Geological history

The basin occupied by Long Island Sound is a product of the period of prolonged erosion of eastern North America that occupied the late Mesozoic and the Cenozoic eras. Because the onshore geological record consists of erosion surfaces, and the products of this erosion are now submerged on the continental shelf, reconstruction of a detailed geological history is not possible. However, the main events are well established. 

When the Atlantic Ocean began to open, about 180 MY bp, the Southern New England land surface had high relief, as shown by block faulting of sediments in the Connecticut Valley, which persisted into the Jurassic. Between the mid-Jurassic and early Cretaceous this relief was reduced to no more than about 100 m (McMaster and Ashraf, 1973, and other references given therein). The eroded surface produced then is now the Fall Zone surface (Flint, 1963) and its northern bound is the Fall Line. 

The Fall Zone surface defines the top of the bedrock beneath Long Island Sound. A simple sequence of events that will account for the formation of the basin now occupied by the Sound is illustrated in the series of sketches in Fig. I. After opening of the Atlantic Ocean (Fig. la), cooling of the continental margin resulted in its subsidence (Fig. lb) at a rate that decreased as the continent moved away from the mid-ocean ridge. Additional subsidence was caused by the weight of the sediment accumu- 

Since the downwarping of the continental margin did not require uplift inland of the Fall Line, erosion rates on much of the land surface supplying sediment to the continental margin must have remained relatively low. Menard (1961) estimated that 7.8 x 10 km of rock must have been removed from the Appalachians over 125 Myr to account for the sediment now on the continental terrace and rise and on the abyssal plains off the east coast of North America. The mean sediment yield required to produce this material is —0.2 kg/(m yr). (For comparison, this is about the same as the sediment yield of the Missouri River drainage basin today.) Matthews (1975) has used the more extensive data on sediment thicknesses off the Atlantic Coast now available to estimate that the sediment yield of eastern North America over the past 60 Myr was 0.012 kg/(m yr) for the northern half of the coast and 0.067 for the southern half. These sediment yields can be attained with a land surface relief of a few hundred meters under temperate climate conditions and so are consistent with the hypothesis that both the elevation and relief of most of the land surface have remained moderate since the opening of the Atlantic Ocean. 

Cretaceous valleys. These authors find that the major valleys on the landward end of the Fall Zone surface join the valleys on the adjacent Fall Zone surface still covered by coastal plain sediments. River valleys on the Connecticut highlands usually follow the rock formations of lowest erosion resistance (Flint, 1963) and it may be supposed that the same is true offshore on the Fall Zone surface. 

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Seam correlations, measurements of rank and geologic history, interpretation of petroleum (qv) formation with coal deposits, prediction of coke properties, and detection of coal oxidation can be deterrnined from petrographic analysis. Constituents of seams can be observed over considerable distances, permitting the correlation of seam profiles in coal basins. Measurements of vitrinite reflectance within a seam permit mapping of variations in thermal and tectonic histories. Figure 2 indicates the relationship of vitrinite reflectance to maximum temperatures and effective heating time in the seam (11,15). 

The geologic history in the Hokuroku district is divided into five phases as follows (Tanimura et al 1983). 

Ohmoto, H. (1983) Geologic history of the Green tuff region. Econ. Geol. Mon., 5, 9-24. 

Berner, R.A. (1987) Models for carbon and sulfur cycles and atmospheric oxygen application to paleozoic geologic history. Am. J. Sci., 287, 177-196. 

The geological history of Mars can be divided into three epochs ... 

The largest evaporate basin formed in recent geological history is the Mediterranean basin. A closed, or almost closed, basin formed when mountain building blocked the Straits of Gibraltar some 6 million years ago. Before the Straits opened again, half a million years later, a layer of 1 kilometer of evaporates had accumulated on the basin floor. 

The intercept term C Ar/ Ar)o, which accounts for igneous, metamorphic, or atmospheric sources, is regarded as the excess contribution present at time = 0, whereas the second term is the radiogenic component accumulating in the various minerals of the isochron by decay of If all the minerals used to construct the isochron underwent the same geologic history and the same sort of contamination by excess " Ar, the slope of equation 11.100 would have a precise chronological... 

Rubey W. W. (1951). Geologic history of seawater. Geol. Soc. Amer. Bull, 62 1111-1147. 

The geological history of this area seems started by sedimentary units of Mesozoic - Cenozoic age which contains Fylisch and Limestone. These units were influenced by intrusion of volcanic and sub volcanic rocks in Miocene - Oligocene age. These igneous rocks mainly contain dacite, trachyandesite and andesite. These young volcanic units exposed in KIAMACCI Mountain vastly and their... 

Another important question concerning the isotopic composition of ocean water is how constant its isotopic composition has been throughout geological history. This remains an area of ongoing controversy in stable isotope geochemistry (see... 

Isotopic Composition of the Ocean during Geologic History... 

Geochemists study chemical processes on and in the Earth as well as meteorites and samples from the other planetary bodies. In geochemical kinetics, chemical kinetic principles are applied to Earth sciences. Many theories in geochemical kinetics are from chemical kinetics, but the unique nature of Earth sciences, especially the inference of geological history, requires development of theories that are specific for geochemical kinetics. 

Nyquist, L. E., Bogard, D. D., Shih, C.-Y. et al. (2001b) Ages and geologic histories of Martian meteorites. Space Science Reviews, 96, 105-164. 

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