Ichnology and sedimentary environment of Cretaceous redbeds in the Ruyang Basin, western Henan Province, China

Abstract

A sequence of terrestrial clastic redbeds of Cretaceous age is exposed in the Ruyang Basin of western Henan Province in China. The rocks consist of conglomerate, sandstone, siltstone and mudstone containing the ichnofossils Psilonichnus, Arenicolites, Palaeophycus, Scoyenia, Planolites, Skolithos and other burrows and rhizoliths. The beds also contain the dinosaur fossil Huanghetitan ruyangensis and Zhongyuansaurus luoyangensis. On the basis of the lithology, sedimentary structures and ichnofossils, it is suggested that the sedimentary environments of the Ruyang Basin during the Cretaceous were primarily alluvial fan in character including middle fan and fan edge subfacies. In this sedimentary setting, eight lithofacies types are distinguished, and two ichnoassemblages are recognized: (1) Scoyenia-Skolithos ichnoassemblage occcuring in braided fluvial deposits of an alluvial fan system, and (2) Psilonichnus-Palaeophycus ichnoassemblage occurring in shallow pond or lake deposits at the fan edge