Collaborative research: Automated sequencing of the fossil record: Improved Methods and insights from Mohawkian (Ordovician) geochronology, tephrochronology, and biostratigraphy

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The end-product of ongoing geoinformatics initiatives in stratigraphy and paleontology will be an onlineelectronic stratigraphic record. It faces three challenges: to compile sufficient data, to integratemultiple databases, and to maintain tools that can assemble all the local data records into a geologic timeline. The third challenge amounts to sequencing the fossil record and we propose to address three of theobstacles it faces: (1) Fossil biotas of the same age may differ as a result of habitat and preservationeffects; (2) Very large data sets must be sequenced in smaller pieces and the results stitched seamlesslytogether; (3) Increasing numbers of dated and fingerprinted ash beds need to used more effectively. Wepropose a case study of manageable geographic and temporal extent that, nevertheless, raises these sameissues. The Ordovician and Silurian periods span almost 100 million years of early Paleozoic time and aretraditionally subdivided by graptolites and conodonts - two fossil clades with different ecological andpreservational traits that restrict their use to largely mutually exclusive domains.The Mohawkian (Late Ordovician) of eastern North America presents precisely the type ofchallenging geological environment in which to build and test the temporal sequencing and stitchingapproaches that we envision. Mohawkian strata are widely exposed in the region and yield a rich fossilrecord that includes diverse, but somewhat endemic, conodont faunas. The epicratonic succession isrimmed along the Appalachian margin by deeper water sediments of the Taconic foreland basin. Thesestrata contain a suite of inter-continentally distributed graptolite faunas, but few described conodontassemblages. Numerous altered volcanic ash deposits (K-bentonites) link these facies through a set oftransitional facies along the interior basin margin. Despite these advantages, the prevalence of shortsections, structural complexity, and facies limitation of the faunas impedes precise and reliable correlationbetween the cratonic and basinal successions, consequently limiting our ability to compare their disparatefaunas and tectonic histories.Intellectual Merit: We propose to combine (1) geochemical fingerprinting (tephrochronology) andU-Pb geochronology of K-bentonites from the Mohawkian and early Cincinnatian with (2) a restudy oflate Mohawkian conodonts and graptolites from eleven regions across eastern North America and (3)computer assisted sequencing of the global Ordovician conodont and graptolite fossil record. This workwill provide a detailed temporal and paleoecological framework within which to refine the application ofbiofacies information to the temporal sequencing of the fossil record via rigorous quantitative techniques.We will focus in steps 1 and 2 particularly on conodont and graptolite-bearing successions that contain Kbentonites,and especially on regions where conodonts and graptolites occur in close association.The results of our work in a time interval that remains troublesome in spite of a wide range of timestratigraphicinformation will bear upon fundamental questions in both local and global stratigraphy. Inthe course of this study we will test existing alternate correlation models for the mid Upper Ordovician ofcentral and eastern North America. The results will provide an improved, age-calibrated basis for studiesof faunal turnover and diversity change in the Ordovician and Silurian. Most importantly, the work willlead to the development of improved techniques for time scale construction and validation.Broader Impact: The data and tools we develop will be shared immediately through the CHRONOSproject and will investigate technological solutions that are not being addressed by CHRONOS tosequence events. The project meets the EARTHTIME goal of cross-training stratigraphers andgeochronologists in developing high precision time-scales. We will train two PhD students (one aminority), and three undergraduates. We will integrate the efforts of four institutions, two with largeminority enrolment (UCR, UALR), in a new collaboration that will facilitate the interaction of all thestudents and PIs at each institution. Undergraduates will participate as field and lab assistants for the PIsand for the graduate students, and will be given pieces of the project as senior research projects. Eachstudent will present aspects of the research at a professional meeting. The project will also include asecondary school teacher who will work alongside PI Leslie during the summer as part of the ArkansasSTRIVE program. The teacher will develop class projects based on their experiences. The project thusimpacts future generations of students by enhancing a secondary education teacher's knowledge base andscientific curriculum.