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

关于陆地植物、昆虫和脊椎动物对P/Tr边界灭绝事件的反应，已经提出了许多假说。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。大多数缺乏用于支持解释的分析中使用的古生物数据的任何上下文约束。因此，不可能知道？趋势？或者？改变？从边界前的组合到过渡和边界后的组合看起来是生态系统的真实反映，或者在地带学上是有偏见的。这一提议假设，边界前、跨界和边界后植物-化石组合的等位相学数据集将允许出现对地球历史上这一关键时刻陆地生态系统这一部分的反应的可信特征。植物化石等位学记录是否会与海洋领域已有的反应平行或相切？或者，生物多样性将不会发生变化？更替和/或更替是否会比直接在P/Tr界线发生的时间更早或更晚？迄今为止，在卡鲁盆地东北部的南非夸祖鲁纳塔尔省进行的研究表明，晚二叠世的大型生物群组合被保存在四种不同的沉积学和挖掘学条件下。每一种巨型植物组合类型都保留了对化石记录做出贡献的植被的截然不同的特征。它们是：(1)类似于现代和其他古代牛尾湖的废弃河道充填层序中的异地组合；(2)保存在大而细粒河流体系中的前积层和复活面上的分散而孤立的异地组合；(3)粗粉砂岩河道推移沙丘内的密集垫状异地组合；以及(4)浊积岩中的分散、分选组合。正文中提供的关于两个地方的数据？布尔沃和瓦根里夫特大坝？证明以前对这些遗址中化石组合的解释是不正确的。如果这些资料被用来作为解释的基础，由此产生的假设是不正确的。随着卡鲁沉积包进入三叠纪的陆表化程度的增加，除最后一种挖掘组合类型外，所有类型的组合都应该在过渡和后界线剖面中遇到。已经确定了保存植物化石和/或脊椎动物的七个跨界和边界后剖面，并将作为2004年野外季节的基础。预计在这部分地层中识别同位素组合将允许将生物多样性指数与目前由包括美国、荷兰和南非科学家在内的国际研究小组的其他成员确定的指数进行直接比较。目前的提议要求资金支持本科生研究，旨在帮助获取南非卡鲁盆地的同位素数据集。通过未来两年的野外工作和实验室分析，将对P/Tr和早中三叠世地区进行评估，以识别和描述在最新的二叠纪中发现的沉积层序。

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.