IGLESIAS, Group

PRE-CAMBRIAN ?

State of Mérida, Venezuela

Author of name: E. Kündig, 1938.

Original reference: E. Kündig, 1938, p. 22.

Original description: ibid.

The name Iglesias "series" was first used by Kündig (1938, p. 22) for a highly metamorphosed series, partly of sedimentary, partly of igneous origin. In the Spanish text of the same publication he refers to it as "Grupo de Iglesias". The use of the name Iglesias group is considered preferable.

The following rock types are mentioned: Biotite ortho-gneisses; migmatitic lit--par-lit, aplitic gneisses; scarce coarse porphyroblastic biotite augen gneisses; fine grained garnet-biotite gneisses and garnet-bearing mica schists. The type locality, according to Sutton (1946, p. 1629), is the Cerro Las Iglesias, part of the Conejos massif, northwest of the city of Mérida, in the state of Mérida. The thickness of the group is unknown but is, according to Sutton (1946, p. 1629), at least several thousand feet. The Mucuchachí group rests on the Iglesias group with probable unconformity.

The group occurs in the Conejos massif on the northwest flank of the Mérida Andes and in the Los Gatos massif on the southeast flank. The Santo Domingo gneiss, a biotitic gneiss with injections of aplite, found by Oppenheim (1937, p. 31) in the upper Rio Santo Domingo valley in north-eastern Mérida, according to Sutton (1946, p. 1629), also belongs to the Iglesias group. No fossils have ever been found, but the position of the Iglesias group beneath the Mucuchachí evidences an age older than upper Devonian. It appears to be entirely or partly pre-Cambrian.

According to Sutton (1946, p. 1629), the Iglesias group is roughly equivalent to the Perijá series on the west side of the Maracaibo basin and to the pre-Cambrian formations of the Guayana Shield.

W. A. Mohler