved from the eastern Arabian Sea was analyzed to elucidate the geologic and climatic controls on the sediment rock magnetic and grain size properties. We report the first record of high energy sediment deposits linked with intense monsoon phases, sea level variations, and extreme natural events during the Northgrippian period (8.27 ka to 4.20 ka). The compilation of magnetic susceptibility profiles of six sediment cores from the western margin of India revealed the presence of multiple sedimentary intervals of enhanced magnetic susceptibility and most likely reflect periods of high sedimentation events controlled by the regional geologic and climatic processes. We identified two anomalous sedimentary magnetic zones (Z-II, Z-IV) marked by an elevated magnetite content and sediment grain size, which reflect the periods of high-sedimentation events on the shelf off Goa. A shift in the magnetic mineral composition, clastic grain size, calcium carbonate, and organic carbon content at ~1.8 ka (Z-I) indicate a abrupt change in monsoon intensity. The elevated organic content within Z-I indicate efficient preservation of labile organic matter which survived oxidation due to rapid sediment deposition. End-member modeling of rock magnetic and grain size properties enabled us to discriminate and quantify the contributions of terrigenous fluxes and post-depositional mineral phases to the bulk magnetic mineral assemblage. We demonstrate that rapid scanning of magnetic susceptibility of sediment cores has the potential to precisely detect the periods of increased continental (magnetic flux) inputs into the marine shelf system. The proposed magnetic mineralogical approach has wider scope to constrain the understanding of how shelf sedimentation responded to past geological and climatic conditions globally.
Published Version
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