OMUGUENA, Formation (misspelling)

See OMUQUENA, Formation.

OMUQUENA, Formation

TERTIARY (upper Eocene and middle Oligocene?)

State of Táchira, Venezuela

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

Original reference: F. A. Sutton, 1946, p. 1673-1675.

Original description: ibid.

Sutton (1946, p. 1673-1675) stated that the name Omuquena is derived from the Río Omuquena in north-central Táchira and is used to designate an interbedded shale and sandstone formation that immediately overlies the gorge-forming Misoa formation short distance downstream from the Las Talas-La Hojita trail crossing. Sutton described the formation as consisting of interbedded, greenish gray to dark gray, locally sandy, carbonaceous, plant-fossiliferous shales, and gray to greenish gray, locally laminated, fine sandstones. He cited a thickness of 335 meters for the Omuquena formation in the type area. Sutton pointed out that the formation is transitional with the Mirador formation below and the Lobaterita formation above. He mentioned that the formation extends from western Táchira to west-central Mérida along the northwest flank of the Mérida Andes. He claimed that the formation contains an impoverished brackish-water to shallow-marine microfauna which resembles the microfauna from similar racies of the Potreritos formation in the northern part of the Maracaibo basin. He listed assemblages of macrofauna (p. 1674) identified by Winkler, and pointed out that the Omuquena formation has been assigned to the upper Eocene based on the listed macrofaunal evidence.

Schaub (1948, p. 221) considered the Omuquena formation to be synonymous with the Carbonera formation and suggested that the name Omuquena be dropped.

Dusenbury (1949, p. 148) pointed out that a Tropical Oil Company field party, with P. P. Wolcott as a member, was able to trace the Omuquena formation of Táchira across the Venezuelan-Colombian border into the Carbonera formation of the Department of Santander del Norte in Colombia. This latter formation was considered to be upper Eocene? - Oligocene in age by Notestein et al. (1944, p. 1196, 1199), and to be upper Eocene and middle Oligocene in age by Sutton (1946, p. 1672-1673). Sutton (1946, p. 1673) listed a fauna, identified by A. A. Olsson, from the fossil locality 150 meters below the top of the Carbonera at El Cerrito, 7 kilometers northeast of Cúcuta, Colombia. Sutton and Olsson considered this fauna to be middle Oligocene in age, a determination which later caused a large amount of disagreement. This fauna, a representative of the Hannatoma fauna of Colombia, is at present considered to be upper Eocene in age according to Durham et al. (1949, p. 145-160). The uppermost 90 meters of the type section of the Carbonera formation may, however, still belong in the middle Oligocene as claimed by Sutton (1946, p. 1673) who stated: "The highest 90 meters (295 feet) of the type section of the Carbonera consist of gray to buff, finegrained, friable sandstones between which lie covered intervals. It is believed that these sandstones are Middle Oligocene in age..."

Mencher et al. (1951 and 1953, correlation charts) still show the Omuquena formation in the upper Eocene of Táchira. The name is misspelled as "Omuguena" in Mencher et al. (1951, correlation chart) and as "Umuquena" in Mencher et al. (1953, correlation chart).

Leo Weingeist