TEMBLADOR, Group
CRETACEOUS
State of Guárico, Venezuela
Author of name: J. M. Patterson and J. G. Wilson, 1953.
Original reference: J. M. Patterson and J. G. Wilson, 1953, p. 2711-2715.
Original description: ibid.
The term, Temblador group, was first used in publication by Patterson and Wilson (1953, p. 2711). Before this publication, the term Temblador was applied as a formation name to Cretaceous beds occurring in Eastern Venezuela. The Temblador formation of Eastern Venezuela is divided into two members, an "upper glaueonitic member" and a "lower mottled member" (Hedberg et al., 1947, p. 2108-10).
Wells drilled in south-central Guárico have encountered both members of the Temblador formation. However, in north-central Guárico, four definite mappable units are indicated in the subsurface. It is on this basis that Patterson and Wilson raised the term Temblador to group rank and subdivided the Cretaceous of northern Guárico into the "Mottled", La Cruz, Infante and Guavinita formations.
For a discussion of any particular formation of the Temblador group, see: "MOTTLED" Formation, LA CRUZ Formation, INFANTE Formation or GUAVINITA Formation. For a more detailed discussion of the Temblador formation or the "upper glauconitic" or "lower mottled" members, see: TEMBLADOR Formation.
S. J. Brown
"MOTTLED", Formation
UPPER CRETACEOUS
State of Monagas, Venezuela
Author of name: H. D. Hedberg et al., 1947.
Original reference: H.D. Hedberg et al., 1947, p. 2108.
Original description: ibid.
In discussing the Temblador formation which occurs on the southern limb of the Eastern Venezuelan Basin, Hedberg et al. used the term "lower mottled member" to designate a subsurface unit demonstrating a predominance of mottled beds. Here the Temblador formation was divided into the "upper glauconitic" and "lower mottled" members. As a result of drilling in central Venezuela, it was found that wells in south-central Guárico encountered the two members. However, in north-central Guárico, it was found that the Temblador is represented by four mappable units, the lowest being the "lower mottled member" of Hedberg. Therefore, Patterson and Wilson (1953, p. 2711) suggested raising the term "Temblador" to group rank and the term "mottled" to formation rank.
The "Mottled" formation of north-central Guárico consists of red, purple, green and gray shales and sandstones which in many places exhibit red and green mottling. In the Greater Oficina Area, the "Mottled" is made up of coarse grits, sandstones, and claystones, all mottled in various dull shades.
The type section for the "Mottled" formation is the interval 6117-6421 feet from well Tigre N° 1 in the southeastern part of the Greater Oficina Area where a cored section established the Cretaceous age and stratigraphic relations of the Temblador formation of Hedberg et al. (1947, p. 2108). Except for plant remains, the "Mottled" formation or member is unfossiliferous, and, therefore, no exact age determination can be made. However, fossils from the overlying "upper glauconitic" member of Hedberg et al. (1947, p. 2109), were determined as being not older than Cenomanian.
In the Mercedes area, the top of the formation is defined as the base of the predominantly marine beds of the La Cruz formation. The contact represents a change of facies from predominant nonmarine deposition below to predominant marine deposition above. The base is marked by a profound unconformity that rests the "Mottled" formation on granitic basement in the Oficina area or on the Carrizal formation to the west.
S. J. Brown