Sediment facies

Figure 4.21. Latitudinal variation of saturation depths (SD) and carbonate sediment facies in the eastern and western Atlantic Ocean basins. (Modified after Berger, 1977.)...

Figure 1.2 Classic estuarine zonation depicted from the head region, where fluvial processes dominate, to the mid- and mouth regions where tidal and wave processes are the dominant controlling physical forces, respectively. Differences in the intensity and sources of physical forcing throughout the estuary also result in the formation of distinct sediment facies. (Modified from Dalrymple et al., 1992, with permission.)...

Figure 3. Schematic representation of sediment facies in terms of sorting and particle size.

Fig. 1.19 Distribution of major sediment facies across the frontal system of the Antarctic Circumpolar Current (ACC) between Africa and Antarctica. Numbers are typical sedimentation rates in mm kyh PF = Polar Front, SAF = Sub Antarctic Front, STF = Subtropical Front.

Schlager, W., and Chermak, A. 1979. Sediment facies of platform-basin transition Toimge of the ocean, Bahamas. In Geology of Continental Slopes, Doyle, L.J., and Pilkey, O.H., eds.. Society of Economic Paleontologists and Mineralogists, Sp>ecial Publication 27, Tulsa, OK, 374pp. 

Stow, D.A.V, and Piper, D.J.W., eds. 1984. Deep-water fine-grained sediments Facies models. In Fine-Grained Sediments Deep-Water Processes and Facies, Geological Society London, Blackwell, Oxford, pp. 611-645. 

Perez A, Luzon A, Roc AC, Soria AR, Mayayo MJ, Sanchez JA (2002) Sedimentary facies distribution and genesis of a recent carbonate-rich saline lake Gallocanta Lake, Iberian Chain, NE Spain. Sediment Geol 148 185-202... 

Paleozoic limestone (Webb et al. 2004). These kimberlites all have similar groundmass mineralogies consisting mainly of carbonate, spinel, and serpentine with lesser monticellite, mica, apatite, and perovskite (Kong et al. 1999) and they are all of volcaniclastic facies near ground surface. Varying thicknesses of clay and fine marine sediments of the Tyrell Sea ( 4000 - 12000 years BP) and 1 to 4 m of peat overlie kimberlites (Fraser et al. 2005). Bioherms composed of coral and skeletal remains of other marine organisms sometimes outcrop. 

Preferred fluid migration pathways are influenced by porosity and permeability, sedimentary sequences, facies architecture, and fractures. Porosity is a measure of pore space per unit volume of rock or sediment and can be divided into two types absolute porosity and effective porosity. Absolute porosity (n) is the total void space per unit volume and is defined as the percentage of the bulk volume that is not solid material. The equation for basic porosity is listed below ... 

Feldspars are the most abundant minerals of igneous rocks, where their ubiquity and abundance of their components influence normative classifications. They are also abundant in gneisses, and may be observed in several facies of thermal and regional metamorphic regimes. Notwithstanding their alterability, they are ubiquitously present in sedimentary rocks, as authigenic and/or detritic phases. Only in carbonaceous sediments is their presence subordinate. 

The bulk composition of the sediments must be normally near the potassium-rich side of the zeolite facies since analcite is not reported in these sediments and potassium feldspar apparently coexists with or replaces the alkali zeolites. 

Zone two can be defined by the absence of montmorillonite and by the tie-line mica-opal (Figure 37). Zone one, which contains montmorillonite shows the coexistence of feldspar and montmorillonite (Figure 37a). Trona and halite found in the sediments are considered to indicate higher alkalinity and alkali content of the pore fluids that effected the crystallization of the feldspar "facies" in zone two at the lake center. Here the evaporated fluids became more concentrated. 

Figure 50. "Facies diagram" for phyllosilicates in pelitic rocks and sediments. Zones I to VI are discussed in the text. M02 = dioctahedral montmorillonites M03 = trioctahedral, fully expandable phases ML =...

BENTONITE. The term applied to alteied fine-grained volcanic ashes which have been blown considerable distance from their origin and deposited m marine waters. The resulting material is usually a white, but sometimes a colored, clay-like sediment which may contain bits of volcanic glass but is composed mainly of colloidal silica which will absorb large quantities of water. Since bentonites are wind-blown deposits they are useful as definite datum planes in stratigraphy, especially in helping to determine the contemporaneity of the different facies of marine sediments. 

Models for the formation of Precambrian sediments suggest that the chemical sediments (such as cherts) of the Isua supracrustal belt have formed as shallow water deposits. This is in agreement with structures locally preserved in the metacherts of the sequence. After deposition, the supracrustals were folded and metamorphosed. Finally, the metamorphism reached lower amphibolite facies and in consequence, most of the primary minerals became recrystallized. As a result all chert now appears as quartzite. But apparently metacherts, magnetite iron formation and quartz carbonate rocks have retained their major element chemistry largely unaltered during metamorphism (Nutman et al., 1984) 119). 

The relative amounts of the extended hop-17(21)-enes (Figure 3e) and, especially, the relative concentrations of the C35 homologue (Figure 3f) show some sudden changes at the facies boundaries. It has been proposed (33-35) that this relative abundance of C35 extended hopenes (Facies B) reflects a hypersaline palaeoenvironment. Others consider this the typical distribution of the extended hopenes in anoxic marine sediments (32). 

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