Guttulatic calcite evidence for carboniferous icehouse climate in the Ordos Basin, North China Craton

Although the Carboniferous Icehouse Climate resulted in extensive glaciation, its impact on the palaeoclimate in the North China Craton remains enigmatic owing to the stratigraphic hiatus that occurred from the Middle Ordovician to the Late Carboniferous. Guttulatic calcite in the rock record is often used as a proxy for frigid climate conditions. By integrating cathodoluminescence (CL), petrological analysis, and in situ geochemical analysis, the guttulatic calcite was identified, enabling teconstruction of the palaeoclimate evolution during the Carboniferous in the Ordos Basin. The guttulatic calcite in the study area is composed of core and annular overgrowth exhibiting multi-bands polarized colours and synergistic CL response changes. The characteristics of major, trace, rare earth elements, and Sr isotope are consistent for the same polarized colour cement but vary among cements with bright and dark colours. Bright and dark calcite cements represent different weathering intensities; bright calcite cement is a faithful recorder of palaeoclimate variations, with guttulatic calcite representing past icehouse events. Part of the Carboniferous palaeoclimate changed from arid to humid and then to semi-arid, corresponding to weathering intensity variations from weak to strong, and then to moderate, indicating the periodic disappearance of an icehouse climate in the Ordos Basin.