Pelagic responses to oceanic anoxia during the Carnian Pluvial Episode (Late Triassic) in Panthalassa Ocean

Abstract

The Carnian Pluvial Episode (CPE) was a short interval of extreme rainfall in the Late Triassic that caused significant changes in marine ecosystems. Global warming induced by Wrangellia volcanism is thought to have resulted in oceanic anoxia during the CPE, but the global extent, duration, and severity of anoxia, and its effects on major marine taxa, remain unclear. To address this, we examined an equatorial record of conditions in the Panthalassa Ocean during the CPE, focusing on marine Os isotope data, redox conditions, and conodont and radiolarian biostratigraphy. The results show that Wrangellia volcanism peaked in the latest Julian (early Carnian), coinciding with development of reducing conditions in the deep-sea Panthalassa. A strong conodont turnover occurred during the period of oceanic anoxia, whereas radiolarians were less affected and their diversity increased after the recovery from anoxia. The increased radiolarian diversity during the early Tuvalian (late Carnian) can be attributed to chemical weathering and enhanced nutrient fluxes associated with global warming and the more humid climate of Pangea.

Multi-proxy record of the Austrian Upper Triassic Polzberg Konservat-Lagerstätte in light of the Carnian Pluvial Episode

“…Depositional records and sections, especially from localities around the western Tethys, documented a climatic transition to warmer and more humid conditions 1 , 2 , 12 , 13 . These climatic perturbations were mainly related to an increase in the volcanic activity at the Wrangellia large igneous province 14 , 15 . This triggered episodes of climate warming, enhanced rainfall and freshwater influx into the marine basins, as well as increased burial of organic carbon and humidification 1 – 5 , 8 .…”

Conodont biostratigraphy of a Carboniferous–Permian boundary section in siliceous successions of pelagic Panthalassa revealed by X-ray computed microtomography

“…Due to the lack of macrofossils and datable tuff beds, microfossils are the key means of age assignment of these successions. In particular, conodonts have proved to be vital in age assignment and correlation with various Palaeozoic to Triassic marine facies in other regions (Isozaki and Matsuda, 1980;Yao et al, 1980;Yamakita et al, 2007;Hori et al, 2011;Yamashita et al, 2018;Muto et al, 2019;Tomimatsu et al, 2020). Pelagic deep-sea sections dated by conodonts are used as sedimentary records of a unique oceanic realm, which also has the advantage of covering extremely long time intervals (millions to tens of millions of years) without receiving strong local effects (Takahashi et al, 2009;Sano et al, 2010;Sano et al, 2012;Nakada et al, 2014;Takahashi et al, 2014;Muto et al, 2018;Muto et al, 2020;Tomimatsu et al, 2020;Grasby et al, 2021;Muto, 2021;Takahashi et al, 2021).…”