Two types of hyperthermal events in the Mesozoic-Cenozoic: Environmental impacts, biotic effects, and driving mechanisms

Abstract

A deeper understanding of hyperthermal events in the Earth's history can provide an important scientific basis for understanding and coping with global warming in the Anthropocene. Two types of hyperthermal events are classified based on the characteristics of the carbon isotope excursion (CIE) of the five representative hyperthermal events in the Mesozoic and Cenozoic. The first type is overall characterized by negative CIEs (NCHE) and represented by the Permian-Triassic boundary event (PTB,~252 Ma), the early Toarcian oceanic anoxic event (TOAE,~183 Ma), and the Paleocene-Eocene Thermal Maximum event (PETM,~56 Ma). The second type is overall characterized by positive CIEs (PCHE) and represented by the early Aptian oceanic anoxic event (OAE1a,~120 Ma) and the latest Cenomanian oceanic anoxic event (OAE2,~94 Ma). Hyperthermal events of negative CIEs (NCHE), lead to dramatic changes in temperature, sedimentation, and biodiversity. These events caused frequent occurrence of terrestrial wildfires, extreme droughts, acid rain, destruction of ozone layer, metal poisoning (such as mercury), changes in terrestrial water system, and carbonate platform demise, ocean acidification, ocean anoxia in marine settings, and various degree extinction of terrestrial and marine life, especially in shallow marine. In contrast, hyperthermal events of positive CIEs (PCHE), result in rapid warming of seawater and widespread oceanic anoxia, large-scale burial of organic matter and associated black shale deposition, which exerted more significant impacts on deep-water marine life, but little impacts on shallow sea and terrestrial life. While PCHEs were triggered by volcanism associated with LIPs in deep-sea environment, the released heat and nutrient were buffered by seawater due to their eruption in the deep sea, thus exerted more significant impacts on deep-marine biota than on shallow marine and terrestrial biota. This work enriches the study of hyperthermal events in geological history, not only for the understanding of hyperthermal events themselves, large igneous provinces, marine and terrestrial environment changes, mass extinctions, but also for providing a new method to identify the types of hyperthermal events and the inference of their driving mechanism based on the characteristics of carbon isotopic excursions and geological records.

Terrestrial expression of the Cretaceous greenhouse regime and its relationship withOAE1a: Evidence from the Jiaolai Basin, eastern China

“…Marine sediment δ 18 O, palaeothermometer TEX 86 , and other palaeoclimatic proxies indicate that the overall temperatures remained relatively high values and may have triggered global OAEs during the mid‐Cretaceous (Ando, Kaiho, Kawahata, & Kakegawa, 2008; Bottini et al, 2015; Bottini, Cohen, Erba, Jenkyns, & Coe, 2012; Hochuli et al, 1999; Keller et al, 2011; Mutterlose, Bottini, Schouten, & Sinninghe Damsté, 2014; Mutterlose, Malkoc, Schouten, Sinninghe Damsté, & Forster, 2010; Zhang, Ji, Du, Dai, & Hou, 2015). Of these, two hothouse regimes, coupling with OAEs are outstanding in the Cretaceous (Hu, Li, Han, & Li, 2020). The first hothouse regime, coupling with the OAE (termed as the OAE 1a, also the Selli event) occurred in Early Aptian (~120 Ma), which has resulted in an increase of 5–6°C and 2–4°C in surface seawater temperature in low‐ and moderate‐latitudes, respectively (Littler et al, 2011; Mutterlose et al, 2010; Mutterlose et al, 2014; Naafs & Pancost, 2016).…”

Marine anoxia linked to abrupt global warming during Earth’s penultimate icehouse

“…Although changes in p CO 2 during the early Cenozoic warming events (foremost, the PETM) were larger in magnitude and more rapid than carbon (C) perturbations of Quaternary glacial–interglacial transitions ( 11 , 12 ), they occurred under a background greenhouse climate state characterized by high baseline atmospheric p CO 2 (∼1,000 ppm). Other periods of pre-Cenozoic C perturbations ( 13 , 14 ), such as the Cretaceous and Jurassic (Toarcian) ocean anoxic events (OAEs) ( 15 , 16 ), and the end-Triassic ( 17 ) and the end-Permian mass extinction events ( 18 ), also occurred during background greenhouse climates ( 19 , 20 ). These greenhouse OAEs have provided constraints on and insights into how to model climate change and marine redox evolution.…”

High‐Resolution C‐Isotope, TOC and Biostratigraphic Records of OAE 1a (Aptian) From an Expanded Hemipelagic Cored Succession, Western Tethys: A New Stratigraphic Reference for Global Correlation and Paleoenvironmental Reconstruction

“…Nevertheless, the p CO 2 record drops back to pre‐OAE values during Ap6 and Ap7 (Heimhofer et al., 2004; Naafs et al., 2016; Figure 6). Although the top of Ap6 is generally considered as the end of OAE 1a, the Ap7 segment records a gradual return to pre‐OAE conditions, and has been considered as the “recovery stage” (Hu et al., 2020), affected by protracted environmental perturbations (Castro et al., 2019). The upper part of Ap7 segment records the highest C‐isotope values of the core, which mark the end of the positive plateau, and the initiation of a decreasing trend that characterizes the base of the upper Aptian.…”