DataSheet1_Paleoenvironmental and Biotic Changes in the Late Triassic of Argentina: Testing Hypotheses of Abiotic Forcing at the Basin Scale.pdf

Paleoenvironmental factors such as climate change are often hypothesized as critical for ecosystem changes over evolutionary time scales. Theoretically, these changes should be observable in the fossil record, but the robust linkage of biotic shifts to climate events remains difficult. The Late Triassic Period is an ideal interval for testing such hypotheses within terrestrial ecosystems because of a number of large-scale climate events, such as the Carnian Pluvial Episode (CPE), and a rich, well-studied fossil record. Nonetheless, at regional to global scales, few linkages have been identified during most of the Late Triassic. Here, we synthesize a multi-proxy basin-scale dataset of paleoenvironmental data, including new information from clay mineralogy and paleosol major- and trace-element geochemistry, to understand paleoclimate changes in the Ischigualasto-Villa Unión Basin of northwestern Argentina. In combination with diversity and relative abundance information from the well-sampled plant and tetrapod fossil record in the basin, we then use accepted evolutionary models of abiotic forcing of changes in ecosystems to test previously proposed hypotheses of floral and faunal variations at a basin scale. We find that although many patterns are best explained by sampling issues and taphonomy, pseudosuchian archosaur diversity and rhynchosaur relative abundance conform to predictions of paleoenvironmental forcing as the climate changed from warmer, drier conditions to more temperate humid conditions. These data demonstrate how high-resolution multi-proxy data and a well-sampled fossil record at a basin-scale can be used to test hypotheses of abiotic forcing of ecosystems in deep time, and highlights where future efforts should be directed in terms of filling data gaps and testing new hypotheses.

诸如气候变化在内的古环境因素，常被学界假说为演化时间尺度下生态系统变迁的关键驱动因子。从理论上讲，这类变迁应能在化石记录中被观测到，但要建立生物类群更替与气候事件之间的可靠关联，仍颇具挑战。晚三叠世（Late Triassic Period）是在陆地生态系统中验证此类假说的理想时段，这是因为该时期存在多起大型气候事件，如卡尼期洪积事件（Carnian Pluvial Episode, CPE），且拥有丰富且被充分研究的化石记录。尽管如此，在区域乃至全球尺度上，晚三叠世多数时段的此类关联仍鲜有发现。本研究整合了一套盆地尺度的古环境多代用指标数据集，其中包含来自黏土矿物学、古土壤常量及微量元素地球化学的全新数据，旨在解析阿根廷西北部伊斯基瓜拉斯托-维拉松盆地（Ischigualasto-Villa Unión Basin）的古气候变迁。结合该盆地中采样充分的植物与四足动物（tetrapod）化石记录所提供的多样性及相对丰度数据，我们借助已被广泛认可的生态系统变迁非生物驱动演化模型，在盆地尺度下检验此前提出的动植物群演变假说。研究结果显示，尽管多数古生态格局可通过采样偏差与埋藏学（taphonomy）过程得到最佳解释，但假鳄类主龙（pseudosuchian archosaur）多样性与喙龙类（rhynchosaur）相对丰度，却符合气候从暖干环境向温湿环境转变时古环境驱动的预测结果。本数据集证实了，盆地尺度下的高分辨率多代用指标数据与采样充分的化石记录，可用于检验深时生态系统的非生物驱动假说，并指明了未来填补数据空白、验证新假说的研究方向。