Bulletin of the Geological Society of America, Volume 5 (Google eBook)

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The Society, 1894 - Geology
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Vols. 1-44 include Proceedings of the annual meeting, 1889-1933, later published separately.
  

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Page 285 - Packer clay" is of complex and varied character, much like till, and with little resemblance to the ordinary lake deposit. The clay is generally a reddish-brown, unstratified, sandy deposit, with a burden of glaciated, angular, and river-rolled material scattered irregularly through it. Very few striated stones have been found in the sections studied, and the bulk of the burden consists of river cobbles and pebbles, with a considerable proportion of perfectly angular fragments, derived from the rocks...
Page 87 - ... feet, being sufficient, probably, to bring the cold climate and ice accumulation of the Glacial period. Marine submergence of the low coastal and Mississippi valley areas occupied by the Lafayette formation is supposed by...
Page 90 - Moines, and its margin was marked by the Altamont moraine, the first and outermost in the series of eleven distinct marginal moraines of this epoch which are recognizable in Minnesota. When the second or Gary moraine was formed, it terminated on the south at Mineral ridge in Boone county, Iowa. At the time of the third or Antelope moraine, it had farther retreated to Forest City and Pilot mound in Hancock county, Iowa. The fourth or Kiester moraine was formed when the southern extremity of the ice-lobe...
Page 96 - Prestwich has well written as follows: "For the reasons before given, I think it possible that the Glacial epoch that is to say, the epoch of extreme cold may not have lasted longer than from 15,000 to 25,<K)0 years, and I would for the same reasons limit the time of .... the melting away of the ice-sheet to from 8000 to 10,000 years...
Page 589 - I think, actually survive at the present day, many but slightly altered. Then the subtropical members decreased, and the temperate forms, never quite absent even in the Middle Eocenes, preponderated. As decreasing temperature drove the tropical forms south, the more northern must have pressed more closely upon them.
Page 590 - Nulatoin the Yukon valley, we find the leaf beds of the Kenai group immediately and conformably overlain by marine beds containing fossil shells which are common to the Miocene of Astoria, Oregon, and to middle and southern California. It is then certain that the Kenai leaf beds immediately preceded and their deposition terminated with the depression (probably moderate in vertical range) which enabled the marine Miocene fauna to spread over part of the antecedently dry land. Further researches along...
Page 94 - McGee to be competent to supply in about 120,000 years a volume of river gravel, sand, and silt equal to the original Lafayette formation in the Mississippi Valley. With the greater altitude and increasing slopes of the land during the deposition of the Lafayette beds it may have required a third or a sixth of the time here mentioned, that is, some 40,000 or 20,000 years. As the elevation continued, however, rapid fluvial erosion of...
Page 285 - ... sections studied, and the bulk of the burden consists of river cobbles and pebbles, with a considerable proportion of perfectly angular fragments, derived from the rocks to the north of the locality where they occur in the clay. In the case of syenitic fragments, they occur near the South Mountain, where they could have been picked up by shore ice and carried a short distance. The greater proportion of the burden, however, are sandstones and chert, with a small amount of limestone and slate....
Page 95 - The loess thus testifies that previous to the farthest glacial advance the land sank to its present altitude, and probably somewhat lower on the area of the early drift, but not to the sea level. The vast weight of the continental glacier seems to have been the chief or only cause of this subsidence, as was first pointed out by Jamieson for the similar depression of the British Isles and Scandinavia at the time of final melting of the European ice-sheet. The explanation of this continuance of the...
Page 111 - Prcstwich, has recently given much attention to this subject, and in a memoir in the Transactions of the Royal Society of London...

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