title: Early Triassic wrinkle structures on land: stressed environments and oases for life.
abstract: Wrinkle structures in rocks younger than the Permian-Triassic (P-Tr) extinction have been reported repeatedly in marine strata, but rarely mentioned in rocks recording land. Here, three newly studied terrestrial P-Tr boundary rock succession in North China have yielded diverse wrinkle structures. All of these wrinkles are preserved in barely bioturbated shore-shallow lacustrine siliciclastic deposits of the Liujiagou Formation. Conversely, both the lacustrine siliciclastic deposits of the underlying Sunjiagou Formation and the overlying Heshanggou Formation show rich bioturbation, but no wrinkle structures or other microbial-related structures. The occurrence of terrestrial wrinkle structures in the studied sections reflects abnormal hydrochemical and physical environments, presumably associated with the extinction of terrestrial organisms. Only very rare trace fossils occurred in the aftermath of the P-Tr extinction, but most of them were preserved together with the microbial mats. This suggests that microbial mats acted as potential oases for the surviving aquatic animals, as a source of food and oxygen. The new finds suggests that extreme environmental stresses were prevalent both in the sea and on land through most of the Early Triassic.
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China.
authors.forename: Daoliang
authors.initials: D
authors.lastname: Chu
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China.
authors.forename: Jinnan
authors.initials: J
authors.lastname: Tong
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China.
authors.forename: Haijun
authors.initials: H
authors.lastname: Song
authors.affiliation: School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, UK.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Benton
authors.affiliation: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Bottjer
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China.
authors.forename: Huyue
authors.initials: H
authors.lastname: Song
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China.
authors.forename: Li
authors.initials: L
authors.lastname: Tian
mesh_terms: D000818:Animals; D002681:China; D017753:Ecosystem; D004777:Environment; D053476:Extinction, Biological; D005580:Fossils; D019015:Geologic Sediments / Q000032:analysis*; D009792:Oceans and Seas; D010100:Oxygen / Q000737:chemistry; D010163:Paleontology / Q000379:methods; D013312:Stress, Physiological / Q000502:physiology
chemical_list: D010100:Oxygen