Continental sediments

The Ir anomaly has been observed in uplifted marine sediments in four locations in Italy, two in Spain, and one in New Zealand. It has not been found yet in continental sediments or deep-sea cores. If the asteroid-impact theory is valid, the Ir anomaly should be found wherever the C-T boundary is intact. 

The distribution of LAS in continental sediments has been studied [55], and the vertical profiles of LAS concentrations with depth in several lake sediments have been established [56,57]. In Swiss lakes, the concentration of LAS increases with depth and this is due to the efficiency of the wastewater treatment plants. Amano et al. [56] have, however, observed a decrease in the concentration of LAS with depth, and detected seasonal variations in the profile of LAS in the uppermost surface layer. 

Neothechnic developments Tectonic depression is apparent here filled with sea - continental sediments sunk in the Pliocene - quaternary layer to more than 1000 m Inter mountain depression filled with Pliocene quaternary continental sediments were sunk in the Pliocene -quaternary layer to more than 1000m. Mostly secondary and Paleogennic structures were lifted to more than 3000 min the neotechtonic period can be noted here. Mostly secondary and pre-secondary structures were lifted to more than 3000 m in die neotechtonic period. Mostly secondary and pre-secondary structures were lifted to more than 4000 m in the neotechtonic period. Continental fractions were sunk to more than2000m in the neotechtonic period. 

Many rock types have a layered structure, individual rock layers varying in thickness from a few centimeters to tens of meters. Layered rocks include marine sediments, most continental sediments, lava flows and volcanic ejecta, and intrusive sills. The hydraulic properties vary from one rock layer to another, often resulting in abrupt changes along the vertical axis. In terms of the permeability coefficient (k) the lateral coefficient (kx) may significantly differ from the vertical coefficient (kz). The alternation of aquifers and aquicludes results from the layered structure of different rocks, and the occurrence of springs is often controlled by the layering of rocks. Fissures may be restricted to individual rock layers or cross several rock beds, in which case water flow is improved, mainly in the vertical direction. 

Najman Y., Pringle M., Godin L., and Oliver G. (2001) Dating of the oldest continental sediments from the Himalayan foreland basin. Nature 410(6825), 194-197. 

The K20/Na20 ratio of sediments and continental basement increased considerably at about the Archean/Proterozoic transition (Figure 18), as already pointed out by Engel et al. (1974). Subsequently, Taylor (1979) and Taylor and McLennan (1985) emphasized that the REE showed similar trends in their overall concentrations, in LREE/HREE and Yb/La ratios, and in the decline of the size of the europium anomaly. The general interpretation of these data was based on the proposition that the compositions of the continental crust, and of continental sediments, reflect a major cratonisation event that spanned... 

Figure 18 The K20/Na20 ratio for undifferentiated continental sediments and their basement, based on the data of Engel et al. (1974) (after Veizer, 1988a).

Botha, G.A. de Wit, M.C.J. (1996) Post-Gondwanan continental sedimentation, Limpopo region, southeastern Africa. Journal of African Earth Science 23, 167-187. 

When pore waters in both marine and continental sediments become significantly depleted in dissolved oxygen (< 0.5 ml/1), three geochemical subzones successively prevail (Fig. 1) (i) nitrate reduction into nitrogen (NR) (ii) manganese reduction to Mn aq. (MnR) and, subsequently, (iii) iron reduction to Fe " aq. (FeR). The type and elemental composition of carbonate cement formed are hence strongly controlled by the amount of Fe-and Mn-oxides/oxyhydroxides. 

This process prevails in anoxic marine and continental sediments and when sulphate is totally reduced in the BSR zone (Fig. 1). Although the precise mechanism is poorly understood, methano-... 

Chlorite replaces kaolinite, clay pseudomatrix, infiltrated clays, micas and heavy minerals. It occurs as rims composed of platelets oriented perpendicularly to grain surfaces. The rims were formed by replacing infiltrated smectitic clay coatings, which were originally oriented tangentially to grain surfaces (Fig. 14A) (see Moraes De Ros, 1990). These infiltrated clays were presumably introduced into the vadose zone of alluvial continental sediments under semi-arid conditions by episodic floods (Walker et al., 1978 Moraes De Ros,... 

Petroleum is usually related with sediments of marine origin and its water content is similar to sea water. Few petroleum deposits are found in continental sediments. 

Seawater Pore water Siliceous oozes Carbonate oozes Pelagic days Clastic sediments Altered basalts Fresh basalts Layer-3 gabbros Continental sediments Sandstones Limestones Shales... 

Relatively little well preserved sedimentary rock and associated C can be found in lithosphere older than 3.0 Ga. The tectonically active Archean marine basins favored rapid destruction of crust by continental collisions, partial melting and mantle/crust exchange (Windley 1984). Most of Archean continental crust had not yet become stabilized by cratonization (Rogers 1996), therefore a greater fraction of continental sediments experienced greater instability and thermal alteration. The freshest sediments occur in the 3.5 to 3.2 billion-year-old Kaapvaal Craton of South Africa and the Pilbara Block of Western Australia (Lowe 1992). These deposits are associated with episodes of greenstone activity and intrusive events that created stable microcontinents or cratons. These cratons became the nuclei of full-sized modern continents. 

Uplifted oceanic sediments, such as the Franciscan sediments, bear higher amounts than continental sediments whose origin is generally... 

Soils derived from igneous rocks (47), mean Soils derived from continental sediments (3 ) Coal, shale, petroleum (i, 24)... 

Model ages for clastic sedimentary rocks are thought to provide an estimate of their crustal residence age (O Nions et a/., 1983), for minimal fractionation of Sm/ Nd accompanies their generation. Since, however, many continental sediments are a mixture of materials from different sources, model Nd ages are the average model age of the sediment and provide a minimum estimate of the crustal residence age or an average crustal residence age. 

Ideally, placing a palaeocoastline on a map is no more than drawing the boundary between the extent of marine sedimentation on one side of a line and continental sedimentation on the other, but adequate data are available mostly in western Europe and North America. In other areas, the low density of the available data means that palaeocoasUines at the global scale must be regarded as very speculative (Smith et al., 1994). Even where relatively detailed data are available, it is very difficult to infer the former coastlines of deformed microcontinents that may also have been partially subducted. 

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