BATATAL, Formation
TERTIARY (Oligocene)
State of Miranda, Venezuela
Author of name: Lee, 1946 ( ? )
Original reference: J. Evanoff, 1951, p. 246.
Original description: J. Evanoff, 1951, p. 246-247.
The name Batatal formation was used for the first time in 1946 by Lee, a geologist of the Texas Petroleum Company, applying the term to beds exposed along the Quebrada Tocoragua, downstream of the settlement of Corozo, which Lee erroneously called Batatal, and located approximately 5 kms. northwest of the small village of Sabana Grande, State of Guárico. The name Batatal formation was published for the first time by Evanoff (1951, p. 246).
The type section selected by Lee is not the most representative of this geologic unit, and for this reason Evanoff selected as standard the one exposed along the Quebrada (Creek) El Baño, a tributary to Quebrada Lele, which passes to the south of Batatal, a small settlement in the State of Miranda. The section starts 280 mts. upstream of the confluence of the two creeks and continues for 770 mts. upstream along Quebrada El Baño.
Pure, thick to massive sandstones make the most prominent exposures of this formation. These sandstones are well consolidated, fairly resistant to erosion and are generally friable. They are saccaroid in appearance and of light colors; white, gray to light-gray, brown to light brown and locally, reddish. In texture, they vary from fine to coarse-grained, frequently conglomeratic. Cross-bedding and ripple-marks are frequent. In the upper part of the f ormation the sandstones become lenticular which makes it rather difficult to establish the contact between these and the overlying Quebradón formation. The sandstones are interbedded with thick layers of shale, which, because of their softness, make very few exposures in the area. In color these shales are rather dark gray, brown and black, frequently carbonaceous. Bedding in the shales is rather poor. Both sandstones and shales are locally micaceous. The shales frequently show gypsum crystals. The formation contains various coal seams, one of which, in Quebrada Tocoragua, has been commercially exploited in the past. The thickness of this unit varies from place to place; in the type section it is 530 m.; in Quebrada Tocoragua 512 m., while in Quebrada Quebradón it only reaches 430 m.
The Batatal formation is in fault contact with the underlying Tememure formation and conformable with the overlying Quebradón.
The formation extends for long distances both east and west of the type section. However, its continuity is interrupted at various points. In the region inmediately north of Altagracia de Orituco the beds are faulted. They appear again to the north of Las Petacas (Altagracia de Orituco-Taguay highway), where they form a very narrow belt which continues westward to a point approximately 2.5 km. west of Río Memo. They appear again in the Galera of Guarumen and continue westward along the foot-hills of the Serranía del Interior, forming various prominent escarpments along the southern boundary of the State of Cojedes. To the east of the type section the formation extends with practically no interruption to, at least, the road from Guanape to Sabana de Uchire.
No diagnostic fossils have been found in the Batatal formation. Sellier de Civrieux (1951, p. 264) describes a poor siliceous-arenaceous fauna, indicative of brackish environment, such as Miliammina fusca (Brady) y Ammobaculites cf. nummus (Garrett). Leaf impressions are fairly common.
The formation is part of the Guarumen group.
See also EL PAO, Formation and GUARUMEN, Group
J. Evanoff