OOID DIAGENESIS: HOLOCENE GEOCHEMISTRY OF THE ROCK/WATER/ATMOSPHERIC SYSTEM (TEXAS, AUSTRALIA, UTAH, BAHAMAS)

Holocene ooids exhibit various crystal morphologies and mineralogies. Although their physical settings have received considerable attention, less well studied have been the chemical controls of inorganic CaCO(,3) ooid precipitation. Consequently, this study focuses on in situ aqueous geochemistry of ooid environments in Brown's Cay (Bahamas), Lizard Island (Australia), Baffin Bay (Texas), and the Great Salt Lake (Utah). Diurnal chemical measurements were made at each of the four study areas in the ambient (overlying) and ooid interstitial waters. Critical parameters examined are temperature, pH, H(,2)CO(,3*) (dissolved CO(,2)), Cl ('o)/oo , A(,Ca++), and A(,CO(,3)).;By examining ooids and aqueous chemistry from four study areas a comparison may be made between ooids with similar water chemistries and various crystal morphologies, and between ooids with similar crystal morphologies and variable water chemistries. While variation in water energies from low to high will probably result in an ooid crystal morphology that is radial (low energy) and tangential (high energy), the controlling variable in Holocene ooid diagenesis (precipitation/dissolution) is the CO(,2) system. Changes in carbonate alkalinity, carbonate activity, and H(,2)CO(,3*) will directly affect aragonite saturation. Monitoring the aqueous chemical system in an ooid environment quantitatively enables determination of where, and at what times, in ooid sediment or ambient waters that precipitation (ooid growth) is most likely to occur.