Terrigenous sediments

Figure 11.28 shows the rhenium and osmium isotopic compositions of black shales and sulfide ores from the Yukon Territory (Horan et al., 1994). The black shale and sulfide layers are approximately isochronous. The superimposed reference isochrons bracket the depositional age of the enclosing shales. One reference line represents the minimum age (367 Ma) with an initial ( Os/ Os)q ratio of one, consistent with the mantle isotopic composition at that age (see later). The other reference isochron is drawn for a maximum age of 380 Ma, with ( 870s/ 860s)o = 12 (the maximum value measured in terrigenous sediments). Further examples of application of Re-Os dating of sediments can be found in Ravizza and Turekian (1989). 

The formation of talc has been accomplished in the laboratory only at high pH for temperatures below 80°C (Siffert, 1962). Talc which is rarely found in terrigeneous sediments is most probably always of detrital origin as is that found in recent Gulf Coast sediments (Isphording, 1971). 

The occurrence of kaolinite is generally erratic but in the terrigenous sediments (Muffler and White, 1969) it can apparently react with dolomite to form the assemblage calcite + chlorite between 120-180°C. Expandable chlorite was noted in shear zones, and iron-rich chlorite is common in most of the rocks becoming more evident at greater depths. In the terrigenous rocks observed, the apparent alumina content of chlorite decreases with depth. Alkali zeolites have been observed at temperatures up to 100°C in the deeply buried rocks. 

Fanale, F. P., Cannon, W. A. (1971) Physical absorption of rare gas on terrigenous sediments. Earth Planet. Sci. Lett., 11, 362-86. 

The diagenesis of carbonates in terrigenous sediments requires further research and its role in global cycles assessed. 

The northwestern region is characterized by large provenance areas, from which alluvial matter is supplied via the deltas of the Danube, Dniester, and Dnieper rivers. The Danube River, which features a wide delta with numerous channels and branches provides the greatest solid runoff to the shelf zone. The delta is composed of terrigenous sediments and is advanced toward the sea by 7-10 km. 

The Crimean region is characterized by alongshore variations in the sediments of the underwater slope. West of the Tarkhankut Peninsula up to Evpatoriya, biogenic coquina deposits dominate they cover the limestone bedrock. On the Crimean shelf, terrigenous sediments are also observed represented by boulders and pebbles in the near-shore zone, sands at depths down to 7-10 m, and fine sands and silty oozes at greater depths. Meanwhile, at depths of about 30 m, there exists a sandy-pebbly bar formed by extreme waves. 

Erftemeijer, P. L. A., Stapel, J., Smekens, M. J. E., and Drossaert, W. M. W. (1994). The hmited effect of in situ phosphorus and nitrogen additions to seagrass beds on carbonate and terrigenous sediments in South Sulawesi, Indonesia.J. Exp. Mar. Biol. Ecol. 182, 123—140. 

Of the remaining insoluble elements, recent evaluation of zirconium and hafriium concentrations derived from terrigenous sediment (McLennan, 2001b) show no significant differences with Taylor and McLennan s estimates, whose upper cmstal zirconium value derives from the Handbook of Geochemistry (Wedepohl, 1969-1978), with hafnium determined from an assumed Zr/Hf ratio of 33. These values lie within —20% of the surface-exposure averages (Table 2, Figure 3). 

The Japanese islands are essentially composed of a series of terranes that have been accreted to the continental margin of the Eurasian plate during the past 400 Myr. These terranes consist of trench-hlling terrigenous sediments with variable quantities of accreted oceanic crust that are intruded and partly overlain by the products of subsequent subduction-related volcanism. Within Japan the ages of the accreted complexes become younger from north to south and from west to east (Kimura et ai, 1994). However, relatively little is known about the trace element chemistry of these oceanic accreted terranes. 

K/Ar ages of Heinrich Event Detritus Nd—Sr—Pb Isotopes in Terrigenous Sediments... 

Harris S. E., Mix A. C., and King T. (1997) Biogenic and terrigenous sedimentation at Ceara Rise, western tropical Atlantic, supports Pliocene-Pleistocene deep-water linkage between hemispheres. Proc. ODP Sci. Results 154, 331 -345. 

Hassold N., Rea D. K., and Meyers P. A. (2003) Grain size evidence for variations in delivery of terrigenous sediments to a Middle Pleistocene interrupted sapropel from ODP Site 969, Mediterranean Ridge. Palaeogeogr. Palaeoclimatol PalaeoecoL 190, 211-219. 

During the latter part of relative sea level rise and part of the following relative sea level fall, the HST occurs and is characterized by an upward increase in abundance, size, and angularity of terrigenous sediments, and by an upward decrease in organic material. The sediments are more bioturbated than TST sediments (Robison et al., 1996). 

The above view is clearly supported by the mass/age distribution of lithologies within the same tectonic domain. For example, carbonates, chert, red clay, and terrigeneous sediments on the ocean floor (Hay et al., 1988) all have the same type of age distribution pattern that is controlled by a single variable, the rate of spreading and subduction of the ocean floor. This sedimentary mass also differs lithologically from its continental counterpart, because it is comprised of... 

The deposits of South Fergana, described originally by Ozerova (1962), occur in Devonian to Permian carbonate and terrigenous sediments with minor intercalated volcanics. The Pb-Zn ores are described as being structurally controlled those deposits... 

The southwest limit of the Sublett basin in Nevada was along the Humboldt highland (17). The Humboldt highland was the principal source of terrigenous sediments incorporated in the Murdock Mountain Formation (18), which is equivalent to the lower part of the Phosphoria Formation (fig. 2). 

The Witwatersrand Basin The best known late Archaean sedimentary basin is the Witwatersrand Basin, for it hosts the world s richest gold province and is also an important source of uranium. For these reasons the geology of this basin is known in considerable detail. The Witwatersrand basin contains a 7 km-thick succession of terrigenous sediments and volcanic rocks, formed between 3.074 and 2.714 Ga ago. 

A fraction of the eroded mass made of small-size particles is transported by winds over subglobal distances, to be ultimately deposited in the open ocean and on other continents. Rates of sediment accumulation in the open oceans are much lower than for sediments in continental bodies of water, where in lakes the rates are typically of an order of 10° 1 mm yr"1 for terrigenous sediments and are higher for deposition of organic-matter-rich muds in areas of strong primary productivity. 

FIGURE 2 Plot of Residence Time against the ratio of concentrations in average seawater to that in the upper continental crust, for selected elements. Elements with very low concentrations in seawater and very low residence times (e.g., REE, Th, Sc) are transferred nearly quantitatively into terrigenous sediments and thus record their distributions in the upper crustal provenance. Some elements with low residence times are less useful due to complex behavior during sediment transport (e.g., Zr, Hf, Sn) or diagenesis (e.g., Fe, Mn, Pb). 

According to rough estimates made by Lisitzin (1996), about 84 % of terrigenous sediment input into the ocean is effected by fluvial transport. 

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