Correlation and stratigraphic implications of the lowermost Cambrian Small Shelly Fossils from new sites of South China

Abstract

Early Cambrian small shelly fossils (SSFs) represent some of the earliest biomineralized examples of metazoans and are often extremely abundant and diverse, so can be useful for regional and intercontinental correlation in pre-trilobitic carbonate or phosphorite deposits. New SSF assemblages chemically extracted from carbonates from the Cambrian Fortunian Stage are reported for the first time from the Yangjiagou Member in the Fucheng area, southern Shaanxi Province, China. The SSFs include anabaritids, protoconodonts, hyolitheminths, maikhanellids, Quadrapyrgites , Archaeooides , Olivooides , and Siphogonuchites . The SSFs recovered represent two previously identified SSF assemblage zones: the Anabarites trisulcatus – Protohertzina anabarica assemblage zone, and the succeeding Paragloborilus subglobosa – Purella squamulosa assemblage zone. The early Cambrian fossil assemblage zones described from this locality are correlated on a regional scale across the Yangtze Platform from eastern Yunnan, the Three Gorge region of the western Hubei, the northern Sichuan, the Ningqiang and Xixiang regions of the southern Shaanxi and the Nemakit–Daldynian Stages of Siberia. The results reveal that the Yangjiagou Member is provisionally equivalent to the Zhongyicun Member of Yunnan, the Yanjiahe Formation of Hubei, the Maidiping Formation of Sichuan, and the Kuanchuanpu Formation of Shaanxi. It offers new evidence and fossil data for the location of the Precambrian–Cambrian boundary in the Micangshan area of the South China.