Vegetation history, diversity patterns, and climate change across the Triassic/Jurassic boundary
Vegetation history, diversity patterns, and climate change across the Triassic/Jurassic boundary
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DOI：
10.1666/09071.1
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发表时间：
2012-03-01
期刊：
影响因子：
2.7
通讯作者：
Kuerschner, Wolfram M.
中科院分区：
文献类型：
--
作者：
Bonis, Nina R.;Kuerschner, Wolfram M.
对欧洲两个主要剖面（奥地利Hochalplgraben和英国St. Audrie’s Bay）浅海三叠系-侏罗系（Tr/J）边界层的高分辨率孢粉资料进行了分析，重建了植被、生物多样性和气候的变化。在Hochalplgraben，有针叶树和种子蕨类植物的硬木裸子植物森林被蕨类植物、棒状苔藓和苔类植物的优势植被所取代，这与最新雷蒂亚时期孢子类型的多样化相一致。多变量统计分析表明，在Hochalplgraben的Tr/J边界上有暖湿化的趋势。圣奥德里湾的植被变化明显不同。这里的裸子植物混交林被单调的以雪蕨科植物为主的植被所取代（80-100%）。这种变化是由向更温暖、更干旱的气候过渡造成的。在圣奥德里湾观察到的多样性减少证实了这一解释。虽然这两个剖面都显示了主要的植被变化，但它们都没有显示出明显的植物大灭绝。世界各地的Tr/J边界剖面汇编表明，在泛古大陆内部存在以cheirolepidiaceae为主导的森林，并且在特提斯洋附近产孢子植物的丰度增加。我们认为Tr/J孢粉记录反映的不均匀植被变化是中大西洋岩浆省火山活动引起的环境变化的结果。温室气体的增加导致气候变暖，并增强了大陆和海洋之间的热对比。因此，季风系统变得更强，导致大陆内部更干燥，特提斯洋边缘附近的降雨更密集。
High-resolution palynological data sets from shallow marine Triassic-Jurassic (Tr/J) boundary beds of two principal sections in Europe (Hochalplgraben in Austria and St. Audrie's Bay in the United Kingdom) were analyzed to reconstruct changes in vegetation, biodiversity, and climate. In Hochalplgraben, a hardwood gymnosperm forest with conifers and seed ferns is replaced by vegetation with dominant ferns, club mosses and liverworts, which concurs with an increased diversification of spore types during the latest Rhaetian. Multivariate statistical analysis reveals a trend to warmer and wetter conditions across the Tr/J boundary in Hochalplgraben. The vegetation changes in St. Audrie's Bay are markedly different. Here, a mixed gymnosperm forest is replaced by monotonous vegetation consisting mainly of Cheirolepidiaceae (80-100%). This change is caused by a transition to a warmer and more arid climate. The observed diversity decrease in St. Audrie's Bay affirms this interpretation. Although both sections show major vegetation changes, neither of them demonstrates a distinctive floral mass extinction. A compilation of Tr/J boundary sections across the world demonstrates the presence of Cheirolepidiaceae-dominated forests in the Pangaean interior and increases in abundance of spore-producing plants adjacent to the Tethys Ocean. We propose that the non-uniform vegetation changes reflected in the Tr/J palynological records are the result of environmental changes caused by Central Atlantic Magmatic Province volcanism. The increase in greenhouse gases caused a warmer climate and an enhanced thermal contrast between the continent and the seas. Consequently, the monsoon system got stronger and induced a drier continental interior and more intensive rainfall near the margins of the Tethys Ocean.