Sedimentary strata

Parsons, A. 2007. Potential for Uranium mobilization from weathered outcrops of uranium-bearing sedimentary strata, southern Nova Scotia. BSc Honours Thesis, Earth Sciences, Dalhousie University. 

The geologic timescale for the Earth is based mostly on stratigraphy (the depositional succession of layers from bottom to top). Most strata are sedimentary rocks. The relative ages of the sedimentary layers are determined by the sequence of deposition and by the fossils that they contain. It is not possible to use radioactive isotopes to measure the time that a sediment was deposited, because deposition does not reset radiometric clocks. However, the absolute ages of sediment layers and the fossils they contain have been determined by measuring radiometric ages of volcanic ash layers in the sequence or lavas that crosscut sedimentary strata. 

Sedimentary strata typically consist of mixtures of clay, silt, sand, organic matter, and various minerals formed by or from deposits of sediments, especially from sand grains or silts transported from their source and deposited in water, such as sandstone and shale or from calcareous remains of organisms, such as limestone. 

Jaeger, J.M., and Nittrouer, C.A. (1995) Tidal controls on the formation of fine-scale sedimentary strata near the Amazon River mouth. Mar. Geol. 125, 259-282. 

Voronov, A.N., Tikhomirov, V.V. and Tikhomirova, V.G., 1969. Specific capacity of helium supply into porous spaces of sedimentary strata. Gcokhimiya, 4 505-507. 

Increased interest in use of subsurface strata as waste-disposal sites, in problems involving seawater encroachment, and in extension of the concept of freshwater resources to water containing as much as lOg/kg total dissolved solids (TDS) (Kohout, 1981) has increased interest in the composition and distribution of deeper saline fluids in sedimentary strata. 

As it has been shown by the investigations, there are several sites within overall field area (340 -400 km") typified by the presence of concentrated heat sources developed in the foundation rocks which are the basement for the volcanogenic-sedimentary strata forming the field (Kiryukhin, 1996). The Middle site of the Paratoon field (2.4 -3.5 km) associated with the northern part of Paratoon hydrothermal system is one of the most perspective in the aspect of thermal waters numerical modeling of groundwater flow and heat exchange processes has been carried out with the orientation to its hydrogeologic conditions. 

Nittrouer, C., and Sternberg, R.W. 1981. The formation of sedimentary strata in an allochthonous shelf environment Application to the Washington continental shelf. Marine Geology, 42 201-232. 

The texm fold is used in the geological sense when one or more originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Throughout... 

A clastic dike is typically a vertical or near-vertical seam of sedimentary material that fiUs a crack in and cuts across sedimentary strata—the dikes are found in sedimentary basin deposits worldwide. Clastic dikes form rapidly by fluidized injection (mobilization of pressurized pore fluids) or passively by water, wind, and gravity (sediment swept into open cracks). Dike thickness varies from millimeters to meters and the length is usually many times the width. 

A concretion is a volume of sedimentary rock in which mineral cement fills the spaces between the sediment grains. Concretions are often ovoid or spherical in shape, although irregular shapes also occur. Concretions form within layers of already-deposited sedimentary strata. They usually form early in the burial history of the sediment, before the rest of the sediment is hardened into rock. 

In the observed area 530 phenomenons of slope processes have been allocated. 249 landslides occurred within the volcano-sedimentary strata. Identified slope processes have different mechanism of displacement, including 74 rockfalls, 30 block landslides, 48 complex landslides, 295 earthflow, 20 from them transformed to mudflow, 60 talus. Among the mapped shallow landslides the predominant type is earthflow (>55%). Formation... 

Landslides of Northern Tien Shan spatially associated with the structures of modem uplifts moving onto sedimentary strata of Chui hollow and... 

The abrupt changes in depositional environments, styles and tectonic setting of Middle and Late Proterozoic rocks and their associated uranium deposits are significant evidence of extensive changes in supracrustal processes. Calc-alkaline volcanic and ophiolitic oceanic crustal suites are lacking in strata of this age. " Rock sequences are dominated by shallow marine to fluvial arenaceous clastic and carbonate sedimentary strata, and subaerial tholeiitic basalt and related shallow intrusions, all deposited in passively subsiding, rift-controlled basins. Oro-... 

---