Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 3 - By Alexander Von Humboldt And Aime Bonpland.
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But This Is Perhaps Merely
The Effect Of Apposition.* (* An-Nicht Auflagerung, According To The
Precise Language Of The Geologists
Of my country.) If we would range
the different members of the tertiary series according to the age of
their
Formation we ought, I believe, to regard the breccia of Cabo
Blanco with fragments of primitive rocks as the most ancient, and make
it be succeeded by the arenaceous limestone of the castle of Cumana,
without horned silex, yet somewhat analogous to the coarse limestone
of Paris, and the fresh-water soil of Victoria. The clayey gypsum,
mixed with calcareous breccia with madrepores, cardites and oysters,
which I found between Carthagena and the Cerro de la Popa, and the
equally recent limestones of Guadalope and Barbadoes (limestones
filled with seashells resembling those now existing in the Caribbean
Sea) prove that the latest deposited strata of the tertiary formation
extend far towards the west and north.
These recent formations, so rich in vestiges of organized bodies,
furnish a vast field of observation to those who are familiar with the
zoological character of rocks. To examine these vestiges in strata
superposed as by steps, one above another, is to study the Fauna of
different ages and to compare them together. The geography of animals
marks out limits in space, according to the diversity of climates,
which determine the actual state of vegetation on our planet. The
geology of organized bodies, on the contrary, is a fragment of the
history of nature, taking the word history in its proper acceptation:
it describes the inhabitants of the earth according to succession of
time. We may study genera and species in museums, but the Fauna of
different ages, the predominance of certain shells, the numerical
relations which characterize the animal kingdom and the vegetation of
a place or of a period, should be studied in sight of those
formations. It has long appeared to me that in the tropics as well as
in the temperate zone the species of univalve shells are much more
numerous than bivalves. From this superiority in number the organic
fossil world furnishes, in every latitude, a further analogy with the
intertropical shells that now live at the bottom of the ocean. In
fact, M. Defrance, in a work* full of new and ingenious ideas, not
only recognizes this preponderance of the univalves in the number of
the species, but also observes that out of 5500 fossil univalve,
bivalve and multivalve shells, contained in his rich collections,
there are 3066 univalve, 2108 bivalve, and 326 multivalve; the
univalve fossils are therefore to the bivalve as three to two. (*
Table of Organized Fossil Bodies, 1824.)
13. FORMATION OF PYROXENIC AMYGDALOID AND PHONOLITE, BETWEEN ORTIZ AND
CERRO DE FLORES.
I place pyroxenic amygdaloid and phonolite (porphyrschiefer) at the
end of the formations of Venezuela, not as being the only rocks which
I consider as pyrogenous, but as those of which the volcanic origin is
probably posterior to the tertiary strata. This conclusion is not
deduced from the observations I made at the southern declivity of the
littoral Cordillera, between the Morros of San Juan, Parapara and the
Llanos of Calabozo.
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