CERRO AZUL, Beds

See CERRO AZUL, Formation.

CERRO AZUL Formation

LATE PALEOZOIC (Devonian? and Pennsylvanian-Permian)

State of Barinas, Venezuela

Author of name: A. N. Mackenzie, 1937.

Original reference: A. N. Mackenzie, 1937, p 258-59.

Original description: ibid.

The Cerro Azul formation as named and described by Mackenzie (1937, p. 258-59), constitutes the oldest rock exposed in the Cerro Azul uplift nine kilometers north of the town of Barinitas in the State of Barinas The outcrop area extends for 22 kilometers in a N 35 E direction over a width of from 2.5 to 3 kilometers. As described by Mackenzie (1937, p. 258-59) the rock is hard, greyish green in color, of microscopic texture and has a smooth fracture. Samples submitted for thin-section study were reported as follows (Mackenzie, 1937, p. 258-59): "The specimens represent a series of sedimentary rocks, derived from original muds and silts, now ranging in composition from nearly pure shale to very fine-grained shaly sandstone. If these specimens be representative, the prevailing rock is a siliceous shale."

Mackenzie (1937, p. 259) further states that between the basal Cretaceous conglomerate and a fault zone, approximately 1,600 meters of the Cerro Azul formation are exposed on the Quebrada Bellaca and 1,800 meters on the Río Calderas. On the Río Masparro, Mackenzie found 20 meters of the Cerro Azul formation underlying his Río Masparro formation, equivalent to the Triassic La Quinta formation.

The presence of a 20 centimeter bed of grey limestone, one meter below the top of the Cerro Azul formation on the Río Masparro, suggests at least a partial correlation of the formation with the Pennsylvanian-Permian Palmarito formation that contains abundant limestones. Liddle (1946, p. 141) considers the Cerro Azul formation, which he called the Cerro Azul beds, to be possibly part of the Devonian Río Momboy series. Granite occurs within the area of outcrop of the Cerro Azul formation in the Cerro Azul uplift in the headwaters of the Quebrada Carmelo branch of the Río Yuca. Although the contact with the Cerro Azul formation was not observed, the presence of the granite would tend to give support to Liddle's correlation because large bodies of granite are known to intrude the Devonian Río Momboy or upper Mucuchachí series in the Venezuelan Andes but not the Pennsylvanian-Permian Palmarito formation. Mackenzie (1937, p. 258) stated that no granite was found in the Cerro Azul uplift but he apparently had failed to go up the Quebrada Carmelo.

H. Alberding