Collaborative Research: AUTOMATED SEQUENCING OF THE FOSSIL RECORD: IMPROVED METHODS AND INSIGHTS FROM MOHAWKIAN (ORDOVICIAN) GEOCHRONOLOGY, TEPRHOCHRONOLOGY, & BIOSTRATIGRAPHY
Charles Mitchell Principal Investigator
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The end-product of ongoing geoinformatics initiatives in stratigraphy and paleontology will be an online<br/>electronic stratigraphic record. It faces three challenges: to compile sufficient data, to integrate<br/>multiple databases, and to maintain tools that can assemble all the local data records into a geologic time<br/>line. The third challenge amounts to sequencing the fossil record and we propose to address three of the<br/>obstacles it faces: (1) Fossil biotas of the same age may differ as a result of habitat and preservation<br/>effects; (2) Very large data sets must be sequenced in smaller pieces and the results stitched seamlessly<br/>together; (3) Increasing numbers of dated and fingerprinted ash beds need to used more effectively. We<br/>propose a case study of manageable geographic and temporal extent that, nevertheless, raises these same<br/>issues. The Ordovician and Silurian periods span almost 100 million years of early Paleozoic time and are<br/>traditionally subdivided by graptolites and conodonts - two fossil clades with different ecological and<br/>preservational traits that restrict their use to largely mutually exclusive domains.<br/>The Mohawkian (Late Ordovician) of eastern North America presents precisely the type of<br/>challenging geological environment in which to build and test the temporal sequencing and stitching<br/>approaches that we envision. Mohawkian strata are widely exposed in the region and yield a rich fossil<br/>record that includes diverse, but somewhat endemic, conodont faunas. The epicratonic succession is<br/>rimmed along the Appalachian margin by deeper water sediments of the Taconic foreland basin. These<br/>strata contain a suite of inter-continentally distributed graptolite faunas, but few described conodont<br/>assemblages. Numerous altered volcanic ash deposits (K-bentonites) link these facies through a set of<br/>transitional facies along the interior basin margin. Despite these advantages, the prevalence of short<br/>sections, structural complexity, and facies limitation of the faunas impedes precise and reliable correlation<br/>between the cratonic and basinal successions, consequently limiting our ability to compare their disparate<br/>faunas and tectonic histories.<br/>Intellectual Merit: We propose to combine (1) geochemical fingerprinting (tephrochronology) and<br/>U-Pb geochronology of K-bentonites from the Mohawkian and early Cincinnatian with (2) a restudy of<br/>late Mohawkian conodonts and graptolites from eleven regions across eastern North America and (3)<br/>computer assisted sequencing of the global Ordovician conodont and graptolite fossil record. This work<br/>will provide a detailed temporal and paleoecological framework within which to refine the application of<br/>biofacies information to the temporal sequencing of the fossil record via rigorous quantitative techniques.<br/>We will focus in steps 1 and 2 particularly on conodont and graptolite-bearing successions that contain Kbentonites,<br/>and especially on regions where conodonts and graptolites occur in close association.<br/>The results of our work in a time interval that remains troublesome in spite of a wide range of timestratigraphic<br/>information will bear upon fundamental questions in both local and global stratigraphy. In<br/>the course of this study we will test existing alternate correlation models for the mid Upper Ordovician of<br/>central and eastern North America. The results will provide an improved, age-calibrated basis for studies<br/>of faunal turnover and diversity change in the Ordovician and Silurian. Most importantly, the work will<br/>lead to the development of improved techniques for time scale construction and validation.<br/>Broader Impact: The data and tools we develop will be shared immediately through the CHRONOS<br/>project and will investigate technological solutions that are not being addressed by CHRONOS to<br/>sequence events. The project meets the EARTHTIME goal of cross-training stratigraphers and<br/>geochronologists in developing high precision time-scales. We will train two PhD students (one a<br/>minority), and three undergraduates. We will integrate the efforts of four institutions, two with large<br/>minority enrolment (UCR, UALR), in a new collaboration that will facilitate the interaction of all the<br/>students and PIs at each institution. Undergraduates will participate as field and lab assistants for the PIs<br/>and for the graduate students, and will be given pieces of the project as senior research projects. Each<br/>student will present aspects of the research at a professional meeting. The project will also include a<br/>secondary school teacher who will work alongside PI Leslie during the summer as part of the Arkansas<br/>STRIVE program. The teacher will develop class projects based on their experiences. The project thus<br/>impacts future generations of students by enhancing a secondary education teacher's knowledge base and<br/>scientific curriculum.