PARAPARA DE ORTIZ, Facies

See "ORTIZ, Flysh Series"

ORTIZ, "Flysh Series"

TERTIARY (Paleocene to ?lower Eocene)

State of Guárico, Venezuela

Probably synonymous with SAN JUAN DE LOS MORROS, Member.

Author of name: Mme. de Cizancourt, 1951.

Original reference: Mme. de Cizancourt, 1951, p. 9.

Original description: ibid, p. 22-23.

According to Mme. de Cizancourt (1951, p. 9): "the Ortiz flysch facies series must be considered as forming a separate unit to the south of San Juan de la Morros. It was named after the locality of "Parapara de Ortiz". The author also used the name "Parapara de Ortiz facies" (p. 26): "The corded nummulites zone in the Parapara de Ortiz facies, pertains to a higher level" (than that of Paleocene age in San Juan de los Morros) and is equivalent perhaps to the beds outcropping in the Tocuyo River, much farther west of San Juan de los Morros". According to Mme. de Cizancourt, that level corresponds to the lower part of the lower Eocene age. The author gives a detailed list of nummulitic (corded nummulites) and orbitoidal fossils (ibid. p. 22-23 and 62).

According to descriptions based on thin sections (p. 22-23), the unit includes limestones and conglomeratic and calcareous sandstones.

The following localities are indicated (p. 22, fig. 9): a) Parapara de Ortiz, b) a place located 10 kms to the east-northeast of Parapara and southeast of "Bejuco" (correct: Mata de Bejuco), c) the site Las Raíces, about 6 kms to the north - northwest of Ortiz, on the Parapara-Ortiz road' d) the bridge across the San Antonio River, some 2 kms north-northwest -of Ortiz.

A good unpublished description of the same sedimentary section was written in 1951, by V. M. Petzall, who observed a minimum thickness of 220 m. Petzall noticed said sediments about 4 kms to the west of Ortiz, near the road to San Francisco de Tiznados. The outcropping area includes a small valley located to the south of Cerro Floreha and Las Patillas Range, and a narrow belt, constituted by blocks sunken by faulting, extending 8 km along the strike towards the northeast, up to the crossing of the Ortiz-Parapara road with the San Antonio River.

The following lithologic description is based on Petzall's observations. He reports to have integrated the sequence to the Ortiz formation, as its Petzall integrated the sequence to the Ortiz formation, as its upper member. This idea is modified in the present writer's definition of the Ortiz formation (see).

Local ferruginous conglomerates with quartz grains, schists, black limestone of the type Guayuta and black, coarse "rained limestone, are found at the base of the unit. These conglomerates are interbedded with greenish and black shales, locally with spheroidal concretions and thin beds of conein-cone structured calcareous sandstone.

From base to top, there are interdigitated and inters/ratified facies of: a) dark gray to black, micro and macrofossiliferous algae reef limestones. b) dark gray to black fossiliferous conglomeratic limestones with fragments of Cretaceous limestone, cherts and green igneous rocks in microfossiliferous calcareous cement, c) conglomerates of the latter type with ferruginous cement, d) hard, microfossiliferous, bluish gray shales, of splintery fracture, e) fine grained, brown colored calcareous sandstones, the maximum thickness of which is 20 cms, locally, with cone-in-cone structured limestone beds, up to 3 cms in thickness. On top of this, there is a thickness of 100 mts of hard, laminated, gray-brown shales with fine-grained, calcareous and argillaceous discoidal concretions.

The remaining 60 m are made-up of medium to coarse-grained, reddishbrown sandstones, locally conglomeratic, containing fragments of Guayuta limestone and basic igneous rocks, in major or minor quantity of ferruginous cement. Sandstones are interbedded with brown, sandy shales. In its conglomeratic part, it contains molds of gastropods, pelecypods and echinoids.

It should be noticed that the name Ortiz, proposed by Mme. de Cizancourt to designate the above mentioned sediments, had been previously used by Liddle and by Kamen Kaye to name a complex of units, the lower part of which also includes upper Cretaceous formations. Actually, it is useful to retain the name 'Ortiz formation'. For the unit cropping up in the Ortiz syncline. The name "Parapara facies", also used by Mme. de Cizancourt (1951, p. 26) in other parts of her text, is neither desirable since Upper Cretaceous sediments do outcrop in the vicinity of Parapara, which is where the type-locality is supposed to be. Further investigations to reencounter there the Tertiary fossiliferous locality mentioned by Mme. de Cizancourt, have come to a failure.

The "separate unit" mentioned by Mme. de Cizancourt in relation to the sediments here discussed, has to a certain extent a bio-stratigraphic significance. This facies presents a great lithologic similarity with the San Juan de los Morros member of the Guárico formation. The word "flysch" assigned to the sequence by Mme. de Cizancourt does not have the tectonic significance given to it by Twenhofel; Mme. de Cizancourt only alludes to the cyclical interlamination of thin beds of different Ethology, which indicates instability and frequent changes in the depositional environment. To this respect there is no doubt about the San Juan de los Morros member and the equivalent beds here discussed presenting an unquestionable lithologic similarity with the typical alpine flysh.

Besides the conglomeratic and calcareous sandstones and the limestones described in thin sections by Mme. de Cizancourt (p. 22-23), the "Flysch series" contains gray-green, dark, fissile, splintery shales containing occasional intercalations of small biostroms, similar to those outcropping at San Juan de los Morros. In the writer's opinión, this section, perhaps trangressive over the Ortiz formation of upper Maestrichtian or Danian age, which outcrops to the south, must be assimilated to the San Juan de los Morros member; in the vicinity of Ortiz this member might be somewhat younger than in the San Juan type-locality, due to the southward transgression. Mme. de Cizancourt suggests an early Eocene age for the outcrops near Ortiz, but it is here believed that the paleontological evidences do not oppose to a Paleocene age, especially if the presence of Rzehakina and "Spiroplectammina", in the shales associated with the limestones containing nummulites, is noticed.

It is evident that the sediments here discussed, together with older sediments, some upper Maestrichtian or Danian, others Turonian and possibly Senonian, have been included in the so-called Ortiz formation of Kamen Kaye (1942). Nevertheless, a restriction of the name Ortiz is here suggested in order to exclude the sediments of the Guárico formation.

The occurrence of conglomerates at the base of the section containing corded nummulites, suggests a possible minor unconformity with the underlying sediments of upper Maestrichtian or Danian age (Ortiz formation sensu strictu). A similar Cretaceous-Paleocene unconformity is observed on the slopes of the Morro del Faro, in the region of San Juan de los Morros, north of Ortiz. Here, the levels that are in contact with the Maestrichtian as well as with the Paleocene seem to be older than those in the region of Ortiz, where there are transgressive facies of both ages.

Northeastward of Ortiz, along the local strike of the narrow Paleocene basin, excellent fossiliferous outcrops of the southern facies of the San Juan de los Morros member are found. Other signs of the supposed transgression over upper Maestrichtian or Danian sediments correlative with those outcrop ping in the Ortiz anticline, can be observed at some 8 kilometers (areal) northeast of Camatagua.

At the same region, Mme. de Cizancourt mentions the occurrence of corded and orbitoidal nummulites, which she refers to a lowermost Eocene age (p 24 fig 11; p 25) (see SAN FRANCISCO DE CARA, Beds).

J. M. Sellier de Civrieux