First fossil foliage record in the red beds from the Upper Jurassic in the Sichuan Basin, southern China

Abstract

Terrestrial red beds are extensively developed in the Upper Jurassic of the Sichuan Basin, southern China, where few fossils have been documented. Recently, abundant silicified wood specimens were found in the central Sichuan Basin, but no plant foliage fossils have been recorded from the same strata. Here, we report the first leafy shoot fossils collected from the red beds of the Upper Jurassic Penglaizhen Formation in Shehong City, central Sichuan Basin. Based on careful comparisons with potential Mesozoic conifer fossils, they were assigned to Pagiophyllum, an extinct conifer taxon of the family Cheirolepidicaceae. The generic classification agreed with the palaeovegetation features of the Penglaizhen Formation which were represented by gymnosperms of Araucariaceae (Agathoxylon-type wood) and Cheirolepidiaceae (Brachyoxylontype wood). The non-coexistence between the leafy shoot fossil and the petrified wood depicted a unique process of fossil preservation, which may be related to the palaeo-flood events in this area. The palaeoclimate background during the Late Jurassic of Shehong was suggested to be a hot and semi-arid or arid condition, supported by the Classopollisdominated (75-90%) pollen assemblage from the Penglaizhen Formation. The fossil foliage was collected from lacustrine or fluvial sediments. This suggests that the rainy season is a key factor in the development of regional lakes or rivers and flood events, which offered a suitable local environment for plant growth and helped construct a more complex ecological system, allowing a variety of creatures to survive in the central Sichuan Basin area.