The American Geologist: A Monthly Journal of Geology and Allied Sciences ..., Volume 12

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Geological publishing Company, 1893
 

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Página 350 - Irvine, in their valuable paper on coral reefs and other carbonate of lime formations in modern seas...
Página 351 - We have little knowledge as" to the thickness of these deposits, still such as we have goes to show that in these organic calcareous oozes and muds, we have a vast formation greatly exceeding in bulk and extent the coral reefs of tropical seas ; they are most widely distributed in equatorial regions, but some patches of Globigerina ooze are to be found even within the Arctic circle, in the course of the Gulf...
Página 196 - Notes on the Clinton Group Fossils, with special reference to collections from Indiana, Tennessee and Georgia, Proceedings Boston Society of Natural History, Vol.
Página 365 - In considering the time-ratios for the Paleozoic, Mesozoic, and Cenozoic rocks of the North American continent, as given by Dana and Williams, I think that a too small proportion has been given to the Mesozoic and Cenozoic. In the Mesozoic of the western-central area occur the coal deposits of the Laramie series and the great development of limestone (from 10,000 to 20,000 feet) in the Cretaceous of Mexico.
Página 346 - Montana, and still further north into Alberta and British Columbia. During Ordovician, Silurian, Devonian and Carboniferous time this entire Mississippian region, except portions in Devonian time, appears to have been covered by a relatively shallow sea that was coextensive with the Appalachian sea and that communicated freely with the Cordilleran sea. During this same age, however, the Rocky mountain area of New Mexico, Colorado, Utah, Wyoming and Montana formed a more or less well defined boundary...
Página 353 - ... the conclusion that the deposition of carbonate of lime is by both organic agency and chemical precipitation. It is not necessary to speak of deposition by mechanical methods except in relation to the deposition of chemically derived granules. This probably takes place, and may be a very important factor in the formation of limestones, in seas receiving a large supply of calcium from the land. Calcareous conglomerates do not enter as a prominent deposit in the Cordilleran area. There is no evidence...
Página 352 - They also conclude that practically all the carbon of marine organisms must ultimately be resolved into carbonic acid, the quantity of that acid produced in this way must be enormous, and cannot but exert a great solvent action not only on the dead calcareous structure, but also on the minerals in the muds on the floor of the ocean.£...
Página 355 - California and southwestern Oregon and to the eastward over the area subsequently covered by the great interior Cretaceous sea. There is also an addition that might be made to allow for the contraction of the area by the later north-and-south faults and thrusts. Dr. GM Dawson estimates that in the Alberta and British Columbia area the width of the zone of the Paleozoic rocks has probably been reduced one-half by the folding and faulting, or from 200 to 100 miles.
Página 347 - The sediments deposited in every sea or lake are derived from land areas either by mechanical or chemical denudation. Mechanical denudation results from the action of the waves and currents along the shore and the agency of rain, frost, snow, ice, wind, heat, etc., on the land. Rain is the most important factor and the result depends mainly upon its amount and the slope or the gradient of the land. The...
Página 354 - Woodward says on the opposite view, that in the earliest geological periods each bed of sand, clay, limestone, etc., had actually to be formed, and that later deposits had the older sedimentary ones to furnish...

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