Stratigraphical and δ13C records of Permo-Carboniferous platform carbonates, South China: Responses to late Paleozoic icehouse climate and icehouse–greenhouse transition

Abstract

Little attention has been focused on the stratigraphical imprints of the Late Paleozoic Ice Age on the equatorial eastern Paleo-Tethys. An integrated study of biostratigraphy, microfacies, and stable carbon isotope stratigraphy was carried out on Pennsylvanian–middle Guadalupian carbonates of the Gongchuan section in the Bama Platform, South China. It records seven cooling and two warming pulses in the pre-Kungurian interval, comparing with ice-proximal stratigraphical records and far-field indirect proxies in lower latitudes. A Kungurian negative δ13C excursion (from +4.4‰ at the base of the Kungurian to +1.6‰) recorded only in the subequatorial belt is documented here. It is followed by a global positive δ13C trend reaching +5.3‰ near the Cisuralian–Guadalupian boundary. Seven third-order shallowing–upward cycles are reported for the first time from the Kungurian succession. The duration of each cycle is estimated to ca. 1myr. These cycles are interpreted as being of glacioeustatic origin and mainly driven by long-period modulations of obliquity (~1.2myr) under major pCO2 decreasing condition. This interpretation is supported by recent climate–ice sheet modeling and Cenozoic glaciation studies, which argue that astronomical forcing will be amplified by large-magnitude perturbations in the carbon cycle, when only localized ice-centers persist. Our results emphasize the need for integration of sedimentological and paleoclimatological proxies in elucidating the dynamics of the deglacial phases of the Late Paleozoic Ice Age.