Implications for catchment weathering, provenance, and climatic records from a late Pleistocene to present sedimentary sequence in Gujarat, India

Abstract

AbstractTo ascertain weathering, provenance, and paleoclimate of the last ca. 29 ka in mainland Gujarat, western India, a sedimentary profile of ~7.5 m was measured, described, and sampled at Pratappura and a multiproxy analysis was conducted. To determine weathering, silty-sand and sandy-silt facies were analyzed, and log Na2O/K2O versus log SiO2/Al2O3 was plotted, which shows clustering in the quartz arenite and sub-litharenite categories, indicating low to moderate weathering. The chemical index of alteration (CIA) is 55–74, and was plotted versus the index of chemical variability (ICV) of 1.50, with samples clustered mainly between subalkali basalt and picrite, indicating the dominance of a mafic component. While depleted chondrite normalized light rare earth element (REE) (La/Yb <1) levels suggest the prevalence of a mafic source in the catchment, identical chondrite normalized REE patterns indicate that sediments were well homogenized. Using multiple proxies, the measured profile was subdivided into five paleoclimatic zones. Zone-I (29–18 ka) exhibits decreasing moisture, Corg, χlf, Al2O3, TiO2, and Fe2O3 trends, while higher values of CO3−2 and δ13C indicate a change from a warm-humid to semiarid climate. Zone-II (18–11 ka) shows signs of the beginning of aridity ca. 18 ka during the Last Glacial Maximum (LGM). Several proxies in zone-III show wetter climatic conditions from the early Holocene (ca. 11–4 ka) due to the onset of the SW monsoon, with the trend continuing in zone-IV (4–2 ka). In zone-V, the climate appears to have been similar to the modern conditions in the area from 2 ka–present.