Paleoclimatic Variations Recorded from Geochemical Weathering Proxies and Provenance Studies in the South Bar and Sydney Mines Formations of the Sydney Basin, Nova Scotia, North Atlantic Canada

Considerable efforts have been dedicated to understanding climatic evolution in the Late Paleozoic Ice Age, as this period marks Earth’s only transition from Icehouse to Greenhouse conditions on a vegetated planet. The South Bar Formation (SBF) and Sydney Mines Formation (SMF) of the Sydney Basin, Nova Scotia, North Atlantic Canada, consist of Bashkirian-Moscovian coastal alluvial plain deposits that record climate variation within a low-latitude setting during the late Paleozoic. In this study, a geochemical investigation was carried out to estimate paleoweathering, paleotemperature, and provenance of these formations. Results from paleoweathering proxies (Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), and CIX of Garzanti et al., 2014 (show variability in chemical weathering intensity throughout the section. Chemical weathering intensity (CIA) ranges from 72–79 in the SBF to 65–86 in SMF. Notably, pronounced cyclicity is observed in the SMF upward from 734 m (SMF boundary). Concurrently this trend is also observed across paleotemperature estimates (LST), which range from 15–19°C in the SBF to 11–23°C in the SMF, and in bulk carbonate δ13C data. This pattern change coincides with the boundary between the SBF and SMF and corresponds to changes in lithofacies and depositional environment. Evidence from paleoweathering, paleotemperature estimates, and stable isotope geochemistry suggests that the paleoenvironment became progressively more seasonal and stressed upward through the Moscovian of Atlantic Canada, leading to a paleoenvironmental crisis near the Moscovian/Kasimovian boundary, a time of widespread extinction of tropical lowland plant taxa in the Euramerican paleotropics.