Synopsis
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. 1922 Excerpt: ...is typically Upper Oligocene, is stated by Mr. K. D. Semmes to occur at the base, as well as in the Nkt portions of this formation. Professor Berkey collected his fossils west of the mouth of the Descalabrados liiver,-just outside of the area under discussion, and west of Ponce. Care was taken to gather them from the base of the Arecibo limestone, which is the younger series of Berkey. These were-identified as: Luina sp. Lucina sp., much like forms from the Chattahoochee. Pecten sp., like Pecten thetidis (Sowerby). Fasciolaria. Amauropsis ocalina, similar to forms in the Ocala limestone of the Gulf States. t Mr. B. T. Hill (1899) states that the Arecibo limestone is in part equivalent to the Arecibo on the north coast and though largely Pleistocene, the lower strata may be as' old as Oligocene. Of the older series Hill (1899a) says: "The rocks of the central mountain region are Cretaceous and possibly of early Eocene age; at least no evidence tending to establish other dates has been as yet discovered." Since these limestones of Upper Oligocene age lie upon a peneplaned surface, they indicate that the Eocene exists either in the great unconformity or is to be found in tho older series. The presence of Venericardia and the large number of Tertiary foraminifera diatoms and radiolaria seems to suggest that the latter is the case. If the age of these formations is correctly determined, then a great break lies between the Eocene and the Oligocene in Porto Pico. The character of the Eoceue-Oligoeene contact in North America is poorly understood. A summary (Cooke, 1916) of the views taken regarding the contact in the area where it is best known shows that the various authorities differ by as much as a whole geological period. Could this divergency of vie...
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