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Glacio‐eustasy and δ 13 C across the Mississippian–Pennsylvanian boundary in the eastern Paleo‐Tethys Ocean (South China): Implications for mid‐Carboniferous major glaciation
Author(s) -
Tian Xiaoxu,
Chen Jitao,
Yao Le,
Hu Keyi,
Qi Yuping,
Wang Xiangdong
Publication year - 2020
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.3551
Subject(s) - geology , carboniferous , carbonate , subaerial , paleontology , pennsylvanian , carbonate platform , glacial period , dolomitization , carbonate rock , sea level , cyclostratigraphy , tethys ocean , sedimentary rock , sedimentary depositional environment , oceanography , facies , structural basin , tectonics , subduction , materials science , metallurgy
A positive carbonate δ 13 C excursion (by ~1.5–3.0‰) has been reported across the Mississippian–Pennsylvanian boundary (MPB) from Euramerican epicontinental seas, implying a coeval atmospheric p CO 2 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 δ 13 C 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 δ 13 C across the MPB (by ~0.5–1.0‰). The relatively small‐magnitude rise in δ 13 C would have resulted from well‐mixed seawater induced by intensified upwelling in the eastern Paleo‐Tethys Ocean during the glacial peak. Hence, the carbonate δ 13 C values recorded in the South China Block may represent a mean δ 13 C of the dissolved inorganic carbon in global ocean water at that time. Correlation between carbonate δ 13 C and previously published conodont δ 18 O and 87 Sr/ 86 Sr 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.