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  • Investigation into geodesy used by Transit system before WGS72; in AGSO library

  • Paper presented at the August 2001 ASEG Conference.

  • The oxygen isotopic record obtained from Globigerina bulloides, Globorotalia inflata, and Neogloboquadrina pachyderma (s.) was analysed for 5 sediment traps moored in the Southern Ocean and Southwest Pacific. The traps extend from Subtropical to the Polar Frontal environments, providing the first analysis of seasonal foraminiferal d18O records from these latitudes. Comparison between the foraminiferal records and various equations for predicted d18O of calcite reveals that the predicted d18O is best captured by the equations of Epstein et al. (1953) [Epstein, S., Buchsbaum, R., Lowenstam, H.A., Urey, H.C., 1953. Revised carbonate-water isotopic temperature scale. Geological Society of America Bulletin 64, 1315-1326.] and Kim and O'Neil (1997) [Kim, S.-T., O'Neil, J.R., 1997. Equilibrium and non-equilibrium oxygen isotope effects in synthetic carbonates. Geochimica et Cosmochimica Acta 61, 3461-3475.]. The Epstein equation shows a constant offset from the -18O of G. bulloides and N. pachyderma (s.) across the full range of latitudes. The seasonal range in -18O values for these two species implies a near-surface habitat across all sites, while G. inflata most likely dwells at 50 m depth. A significant finding in this study was that offsets from predicted -18O for G. bulloides do not correlate to changes in the carbonate ion concentration. This suggests that [CO32-] in and of itself may not capture the full range of carbonate chemistry conditions in the marine system. This sediment trap deployment also reveals distinct seasonal flux patterns for each species. Comparison between flux-weighted isotopic values calculated from the sediment traps and the isotopic composition of nearby surface sediments indicates that the sedimentary records retain this seasonal imprint. At the 51°S site, G. bulloides has a spring flux peak while N. pachyderma (s.) is dominated by summer production.

  • The pore water chemistry of mud volcanoes from the Olimpi Mud Volcano Field and the Anaximander Mountains in the eastern Mediterranean Sea have been studied for three major purposes: 1) modes and velocities of fluid transport were derived to assess the role of (upward) advection, and bioirrigation for benthic fluxes. 2) Differences in the fluid chemistry at sites of Milano mud volcano (Olimpi area) were compiled in a map to illustrate the spatial heterogeneity reflecting differences in fluid origin and transport in discrete conduits in near proximity. 3) Formation water temperatures of seeping fluids were calculated from theoretical geothermometers to predict the depth of fluid origin and geochemical reactions in the deeper subsurface. No indications for downward advection as required for convection cells have been found. Instead, measured pore water profiles have been simulated successfully by accounting for upward advection and bioirrigation. Advective flow velocities are found to be generally moderate (3-50 cm y- 1) compared to other cold seep areas. Depth-integrated rates of bioirrigation are 1-2 orders of magnitude higher than advective flow velocities documenting the importance of bioirrigation for flux considerations in surface sediments. Calculated formation water temperatures from the Anaximander Mountains are in the range of 80 to 145 °C suggesting a fluid origin from a depth zone associated with the seismic decollement. It is proposed that at that depth clay mineral dehydration leads to the formation and advection of fluids reduced in salinity relative to sea water. This explains the ubiquitous pore water freshening observed in surface sediments of the Anaximander Mountain area. Multiple fluid sources and formation water temperatures of 55 to 80 °C were derived for expelled fluids of the Olimpi area.