Page A Many hypotheses have been proposed for the response of the land plants, insects, and vertebrates to the P/Tr boundary extinction event. Many of these hypotheses are based on poorly unconstrained spatial and/or temporal data. Most lack any contextual constraint of 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 the preboundary assemblages into the transitional and post-boundary assemblages are a true reflection 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 of a credible characterization of the response within this part of the terrestrial ecosystem at this critical point in Earth history. Will the isotaphonomic plant-fossil record parallel or be tangential to the well established response in the marine realm? Or, will there be no change in biodiversity; might the replacement and/or turnover occur earlier or later in time than directly at the P/Tr boundary? Research conducted, to date, in KwaZulu Natal Province, South Africa, in the northeastern part of the Karoo Basin indicates that Late Permian megafloral assemblages are preserved in four different sedimentologic and taphonomic conditions. Each megafloral assemblage type preserves a very different signature of the vegetation contributed to the fossil record. These are: (1) parautochthonous assemblages within abandoned fluvial channel fill sequences, similar to modern and other ancient oxbow lakes; (2) dispersed and isolated, allochthonous assemblages preserved on foreset beds and reactivation surfaces within large, fine-grained fluvial regimes; (3) concentrated, mat-like allochthonous assemblages within bedload dunes of coarse siltstone channels; and (4) dispersed, sorted assemblages in turbidites. Data presented in the text concerning two localities ? Bulwer and Wagendrift Dam ? demonstrate that previous interpretations of the fossil assemblages in these sites are incorrect. And if these data are used from the literature as the basis for interpretation, the resulting suppositions are inappropriate. With an increasing continentalization of the sedimentary package in the Karoo into the Triassic, all but the last taphonomic assemblage type should be encountered in the transitional and post-boundary sections. Seven cross boundary and post boundary sections have been identified in which plant fossils and/or vertebrates are preserved, and will serve as the basis for the 2004 field season. It is anticipated that identification of isotaphonomic assemblages in this part of the stratigraphy will allow for direct comparison of biodiversity indices with those presently being determined by other members of an international research team, involving U.S., Dutch, and South African scientists. The present proposal requests funds to support undergraduate student research designed to assist 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 middle Triassic localities will be assessed to identify and characterize those depositional sequences as found in the latest Permian.
