Geological Age

Inclusion of one rock type (usually igneous) into surrounding rocks is invariably younger than the rocks it intrudes. Inclusions are useful in determining relative geologic ages. 

Physiographic development of the surface of the earth refers to the landforms and shapes of the landscape. These surface features are subject to continuous change from constructive (e.g., uplift, volcanic activity, and deposition of sediments) and destructive (e.g., erosion) processes. Landform modifications are continuous and sequential. These modifications establish a predictable continuity that can be helpful in determining certain aspects of relative geologic ages. 

Evaporitic sulfur has a range of sulfur isotopic composition from +10%o to +30%o, while sedimentary sulfur is depleted in the heavy isotope and has a range of isotopic composition of about —40%o to +10%o. Most of this variation reflects systematic changes with geological age. The source fractions of a river water can be estimated from an isotopic mass balance ... 

Kanomata, N. (1961) The geology of the Yamizo, Torinoko and Toriashi mountain blocks and their geologic age. J. Coll. Arts Sci. Chiba (/., 3, 351 -367 (in Japanese). 

South African coals differ from most Northern Hemisphere coals in their geological age, unusual petrology and their high mineral matter content. If these coals are to be used for conversion to synthetic fuels then criteria must be found to enable predictions of their behaviour under liquefaction conditions to be determined. This paper describes the hydrogenation of a number of South African coals using two different techniques, to ascertain whether well known coal properties can be used to predict their hydrogenation behaviour. 

Once the ratio of parent-to-daughter isotopes has been determined, the geological age of the sample is given by ... 

Ahrens LH (1951) The feasibility of a calcium method for the determination of geological age. Geochim Cosmochim Acta 1 312-316... 

The abundance of phosphate in sedimentary rocks as a function of geologic age showing the episodicity of giant phosphorite deposition. Source-. From Cook, P. J., and McElhinny, M. W. (1979) Economic Geology 74, 315-330. 

Depending on the geological age, the organic material will transform into the following members of the coal family ... 

Lignite. This contains considerable amount of water and volatiles and some mineral matters. It is yonngest in geological age. 

Anthracite. This contains veiy little water or moisture but a large amount of carbon. It is the oldest in geological age. 

It would appear that their frequence decreases in older rocks, especially the Paleozoic (Weaver, 1959). The assembled studies of Perry and Hower (1970), Dunoyer de Segonzac (1969), Muffler and White (1969), Browne and Ellis (1970), Weaver (1959), Weaver and Beck (1971), Burst (1959), van Moort (1971) and Iijima (1970) demonstrate that the conversion of montmorillonite to other minerals in sequences of deeply buried sedimentary rocks is independent of time or geologic age and appears to be a function of the geothermal gradient which the rocks have experienced. These studies indicate that fully expandable dioctahedral montmorillonite is not stable above 100°C at depths of two kilometers or more. The occurrence of these minerals in sedimentary rocks can be considered to be controlled by their orogenic history. 

Geologic Age Lower Ordovician Lower Ordovician Middle Ordovician Middle Silurian... 

Bituminous Substances. The distribution of hydrocarbons and other bitumens in some of the Paleozoic rocks of the area is shown in Tables I and II, the latter summarized after Swain (7). The presumed saturated hydrocarbons of the Ordovician, Silurian and Lower Devonian samples are measurably less than in the Middle and Upper Devonian samples. The presumed aromatic hydrocarbons are not as well differentiated. The pyridine-plus-methanol-eluted chromatographic fractions, arbitrarily taken as asphaltic material, also appear, like the aromatic fractions, to be controlled more by local variations than by geologic age. 

Many authors have studied anthraxolite and related substances since Vanuxem s first account in 1842 (39). It has been reported as cavity fillings, veins, and dikes and as laminations in rocks of all geologic ages and types on all continents (e.g., I, 15, 20, 31, 32, 37, 38). Except for obvious cases of contact metamorphism near igneous intrusions, earlier workers have generally recognized a fluid origin and low temperature history for these substances. 

Time generally is considered to have relatively small influence on the coalification process. To prove this it is usual to offer the example of the Mississippian lignites from the Moscow Basin which, despite their great geological age, still lack bituminous characteristics. These coals, however, were never buried to any great depth. 

Fossil Any impression or trace of an animal or plant of past geological ages which has been preserved in the earth s crust. 

HABITAT OF Oil BY GEOLOGICAL AGE (X RESERVES OF TOTAL FREE WORLD)... 

Distribution of Amino Acids and Oxygen Isotopes in Petroleum Brine Waters of Various Geologic Ages, Sedimentology (1964) 3, 199-225. 

The estimated ultimate recovery is also reported by the geologic age of the reservoir. It is recognized that problems may arise where the geologic age of a reservoir cannot be determined specifically, such as Permo-Pennsylvanian and Cambro-Ordovician, or where production from reservoirs of different geologic age is combined. 

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