Alyssa Bancroft
Geological Research at the IGS

Chemostratigraphy and biostratigraphy of IGS – Survey Drill Holes (SDHs)

Status Start Date End Date Locations
completed Dec 7, 2015 Jun 30, 2016 All Counties
Director: Patrick McLaughlin
Other Researchers: Alyssa Bancroft
Funding: Indiana University - Indiana Geological & Water Survey
Issue: Conodont concentration (number of elements/kg) is regularly reported in biostratigraphic studies. Review of Rexroad’s voluminous literature on the conodont biostratigraphy of Indiana and the surrounding region demonstrates that conodont concentration varies significantly within and between formations and different localities. The origin of this variability has received little attention. Possible causes include: 1) environmental variation (some environments were inhabited by more conodont animals than others or the conditions were more conducive to conodont preservation), 2) burial diagenesis (conodonts are altered and ultimately destroyed under certain burial conditions), or 3) changes in sea water chemistry controlled the population structure of conodonts animals and ultimately the net flux into the sedimentary record.
Objective: Hypothesis: Conodont concentration correlates with whole rock composition.
Approach: Utilizing conodont biostratigraphy documented by Rexroad in (no fewer than 33) Survey Drill Holes (SDHs), examine the pXRF chemostratigraphy, including the sampled intervals, to reveal the origin of variability in conodont concentration. The results of this study will not only shed light on potential biases in the fossil record of early marine chordates, but build predictive models for more efficient conodont biostratigraphic studies that are the foundation of chronostratigraphic correlation in the Paleozoic.
Products: IGS Report of Progress, possibly an external publication.
Benefits: Assessment of whether the chemostratigraphy of a geologic section can be used as a proxy for or in correlation with its biostratigraphy.

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