DataSheet2_Vegetation changes and climate shift during the latest Ladinian to the early Carnian: Palynological evidence from the Yanchang Formation, Ordos Basin, China.pdf

The Middle–Late Triassic climates have attracted the attention of paleontological and geological scientists for the Carnian pluvial event in the early Late Triassic. The event is well-documented in the pelagic and epi-continental marine deposits of the Tethys, Gondwana, and Laurasia. However, inland terrestrial deposits are less frequently depicted, with high-resolution palynological biostratigraphy constraints. In this study, we report the palynological records from the YC8-1 and YC7-3 sub-members of the Yunmeng profile in the Ordos Basin, China, where the YC7-3 was dated at 236.0–234.1 Ma. Two palynological assemblages were recognized and named the Lundbladispora watangensis–Taeniaesporites combinatus assemblage and Lundbladispora communis–Discisporites granulus assemblage for the YC8-1 and YC7-3 sub-members, respectively. Their ages were determined to be the latest Ladinian and early Carnian, respectively, for their stratigraphic correlations with the global boundary stratotype section and point (GSSP) of the base of Carnian in Europe and additional co-occurring floras with condonts in the Upper Triassic of South China. The coexistence of Cyathidites minor (Couper, 1953), Dictyophyllidites harrisii (Couper, 1958), Apiculatisporis bulliensis (Helby ex De Jersey, 1972), Aratrisporites xiangxiensis (Li and Shang, 2011), Piceaepollenites omoriciformis (Bolkh.) (Xu and Zhang, 1984), Podocarpidites ornatus (Pocock, 1962), Discisporites granulus (Zhang, 1984), and Classopollis (Pflug, 1953) is equivalent to the Carnian palynostratigraphic criterion reported in the North China palynofloristic realm. Vegetational changes, especially those occurring at the boundary between Ladinian and Carnian, account for approximately 70% of ferns and over 30% of gymnosperms lost. These were discovered and attributed to the strong seasonal arid climate, indicated by the emergence of Cheirolepidiaceae and Pinuspollenites. We thus know that the climate during the latest Ladinian and early Carnian was “hot house” with seasonal aridity. In addition, three strong monsoonal pluvial pulses were signaled by the humidity index of lowland plants. The present study will enable a better understanding the Carnian pluvial event in the Late Triassic inland basin.

中晚三叠世时期，晚三叠世早期的卡尼期湿润事件（Carnian pluvial event）一直备受古生物与地质学者关注。该事件在特提斯洋、冈瓦纳大陆与劳亚大陆的远洋及陆表海沉积中均有充分记录，但内陆陆相沉积的相关记录较为稀少，且受限于高分辨率孢粉生物地层学研究。本研究报道了中国鄂尔多斯盆地云梦剖面YC8-1亚段与YC7-3亚段的孢粉记录，其中YC7-3亚段的年代限定为236.0–234.1百万年(Ma)。研究识别出两个孢粉组合，分别将YC8-1亚段的组合命名为旺加伦巴德孢（Lundbladispora watangensis）-联缝带孢（Taeniaesporites combinatus）组合，YC7-3亚段的组合命名为普通伦巴德孢（Lundbladispora communis）-粒状盘孢（Discisporites granulus）组合。通过与欧洲卡尼阶底界全球界线层型剖面和点位（Global Boundary Stratotype Section and Point, GSSP）的地层对比，以及华南上三叠统中与牙形石伴生的同期植物群对比，确定二者的地质年代分别为拉丁阶最末期与卡尼阶早期。小杯孢（Cyathidites minor (Couper, 1953)）、哈氏网叶孢（Dictyophyllidites harrisii (Couper, 1958)）、布利尖面孢（Apiculatisporis bulliensis (Helby ex De Jersey, 1972)）、湘西锥环孢（Aratrisporites xiangxiensis (Li and Shang, 2011)）、云杉型云杉粉（Piceaepollenites omoriciformis (Bolkh.) (Xu and Zhang, 1984)）、饰状罗汉松粉（Podocarpidites ornatus (Pocock, 1962)）、粒状盘孢（Discisporites granulus (Zhang, 1984)）与克拉梭粉属（Classopollis (Pflug, 1953)）的伴生组合，与华北孢粉植物区已报道的卡尼期孢粉地层学标准一致。植被更替，尤其是发生在拉丁阶-卡尼阶界线处的更替，导致约70%的蕨类植物与超过30%的裸子植物消失。这一现象与掌鳞杉科（Cheirolepidiaceae）和松型粉属（Pinuspollenites）的出现所指示的强季节性干旱气候相吻合。据此可知，拉丁阶最末期至卡尼阶早期的气候处于“温室”状态且伴随季节性干旱。此外，低地植物湿度指数揭示了三期显著的季风格湿润脉冲事件。本研究有助于更深入地理解晚三叠世内陆盆地中的卡尼期湿润事件。