HIGH RESOLUTION STRATIGRAPHIC AND TEMPORAL ANALYSIS OF DEPOSITION, NON-DEPOSITION, AND EROSION WITHIN THE ORDOVICIAN KOPE FORMATION

Deposition of the Ordovician Kope Formation was punctuated by high energy events that scoured the seafloor as well as intervals of non-deposition recorded as diastemic surfaces defined by lithologic transitions, distinct changes in bioturbation, in situ fossil assemblages, or lags of shelly and organic debris. Analysis of an 8-meter split and polished core through the Snag Creek-Alexandria Submembers boundary (cycles 23 to 27) of the Kope Formation from Boone County, Kentucky reveals the presence of 87 erosional surfaces and 287 diastemic surfaces bounding beds of grainstone, packestone, wackestone, silt, silty mud, and lime mud. Collectively and individually, these lithologies exhibit exponential thickness frequency distributions. The high-resolution scans of the polished core allow for detailed observations of the muddy layers impossible to achieve on the outcrop. The resulting dataset consists of the stratigraphic positions of bounding surfaces, as well as the thicknesses and lithologic characteristics of the beds they contain and allows for the testing of two questions. First, are the bounding surfaces stratigraphically organized? Lacunarity analysis suggests that both diastemic and erosional surfaces are distributed randomly, rather than clustered or ordered, throughout the core. Those results, coupled with the observation of an exponential distribution of stratigraphic thicknesses supports an interpretation of stochastically driven episodes of deposition, non-deposition, and erosion. Second, what understanding can be gained regarding the degree of temporal completeness of this portion of the Kope Formation? Forward modeling based on the Markov point-sedimentation approach (sensu Tipper, 2015) can be used to reveal the sensitivity of stratigraphic completeness to frequencies, durations, and intensities of stasis and erosion. Preliminary modeling results suggest consistent patterns of the degradation of preserved diastemic and erosional surfaces with increasing frequencies and intensities of stratigraphic scouring. Ongoing efforts to expand understanding of temporal patterns of deposition will focus on extending these analytical methodologies to other portions of the succession as well as incorporating facies specific accumulate rate estimates in forward models.