Fusulinid-bearing oolites from the Tengchong Block in western Yunnan, SW China: Early Permian warming signal in the eastern peri-Gondwana

Abstract

Discovery of fusulinid-bearing oolites from the Tengchong Block in western Yunnan, China, provides new insights into Permian paleoclimatic history of the eastern peri-Gondwana. In the northern Tengchong Block, new carbonate samples from the lower part of the Dadongchang Formation yield a monotonous fusulinid assemblage, comprising Eoparafusulina tschernyschewi tschernyschewi, E. tschernyschewi oblonga, E. tibetica, E. aff. tschernyschewi tschernyschewi and E. aff. laudoni. This assemblage correlates well to late Sakmarian–Artinskian fusulinids widespread among the Cimmerian blocks in peri-Gondwana, which were characterized by low diversity and dominance of cosmopolitan taxa. Such fusulinids have been interpreted to indicate temperate-water environment in the aftermath of late Paleozoic glaciation. Moreover, the eastern Cimmerian region has been suggested, by both paleontological and sedimentological data, to be even cooler than the western region especially during the Early Permian. However, the fusulinids of this study unexpectedly occur within oolites, as ooids diagnostic for warm-water settings, have never been recorded from Early Permian strata of any eastern Cimmerian block. This new finding in the northern Tengchong Block indicate that the shallow marine there was warm enough to accommodate not only poorly diversified fusulinids but also oolites, even immediately posterior to the late Paleozoic glaciation. The appearance of these oolites is more likely ascribed to a warming pulse of sea-surface temperature in the context of post-glacial climatic amelioration than to the northward drift of the Tengchong Block.