A review of interstitial water samples collected from Sites 1003-1007 of the Bahamas Transect along with a shore-based analysis of oxygen and carbon isotopes, minor and trace elements, and sediment chemistry are presented. Results indicate that the pore-fluid profiles in the upper 100 meters below seafloor (mbsf) are marked by shifts between 20 and 40 mbsf that are thought to be caused by changes in sediment reactivity, sedimentation rates, and the influence of strong bottom currents that have been active since the late Pliocene. Pore-fluid profiles in the lower Pliocene-Miocene sequences are dominated by diffusion and do not show significant evidence of subsurface advective flow. Deeper interstitial waters are believed to be the in situ fluids that have evolved through interaction with sediments and diffusion.
Pore-fluid chemistry is strongly influenced by carbonate recrystallization processes. Increases in pore-fluid Cl- and Na+ with depth are interpreted to result mainly from carbonate remineralization reactions that are most active near the platform margin. A lateral gradient in detrital clay content observed along the transect, leads to an overall lower carbonate reactivity, and enhances preservation of metastable aragonite further away from the platform margin. Later stage burial diagenesis occurs at slow rates and is limited by the supply of reactive elements through diffusion.
1Swart, P.K., Eberli, G.P., Malone, M.J., and Sarg, J.F. (Eds.) , 2000. Proc. ODP, Sci. Results, 166: College Station TX (Ocean Drilling Program). Available from World Wide Web: <http://www-odp.tamu.edu/publications/166_SR/166TOC.HTM>. [Cited YYYY-MM-DD]
2Department of Marine Geology and Geophysics, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami FL 33149, USA. Correspondence author: PKramer@RSMAS.MIAMI.EDU
3Department of Oceanography, SOEST, 1000 Pope Road, University of Hawaii at Manoa, Honolulu HI 96822, USA.
4Geological Museum, University of Copenhagen, Oester Voldgade 5-7, DK-1350, Copenhagen K, Denmark.
Date of
initial receipt: 29 March 1999
Date of acceptance: 16 August 1999
Ms 166SR-117