| Abstract: | It has been recently recognized that the formation of Large Igneous Provinces (LIPs), in particular oceanic plateaus, correlates closely in time with a number of rapid, global oceanographic changes including the long recognized and well documented ocean-wide anoxic events of the mid to late-Cretaceous. Hydrothermalism associated with large-scale submarine volcanism (e.g. event plumes) may have been responsible for the periodic exhaustion of water column O2, resulting in anoxic conditions and increased preservation of organic carbon. However, a causal relationship between these two, if it exists, is still unclear.
In order to determine a specific link between anoxic events and event plume hydrothermalism associated with ocean plateau eruptions, we are determining the distribution of major, minor and trace element abundances in pelagic carbonate and black shale sequences from a number of sites around the world. An important aspect of event plume hydrothermalism is that the chemical exchange of elements to seawater is controlled by volatility rather than solubility and therefore the abundance pattern of elements released to seawater are different than those derived from typical steady-state hydrothermal vents. Specifically, we are examining for evidence of event plume activity, in the form of appropriate trace metal anomalies, before, during and after the "Livello Bonarelli" Ocean Anoxic Event (OAE[2]). This prominent black shale layer has been correlated with the formation of the Caribbean ocean plateau (~ 90Ma). By looking at the stratigraphic position and global distribution of trace element anomalies from these three sites, we hope to further extend the knowledge about the distribution and timing of any biogeochemical responses (e.g. anoxia, isotopic changes) related to Caribbean Plateau eruptions and the associated hydrothermal activity.
Recently, we have measured ±30 trace, minor and major element abundances in whole rock samples by ICP-MS and ICP-AES analyses from three sites; Rock Creek Canyon section, Pueblo, CO, ODP Site 1138 from the central Kerguelen Plateau and, Bass River, NJ (ODP Leg174AX). After normalizing element concentrations to Zr to remove the effect of terrestrial sediment, prominent trace metal anomalies are obvious in both the Rock Creek Canyon and Kerguelen Plateau sections. Complete and detailed results from all three sites will be presented at this conference. |