CACO3% AND MAGNETIC SUSCEPTIBILITY VARIABILITY THROUGHOUT THE PALEOCENE-EOCENE BOUNDARY INTERVAL

The Paleocene–Eocene (P–E) boundary interval is import due to the global climatic shift from near Icehouse conditions in the Paleocene, to Greenhouse conditions beginning in the Eocene. Carbonate percent and magnetic susceptibility (MS) measurements through the P–E boundary have been performed on samples from four different localities in Egypt, Spain and the USA, locations representing shallow marine environments. The data show an inverse correlation between carbonate percent and MS, where carbonate percent decreases as MS increases. These measurements were then compared to stable carbon isotope data that were used in defining the P–E boundary at the four locations studied, based on a negative carbon isotope (δ¹³C) excursion representing the beginning of the Paleocene–Eocene Thermal Maximum (PETM). Here, δ¹³C is correlated to the carbonate percent variation, where δ¹³C values get increasingly more negative at the same time as the carbonate percentages decrease toward zero. This study uses past research to argue that the increasingly negative δ¹³C causes ocean acidification, which in turn causes dissolution to occur, followed by a period of slow recovery. This change matches the carbonate data, in that the percent decreases for a period of time, and then slowly recovers. This correlation is evident in all of the study areas except the P–E in the USA. This location does not contain very much carbonate, therefore it does not contain a large degree of variation throughout the boundary interval. This study also presents evidence for a small hiatus at the Global boundary Stratotype Section and Point (GSSP), located near Luxor in Egypt. The hiatus corresponds to a sharp shift in all of the data sets (MS, Carbonate percent, and carbon isotopes) at the P–E boundary. This is in direct contrast to a gradual change in each of the other three study locations. Because of this hiatus, it is proposed that the GSSP be replaced by a more complete section at Zumaia in Spain as indicated in the data reported in this presentation.