Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 1 - By Alexander Von Humboldt And Aime Bonpland.
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The oysters and pectinites being sometimes
arranged in families.
The whole are easily detached, and their
interior is filled with fossil madrepores and cellepores. We have
now to speak of a fourth formation, which probably rests* on the
calcareous sandstone of Araya, I mean the muriatiferous clay. (* It
were to be wished that mineralogical travellers would examine more
particularly the Cerro de la Vela. The limestone of the Penas
Negras rests on a slate-clay, mixed with quartzose sand; but there
is no proof of the muriatiferous clay of the salt-works being of
more ancient formation than this slate-clay, or of its alternating
with banks of sandstone. No well having been dug in these
countries, we can have no information respecting the superposition
of the strata. The banks of calcareous sandstone, which are found
at the mouth of the salt lake, and near the fishermen's huts on the
coast opposite Cape Macano, appeared to me to lie beneath the
muriatiferous clay.) This clay, hardened, impregnated with
petroleum, and mixed with lamellar and lenticular gypsum, is
analogous to the salzthon, which in Europe accompanies the sal-gem
of Berchtesgaden, and in South America that of Zipaquira. It is
generally of a smoke-grey colour, earthy, and friable; but it
encloses more solid masses of a blackish brown, of a schistose, and
sometimes conchoidal fracture. These fragments, from six to eight
inches long, have an angular form. When they are very small, they
give the clay a porphyroidal appearance.
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