PUNCHE, Formation

TERTIARY (upper Miocene)

State of Anzoátegui, Venezuela

Author of name: unknown.

Original reference: González de Juana, 1946, p. 29.

Original description: ibid.

The name Punche formation was published by C. González de Juana (1946, p. 29). The name is derived from a property called Punche in the Distrito Aragua, and the type section Is given as: from a point two kilometers east of El Chaparro, in a southeast direction as far as the upper part of the eastern scarp of the Misencantada river. The formation is described as composed predominantly of bluish-gray, plastic, compact clays, with yellow ferruginous stains where weathered; intercalated in the clays there are some grey and brown sands, sometimes clayey, sometimes pure and friable. The formation is said to contain some non-diagnostic macrofossils, especially Leda and Tellina, but also a microfauna of upper Miocene age.

In a discussion of the overlying Campo Santo formation, González de Juana (p. 28), states that in the flanks of the Santa Ana anticline in the same Aragua district of Anzoátegui, there is an important unconformity which appears to mark the Pliocene transgression in the zone of Orijuan-San Mateo. The 12 meters of beds above this unconformity are marine, but the succeeding beds are brackish-water. Admitting that structurally these 12 meters of marine sediments above the unconformity are allied to the Campo Santo, González de Juana prefers to exclude them from that formation and include them with the Punche formation, with which their Ethology, mineralogy and paleontology are considered to ally them. In other words (that author says), the folding of the San Josquín-Santa Ana-southern Anzoâtegui region was slightly anterior to the invasion of brackish-waters.

In a discussion of the underlying Suata formation, González de Juana (p. 30) mentions "el paquete de Agua Amarilla" in the lower part of the Punche formation, 50 meters of this member were found in a water well in Aragua de Barcelona, the beds being fine-grained, decidedly clayey sands in thin beds intercalated in massive or laminated clays.

No figure is given for the thickness of the Punche formation as a whole.

Hedberg (1950, p. 1205) states that the Punche is the same as the subsurface Freites formation of Hedberg, Sass and Funkhouser (1947) and proposes that the name Punche be dropped in favor of the more widely used Freites. The undersigned would prefer to retain the name Punche for the surface formation, in accordance with the spirit of the Stratigraphic Code, that preference should be given to formations with accessible surface outcrops. The following observations by Hedberg (ibid.) make clear the relations between the subsurface formation (Freites) and the outcropping formation, for which we would retain the name Punche:

"The Freites formation extends with remarkable lithologic constancy throughout the southern and south-central part of north Anzoátegui and Monagas, and it has also been identified in the north-central part of the Eastern Venezuela Basin. Towards the west, it has been traced by core drilling up dip to the surface outcrop, and it constitutes the uppermost exposed unit of the Santa Inés group in central and southern Anzoátegui, where it forms a broad band of outcrop from the vicinity of Aragua de Barcelona on the north southward into the district of Monagas, Anzoátegui. In the central part of this outcrop belt, it possesses much the same character as in the Oficina field. To the south it shows a more brackish-water environment and to the north it becomes sandy and less persistently marine and grades laterally into the upper member of the Quiamare formation ... The outcropping unit has been referred to as Aragua formation and as Punche formation ... "

Hedberg (1950, p. 1212) refers the Freites to the late middle Miocene. He also states that there is no sharp break, but gradual transition, to the "increasingly sandy and less marine sediments constituting the Las Piedras" (i. e. Campo Santo) "formation of the overlying Sacacual group" of the upper Miocene over much of the area. The Freites is now assigned to the lower and middle Miocene.

(See also FREITES, Formation and ARAGUA, Formation).

Frances de Rivero

FREITES, Formation

TERTIARY (Miocene)

States of Anzoátegui and Monagas, Venezuela

Author of name: H. D. Hedberg, 1936 (private report).

Original reference: H. D. Hedberg, L. C. Sass and H. J. Funkhouser, 1947, p. 2105-2107.

Original description: ibid.

The Freites formation was named by Hedberg (1936, private report) with type locality in wells of the Oficina field, District of Freites, Anzoátegui, and first published by Hedberg et al. (1947, p. 2105-2107) who divided it into three members, based on the presence of sandstones near the top and base of the formation in contrast to the middle and thicker shaly part. The formation thickens northeastward in the Greater Oficina area from 1,100 feet in well Yopales Nº 1 to 2,000 feet in West Guara, Nipa and North Leona. The upper member is 300 feet thick and includes thin, shaly, fine-grained, whitish-gray and slightly glauconitic sandstones, remarkably continuous laterally; the lower sandy member is also 300 feet thick, and besides the typical greenish-gray fissile shales forming the major part of the formation (middle member), includes yellowish-green, medium to coarse-grained, glauconitic, calcareous or sideritic highly fossiliferous sandstones; common calcareous clay-ironstone concretions occur throughout the shales. Sand bodies in the Freites formation are designated (from top to bottom) by the greek letters Sigma, Rho, Mu and Lambda. The formation grades upward into the Las Piedras formation, contact being placed at the top of the first marine horizon in the section (base of the Tau sand). The contact with the conformably underlying Oficina formation is placed where the greenish-gray Freites shales give way to the brownish-gray Oficina sediments. The lower member of the Freites is rich in shallow-water marine fossils; the middle shale member represents a moderately deep-water marine environment, and the upper member is dominantly brackish. Foraminifera and mollusks indicate an upper middle to lower upper Miocene age, and the formation is correlated with the uppermost Santa Inés group of northern Anzoátegui.

According to Funkhouser et al. (1948, p. 1865-1866) the thickness of the Freites formation in the Greater Anaco area ranges from 1,500-2,000 feet southwestward, to 2,600 feet in outcrops along the Aragua de Barcelona road in the northwestern part. In well RG-1 (Santa Rosa field), the formation is divided into (1) the upper member, 1,135 feet thick, of interbedded greenish-gray shale and sandstone, locally glauconitic, with 100 feet of basal mottled claystone, barren of fossils; (2) the middle member, 565 feet thick, of greenish-gray shale, with basal fossiliferous grits and alternating marine and brackish-water faunas; (3) the lower member, 530 feet thick, of fossiliferous grits, black chert conglomerate, sandy limestone, "pepper and salt" sandstones and greenish-gray, shale, with shallow-water mollusks. A slight unconformity with the underlying Oficina formation is suggested on structural highs; the unit is unconformably overlapped by the Sacacual group in this area.

Hedberg (1950, p. 1205) recommends substituting the names of Aragua (pre-occupied by Garner (1926) for sediments now included within the Santa Anita group) and Punche formations for the more widespread term Freites formation. Although he includes Freites formation into the Santa Inés group, all geologists are not in agreement with this designation.

Mencher et al. (1951, p. 68) divide the Freites formation in the Temblador area into four members which are from top to bottom: sandy - shaly - sandy - shaly, with a total thickness of 1,600 feet, increasing northward and decreasing southward. A lower and middle Miocene age is here assigned to the formation.

Cecily Petzall