Planktonic foraminiferal datum levels of ODP Leg 133 sites

This preliminary report does not present the distribution of selected key planktonic species in each Leg 133 hole, but rather, extracts the best chronodatum levels in two sets of holes, which comprise the Queensland Trough and Townsville Trough transects. In general, the sampling interval was 1.5 m, but sometimes was larger. To convert the datum levels into time, the absolute ages of Berggren et al. (1985, doi:10.1144/GSL.MEM.1985.010.01.18) were used. Extinction levels were employed in the main, because they are the most easily recognized, the order of events seems to be consistent from hole to hole, and they correlate reasonably well with chronodatum levels obtained from nannofossil biostratigraphy (see Gartner et al., 1993, doi:10.2973/odp.proc.sr.133.213.1993).

Global compilation of benthic data sets I

Approaches to quantify the organic carbon accumulation on a global scale generally do not consider the small-scale variability of sedimentary and oceanographic boundary conditions along continental margins. In this study, we present a new approach to regionalize the total organic carbon (TOC) content in surface sediments (<5 cm sediment depth). It is based on a compilation of more than 5500 single measurements from various sources. Global TOC distribution was determined by the application of a combined qualitative and quantitative-geostatistical method. Overall, 33 benthic TOC-based provinces were defined and used to process the global distribution pattern of the TOC content in surface sediments in a 1°x1° grid resolution. Regional dependencies of data points within each single province are expressed by modeled semi-variograms. Measured and estimated TOC values show good correlation, emphasizing the reasonable applicability of the method. The accumulation of organic carbon in marine surface sediments is a key parameter in the control of mineralization processes and the material exchange between the sediment and the ocean water. Our approach will help to improve global budgets of nutrient and carbon cycles.

(Table 1) Stable isotope ratios of Globigerinoides ruber and pore water, and Cl measurement at ODP Hole 133-817C

The oxygen isotopic composition of pore waters squeezed from sediments in Hole 817C co-varies with the oxygen isotopic composition of Globigerinoides ruber below 8 mbsf. The magnitude of the variation in the pore water d18O is approximately 30% of the variation in the foraminifers. Overall, the d18O of the pore waters increases down the core, a trend that is also present in the Cl- concentrations. The variations in the d18O of pore waters may be the result of either of two phenomena. First, these may reflect original variations in the waters, the magnitude of which has been subsequently reduced by process of diffusion. Second, these may reflect recrystallization of the precursor sediment and isotopic exchange between the fluids and the recrystallized sediment. At the moment data are not available to ascertain which process is responsible although the correlation between the Cl- and the d18O data suggests that these values reflect the original composition modified by diffusion.