CAPACHO, Formation

CRETACEOUS (middle Albian to Vraconian)

State of Táchira, Venezuela

Author of name: W. Sievers, 1888.

Original reference: W. Sievers, 1888, p. 24.

Original description: ibid.

The term Capacho limestone was published first by W. Sievers of the limestones (and shales) of the Middle Cretaceous (Albian), exposed on Cerro de Capacho, south of the town of Capacho (Independencia), Táchira (Sievers, 1888, p. 24; see Sievers, 1896, p. 249).

The ammonite-bearing shales and "blue" limestone of Barbacoas, Lara, referred to by W. Sievers as Barbacoas shale and Barbacoas limestone (Sievers, 1888, p. 24; Sievers, 1896, p. 95-96), correspond to the Capacho limestone.

R. A. Liddle (1928, p. 124, 148) applied the name Capacho "series" in a broad sense to the Lower Cretaceous sequence, from above the basal clastics up to the base of the Upper Cretaceous La Luna formation (=Cogollo group of present-day usage). He later discarded the term Capacho altogether (Liddle, 1946).

Extending W. Sievers' Capacho limestone from western Táchira into the Sierra de Perijá, Zulia, F. A. Sutton designates the stratigraphic interval between the Aguardiente formation and the La Luna formation as Capacho formation (Sutton, 1946, p. 1647).

At its type locality in Táchira, the Capacho formation is faulted; better exposures are found on Río de Oro, northern Táchira, from where the Capacho formation is described as follows (Sutton, 1946, p. 1647): . . . "The formation can be divided roughly into a lower and upper member. The lower member has a thickness of about 242 meters (794 feet) and is composed largely of massive, dark gray to black hard shale with a few beds, up to one meter thick, of dark gray, hard, fine-grained, calcareous sandstone. The calcareous sandstones are generally more pronounced in the basal part of the formation and some observers may wish to include them with the underlying Aguardiente formation. The upper member is about 120 meters (394 feet) thick and is composed of massive to thickly bedded, gray, hard, crystalline, fossiliferous limestone with a few thin beds of hard black shales".

The socalled "Cogollo formation" of the Venezuelan Andes and of the Barco Concession, Colombia, is the exact equivalent of F. A. Sutton's Capacho formation of western Zulia (interval between the Aguardiente and La Luna formations) (see Cogollo formation).

The Capacho formation of the Barco Concession is subdivided as follows.

Lower part. Black organic, bituminous, calcareous foraminiferal shale, laminated, and dark gray foraminiferal limestone with a few megafossils ("Lower Cogollo" Notestein et al., 1944).

Grading into:

Middle part. Black shale, non-calcareous, containing some interbeds of argillaceous fossiliferous limestone and some rare beds of siltstone and silty shale ("Middle Cogollo" Notestein et al., 1944).

Upper Part. (Guayacán Member). (Name derived from Quebrada Guayacán, Barco Concession, Colombia).

40 meters of brownish-gray, very fossiliferous massive limestones interstratified with black silty to micaceous shales and some siltstones. Ostrea zone about 15 meters below the top. The Guayacán member is also present in the Tarra Field, Zulia (Staff of Caribbean Petroleum Company, 1948, p. 612), and was recognized below the La Luna formation in the La Paz Field (Smith, 1951, p. 62) where it is composed of oysterbank limestone: oölitic, pellet, and lithographic limestones with shale and marl beds. The thickness of the Capacho formation attains 240-310 meters (Táchira) and 460 meters (Trujillo); in Zulia, it is stated to amount to 223 meters (Río Cachirí), to 400 meters (Río Apón) (Sutton, 1946, p. 1647); to 222-274 meters (Terra Field) (Staff of Caribbean Petroleum Company, 1948, p. 612, 614); and to 425 meters (Mara-La Paz Field) (Smith, 1951, p. 62). In the Barco Concession, thicknesses of 175 to 435 meters of the Capacho formation are reported (Notestein et al., 1944, p. 1179). The ammonite-bearing Capacho formation was found to reach a thickness of about 350 meters in the Barbacoas-Carora area, Lara (Rod and Maync, 1954, p. 214-215).

As a rule, a conformable contact exists between the Capacho and the subjacent Aguardiente formation. In the Chejendé section (Trujillo), however, this contact seems to be unconformable (Rod and Maync, 1954, p. 278). The boundary with the overlying La Luna formation is conformable.

E. Rod's field work in the Sierra de Perijá has shown that the lower part of the Capacho formation as applied by F. A. Sutton belongs for lithologic reasons to the Aguardiente formation. On this account, he includes the entire sandy glauconitic rock unit (Aguardiente and lower part of the Capacho formation of Sutton) in his Lisure formation and discriminates the generally non-glauconitic limestones above (upper part of Sutton's Capacho formation) as Maraca formation (see Lisure and Maraca formations).

Fauna: Except for some mollusks, the Capacho formation (Trujillo, Lara) harbors rich ammonite faunas (lower part of the formation). Extensive faunal lists have been published, especially from the classic localities near Barbacoas, Lara (Karsten, 1886, Sievers, 1888, Stieler, 1920, etc.; see Liddle, 1946, p. 213; Rod and Maync, 1954, p. 227-228). Additional collections have recently been determined by R. W. Imlay (Rod and Maync, 1954, p. 227). Representatives of the genera Venezoliceras Oxytropidoceras, Pervinquieria, Prohysteroceras (Goodhallites), Puzosia, Turrilites, Mariella, occurring in abundance, indicate a middle and upper Albian age of the Capacho formation. Mariella bergeri (Brongn.) suggests upper Albian-Vraconian to lower Cenomanian.

Wolf Maync

COGOLLO FORMATION

CRETACEOUS (Aptian to Cenomanian)

State of Zulia, Venezuela

Author of name: A. H. Garner, 1926.

Original reference: A. H. Garner, 1926, p. 679

Original description: ibid.

The term Cogollo was first published by A. H. Garner (Río Cogollo limestone) for the gray massive crystalline fossiliferous limestone that underlies the La Luna formation on Río Cogollo, Sierra de Perijá, Zulia (Garner, 1926, p. 678-679).

R. A. Liddle and others used the name Cogollo formation or Cogollo limestone for the complex of gray hard massive limestones and interbedded gray to black shales which are widely distributed in Western Venezuela and which occupy the stratigráphic interval between the clastic deposits of the basal Cretaceous (Río Negro formation) and the Upper Cretaceous La Luna formation (Liddle, 1928; Hedberg, 1931; Hedberg and Sass, 1937; Sutton, 1946, etc.). The names Cogollo formation or Cogollo limestone have unfortunately been used by some authors in a very restricted sense, viz. to represent only the uppermost part of the Cogollo Group, i e., the Capacho formation of the Andes and the Capacho-Maraca formations of the Sierra de Perijá (Kehrer, 1937, p. 54; Tomalin, 1938, p. 12; Notestein et al., 1944, p. 1178; Liddle, 1946, pars; Staff of Caribbean Petroleum Company, 1948, p. 612; Mencher et al., 1953, p. 730). J. E. Smith (1951), on the other hand, includes the entire Cretaceous of pre-La Luna age in the Cogollo formation (=Río Negro formation + Cogollo Group); this use of the term Cogollo is also accepted by the Shell Group in the Maracaibo-Mara region (Mencher et al., 1953, p. 723). J. E. Smith's term Cogollo limestone equals the Cogollo group; his lower Cogollo is lower Apón, his "Middle Cogollo Shale Break" is middle Apón, his middle Cogollo is upper Apón, and his upper Cogollo is Lisure-Capacho-Maraca (see APON, LISURE, CAPACHO, and MARACA Formations).

In the original type section on Río Cogollo, Sierra de Perijá, the top beds (Maraca formation) and the base of the Cogollo formation are cut out by faulting (Rod, 1950, see Rod and Maync, 1954, p. 200 etc.). On account of this incomplete section at the type locality and of the considerable stratigraphic span attributed to the Cogollo formation, the popular name Cogollo is retained as a group term (Sutton, 1946, p. 1641).

The comprehensive name Cogollo formation (or Cogollo limestone) is replaced by a group of minor stratigraphic units, viz. (from bottom to top) the Apón, Aguardiente - Lisure, and Capacho - Maraca formations (Sutton, 1946, p. 1630, 1642, etc.; Rod and Maync, 1954, p. 202 etc.).

Wolf Maync