GUAYUTA, Group

CRETACEOUS (Cenomanian to upper Campanian)

State of Monagas, Venezuela

Author of name: R. A. Liddle, 1928.

Original reference: R. A. Liddle, 1928, p. 154.

Original description: ibid.

Liddle (1928, p. 154-161) named and described the Guayuta formation, which he included into the "Guanoco series" of Garner (1926, p. 679). The formation was named from Rio Guayuta, between Aragua de Maturín and Punceres, State of Monagas, where the type locality is situated. Here the formation consists of "brownish-gray to black, arenaceous, concretionary, calcareous, pyritic and sulphurous, fissile shale, interbedded with thin, hard, blue-black or gray-black limestone, especially in the lower part of the formation, and a few hard thin sandstones in the upper part. Throughout the greater part of its thickness and extent, it is carbonaceous or petroliferous and highly folded". The thickness of the formation varies from 3000 to 3500 feet. It is apparently in conformable contact with the underlying El Cantil formation, but the stratigraphic relations with the overlying Aragua formation are not clear. Based upon the occurrence of Ammonites, Inoceramus and Turrilites, the age range of the Guayuta formation is given as Cenomanian to Turonian, possibly extending into the Senonian. The formation outcrops in the Serranía del Interior in northeastern and north-central Venezuela.

The confusion which has existed over the years as to the exact meaning of the term Guayuta in its original sense, was clarified by Liddle (1946, p. 260) by stating that when he introduced the name for a formation in 1928 he had included the rock series that is now known as the Querecual, San Antonio, San Juan and lower part of the Vidoño formations, but elsewhere (p. 236) he mentions that in the area east of the Río Querecual the Guayuta group comprises the Querecual formation, the Guayuta shale, and the San Antonio formation.

Hedberg (1937a, p. 242) elevated the Guayuta formation to the rank of group for a sequence of black, thin-bedded limestones and calcareous shale of Upper Cretaceous age, to include the Querecual and San Antonio formations. These formations were properly defined and described by him (1937b, p. 1989-1994) from a newly designated type section on Río Querecual in northern Anzoátegui. In 1950 (p. 1190) he assigned a thickness of 3000-4000 feet to the group which is in transitional stratigraphic contact with the underlying Sucre group (Chimana and El Cantil formations) and with the overlying Santa Anita group (San Juan sandstone or Vidoño shale).

González de Juana (1947, p. 695-696) said that an unconformity between the Chimana formation and the Guayuta group has not yet been proved although it is suggested. He claimed to have found a thin conglomerate of black pebbles about 3/8" in diameter at or near the base of the Guayuta. At present, most workers seem to agree that the incompetent nature of the sediments comprising the Guayuta group and their position between the competent overlying Santa Anita group and the underlying massive Sucre group, present the false impression of unconformable relations, especially at the top of the San Antonio formation.

Mencher et al. (1951, Correlation Chart) indicate that the Guayuta group ranges from Cenomanian to upper Campanian in age.

Recent work by E. Rod and W. Maync (1945, p. 193-283) indicates that there are numerous local unconformities between their newly proposed Boquerón-Majagual formation (topmost Sucre group) and the overlying Querecual formation of the Guayuta group.

Wm. K. MacFarquhar