Reports: UNI850242-UNI8: Testing Depositional Models Across an Upper Ordovician Facies Transition in Kentucky, Ohio, and Indiana

Benjamin F. Dattilo, PhD, Indiana University-Purdue University (Fort Wayne)


The aim of this research was to test the hypothesis that eustatic fluctuations drove sediment supply  to create Cincinnatian (Upper Ordovician) meter-scale cycles. The approach was to correlate meter-scale cycles from the subtidal facies exposed in the Cincinnati Region to the peritidal facies exposed southward in Kentucky. My students and I have made significant progress has been made to this end by demonstrating the presence of peritidal depth fluctuations which are correlated with traceable gamma-ray logs. The efforts have produced two serendipitous discoveries as well, both of which contribute to knowledge about the burial of organic matter. Students were involved in all steps of this research and benefited from the financial assistance, research experience, writing tasks, and interactions with academics and professionals at meetings.

Research Progress

Over the 2011-2012 year we finished gathering borehole logs and began correlating them across the study area. We also gathered geophysical information directly from outcrops, intensified facies analysis of outcrops and conducted petrographic analysis of samples collected over the previous grant year.

From these data we were able to establish that:

1)  meter-scale cyles as reflected in gamma-ray logs are consistently present from the northern subtidal facies to the southern peritidal facies, suggesting that they are through-going.

2)  Meter-scale cycles in the subtidal facies are defined by depth-related microfacies, so the cycles represent depth fluctuations.

3)  The microfacies cycles correspond to cycles in Magnetic susceptibility as well as the gamma rays used in subsurface correlation. Thus gamma ray logs, even in peritidal facies, can be used as a proxy for depth fluctuations.

These discoveries have led to one published paper and two student-coauthored manuscripts in preparation.

Unusual taphonomy

One serendipitous discovery that resulted from this work was of an unusual shell-bed limestone that recorded dead-live interference during a storm event. This discovery has resulted in one student coauthored manuscript in revision and one in preparation.

Burial of organic matter and phosphogenesis

A second serendipitous discovery, following on the previous concept of live burial in shell beds was that evidence of live burial is common if not universal in Cincinnatian shell beds. Furthermore, the chemical analysis of some of these beds resulted in the discovery of phosphate concentrations that firmly link direct evidence of live burial with phosphogenesis.  This discovery has to date resulted in three student-coauthored manuscripts in preparation. I am currently working to apply for further funding to investigate this evidence, which may shed light on the process of organic burial in the coeval and contiguous Utica Shale.

Student outcomes

I believe that paid research assistantships provided by this grant have made an invaluable contribution to the continuing success of the undergraduate participants.

Many of the students in this department work long hours by necessity. Often this work takes them away from their studies and distracts them from their educational goals.  Because their work was at the university, the students who were supported by this grant have remained universally involved in departmental activities, in part because they reported to the lab for research work at the geosciences department on a regular weekly schedule. Of course these students were also involved in field work, sample preparation, petrographic analysis, and correlation of core logs and geophysical logs in the subsurface. In addition to this, the research and conference funding assisted students in attending Geological Society of America conferences where they presented four posters and one talk in the 2011-2012 school year.  This exercise involved them fully in the research process, requiring them to clearly and succinctly state hypotheses, discuss observations, and make interpretations in written, graphic, and oral formats.

This experience has helped IPFW students in their graduate school applications. One research student has begun his first year in a MS program in geology and reports that the research experience and ready-made presentation has given him a significant competitive edge.  Two other research students are applying to graduate school, and have already received enthusiastic feedback from potential graduate mentors.