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THE GREENSANDS OF NEW JERSEY.
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than 900 fathoms, and most commonly takes place between 100 and 200 fathoms. The entrace of large rivers into the sea or the prevalence of strong currents would tend to interfere with its formation, so that the area of distribution of greensand is seldom continuous for great distances.

Although greensand is not known to be formed except in the presence of land-derived materials its production is accomplished through the intervention of foraminifera. Their connection with the formation of glauconite was first shown by Ehrenberg[1] in 1855 as the result of a study of greensand from many deposits in Europe and America. Professor Bailey[2] the succeeding year stated that the formation of greensand is likewise taking place on the floor of existing seas, and under the same conditions that existed in past geological ages.

According to Murray and Renard the chambers become filled with muddy sediment, and "if we admit that the organic matter enclosed in the shell, and in the mud itself, transforms the iron in the mud into sulphide, which may be oxidized into hydrate, sulphur being at the same time liberated, this sulphur would become oxidized into sulphuric acid, which would decompose the fine clay, setting free colloid silica, alumina being removed in solution; thus we have colloid silica and hydrated oxide of iron in a state most suitable for their combination." The potash which is necessary to complete the composition of glauconite may be derived from the decomposition of the fragments of crystalline rocks or their common constituents, orthoclase and white mica.

Two conditions then are requisite for the production of glauconite, first the deposition of mineral particles of land-derived origin; and second, the presence of foraminifera. In the absence of either the production of greensand will not take place. It is further seen that the formation of greensand is retarded and finally ceases altogether as the amount of deposition of land-derived materials increases adjacent to the coasts. Only

  1. ↑ Abhandl. d. k. Akad. d. Wissenschaften zu Berlin, 1855, pp. 85-176.
  2. ↑ Boston Soc. Nat. Hist., Proc., Vol. 5, 1856, pp. 364-368.
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