Or1yaaaayaaj

Or1yaaaayaaj

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1919 edition. Excerpt: ...shales represent all gradations between ordinary shales and the pure diatomaeeous earths. Under the microscope the shales are seen to consist of the skeletons of diatoms and irregular quartz grains scattered through a very fine grained matrix, the nature of which cannot always be determined by the microscope. Some of the finer materials of these shales may consist of the finely broken frustules of diatoms, but argillaceous matter is also present in variable amounts, as is indicated by chemical analysis (p. 290). They often contain notable amounts of lime and magnesia as carbonates. By increase in these different constituents, the diatomaeeous shales pass into calcareous or argillaceous rocks. The diatoms are not the only organic remains in these rocks. A few sponge spicules and radiolarian skeletons are also found. Locally the diatomaceous shales contain many radiolarian skeletons, in an excellent state of preservation. The less siliceous shales also contain numerous scales of fish, and occasionally the bones of fish are found. In a few instances bones of whales or other marine animals have been discovered. Shells of foraminifera are characteristic of many of the rocks of the Monterey group and are found abundantly in many beds in a state of excellent preservation. Very often also they have been dissolved out, leaving characteristic moulds. These diatomaeeous shales have been regarded as the source of a large part of the petroleum of the California Coast Ranges; it is believed that the petroleum came from the organic matter of the diatoms whose remains are found in them. The earths and shales contain considerable amounts of hydrocarbons and the term "bituminous shale" or "bituminous slate" is often applied to them. The...show more

Product details

  • Paperback | 196 pages
  • 189 x 246 x 11mm | 358g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236548787
  • 9781236548788