Early to Middle Permian fusulinids from the northern Changning-Menglian Belt, western Yunnan, China: Taxonomic features and insights for Tethyan paleogeography

Abstract

The Changning-Menglian Belt in western Yunnan, China, which hosts probable seamount-related limestones, represents a key Tethyan suture in Asia. Fusulinids in these limestones are both age- and environment-sensitive, and thus offer insights into this belt's complex paleogeography and the hitherto understudied benthic faunas within the pelagic Tethys. This study presents late Early to Middle Permian fusulinids from the northern part of this belt, mainly collected from the Lizishu Section. Key taxa in these collections, notably Neoschwagerina brevis and N. margaritae, indicate a Roadian-Capitanian age. Furthermore, qualitative and quantitative comparison, including cluster and network analysis, reveal that Middle Permian fusulinids in this belt exhibit the highest Jaccard similarity with those of the peri-Gondwana Baoshan Block, whereas Early Permian fusulinids of this belt show closer affinity to coeval ones from Cathaysian South China. The reduced connectivity between this belt and South China differs markedly from the enhanced similarities between the peri-Gondwana and Cathaysian regions from the Early to Middle Permian. This pattern suggests that the limestone successions now preserved in this belt probably represent carbonate caps of seamounts generated at different ages within the Tethyan Ocean. The carbonates of mainly Middle Permian ages likely were situated farther from equatorial South China than their Early Permian counterparts. Specifically, the Middle Permian fusulinids of this belt may inhabit paleolatitudes akin to those of the Baoshan Block, considerably higher than Cathaysian and western peri-Gondwana localities. These findings underscore the unique role of seamounts as dynamic habitats for fusulinids and paleogeographic markers in the Tethyan Ocean.