Oceanic anoxic events in the Earth’s geological history and signature of such event in the Paleocene-Eocene Himalayan foreland basin sediment records of NW Himalaya, India

• Published in: Arabian journal of geosciences Vol. 15; no. 3
• Main Authors: Singh, Bhart, Singh, Seema, Bhan, Uday
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01-02-2022; Springer Nature B.V
• Subjects: Anoxia; Anoxic sediments; Basins; Biogeochemical cycle; Biogeochemical cycles; Carbon cycle; Cenozoic; Climatic conditions; Deposition; Earth; Earth and Environmental Science; Earth science; Earth Sciences; Eocene; Geological history; Geology; Ironstone; Marine sediments; Ocean-atmosphere system; Palaeocene; Paleocene; Phanerozoic; Phosphorite; Records; Review Paper; Sediment; Sedimentary facies; Sedimentary rocks; Sediments; Shale; Tectonics; India; Himalayan orogeny; Subathu formation; Oceanic anoxic events (OAEs); Himalayan foreland basin (HFB) sediments; Paleocene-Eocene thermal maximum (PETM)
• ISSN: 1866-7511; 1866-7538
• DOI: 10.1007/s12517-021-09180-y

Oceanic anoxic events (OAEs) represent changes in global carbon cycle as well as biogeochemical cycles and are robust recorders of major changes brought in the ocean-atmosphere system of the Earth. In the present study, a comprehensive compilation of well-documented OAEs in the Earth’s geological history indicates that compared to the plethora of OAE studies in different parts of the world, the Indian part lacks sufficient such geological studies. Also, it has been observed that despite the variety of causes referred by researchers for the occurrence of OAEs based on various geological proxies, their development tends to cluster in particular periods having unique geological settings under specific climate conditions of the Earth. OAEs usually coincided with Earth’s greenhouse condition and in marine to shallow marine depositional settings, which have been associated with rapid alternating phases of transgression and regression. The Paleocene-Eocene thermal maximum (PETM) at the Paleocene-Eocene boundary comprises the last OAE of the Phanerozoic Eon and the only identified OAE in the Cenozoic. The deposition of Himalayan foreland basin sediments during Paleocene-Eocene time coincides with the India-Eurasia collision and PETM. Characteristic litho sections of Paleocene-Eocene HFB shallow marine sediments represented by the Subathu Formation occur in and around the Jammu region (of the Ramngar sub-basin) and Simla region (of the Subathu sub-basin) of NW Himalaya (India) and have been explored for OAE records. Besides the fact that deposition of these sediments coincides with PETM, there are many other reasons which suggest possible representation of these as records of OAE. For example, these sediments show OAE specific sedimentary and biostratigraphic facies associations which are characteristic of alternating transgressive-regressive successions. The base of these early HFB sediments consists of sideritic ironstone, phosphorite, and black shale association indicating commencement of basinal sedimentation under euxinic, shallow marine conditions. Though these Paleocene-Eocene HFB sediments comprising dominantly black to gray-green shales are regionally extensive, however, these occur in discontinuous patches all along the HFB and also greatly vary in thickness due to the tectonic complexity of the Himalayan region.