Paper No. 282-2
Presentation Time: 9:00 AM-6:30 PM
UTILIZING STATISTICAL ANALYSES TO INVESTIGATE REGIONAL CONTROLS ON THE CAMBRIAN SPICE EVENT AND ITS RELIABILITY AS A GLOBAL CHRONOSTRATIGRAPHIC MARKER
The Steptoean Positive Carbon Isotope Excursion (SPICE) is a prominent chemostratigraphic feature in the Lower Paleozoic. It has been used to correlate Upper Cambrian carbonate strata globally, and is cited as intimately linked to the Crepicephalus-Aphelaspis trilobite extinction event. Schiffbauer et al. (2017) documented that, in cores taken over a paleodepth gradient in southeast Missouri, the SPICE event is facies-dependent, time-transgressive, and decoupled from biotic crises. Despite the global nature of the SPICE event, local biotic, oceanic, and sedimentologic conditions serve as a control on the expression of the SPICE event in the rock record. In light of this, and to better understand how reliable the SPICE event is as a chemostratigraphic tool for correlation, we have created a database of published SPICE data and will be evaluating their similarity using statistical analyses. We have compiled data (i.e., δ13C values, formation, lithology, facies, biomere, chronostratigraphic stage) from more than 50 stratigraphic sections and drill cores presented in >20 papers published from 1995 – present. Study sites include United States, Canada, Argentina, England, Sweden, Russia, China, Australia, and Kazakhstan. For each section, we have assessed stratigraphic thicknesses, magnitudes of δ13C shifts, and rates of change for the rising limb, peak, and falling limb of the SPICE event. Following non-metric multidimensional scaling (nMDS) to elucidate the patterns and impacts of such categorical variables as sedimentary facies, paleodepth, paleocontinent, and paleolatitude, our results demonstrate the importance of using quantitative methods when comparing isotopic curves, as opposed to relying solely on more qualitative methods (i.e., wiggle matching). Furthermore, these analyses have the potential to allow us to parse out regional controls on the carbon cycle, and better understand the effects they have on a presumably global signature.