CARIBBEAN, "System"

See CARIBBEAN, "Series"

CARIBBEAN, "Series"

predominantly MIDDLE and UPPER MESOZOIC

Northcentral and northeastern Venezuela

Author of name: G. P. Wall.

Original reference: G. P. Wall, 1860, p. 465.

Original description: ibid.

The name Caribbean "system" was used by G. P. Wall (1860, p. 465) to designate a unit of metamorphic rocks outcropping in northeastern Venezuela (Paria and Araya Peninsulas) and northern Trinidad. The name was changed to Caribbean "series" by Wall and Sawkins (1860). They intended to subdivide the "series" into an old group and a young group. Nevertheless, due to the complexity of the units which constitute the Caribbean "series", the establishment of a type-section has not been attempted so far.

The name Caribbean "series" has been frequently used in Venezuela and Trinidad.

The sediments of the Caribbean "series", today metamorphosed, were affected by the formation of a great downbuckle or tectogene. Crushed rocks of said tectogene are now forming a geotectoclinal (Caribbean arch).

Liddle (1946, p. 46) intended to restrict the use of the name Caribbean "series" to a pretended Paleozoic schists sequence ("lower schists series") and to differentiate it from what he considered to be another sequence, of Mesozoic age.

Today it is well known (see Dusenbury and Wolcott, 1949, p. 17-19, and Bucher, 1952, p. 39-40) that such differentiation was based on an identification of Silurian fossils made by Dreverman. As it was demonstrated by Schuchert (1928, D. 951-952) the fossils did not come from Venezuela (see VALENCIA, Limestone). The only "proof" for the occurrence of Paleozoic schists in the Caribbean "series" was thus gone and consequently the name "Lower Schists" had no value.

According to Kugler (1953, p. 35) the Caribbean series in the Island of Trinidad includes the following formations: a) (pre-Triassic or ?Jurassic) Dragón formation; b) (Jurassic) Maracas beds, Maraval beds, Laventille formation, Río Seco Formation, Grande Riviere formation; c) (Lower Cretaceous) Cumana formation, Galera formation, Toco formation, Sans Souci formation. According to the author, the first four formations are also represented in northeastern Venezuela. According to Kugler (ibid., p. 33) the series total thickness in northern Trinidad is of approximately 18,770 meters, number which according to some geologists seems exaggerated.

In the regions of north-central Venezuela studied so far, the Caribbean "series", locally unconformable over the ancient igneous complex (Sebastopol complex), begins with the Caracas group (Las Brisas formation with the tecto-phase of the Peña de Mora augengneiss; Antímano formation, Las Mercedes formation, and-according to Dengo, 1951-Tacagua formation). The Paracotos formation (of a lower metamorphic grade) unconformably overlies the Caracas group (fide Smith, 1952). The Paracotos is locally overlain by the volcanic rocks of Tiara or sediments of a very low metamorphic grade, the study of which has not been published yet.

Although it would be precocious to indicate the total thickness of the Caribbean "series" in northern-central Venezuela, the information available on the average thickness of the formations that constitute it, suggests a much lower thickness than that given by Kugler in Trinidad. Maxwell and Dengo (1950, p. 152) indicate a thickness of 1,500 to 3,000 meters for the Caracas group. The metamorphic section which outcrops in Carúpano, State of Sucre, and considered by said authors as probably correlative with the Caracas group, is 3,100 meters thick. The Paracotos formation, overlying the Caracas group, is 2,300 meters thick as appreciated by Smith (1952, p 363).

The age of the rocks constituting the Caribbean "series" has been and continues to be a matter of great discussion. According to Kugler (1936, p. 1441) Cunningham Craig was probably the first author to suggest the occurrence of Cretaceous rocks in the Northern Range of Trinidad; he based himself on lithologic similarities with Cretaceous rocks of the Central Range and mentioned the presence of limestone lenses containing caprinids, in calcareous schists of the Northern Range. He considered that the fauna is "Cenomanian in age and identical to the Cogollo limestone of Venezuela". Jurassic fossils were found by Hutchison (1939, p. 1243) in the Northern Range. Said age is today accepted for the lower part of the Caribbean "series" in the Island of Trinidad (see MARACAS, Beds and MARAVAL, Beds).

Hedberg (1942, p. 202) and Kugler (1953, p. 30-31) believe that in the Paria-Araya region (Venezuela) there are rocks probably equivalent to the Jurassic limestone of the Northern Range of Trinidad. González de Juana (1947, p. 694) states that the "Araya-Paria metamorphic group" includes "not only Jurassic... but some older rocks as well". He further states that the metamorphic rocks of the region of Paria and Araya are unconformably below the Lower Cretaceous (Barranquín formation) and therefore the main metamorphic period in the geotectoclinal was pre-Cretaceous.

In northern-central Venezuela, S. E. Aguerrevere and G. Zuloaga (1937, p. 22) proposed to correlate the lower part of the Caribbean series (Caracas group) with Cretaceous sediments of western Venezuela; they based themselves on lithologic similarities only. They also correlated the limestones near Villa de Cura (post-Caracas in age) with those of the vicinity of San Juan de los Morros; the Las Mercedes formation with the Colón formation; the "Los Colorados phase" with the La Luna formation; the Zenda phase with the Cogollo "formation" and Las Brisas formation with the Río Negro conglomerate. Kehrer (1937, p. 62) admits the possibility of such correlations saying that the transition from metamorphosed Cretaceous to normal Cretaceous can be seen in the Quebrada Auro, between Acarigua and Sarare, and in the Duaca-Aroa section, in western Venezuela.

The possibility of correlating the lower part of the Caribbean "series" in northern-central Venezuela (Caracas group) with the nonmetamorphosed Cretaceous section has been accepted by a number of geologists, for instance W, H. Bucher (1952). Bucher (ibid., p. 49) as well as other authors, indicates that equivalents of the metamorphic Jurassic of Trinidad and western Venezuela might occur in the Caracas group. When discussing the same problem, Hedberg (1942, p. 203) states that the possibility of a metamorphosed Triassic-Jurassic Caracas "series" should be also considered. He also says that it is interesting to notice that at the base of both Cretaceous and Triassic-Jurassic groups there is a sequence of sandstones and conglomerates which pass gradually into limestones and shales, towards the upper part. According to Hedberg, the character of the Caracas metamorphic rocks might be compared with the Triassic-Jurassic sequence as much as to the Cretaceous sequence.

Kugler (1953, p. 30) when discussing the gypsiferous facies in the Jurassic metasediments of the Paria Peninsula and Trinidad, emphasizes their importance in the correlation of the Caribbean "series" (see MARAVAL, Beds). On the other hand (see LAS MERCEDES, Formation) gypsiferous facies have been recently observed by the writer of the present article in the upper part of the Caracas group. Nevertheless, it should be found out whether the gypsum contained in said formations is of a primary origin or not, in order to be able to use the datum for correlation purposes. It should be mentioned here that gypsum veins of a secondary origin have been locally observed in the Lower Cretaceous of Venezuela (Chimana formation) (c. Francken, oral information).

Paleontological evidences in the Caribbean "series" of northern-central Venezuela are scarce. The available data consists of a microfauna collected by Wolcott (1943, p. 1632) in rocks of the Caracas group. It was originally considered Cretaceous or Jurassic, and "distinctly Upper Jurassic" by Bucher (1952, p. 42).

Other fossiliferous samples were collected by Wolcott in 1940, in a place located 5 kilometers to the south-southwest of Capaya, upstream in the Quebrada Yaguapa, from the crossing of the Quebrada Yaguapa with the old road to Caucagua (State of Miranda), a place which is located about 70 kilometers to the east-southeast of Caracas (Dusenbury and Wolcott, 1949, p. 22). The age of said microfauna is Turonian "because all the foraminifera species have been previously found in the Turonian section of the Querecual and La Luna formations and the radiolaria species in the Turonian section of the Querecual formation in Guárico" (ibid., p. 23).

The Paracotos formation, of a lower metamorphic grade than the underlying Caracas group and according to Smith in unconformity over said group, has provided Upper Cretaceous microfaunas in some localities, probably Cenomanian. The first mention in this respect is due to R. J. Smith (1952, p. 367) and it is based on a sample collected by H. H. Hess and studied by H. H. Renz. Other localities containing a similar fauna were studied by the writer of the present article. Recent studies by H. H. Renz indicate the Maestrichtian age of a part of the above mentioned formation. (see PARACOTOS, Formation).

Further information on the igneous rocks intimately associated with the formations of the Caribbean "series" could be found in the article "CORDILLERA DE LA COSTA" (IGNEOUS IN).

J. M. Sellier de Civrieux