SOCUY, Limestone Member

UPPER CRETACEOUS (upper Campanian-lower Maestrichtian)

State of Zulia, Venezuela

Author of name: A. N. Dusenbury Jr. (private report).

Original reference: J. M. Sellier de Civrieux, 1952, p. 235.

See COLON, Formation

COLON, Formation

CRETACEOUS (upper Campanian Maestrichtian)

State of Táchira, Venezuela

Author of name: Geologists of Shell companies (private report).

Original reference: R. A. Liddle, 1928, p. 166.

Original description: ibid.

The name Colón shale, which according to Hedberg and Sass (1939, p. 81), was introduced by geologists of Shell companies, was first published by Liddle (1928, p. 166), who stated that the term was taken from the district of Colón in southwest Zulia as well as from the town of Colón in the state of Táchira. Hedberg and Sass (1937, p. 81) report that the name was originally taken from the town of Colón, near the Colón anticline in Táchira, where an excellent section is exposed just north of the town of Colón on the Río Lobaterita, designated by Hedberg as the type section. Sutton (1946, p. 1651) changed the name into Colón formation. According to him the formation at the type locality and along the entire northwestern flank of the Mérida Andes, is composed almost entirely of masssive, dark grey to black, hard, locally pyritic, conchoidal to irregular-fracturing shale. In places, some very thin beds of grey, hard, dense limestones are present in the upper part of the formation. Sandstones are rare. In the Mara-Maracaibo area, the so called Basal Colón limestone, is found at the base of the La Paz "series" (base of Colón shale) as published by the Staff of Caribbean Petroleum Co. (1948, p. 599) and Smith (1951, p. 59). This limestone has been called by Sellier de Civrieux (1952, p. 235) the Socuy limestone member of the Colón formation. Formerly this member has sometimes been included in the La Luna formation. According to González de Juana (1952, p. 208) the Santa Rosa formation of the geologists of Richmond Petroleum Exploration Co. is a synonym of the Socuy limestone member.

The thickness in the type section according to Sutton (1946, p. 1651) is 900 meters. Notestein et al. (1944, p. 1183) report a thickness of 215-460 meters in the area of the Barco concession in Colombia. In western Zulia the thickness of the Colón formation is 470 meters.

The Colón formation is underlain by the La Luna formation and overlain by the Mito Juan formation, both contacts seeming to be conformable.

The formation is distributed widely throughout western Venezuela and eastern Colombia, and is believed to underlie the entire Maracaibo basin.

The Colón formation is characterized by an abundance of smaller foraminifera which afford an excellent means of zoning (Cushman and Hedberg, 1941, p. 79-80). These authors proposed a subdivision into a Pullenia cretacea zone (lower 1,000 feet of Colón shale) and a Siphogenerinoides bramlettei zone (upper 500 feet of Colón shale). For fossil lists it is referred to Sutton (1946, p. 1652-1653) and Sellier de Civrieux (1952, fig. 9). According to Sellier de Civrieux (1952, p. 240-241) the age of the lower part of the Colón formation is upper Campanian or lower Maestrichtian.

According to Sutton (1946, p. 1653) the Colón formation is probably the equivalent of the Churricurri shales of Colombia and the upper part of Liddle's Guayuta formation of eastern Venezuela, now known as the San Antonio formation of the Guayuta group.

According to Liddle's correlation chart (1928) the Colón shale also been called the Carmelo shale in the Venezuelan Andes.

The shales of the Colón, Mito Juan and Guasare formations are sometimes called La Paz shale, and the Colón limestone, La Paz shales and the Guasare formation together are the La Paz "series".

W. A. Mohler