Date of Award
Geology, Stratigraphic, Tertiary, Paleontology, Goajira Peninsula (Colombia and Venezuela), Paleontology
Doctor of Philosophy (PhD)
William D. MacDonald
James E. Sorauf
James R. Beerbower
Science and Mathematics
Rocks of the Tertiary System of the Guajira Peninsula of northern Colombia are exposed in three sedimentary basins surrounding older uplifted areas. The Portete (north central Guajira) and Chichibacoa (northeastern Guajira) basins are newly recognized. Certain previously proposed stratigraphic units for the Cocinetas Basin (southeastern Guajira) are accepted with modification.
Lower Tertiary rocks are represented by two Upper Eocene formations, the Macarao and Nazareth (new). Rocks of Paleocene and Lower to Middle Eocene age are apparently not present in outcrop.
Middle and Upper Tertiary formations in the peninsula record a transgressive—regressive marine cycle. The Upper Oligocene Sillamana Limestone suggests an initial transgression. The shaly Uitpa Formation (Lower Miocene) represents the maximum extent of the marine invasion. A sequence of chalky marls exposed in the Portete Basin is the newly defined Peerpana Member of the Uitpa Formation. The Jimol Formation, exposed in the Cocinetas Basin, is composed of beds of sandstone and sandy limestone, and indicates an early Middle Miocene regression of the sea. Higher in the Tertiary section of the Cocinetas Basin, the Castilletes Formation (a limestone and clay shale sequence) represents the final regression of the sea during the late Middle Miocene to Late Miocene.
In the Portete and Chiohibacoa basins. the newly defined Taroa Formation (sandy limestone and calcareous sandstone) is a record of Late Miocene regression. The younger Gallinas Formation (new), of questionable age, is a thin sequence of sandy limestone beds representing a brief marine incursion.
The Upper Miocene beds of sandy limestone and clay shale exposed in southwest Guajira are the only record of a Tertiary transgression in this area. The name Orochó is proposed for these beds.
A The molluscan fauna was largely derived from the Castilletes Formation, although some molluscs from each formation are represented in the descriptions. Two bi- valves, Anadara (Scapharca) guajirensis, n. sp. and Venericardia (Venericor) guajirensis. n. sp. are new. The faunas show an endemism typical of the Caribbean Tertiary faunal a province.
Thomas, David John, "The tertiary geology and systematic paleontology (phylum mollusca) of the Guajira Peninsula, Colombia, South America" (1972). Graduate Dissertations and Theses. 184.