BEBEDERO, Formation

BEBEDERO, Formation

TERTIARY (upper Oligocene or lower Miocene)

State of Táchira, Venezuela

Author of name: P. P. Wolcott, 1943 (private report).

Original reference: F. A. Sutton, 1946, pp. 1691-1692.

Original description: ibid.

Sutton (1946, pp. 1691-1692) stated that the type locality of the formation is exposed along a ridge about 250 meters southeast of a wayside inn called "Bebedero Parado" near the Las Mesas end of the Seboruco-Las Mesas road in north-central Táchira. Sutton described the formation as consisting almost entirely of massive to well bedded, light gray to buff, fine and powdery to medium-grained, locally carbonaceous, plant-fossiliferous, ripple-marked sandstone. When fresh, the sandstone is generally hard but upon weathering becomes soft, friable, and sugary. Beds of gray, hard clay or shale, that never exceed a thickness of 2 meters, are present in very subordinate amounts. The formation exhibits a fresh to slightly brackish-water type of sedimentation. Sutton cited 100 meters as a minimum thickness and 500 meters as a maximum thickness for the Bebedero formation. It lies unconformably on the "Lobaterita formation" and appears to be disconformable with the overlying Palmar formation. The outcrop occurrence is limited, according to Sutton, to the northwest flank of the Mérida Andes in Táchira and southwestern Mérida. No fossil fauna has been found in the formation and Sutton assigned the formation to the middle Oligocene based on its stratigraphic position and lithology.

Information taken from private reports and from personal communications indicates that the author of the name now coirsiders the Bebedero sandstone to be the basal member of the Palmar formation. The upper contact of the Bebedero, described by Sutton (1946, p. 1692) as appearing to be disconformable, is now known to be gradational. The Bebedero is believed to be upper Oligocene or lower Miocene.

See also PALMAR, Formation

Leo Weingeist

PALMAR, Formation

TERTIARY (upper Oligocene or lower to middle Miocene)

State of Trujillo, Venezuela

Author of name: P. P. Wolcott (private report).

Original reference: F. A. Sutton, 1946, pp. 1701-1703.

Original description: ibid.

Sutton (1946, pp. 1701-1703) stated that the name Palmar formation derives from the village of Mesa Palmar in southwestern Trujillo and is used to designate a series of interbedded shales, sandstones, and clays which crop out along the Río Buena Vista just below the village. The base of the formation is 700 meters downstream from the crossing of the Monte Carmelo-Las Pavas trail and the top is 1,050 meters farther downstream. Sutton described the clays as mottled dull red, olive-brown, and dark green and locally sandy, indurated, carbonaceous, and plant-fossiliferous. The sandstones are light gray, friable, fine-grained to locally conglomeratic, commonly poorly sorted, and locally micaceous and carbonaceous. The shales are dark gray to black, hard, locally carbonaceous and fossiliferous. Some thin beds of lignitic coal and hard siltstone are present here and there. The type of sedimentation is brackish-water to shallow-marine. Sutton cited a thickness of 570 meters for the formation at its type locality. Southward in west-central Mérida, he stated, the thickness is 590 meters. The Palmar formation is overlain by the Isnotú formation conformably. In southwestern Trujillo and west-central Mérida, the Palmar rests unconformably on the Paují and "Lobaterita" formations. Sutton stated that southward, in south-western and northern Táchira, it is disconformable with the underlying Bebedero formation. The outcrop occurrence of the Palmar formation extends from the Río Buena Vista in southwestern Trujillo along the Andean front to the Colombian border. Northward from the Río Buena Vista, the formation is overlapped by the Isnotú formation. A middle Miocene fauna has been recovered from the upper part of the formation (see Sutton, 1946, p. 1702). No diagnostic fossils have been found in the middle and lower parts. Sutton gave a lower and middle Miocene age to the formation.

Schaub (1948, p. 220) expressed the opinion that Sutton's Isnotú and Palmar formations are one and the same. He proposed to discontinue the use of the name Isnotú since the outcrops near Mesa del Palmar were better suited for a type section than those of the Isnotú.

Mencher et al. (1951, correlation chart) placed the Palmar as the basal formation of the Betijoque group in Trujillo and Táchira. They indicate an upper Oligocene (or older) and lower Miocene age for the formation. The Palmar is shown to be overlain conformably by the Isnotú formation and to rest unconformably on the "Lobaterita formation" in Táchira and to rest either conformably or unconformably on the Pauji formation in the State of Trujillo.

Information taken from private reports and from personal communications indicates that the author of the name now considers the Bebedero to be the basal sandstone member of the Palmar formation. The contact between Sutton's Palmar and Bebedero formations is now known to be gradational. The Palmar formation, including the Bebedero as its basal sandstone member, is now considered to be upper Oligocene or lower Miocene to middle Miocene in age.