Studies of the dC of pore water dissolved inorganic carbon (dC-DIC) were carried out in shallow water carbonate sediments of the Great Bahamas Bank (GBB) to further examine sediment–seagrass relationships and to more quantitatively describe the couplings between organic matter remineralization and sediment carbonate diagenesis. At all sites studied dC-DIC provided evidence for the dissolution o...

Carbonate mud is a major constituent of recent marine carbonate sediments and of ancient limestones, which contain unique records of changes in ocean chemistry and climate shifts in the geological past. However, the origin of carbonate mud is controversial and often problematic to resolve. Here we show that tropical marine fish produce and excrete various forms of precipitated (nonskeletal) cal...

Optical lightness is increasingly being used as a proxy for the carbonate content of marine sediment. We compared three measurements of optical lightness, gray scale, brightness and L, to carbonate content to test the reliability of these Ž . measurements as carbonate content proxies. In five piston cores from isotope stages 1 though 6 0–;130 ka , all measures of optical lightness are reasonabl...

The continental margin off northeast Australia, comprising the Great Barrier Reef (GBR) platform and Queensland Trough, is the largest tropical mixed siliciclastic /carbonate depositional system in existence. We describe a suite of 35 piston cores and two Ocean Drilling Program (ODP) sites from a 130 × 240 km rectangular area of the Queensland Trough, the slope and basin setting east of the cen...

Coordinated taphonomic, geochronologic, and geochemical studies of bivalve death assemblages and their sedimentary environments of San Blas, Caribbean Panama, permit us to identify the major factors controlling skeletal degradation in mixed carbonate-siliciclastic tropical shelf sediments. Ten sites were studied along environmental gradients including water nutrients, grain size, and sediment c...

In this study we estimate sediment carbonate dissolution rates for sandy sea grass sediments on the Bahamas Bank using an inverse pore-water advection/diffusion/reaction model constrained by field observations. This model accounts for sea grass O2 input to these sediments, and also parameterizes pore-water advection through these permeable sediments as a nonlocal exchange process. The resulting...

On the upper slope of the northern Gulf of Mexico, topographic features are often associated with authigenic carbonate, which provides hard substrate for sessile benthic communities. At depths >300 m, large Lophelia pertusa colonies frequently occur on these carbonate outcroppings. Surficial sediments at these depths are dominated by fine-grained particulates, which are readily resuspended duri...

This study presents a special problem on vertical distribution for sediment and copper in hyper-concentrated turbulent solid-liquid system that is essentially different from the ordinary low-concentrated turbulent system. A resonance type turbulent simulation equipment is used for the experimental study in which a vertically uniform turbulent field of the mixture of loess and water is produced ...

Carbonate dissolution has been widely observed in shallow water tropical sediments. However, sediment budgets have generally not been closed with respect to the amount of acid required to produce the observed carbonate dissolution. Recently it has been suggested that enhanced oxygen transport into sediments through the roots and rhizomes of sea grasses might play a role in resolving this mass b...

Records from lake sediment cores are critical for assessing the relative stability of climate and ecosystems over the Holocene. Duck Lake in south-central Lower Michigan, USA, was the focus of a study that identified how changes in the geochemical variables in lake sediments relate to variations in regional climate and local land use during the Holocene. More than 8.5 m of lacustrine sediment w...