THREE DIMENSIONAL ORIENTATIONS OF CRINOID PLURICOLUMNALS VERIFY DEPOSITIONAL PROCESSES

Three dimensional orientations of crinoid pluricolumnals validate predicted mass flow modes from debrites versus turbidites that were determined using architectural element analysis. This analysis was completed on beds of the Fort Payne Formation (late Osagean), exposed in Cumberland County, Kentucky. In this region, the Fort Payne Formation is a mixed carbonate and siliciclastic marine unit. Depositional history of the Fort Payne Formation was interpreted using architectural element analysis of a 600 m-long outcrop along Kentucky Hwy 61 south of Burkesville. Individual elements were interpreted as turbidites or small-scale debrites. The purpose of this research is to qualitatively and quantitatively test whether the pluricolumnal fabrics correlate to the predicted depositional processes of turbidity currents and debris flows.

Plunge, trend, width, and minimum length of crinoid pluricolumnals were measured in 8 elements (400 measurements). Four of the elements are turbidites, three are debrites, and one element is a mixed package of turbidites and debrites. Orientation of crinoid pluricolumnals are evaluated using plunge, rose diagrams, and stereonets. The turbidite elements have lower plunge values and lower plunge standard deviation than debrite elements. The highest ratios of length to width exhibit some of the lowest plunges. As a result of these plunge differences, the turbidite fabric is more uniform and the debrite fabric is more chaotic.

Azimuth trends of crinoid pluricolumnals produced bidirectional rose diagrams that have distinctive patterns. Overall, the rose diagrams are symmetrical with at least two primary modes at oblique angles to each other. The bisector of this oblique angle indicates paleoflow direction. Paleoflow was generally from the ENE to the WSW, but variability between elements could be a result of dilute bottom flows and/or paleotopography.