Benthic foraminiferal morphogroups at the end-Guadalupian extinction in eastern Sichuan Basin, China

Abstract

Benthic foraminiferal morphogroups near the Permian Guadalupian-Lopingian (GLB) reveal their responses to palaeoenvironmental and palaeoecological changes in the eastern Sichuan Basin, China. According to the shell forms, coiling modes, and life positions linked to the life styles and feeding strategies, seven types of benthic foraminiferal morphogroups were recognized in Guadalupian and lower Wuchiapingian carbonate rocks from four lithological profiles. During the Guadalupian Epoch, highly diversified and large number of benthic foraminifera and their various feeding strategies indicated sufficient trophic resources for food. However, the foraminiferal assemblages dropped dramatically after the end-Guadalupian extinction event, reflecting remarkable changes in the nutrient sources and oxygen conditions in the ocean. In the early Wuchiapingian Epoch, nutrient input and plant debris decreased rapidly, while terrigenous detritus increased. As a result, the number of herbivores significantly declined, and suspension feeders and detritivores dominated. Changes in foraminiferal morphogroups in the eastern Sichuan Basin confirmed the existence of a end-Guadalupian extinction event. Surviving benthic foraminifera in Wuchiapiangian, such as Codonofusiella and Eotuberitina, prefer epiphytism, multiple feeding strategies, and low oxygen concentrations, which helped them sustain in a severe ecological environment. The dominant Wuchiapingian foraminifera has changed to other genera, which had to alter their living habits by enlarging the bottom contact area to resist waves and expanding semi-shells to increase feeding capacity. Benthic foraminiferal assemblages from adjacent regions (south China, Tibet, Iran, and Greece) were consistent with our investigation of the morphogroups and showed a similar response to the end-Guadalupian extinction event.