Enhanced global terrestrial moisture from the Early Triassic to the Late Triassic: Evidence from extensive Neocalamites forests in North China

Multistorey vegetation was reestablished in the Middle to Late Triassic following the end-Permian mass extinction, ultimately forming extensive forests worldwide. There are some cosmopolitan elements in these communities, such as the Neocalamites (Sphenophyta), that bear significant climatic implications. Here, we report an in situ fossil forest of the extinct Sphenophyta Neocalamites from the Chang-8 member of the Middle Triassic Yanchang Formation (ca. 242 Ma) in North China. The in situ pith casts of more than 210 Neocalamites, ranging in diameter from 6 cm to 35 cm with a spacing ranging from 0.1 m to 4.5 m, remain in their original growing positions at the Tongchuan, Jiyuan, and Huangling localities. Preliminary estimates suggest that the height of Neocalamites ranges from 15 m to 35 m, potentially reaching up to 70 m. Sedimentological analysis of plant-bearing deposits revealed that these Neocalamites plants grew along distributary channels within interdistributary swamps in humid delta plain environments. Neocalamites first appeared in the Late Permian, diversified during the last stage of the Middle Triassic, and occurred in different areas of the Pangaea supercontinent; this is believed to be coupled with Triassic global climatic wetting and terrestrial ecosystem recovery processes. Neocalamites, which formed the earliest monotypic stands of the Triassic during the Ladinian stage (ca. 242 Ma), serve as a paleontological proxy for global climatic wetting during the Triassic, indicating the wide-scale intensification of the hydrological cycle prior to the Late Triassic Carnian Pluvial Episode.