Clay abyssal

Global sedimentary budget. Finally, on a global scale, we point to an interesting model by Berner and Canfield (1989), which took as a given an organic carbon and reduced sulfur concentration of sediments of different type (nearshore sands, offshore clays, abyssal clays, etc.). In this view, a net source or sink of O2 to the atmosphere could be driven by rearrangement of the sedimentary rock mass of the Earth, from abyssal clays to nearshore clays, for example. 

While rapid burial enhances preservation, the type of sediment produced is determined by the relative particle composition of the deposit. For example, rapid burial of biogenic silicate by clay minerals helps protect the shells against dissolution, but the resulting deposit is classified as an abyssal clay, rather than a siliceous ooze, if the sediment is less than 30% by mass BSi. Thus, prediction of the sediment type likely to be found at a given location requires knowledge of the relative magnitudes of the accumulation rates of all particle types. 

Figure 20.1 illustrates that the major sediment type on the abyssal plains are the abyssal clays with some local exceptions, including equatorial radiolarian oozes, manganese nodifles, and metalliferous sediments. 

The abyssal clays are composed primarily of clay-sized clay minerals, quartz, and feldspar transported to the siuface ocean by aeolian transport. Since the winds that pick up these terrigenous particles travel in latitudinal bands (i.e., the Trades, Westerlies, and Polar Easterlies), the clays can be transported out over the ocean. When the winds weaken, the particles fell to the sea siufece and eventually settle to the seafloor. Since the particles are small, they can take thousands of years to reach the seafloor. A minor fraction of the abyssal clays are of riverine origin, carried seaward by geostrophic currents. Despite slow sedimentation rates (millimeters per thousand years), clay minerals, feldspar, and quartz are the dominant particles composing the surface sediments of the abyssal plains that lie below the CCD. Since a sediment must contain at least 70% by mass lithogenous particles to be classified as an abyssal clay, lithogenous particles can still be the major particle type in a biogenous ooze. 

Latitudinal patterns in clay mineral distributions are pronounced in abyssal plain sediments as illustrated in Figures 14.8 through 14.11. These latitudinal bands reflect the... 

Abyssal clays are found in greater abundance on the western side of the Atlantic Ocean than on the eastern side. This is due to bottom topography that restricts the flow of North Atlantic Deep Water and Antarctic Bottom Water to the western side of the basin. The lower temperature of the western waters causes the CCD to be somewhat shaUower than on the east side of the basin as calcite solubility increases with decreasing... 

In the South Pacific, the CCD is deep enough to permit the preservation of calcareous oozes except in the center of the basin, which as a result is covered by abyssal clays. The relatively rapid supply of hydrogenous sediments prevents the accumulation of calcareous oozes on the East Pacific Rise. In the North Pacific, abyssal clays dominate as this is the location where the CCD is shallowest. Aeolian transport is the source of the clay minerals that make up these deposits. 

Like the Atlantic, the Indian Ocean is characterized by foram oozes along its mid-ocean ridge and most of its abyssal plains. Only in basins where the water depths exceed 5000 m are abyssal clays abundant. 

Melson, W. G. Thompson, G. 1973. Glassy abyssal basalts, Atlantic sea floor near St Paul s rocks petrography and composition of secondary clay minerals. Geological Society of America Bulletin, 84, 703—716. 

In most mathematical analyses used to establish bounds for radionuclide migration rates through the abyssal red clays, the sorption properties of the sediment are generally represented mathematically by the sorption equilibrium distribution coefficients for each of the species involved. These coefficients are usually denoted by Kp. and are defined by... 

General. The abyssal red clays were, in part, originally selected for study because previous investigations of their sorption properties had been encouraging (6,7), and because generally the types of minerals occurring in the sediment exhibit very favorable ion-exchange and adsorption properties. In... 

Apart from the pelagic clays of the abyssal plains and the terrigenous sediments deposited along... 

Clay mineral content may possibly affect the alteration process and influence the distribution of organic compounds. It is especially sensitive when using pyrolysis (Peters, 1986). The abyssal plain samples have smectite as the main clay mineral (Martine Gerard, personal communication). The Shipboard Rock Eval pyrolysis gave the following parameters for MAP samples with TOC >1.3 wt% T ax from 400 to 430°C and PI average around 0.2 S2 range 2.15-4.73 mg C/g rock with HI 20-252 mg HC/g TOC. 

North Pacific North Central Clay 0.3. 5 4 X SUva and Jordan Abyssal hill region with... 

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