Clastic basins

Fig. 1. Typical pressure profile in clastic basins. Top of hard pressure is defined as that pressure where effective stress is 1000 psi. When effective stress reaches this value, the likelihood of seal failure increases considerably.

In summary, the new technique developed at BP uses a proprietary transformation that relates velocity directly to effective stress, temperature and gross lithology, takes account of the major causes of overpressure in clastic basins (namely, undercompaction, clay dehydration and diagenesis, buoyancy and charging of fluids in dipping, permeable beds), and predicts effective stress directly, which is the most fundamental quantity for pressure prediction. 

As a first example, we consider the diagenesis of clastic sandstones in the Gippsland basin, southeastern Australia, basing our model on the work of Harrison (1990). The Gippsland basin is the major offshore petroleum province in Australia. Oil production is from the Latrobe group, a fluvial to shallow marine sequence of Late Cretaceous to early Eocence age that partly fills a Mesozoic rift valley. 

Amy Berger helped me write Chapter 10 (Surface Complexation), and Chapter 31 (Acid Drainage) is derived in part from her work. Edward Warren and Richard Worden of British Petroleum s Sunbury lab contributed data for calculating scaling in North Sea oil fields, Richard Wendlandt first modeled the effects of alkali floods on clastic reservoirs, and Kenneth Sorbie helped write Chapter 30 (Petroleum Reservoirs). I borrowed from Elisabeth Rowan s study of the genesis of fluorite ores at the Albigeois district, Wendy Harrison s study of the Gippsland basin, and a number of other published studies, as referenced in the text. 

Zimmermann, U. Bahlburg, H. 2003. Provenance analysis and tectonic setting of the Ordovician clastic deposits in the southern Puna Basin, NW Argentina. Sedimentology, 50, 1079-1104. 

The Athabasca Basin occurs within the southwestern part of the Churchill Structural Province of the Canadian Shield. The 100,000 km basin is filled by an unmetamorphosed clastic sequence of the Mesoproterozoic (Helikian) Athabasca Group. The basin is underlain by an Archean/Paleoproterozoic basement complex that was strongly deformed and metamorphosed during the Hudsonian... 

The probable absence of any pre-Martinsburg carbon concentrations precludes a clastic origin for the nodules. In any case, they are found in the uniform gray slate (originally mud), which was precipitated in the deep, still basin very slowly and are not associated with the clastic debris of the turbidite sequences. Turbulent conditions would have been needed for transport of such pebbles into the environment. 

If substantial arsenic is present in a sandstone or conglomerate, it may occur in hematite or other iron (oxy)(hydr)oxide cements or coatings on mineral grains. Arsenic may also be enriched in sandstones, conglomerates, and other clastic sedimentary rocks if hydrothermal or other secondary sulfide minerals are present (e.g. St. Peter Sandstone, (Gotkowitz et al., 2001) arsenian pyrite cement in the Marshall Sandstone of the Michigan Basin, USA, (Kolker et al., 2000 Szramek, Walter and McCall, 2004)). Sections of the St. Peter Sandstone in eastern Wisconsin, USA, are enriched in sulfide minerals and contain about 500 mg kg-1 of arsenic. In contrast, unmineralized portions typically have <10 mg kg-1 (Gotkowitz et al., 2001). If present in sedimentary rocks, hydrothermal sulfide deposits often tend to concentrate in veins and faults more than the rock matrices. 

Barataria Basin deposits are described by Kosters et al. (19) as lobe deposits located between the present Mississippi River and Bayou LaFourche. They consist of clays, mucks and true peats. True peat horizons are located in the top 1 meter of the section and developed during times of reduced clastic input from adjacent distributaries. Salinities of this site are relatively low, averaging 0.23 ppt in surface water and 1.11 ppt in porewater, because the site is about 80 km inland from the Gulf of Mexico, but are increasing with time. A cross section of the site is shown in Figure 4. 

A simple classification based on the CH4 and carbide contents parallels this classification. The F—2, F—3 and F-4 breccias contain low concentrations of both species, in agreement with the hypothesis114 that these clastic rocks were transported to the Fra Mauro site at the time of the impact which produced the Imbrium Basin. Either the material was ejected from considerable depth, /. e. not exposed on the surface, or the gaseous hydrocarbons and a high proportion of the carbide (as gaseous species) were lost at the temperature attained by the ejecta47,11S. ... 

Goodwin (1961, 1973b) considers the BIF of the Canadian shield to be the products of chemical precipitation in submarine volcanic regions as a result of extensive development of hot springs and fumarolic activity. A typical feature of the Archean crust was the production of volcano-tectonic basins with exhalative-clastic-effusive filling. Universal emission of basic effusives, rhythmic eruption of acid pyroclastic material, and extensive development of exhalative activity were observed in their formation. After the ore components arrived in the sea water they were deposited mainly near springs, but substantial amounts of SiOj and part of the Fe were widely disseminated. 

In some works a tendency toward convergence of the volcanogenicsedimentary and clastic-sedimentary hypotheses is noted. Belevtsev et al. (1966), who considered mainly the clastic-sedimentary hypothesis, postulate the extensive occurrence of acid waters in the Precambrian hydrosphere as the result of intensive volcanic activity. Tyapkin and Fomenko (1969) believe that the main source of iron and silica in the Precambrian was the basic rocks which were the chief constituent of the Earth s crust at that time, but that some was also derived from basaltic rocks erupted along abyssal faults and other products of basic volcanism. In this case it is impossible to deny the possibility that part of the iron and silica was supplied to the sea basins along with products of volcanic activity. In this scheme the role of volcanic activity in the formation of the BIF comes down chiefly to the creation of acid environments which promoted the leaching of iron compounds from basic rocks and its transport and subsequent accumulation. The primary banding is explained by periodic revival and extinction of volcanic activity, as a result of which the pH of the water basin varied, which ultimately led to deposition of iron or cherty sediments in turn. The periodicity of those cycles might have been of the order of several hundred years. 

Recent sediments of water basins. In recent basins iron sediments consist mainly of the iron hydroxides Fe(OH)3 or Fe203-nH20, but in very rare cases silicates and carbonates of Fe ", pyrite, and hydrotroilite enter into the composition of the sediment all together they constitute reactive (mobile) iron, which actively takes part in the diagenetic processes. A mixture of clastic minerals, which decompose negligibly and take practically no part in the processes of diagenesis, constitute another group. 

Thus secondary differentiation among the purely chemogenic iron sediments was possible, as a result of which the maximum of hydroxide accumulation was shifted to the deeper-water part of the basin and the maximum accumulation of Fe-Mg carbonates was shifted to the shallow-water parts, where finely dispersed clay sediments were being deposited. The maximum accumulation of organic matter was shifted still more into the region of deposition of clastic sediments. 

Hanor J. S., Land L. S., and Macpherson L. G. (1993) Carboxyhc acid anions in formation waters, San Joaquin Basin and Louisiana Gulf Coast, USA—Implications for clastic diagenesis. Critical comment. Appl. Geochem. 8, 305-307. 

Sugitani K., Yamamoto K., Adachi M., Kawabe 1., and Sugisaki R. (1998) Archean cherts derived from chemical, biogenic and clastic sedimentation in a shallow restricted basin examples from the Gorge Creek Group in the Pilbara Block. Sedimentology 45(6), 1045-1063. 

Mathisen M. E. (1984) Diagenesis of Plio-Pleistocene nonmarine sandstones, Cagayan Basin, Phillipines early development of secondary porosity in volcanic sandstones. In Clastic Diagenesis (eds. D. A. McDonald and R. C. Surdam). American Association of Petroleum Geologists, Tulsa, OK, vol. 37, pp. 177-193. 

CLASTIC SEDIMENTS IN FLUVIOKARST DRAINAGE BASINS 3.1 Inputs of Clastic Sediments to Caves... 

The sources for clastic sediments in the fluviokarst carbonate aquifers found commonly in the eastern United States are shown in schematic form in Figure 1. This conceptual model is appropriate when a portion of the drainage basin lies on noncarbonate rocks. Drainage basins such as this provide the following sources for clastic sediments. 

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