Sedimentary facies and anoxic indicators in the Himalayan Foreland and Kutch Basins, India: a geochemical comparison
摘要
Oceanic Anoxic Events (OAEs) are crucial events in Earth’s geological history. Due to the tough terrain, less information is available for the Himalayan foreland basin (HFB) sequence in India. This study focuses on the Kalakot shale of the Jammu region and the Bhuj shale of the Kutch region. We compare the HFB shale (Jammu region) with the Bhuj shale (Kutch region) using sediment geochemistry to glean the prevalence of anoxic conditions. Various shale litho-facies in the Kutch region indicate a depositional environment, whereas the Jammu region shows a low-energy lagoonal to sub-tidal environment. Among the major elements, Al2O3 and Fe2O3 in the Kalakot shale of Jammu and the Bhuj shale of Kutch were analyzed. The Bhuj shale shows Ni/Co ratios varying between 24.25 and 1.65 (average 8.5), indicating the prevalence of anoxic conditions. Further, the values of V/ (V + Ni) lie between 0.7 and 0.8, corroborating with PAAS values and exposure to anoxic to dysoxic conditions. This aligns well with V/Cr values in the range of 1 to 3, indicating dysoxic to sub-oxic conditions. In the Kalakot samples, the Ni/Co ratio (average = 2.5) and V/ (V + Ni) ratio (average ~ 0.81) corroborate the prevalence of sub-oxic to anoxic depositional settings. In Kalakot, the Ni/Co ratio varies between 0.2 and 24 (average 2.5), and the V/ (V + Ni) ratio lies between 1.0 and 0.8, indicating sub-oxic to anoxic conditions. The intercomparison of geochemical data between Kutch and HFB revealed that the understanding of regional and global OAEs are crucial for deciphering the paleo depositional conditions.