RUI: Taphonomic Character of Plant Fossil Assemblages at the Permian-Triassic Boundary, Karoo Basin, South Africa

关于陆生植物、昆虫和脊椎动物对P/Tr边界灭绝事件的响应，人们提出了许多假设。这些假设中的许多都是基于不受约束的空间和/或时间数据。大多数都缺乏用于支持解释的分析中使用的古生物学数据的上下文限制。因此，不可能知道这些趋势是否会改变？或变化?从边界前的组合到过渡和边界后的组合都是生态系统的真实反映，或者在地理上是有偏见的。本研究假设，边界前、跨边界和边界后植物化石组合的等剖面数据集将允许在地球历史的这一关键时刻出现陆地生态系统这部分响应的可信特征。等层植物化石记录与海洋领域中已确立的反应是平行的还是相切的？或者，生物多样性不会发生变化；更替和/或更替是否会比直接在P/Tr边界发生得更早或更晚？迄今为止，在南非夸祖鲁纳塔尔省卡鲁盆地东北部进行的研究表明，在四种不同的沉积学和地学条件下，晚二叠纪巨型植物组合得以保存。每种巨型花组合类型都保留了对化石记录有贡献的植被的非常不同的特征。它们是：(1)在废弃河道填充层序内的副原生组合，类似于现代和其他古代牛轭湖；(2)分散和孤立的异域组合，保存在大型细粒度河流体系内的森林床和再活化面上；(3)粗粉砂岩河道层质沙丘内集中的席状异质组合；(4)浊积岩中分散、分选的组合。文中提供的关于两个地方的数据？布尔沃和旺根德利夫大坝？证明以前对这些地点的化石组合的解释是不正确的。如果将这些数据作为解释的基础，那么由此产生的假设是不恰当的。随着卡鲁沉积包体在三叠纪的大陆化，除了最后一种沉积组合类型外，其他所有的沉积组合类型都应该出现在过渡期和后边界段。已经确定了七个跨界和跨界后的区域，其中保存了植物化石和/或脊椎动物，并将作为2004年实地考察季节的基础。预计对这部分地层的等地层组合的鉴定将使生物多样性指数与目前由一个国际研究小组的其他成员（包括美国、荷兰和南非的科学家）确定的生物多样性指数进行直接比较。本提案要求资金支持本科生的研究，旨在协助获取南非卡鲁盆地的等面层数据集。通过接下来两年的野外工作和实验室分析，将评估P/Tr和早三叠纪到中三叠纪的位置，以识别和表征在二叠纪晚期发现的沉积序列。

PROJECT SUMMARYPage AMany hypotheses have been proposed for the response of the land plants, insects, andvertebrates to the P/Tr boundary extinction event. Many of these hypotheses are based onpoorly unconstrained spatial and/or temporal data. Most lack any contextual constraintof the paleontological data used in the analysis used to support the interpretation.Hence, it is not possible to know if the ?trends? or ?changes? seen to occur from thepreboundary assemblages into the transitional and post-boundary assemblages are a truereflection of the ecosystem or are biased taphonomically.This proposal hypothesizes that an isotaphonomic data set of pre-boundary,trans-boundary, and post-boundary plant-fossil assemblages will allow for the emergence ofa credible characterization of the response within this part of the terrestrial ecosystemat this critical point in Earth history. Will the isotaphonomic plant-fossil recordparallel or be tangential to the well established response in the marine realm? Or, willthere be no change in biodiversity; might the replacement and/or turnover occur earlier orlater in time than directly at the P/Tr boundary?Research conducted, to date, in KwaZulu Natal Province, South Africa, in the northeasternpart of the Karoo Basin indicates that Late Permian megafloral assemblages are preservedin four different sedimentologic and taphonomic conditions. Each megafloral assemblagetype preserves a very different signature of the vegetation contributed to the fossilrecord. These are: (1) parautochthonous assemblages within abandoned fluvial channel fillsequences, similar to modern and other ancient oxbow lakes; (2) dispersed and isolated,allochthonous assemblages preserved on foreset beds and reactivation surfaces withinlarge, fine-grained fluvial regimes; (3) concentrated, mat-like allochthonous assemblageswithin bedload dunes of coarse siltstone channels; and (4) dispersed, sorted assemblagesin turbidites. Data presented in the text concerning two localities ? Bulwer andWagendrift Dam ? demonstrate that previous interpretations of the fossil assemblages inthese sites are incorrect. And if these data are used from the literature as the basisfor interpretation, the resulting suppositions are inappropriate.With an increasing continentalization of the sedimentary package in the Karoo into theTriassic, all but the last taphonomic assemblage type should be encountered in thetransitional and post-boundary sections. Seven cross boundary and post boundary sectionshave been identified in which plant fossils and/or vertebrates are preserved, and willserve as the basis for the 2004 field season. It is anticipated that identification ofisotaphonomic assemblages in this part of the stratigraphy will allow for directcomparison of biodiversity indices with those presently being determined by other membersof an international research team, involving U.S., Dutch, and South African scientists.The present proposal requests funds to support undergraduate student research designed toassist in the acquisition of an isotaphonomic data set in the Karoo Basin, South Africa.Through the next two years of field work and laboratory analysis, P/Tr and early to middleTriassic localities will be assessed to identify and characterize those depositionalsequences as found in the latest Permian.