HOW MANY BULK SAMPLES DOES IT TAKE TO KNOW A DYSOXIC BIOFACIES?: A CASE STUDY OF THE AMBOCOELIA-CHONETES BIOFACIES, MIDDLE DEVONIAN, NEW YORK

Paleoecological studies of apparent prolonged stasis and geologically rapid faunal turnover require a detailed understanding of the appropriate methodologies not only for sampling fossil faunas but also analyzing the collected data. This is further complicated by differences in opportunistic verses mature communities as well as the reaction of a biofacies to sea level rise and fall. Dysoxic biofacies are typically dominated by eurytopic species. The gregarious nature of some of these organisms, and the resulting faunal patchiness often confound attempts to quantitatively characterize relative abundance within these biofacies. Our research tests the appropriate sampling regime for bulk sampling biofacies composition by utilizing random sub-samples of bulk sampled intervals as well as multiple samples within localities and comparisons between localities across New York State. This sampling approach was then repeated over several temporal periods. As a consequence of the effort required in bulk sample processing, it is important to minimize sampling effort while still fully characterizing variation in biofacies composition. Analysis of data by cluster significance testing using ANOSIM, SHEBI, and multinomial models using maximum likelihood and information theory to assess model fit are performed and results compared. Preliminary results of all statistical analyses indicate a statistically significant variation in biofacies composition dependent upon basin location at a single temporal interval. Furthermore, there is evidence of patchiness within localities, on a 5 to 15 meter scale.