Geology, structure and metamorphism of the Chuacús Group, Rio Hondo Quadrangle and vicinity, Guatemala

<p>The Chuacús Group, of probable Paleozoic age, crops out in the Rio Hondo, San Agustín Acasaguastlán, and El Cimiento quadrangles, east-central Guatemala. Its members, in structurally ascending order, are: the San Agustín Formation (cataclastic gneiss and migmatite), the Jones Formation (dominantly phyllite and mica schist), and the San Lorenzo Formation (marble).</p> <p>Chemical study of these rocks suggests that the San Agustín Formation is an orthogneiss of quartz monzonitic composition, while the Jones and San Lorenzo Formations comprise a distinct sequence of metasediments. The Jones Formation contains minor greenstones the chemistry of which suggests affinity with calc-alkaline basalts. The sediments probably accumulated in the vicinity of a tectonically active continental margin.</p> <p>At least two periods of deformation are recorded in the Chuacús Group. The early deformation may have involved formation of large scale recumbent isoclinal folds (?nappes?) in bedding (S₀) by transposition along flow planes (S₁). The late deformation produced asymmetric slip folds in S₁ by differential movement on steeply dipping slip cleavage (S₂). These folds are developed in the Jones and San Lorenzo Formations. The same late deformation was responsible for regional cataclasis of the underlying San Agustín Formation.</p> <p>Although relicts of amphibolite, and even granulite, facies metamorphism are preserved in some parts of the Chuacús Group, the dominant metamorphic grade of these rocks is greenschist to epidote-amphibolite facies. This is believed to be a result of regional retrograde metamorphism associated with the cataclastic deformation.</p> <p>The character and history of the Chuacús Group, and the nature of the regional geology in adjacent areas, suggests that tectonic evolution of the Motagua Fault Zone involved minimal strike-slip displacement as compared to compression and transport perpendicular to the Motagua trend. A speculative tectonic evolutionary sequence, consistent with available geologic data in the area, could have involved poly-episodic tectonism along a plate boundary of convergent character.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Geological Sciences

Year

1975

Author dc:creator

• Newcomb, Walter Edwin

Contributors dc:contributor

• Thomas W. Donnelly
• Marc W. Bodine, Jr.
• William D. MacDonald

• Geology
• Guatemala
• Hondo River (Guatemala
• Mexico
• and Belize)

Repository record dc:identifier

https://orb.binghamton.edu/dissertation_and_theses/347

OAI identifier oai:identifier

oai:orb.binghamton.edu:dissertation_and_theses-1350