MUNDO NUEVO, Formation

TERTIARY (upper Eocene)

State of Anozátegui, Venezuela

Author of name: J. W. Nance, 1942 (private report).

Original reference: H. D. Borger, 1952, p. 2302-2303.

Original description: ibid.

Borger (1952, p. 2302-2303) stated that the reefal limestones and sandstones of the Eocene Mundo Nuevo formation were deposited in shallow seas and were penetrated by a few wells in the Quiriquire oil field of northern Monagas. His composite log (fig. 5) shows that the only Eocene in the Quiriquire field is upper Eocene, while the text shows that the only Eocene in the field is the Mundo Nuevo formation. It can therefore be logically deduced that the Mundo Nuevo of the text and the upper Eocene of the composite log are identical. The upper Eocene of the composite log is shown as an apparent thickness of 2500 feet of sandstone, shale and orbitoidal glauconitic limestone, reposing unconformably upon the Upper Cretaceous Santa Anita group and unconformably beneath basal Oligocene sandstones.

Much of the following additional information has been abstracted from the description of Nance (1942, private report). The Mundo Nuevo formation was named after the village of Mundo Nuevo in northeastern Anzoátegui. The type section, much of which is rather poorly exposed, is on the Río Amana downstream from and approximately 3.5 kilometers southwest of the village, which is situated on the Cretaceous Querecual formation. Nance considered the name Mundo Nuevo formation to be not well chosen and tentative, but no acceptable substitute has as yet been suggested. The lower part of the Mundo Nuevo formation is composed of light gray, massive, often quartzitic, gorge-forming sandstones which measure 590 feet on the Río de Oro and about 230 feet on the Río Querecual. The upper part of the formation consists of interbedded glauconitic, calcareous sandstones, siltstones and shales with scattered limestone biostromes and small bioherms. From the Río Orégano westward dolomitic siltstones and impure dolomites become common. On the Río Querecual, the upper part of the formation is about 460 feet thick. The maximum measured thickness for the entire Mundo Nuevo outcrop belt is 313 meters (1027 feet) in the Río de Oro section.

The Mundo Nuevo formation was established by Nance to include all of the upper Eocene beds in Anzoátegui and Monagas. These upper Eocene strata have usually been assigned in part to the Merecure group and in part to the Santa Anita group. They include the "Merecure limestones at La Pedrera and Pehas Blancas in the vicinity of the Río Unare 50 kilometers west of Barcelona" (Hedberg and Pyre, 1944, p. 18), the basal limestone of the type Tinajitas formation (loc. cit.) and the underlying dolomites and sandstones of the entire Caratas formation in the Barcelona area (loc. cit. p. 6), the 460 feet of dolomitic sandstones, siltstones and limestones containing upper Eocene nummulites, orbitoids and echinoids and the underlying 230 feet of sandstone at the top of the Caratas formation on Río Querecual (loc. cit.), a much thinner section (reduced by thrust faulting) in Río Orégano and Quebrada Pegua; the type section of the Mundo Nuevo on the Río Amana with its abundantly fossiliferous limestone near the top (Cooke, 1941, p. 305), a limestone containing large foraminifera ot upper Eocene age on the Río Areo (Hedberg and Pyre, 1944, p. 18-19) and on the Río de Oro, upper Eocene beds in wildcat wells north of the Jusepín field, and the Mundo Nuevo in the wells of the Quiriquire field. The Mundo Nuevo lies disconformably upon the Paleocene portion of the Vidoño and Caratas formations of the Santa Anita group and with at least local disconformity beneath the lower Oligocene Los Jabillos sandstone of the Merecure group and the equivalent sandstones and shales of the Tinajitas formation. Geologists who use the name Mundo Nuevo formation for the upper Eocene restrict the Santa Anita and Merecure so as to exclude the upper Eocene strata. The upper Eocene species of the Mundo Nuevo include Bulimina jacksonensis Cushman, Operculinoides kugleri Vaughan and Cole, O. trinitatensis (Nuttall), Asterocyclina asteriscus (Guppy), Lepidocyclina (Pliolepidina) pustulosa (H. Douvillé), L. (Nephrolepidina) sanfernandensis Vaughan and Cole, Tubulostium clymenoides (Guppy), Oligopygus nancei Cooke, O. curasavicus Molengraaf and Raetomya sp. The shallow marine deposits of the Mundo Nuevo accumulated in a narrow trough sea extending east and west through northern Anzoátegui and Monagas.

A. N. Dusenbury, Jr.