Upper Devonian conodont fauna from Western Hubei, China and its significance

Abstract

ABSTRACT Pelagic standard conodont biozonation is less applicable to nearshore shallow-water depositional settings close to the peritidal, where it is needed to establish its own conodont zonation. The Upper Devonian Xiejingsi Formation in South China is an important unit for nearshore conodont biostratigraphy investigation as its deposits in the nearshore argillaceous-carbonate mixed facies which yield numerous marine fossils. 25 conodont species belonging to 6 genera of platform elements were described in four sections of this formation in western Hubei, including 9 new species. Based on the conodont distribution in these sections, six nearshore conodont biozones are introduced in ascending order: Polygnathus brevis – Polynodosus changyangensis sp. nov. Assemblage Zone, Icriodus cornutus – Pelekysgnathus arcuatus sp. nov. – Polygnathus brevilaminus Assemblage Zone, Palmatolepis angulata Zone, Palmatolepis angulata – Palmatolepis quadrantinodosalobata Assemblage Zone, Palmatolepis quadrantinodosalobata Zone and Polygnathus planirostratus Zone. The correlation of these biozones with those of pelagic standard ones indicates an age of the Xiejingsi Formation in western Hubei from at least the Frasnian linguiformis Zone to the Famennian Lower rhomboidea Zone. Through constructing nearshore shallow-water conodont biozones based on the establishment of comprehensive conodont succession, this paper provides a case study for high-resolution conodont biostratigraphy investigation in the shallow-water settings.