Glacio‐eustasy and δ¹³C across the Mississippian–Pennsylvanian boundary in the eastern Paleo‐Tethys Ocean (South China): Implications for mid‐Carboniferous major glaciation

Abstract

A positive carbonate δ13C excursion (by ~1.5–3.0‰) has been reported across the Mississippian–Pennsylvanian boundary (MPB) from Euramerican epicontinental seas, implying a coeval atmospheric pCO2 decrease and Gondwanan glaciation at that time. This excursion was mainly observed in carbonate platforms which experienced repeated subaerial exposure. The South China Block was located in the middle of the Paleo‐Tethys Ocean and the Panthalassic Ocean during the Carboniferous and contains well‐preserved carbonate slope strata across the MPB. Four lithofacies were defined in the studied Naqing, Narao, and Dianzishang sections, including thin‐bedded lime mudstones, laminated wackestones to packstones, normally‐graded packstones, and slumped limestones. Immediately above the MPB, a bed of normally‐graded packstones or slump masses occurs in the studied sections, which together with coeval subaerial‐exposure features in shallow‐water carbonate platform of South China, suggests a significant sea‐level fall across the MPB. Carbonate δ13C records show a consistent value of ~3.0‰ below the MPB in the Naqing and Narao sections, and both sections show an obvious rise in δ13C across the MPB (by ~0.5–1.0‰). The relatively small‐magnitude rise in δ13C would have resulted from well‐mixed seawater induced by intensified upwelling in the eastern Paleo‐Tethys Ocean during the glacial peak. Hence, the carbonate δ13C values recorded in the South China Block may represent a mean δ13C of the dissolved inorganic carbon in global ocean water at that time. Correlation between carbonate δ13C and previously published conodont δ18O and 87Sr/86Sr records suggests that the MPB glaciation was mainly driven by enhanced continental weathering, rather than increased organic carbon burial, although further quantitative simulation is required to better understand the interlinked processes during the Earth's penultimate icehouse.

Exploring Icehouse Cyclicity Pattern and Seawater Dynamics on an Ancient Carbonate Platform With Nd Isotopes (Carboniferous, Southern Kazakhstan)

“…All these components are characterized by relatively uniform 87 Sr/ 86 Sr ratios that lie within a very narrow interval of 0.7079–0.7081 (Figure 8). Like radiaxial cement δ 13 C and δ 18 O values, these Sr isotope ratios are also consistent with Sr isotope signatures of seawater during the Serpukhovian (see Chen et al., 2018; Tian et al., 2020).…”

“…The proposed hypothesis requires further evaluation in other Carboniferous carbonate successions in the Uralian-Turkestan Ocean and, more broadly, in the Paleo-Tethys realm, for which upwelling activity was postulated based on carbonate δ 13 C records and other data (e.g., Macarewich & Poulsen, 2022;Tian et al, 2020). Further Nd isotope studies in shallow-water carbonates in the Paleo-Tethys and Panthalassic oceans will also be necessary to elucidate potential high-frequency, sub-Milankovitch cyclicity during Carboniferous glaciations.…”

“…During late Mississippian‐early Pennsylvanian times, enhanced climate‐driven upwelling was suggested to have occurred in the western margin of Euramerica (located in the eastern Panthalassic Ocean) and in the eastern Paleo‐Tethys, based on regional variations in δ 13 C records and the distribution of phosphatic black shales (Algeo & Heckel, 2008; Liu et al., 2015; Mii et al., 2001; Tian et al., 2020). Recently, Macarewich and Poulsen (2022) provided global estimates of ocean circulation during the latest Carboniferous‐early Permian, using the Community Earth System Model.…”

Theory and classification of mass extinction causation

“…The Late Mississippian mass extinction, which occurred during the Serpukhovian Stage at ∼330–324 Ma, resulted in large losses of diversity among brachiopods [ 183 ] and reef fauna [ 184 ], although this biocrisis was at least partly due to low origination rates [ 185 ]. It coincided with a major expansion of continental ice mass in Gondwana [ 186 ], a large mid-Carboniferous eustatic fall that produced a deep unconformity in North America and elsewhere [ 187 , 188 ], and strong climatic cooling, as recorded in O-isotope records [ 184 , 189 ]. These features, accompanied by PCIEs [ 189 ], mark the Late Mississippian biocrisis as a carbon-burial event (Fig.…”

Evolution of the conodont Diplognathodus ellesmerensis from D. benderi sp. nov. at the Bashkirian–Moscovian (lower–middle Pennsylvanian) boundary in South China

“…These limestones can be replaced by chert to varying degrees, forming either nodular or irregular beds (Tian et al . 2019). Two nearby additional reference sections in the Luodian area, Luokun and Narao (Fig.…”