Palaeoenvironments and elemental geochemistry across the marine Permo‐Triassic boundary section, Guryul Ravine (Kashmir, India) and a comparison with other North Indian passive margin sections

Abstract

The Guryul Permian-Triassic sediments were deposited on a passive margin in a partially enclosed basin, at a latitude of about 45°S along the southern margin of the Neotethys Ocean. The closest modern analogy is the Japan Sea rotated into a southern hemisphere orientation. Guryul element variations are subdued, mostly lithological, and take place across the change from the dominantly sandy shallow-water Permian Zewan Formation into the dominantly shaly deeper-water latest Permian-Triassic Khunamuh Formation, and not at the palaeontological Permian-Triassic boundary.The overall geochemistry of the Guryul sediments is very similar to that of the Ulleung Basin in the Japan Sea, where the sediments are 40%-60% eolian from loess and redeposited loess in the North China Basin. The overall Guryul geochemistry indicates that the sediments were derived from dominantly silica-rich continental rather than silica-poor sources although with some more silica-poor inputs at times. Element ratios suggest increasing aridity and wind abrasion across the Permian-Triassic boundary. Various geochemical redox proxies suggest mainly oxic depositional conditions, with episodes of anoxia, but with little systematic variation across the extinction boundary. Productivity proxies suggest a slight decrease across the Permian-Triassic boundary, and at least one more decreased interval in the Early Triassic. The similar geochemistry of other localities indicate that the Guryul geochemical changes are regional in extent and representative of the North Indian Permian-Triassic passive margin. The lack of consistent element geochemical changes across the boundary accompanied by significant C, S, and other isotopic changes suggests that atmospheric and oceanic chemistry rather than physical changes, such as provenance, climate and sea-level changes, drove the Permian-Triassic environmental changes and extinctions at least on the mid-latitude Tethyan shelf of northern India. K E Y W O R D S Extinction, geochemistry, Kashmir, Permian-Triassic 76 | BROOKFIELD Et aL. F I G U R E 1 Late Permian palaeogeography (courtesy of Chris Scotese): Early Triassic "dead zone" from Sun et al. (2012); Winds from Kiehl and Shields (2005). Locations of cited Permo-Triassic boundary section in open circles with names in bold face 78 | BROOKFIELD Et aL. F I G U R E 8 Biostratigraphy of the Guryul Permian-Triassic boundary section showing stratigraphic range of fossils and number of species in each subdivision (data from Nakazawa et al., 1975). Bryo -bryozoans. Gastr -gastropods. Note that there is little extinction at the Zewan-Khunamuh Formation boundary and the main extinction (and new species appearance) is at the FAD of Hindeodus parvus, and the first inferred anoxic level marked by pyrite framboids.

Hg Isotopes and Enhanced Hg Concentration in the Meishan and Guryul Ravine Successions: Proxies for Volcanism Across the Permian-Triassic Boundary

“…Based on the variation in carbonate content, this formation was subdivided into four members (A-D) and the overlying Khunamuh Formation, into six members (E-J) according to Nakazawa et al (1975). The Guryul Ravine section exhibits gradual faunal changes across the PTB, similar to the other Neotethys P-Tr sections (e.g., Nakazawa et al, 1970;Teichert et al, 1970;Nakazawa and Kapoor, 1981;Sheng et al, 1984;Brookfield et al, 2013Brookfield et al, , 2019Baud and Bhat, 2014). Conodont biostratigraphy of this section can be found in Murata (1981), Matsuda (1981Matsuda ( , 1982Matsuda ( , 1983Matsuda ( , 1984, and .…”

“…Kashmir was once a part of the Gondwana supercontinent at the southern side of the Paleotethys Ocean and adjacent to Oman during the late Paleozoic (Brookfield et al, 2013). Widespread marine transgression in northern India (e.g., Kapoor, 1992;Garzanti et al, 1998) followed the rapid subsidence of the northern Gondwana margin with separation of tectonic blocks and opening of the Neotethys Ocean (e.g., Brookfield, 1993;Garzanti et al, 1996;Brookfield et al, 2013Brookfield et al, , 2019. The Guryul Ravine section and the Spiti Valley, another remnant of the peri-Gondwanan shelf in India (Ghosh et al, 2016), are probably the two best geologically documented Neotethys Ocean PTB sections in India.…”

“…The Guryul Ravine section and the Spiti Valley, another remnant of the peri-Gondwanan shelf in India (Ghosh et al, 2016), are probably the two best geologically documented Neotethys Ocean PTB sections in India. Geological and paleoredox aspects of the Guryul Ravine and the Spiti sections are well documented (e.g., Murata, 1981;Matsuda, 1981Matsuda, , 1982Matsuda, , 1983Matsuda, , 1984Brookfield et al, 2003Brookfield et al, , 2013Brookfield et al, , 2019Wignall et al, 2005;Algeo et al, 2007;Korte et al, 2010;Tewari et al, 2015;Ghosh et al, 2016;Kumar et al, 2017;Huang Y. et al, 2019), resulting in significant advances in the sedimentological and biostratigraphical understanding of these two sections. These Tethyan sedimentary successions in Kashmir have experienced greenschist-facies metamorphism (Herren, 1987;Dèzes, 1999;Algeo et al, 2007).…”

Gullies and badlands of India: Genesis, geomorphology and land management

“…Tewari et al, 2015;Brosse et al, 2017), geochronological (e.g. Mir et al, 2016;Brookfield et al, 2020;Sial et al, 2021) or biological aspects (e.g. Joshi and Chauhan, 1982;Joshi, 1983;Mukhopadhyay et al, 2021) and mineral exploration potential (e.g.…”

Palaeoenvironments and elemental geochemistry across the Permian–Triassic boundary at Ursula Creek, British Columbia, Canada, and a comparison with some other deep‐water Permian–Triassic boundary shelf/slope sections in western North America

“…Few Permian-Triassic (PTr) boundary sections have been studied in sufficient detail (at less than 1 m sample spacing), to document the relatively short-term environmental changes proposed to account for the extinction which usually takes place between a major change in lithology, the End Permian Event Horizon (EPEH) and the biostratigraphic start of the Triassic, the First Appearance Datum (FAD) of the conodoont Hindeodus parvus. This is now being remedied (Brookfield et al, 2020a(Brookfield et al, , 2020b(Brookfield et al, , 2020cDudás et al, 2021;Williams et al, 2021), although geochemical studies tend to concentrate on a specific group of elements (Georgiev et al, 2011;Li et al, 2021;Rampino et al, 2017;Saitoh, 2021).…”