NARICUAL, Formation

TERTIARY (upper Eocene-Oligocene)

State of Anzoátegui, Venezuela

Author of name: Ralph Arnold, 1913 (private report).

Original reference: H. D. Hedberg and A. Pyre, 1944, p. 15-21.

Original description: ibid.

The name Naricual member was given by Ralph Arnold (1913, private report) and published for the first time by Hedberg and Pyre (1944, p. 1518) to designate the thick upper part of the Merecure formation above the Los Jabillos and Tinajitas members. The type locality is in the vicinity of the coal-mining town of Naricual and the type section is well exposed in the valley of Río Naricual, in the mines, and along the roads of this area. The lower 1600 feet of the member consist of carbonaceous shales, sandy shales and sandstones, followed by the main coal-bearing series, about 3000-3500 feet thick, which contains the coal groups or "paquetes" of Santa Maria, Mallorquín and Aragüita of González de Juana and Aguerrevere (1938, p. 18-20); this series appears to be included in the Naricual coal measures of Garner (1926, p. 680). This interval also includes numerous sandstones and shales. The upper part of the member, about 1500 feet thick, contains few coals and consists largely of topographically prominent sandstones separated by gray barren shales. The lower, more shaly part of the member commonly forms a broad valley along the mountain front between the resistant Los Jabillos member and the upper Naricual sandstones. The sandstones of the Naricual member are typically massive, light-colored, quartzose, sugary to quartzitic, and medium to coarse-grained. The stratigraphic relation between the Naricual member and the overlying Santa Inés sediments appears to be of transitional character everywhere throughout northeastern Anzoátegui, although the general distinction between the two units is clear.

Hedberg (1950, p. 1196-1197) raised the Merecure formation to group rank, and its Tinajitas, Los Jabillos and Naricual members to formations.

In the Anaco fields, the Periquito formation (Funkhouser et al., 1948, p. 1870-1872) is probably equivalent to the Naricual formation and underlies conformably the Oficina formation, included by Hedberg (1950, p. 1204-1205) in the Santa Inés group. Furthermore, attention is drawn to the fact that the uppermost part of the Periquito formation grades laterally into the basal Oficina "U-sands" of the Greater Oficina fields.

Hedberg (1950, p. 1198, 1204) points out that in northwestern Anzoátegui and northern Guáriço the differences existing farther east between the Merecure and basal Santa Inés groups become indistinct, with the appearance of a somewhat different facies called Cailo Dulce formation, and considers that the La Pascua formation of central Guárico and Kamen-Kaye's (1942, p. 128-133) Guarumen group of western Guárico are probably time-equivalents of the upper part of the Merecure and lower part of the Santa Inés groups.

In northwestern most Monagas and northeasternmost Anzoátegui, a lateral facies of the lower part of the Naricual formation was named Areo shale by Hedberg (1950, p. 1197-1198).

The paleontological evidence appears to indicate an upper Eocene to Oligocene age for the Naricual formation (Hedberg and Pyre, 1944, p. 19-21).

Gustavo Feo-Codecido