The History of Cuba, vol. 1

by Willis Fletcher Johnson

The surface upon which the cretaceous sediments were deposited, appears to have been reduced by erosion to a very low relief, so that the land was a featureless plain when the cretaceous subsidence began. The time interval required for the accomplishment of this erosion must have been very long, since when it began the region was undoubtedly mountainous.

The complex character and disturbed altitude of the pre-cretaceous rocks, the granites, diorites and other granular rocks which appear on the surface because of this erosion, were originally formed deep within the crust of the earth, and therefore furnish a reason for believing that this period of erosion was exceedingly long.

It has been suggested that during the Jurassic times, the southeastern coast of the United States was connected by a long isthmus, following the line of the Antilles, to the northeastern coast of South America. The data presented would seem to indicate that at least the eastern half of Cuba stood high above the level during this period of the earth's history, and although data concerning the western half are less definite, it too was probably composed of high land masses.

The elevation, and long period of erosion just described, were followed by subsidence, and on the surface of these old rocks the cretaceous formations were deposited. The lowest cretaceous rocks yet found are composed of an arkose, derived in large part from the original igneous mass. The main body of the strata is composed of limestones, and such fossils as they contain belong to the genera similar to those of the cretaceous rocks of Jamaica—Radiolites, Barrettra, Requienia, etc.

During this time the whole of the Island of Cuba was probably submerged below the level of the sea. The cretaceous rocks in Santa Clara province occur in the bottoms of synclines, and the projected dips appear sufficiently to carry the beds over the tops of the dividing anti-clinal axis. It is believed, however, that the depth of the cretaceous sea over the island was probably never very great.

Owing to a lack of paleontological data, the history of the island during the Eocene time is vague, but it is probable that a large part of it was submerged. This is certainly true of the province of Oriente, where Eocene fossils have been collected. During, and possibly previous to that period, volcanic agencies were active in Oriente, since volcanic rocks are found interbedded with sediments of the Eocene age. The same forces were probably active in other sections of the island, and the intrusion of Diorite porphyries in Santa Clara and other provinces probably took place during that period.

A portion of the island, at least in the vicinity of Baracoa, was deeply submerged during the lower Oligocene times, as is proved by the occurrence of radiolarian earth beneath the upper oligocene limestones near the above town. Radiolarian oozes are at present being formed on the sea bottom at depths of between 2,000 and 4,000 fathoms. This, of course, does not prove that the deposits of Baracoa were laid down at so great a depth as present day dredging would indicate, but we can at least feel confident that they were formed in very deep water. This does not imply however that the whole island was sunken to the abysmal depths.

During the upper Oligocene time very nearly the whole island was undoubtedly submerged. Previous to this volcanic agencies had been very active throughout the larger portion of the island. Mountain building in Oriente had begun before the deposition of upper Oligocene strata, and the Sierra Maestra had already been elevated to a considerable height above the sea. It is probable that the sea at this time covered the whole of the island, with the exception of portions of Oriente province along its north and south coast, and occasional high peaks along the axis of the provinces further west.

The Miocene period was one of general uplift. The whole of the island as we at present know it, was above the level of the ocean's waters. There were foldings and uplifts during this period, and volcanic elevation along the axial line being greater than at the sides. It is probable that the folding of the Oligocene strata noted in the vicinity of Havana and Matanzas took place during this time. It may be inferred that the central portion of the province of Oriente was more highly elevated than the coastal portions, since upper Oligocene limestones occur in this section at considerably higher elevations than along either the north or south coast.

It is furthermore very probable that the terracing of the Oligocene coral reefs, such as may be seen in the vicinity of the city of Santiago, was taking place during that time. All the evidence goes to show that these are wave-cut terraces. It may be added here that all of the elevated Pleistocene coral reefs recorded are plastered on the surface of the upper Oligocene formations, or in some instances older geologic rocks. This applies to every later coral terrace that has been described, beginning with Cabanas and extending entirely around the island to the City of Santiago.