CUICAS, Limestone Member

TERTIARY (middle Eocene)

State of Trujillo, Venezuela

Author of name: F. A. Sutton, 1946.

Original reference: F. A. Sutton, 1946, p. 1667-1668.

See VALLE HONDO, Formation.

VALLE HONDO, Formation

TERTIARY (Paleocene to middle Eocene)

State of Trujillo, Venezuela

Author of name: J. W. Nance, 1942 (private report).

Original reference: C. M. B. Caudri, 1948, p. 479.

Original description: A. Salvador, 1950, Ph. D. Thesis, Stanford University.

J. W. Nance (1942, private report) assigned the name Valle Hondo to the formation exposed near the settlement of Valle Hondo, 4.5 kilometers southwest of La Cuchilla, State of Trujillo. The type section designated by A. Salvador (1950) is situated along the Transandean highway from Casa de Zinc, on Río Carache, to Valle Hondo. Other good sections, though not so complete, are at Balambay and Cerro El Cumbe.

The formation was described by Salvador (1950) as composed of a thick sequence of interbedded sandy shale, siltstone, fine-grained sandstone and hard, quartzitic sandstone. The reef limestones are very sandy, coarsely crystalline, thick-bedded and bluish-gray to gray. The limestones are a minor but characteristic part of the formation and though extremely variable over short distances, they have been separated and named. The most prominent limestones are, from bottom to top, the La Paz, the Cuicas and the El Cumbe limestone members.

The La Paz limestone member was named and described by Salvador (1949, private report; described 1950) for the exposures of reef limestone about 600 meters east of the settlement of La Paz, 2 kilometers west of Casa de Zinc on the Transandean highway. The La Paz limestone is described as a 13-foot (4 meter) sequence of light to dark gray, dense, thick-bedded, very sandy reef limestone. Its stratigraphic position is 400 feet (125 meters) below the base of the Escuque formation (Misoa formation of González de Juana, 1951, p. 285) and 275 feet (84 meters) below the Cuicas limestone member. H. H. Renz (1949, private report) and M. de Cizancourt (1951, p. 45) considered the La Paz to be upper lower Eocene, based upon Discocyclina barkeri, D. mestieri and D. cristensis (see faunal list, de Cizancourt, 1951, p 35, 36).

The Cuicas limestone member was named and introduced into print by Sutton (1946, p. 1667, 1668) as constituting the basal part of his Misoa formation. The limestones were named for the village of Cuicas and outcrop along the road nearby. Salvador (1950) selected as type locality the exposure at Cerro El Cumbe, along the cliffs facing Valle del Cumbe. It is composed of 6.5 feet (2 meters) of greenish-gray to greenish-brown, dense, massive, calcareous siltstone to sandy limestone, with concentrations of large orbitoids. Its stratigraphic position is about 130 feet (40 meters) below the base of the Escuque formation, and 115 feet (20 meters) below the El Cumbe limestone member. Renz (1949, private report) placed the Cuicas in the middle Eocene and M. de Cizancourt (1951, p. 46, 47) corroborated the determination as low middle Eocene, based on the coexistence of Pseudophragmina (Proporocyclina) renzi and Operculinoides oliveri (see faunal list, de Cizancourt, 1951, p. 37-41). De Cizancourt and Frizzell referred to this limestone as the Cuicas formation (1949, p. 496-497).

The El Cumbe limestone member was introduced by Salvador (1950) for a 25-foot (8 meter) bed exposed on the cliffs of Cerro El Cumbe. Along this cliff, north of the El Cumbe-Sabana trail, excellent outcrops afford a good type locality. It is composed of light to dark gray, dense, thick-bedded, very sandy reef limestone. It is situated 65 feet below the base of the Escuque formation. The presence of Lepidocyclina (Polylepidina) antillea, Operculinoides jennyi, Ferayina coralliformis and Discocyclina (Asterocyclina) barbadensis indicate an upper middle Eocene age (de Cizancourt, 1951, p 46-47).

The lowermost beds of the Valle Hondo formation are a sequence of reddish brown, massive, ferruginous, sandy limestones containing abundant Venericardia (Venericor) toasensis. The sequence between the Venericardia limestone and the La Paz limestone contains an abundant fauna of Orbitoids and Nummulites, including Nummulites scotlandica, N. barbadica and Discocyclina grimsdalei (de Cizancourt, 1951, p. 28-35) that provide a Paleocene to lower lower Eocene age.

The thickness of the Valle Hondo formation varies from about 975 feet (300 meters) at its lateral contact with the Ranchería formation to more than 2,800 feet (800 meters). The formation overlies the Colón formation conformably and is conformably overlain by the Escuque formation.

Based on abundant and diagnostic fossils, the age of the Valle Hondo formation can be determined as Paleocene, lower and middle Eocene. The lower part of the formation (1,290 feet = 427 meters) has been assigned to the Paleocene, the upper part to the lower and middle Eocene. The formation is a lateral equivalent of the Ranchería formation and is equivalent to the lower Misoa-Trujillo formation of Tash (1937, p. 167-169) where the "second Orbitoid level" is correlated with the Cuicas limestone member, and of the "Third Coal horizon" of Liddle (1928, p. 181-204). Based on age alone, Sutton included the upper Valle Hondo and the Cuicas member in his Misoa formation (1946, p. 1667) and included the Paleocene portion in the Guasare formation.

Gordon A. Young