Geology of the Zacapa Quadrangle and vicinity, Guatemala, Central America

Author

David Philip Schwartz

Document Type

Dissertation

Date of Award

1976

Keywords

Geology, Guatemala, Zacapa

Degree Name

Doctor of Philosophy (PhD)

Department

Geological Sciences

First Advisor

Thomas W. Donnelly

Second Advisor

Francis T. Wu

Third Advisor

William D. MacDonald

Abstract

Geologic mapping in the Zacapa quadrangle and southern Rio Hondo quadrangle has shown that the Las Ovejas Complex, of probable pre-Early Pennsylvanian age and the oldest rock south of the Motagua fault zone, is a sequence of interlayered schist, marble, amphibolite, gneiss and associated penetratively deformed diorite, tonalite and granodiorite. Metavolcanic, metavolcaniclastic, and metasedimentary rock includes original basalt, dacitic and rhyodacitic tuff, minor andesite, limestone and pelite. Emplacement of diorite coincided with regional prograde metamorphism to middle and upper amphibolite facies. Hornblende, diopside, staurolite, sillimanite, and K-feldspar formed in rock of appropriate bulk composition. In the Zacapa quadrangle, metamorphic grade increases from southeast to northwest, oblique to the trend of the Motagua fault zone, across a northeast-trending sillimanite isograd. The main deformation produced asymmetric to isoclinal folds with wavelengths up to 1 km. Foliations strike NSOE, oblique to the Motagua trend, and linear structural elements plunge southwest between 7 degrees and 35 degrees. There are no known correlatives of the Las Ovejas Complex north of the Motagua fault zone.

Plate convergence during the Late Cretaceous deformed and thrust the El Tambor Formation south over the Las Ovejas Complex, producing a zone of cataclasis and retrograde metamorphism at the contact of the two units.

Continental clastic sedimentation in fault bounded troughs, and volcanism, led to deposition of the Subinal Formation (Late Cretaceous(?)- Eocene), Chanchan Formation (Eocene), and Guastatoya Formation (Miocene?) within the Motagua fault zone and the Padre Miguel Group (Miocene) south of the Motagua Valley.

Faulting of Tertiary age on the north side of the Motagua fault zone is characterized by south—dipping thrust, high angle reverse, and strike—slip faults that define linear, coherent sheets of various rock types. This style of faulting may have been operative since at least Miocene but the age of initiation remains uncertain.

Pervasive, regionally developed N25E to N35E trending faults, fractures, and grabens occur south of the Motagua Valley. The slip component is dominantly normal. These faults may have originated in direct response to initiation of strike—slip faulting along the Motagua fault zone. Quaternary structural trends associated with the Ipala graben extend as far north as the Motagua fault zone.

The Cabañas fault, a major active left—lateral strike—slip fault on the south side of the Motagua Valley, is characterized by sag ponds, offset drainages, shutter ridges, groundwater barriers, and scarps. Minimum displacement of 60 m to 80 m is observed in Quaternary terrace deposits. The Cabañas fault, and the Chixoy-Polochic fault zone are presently accommodating the slip produced by spreading in the Cayman Trough.

Comments

Additional advisor: Robert L. Pompi

Recommended Citation

Schwartz, David Philip, "Geology of the Zacapa Quadrangle and vicinity, Guatemala, Central America" (1976). Graduate Dissertations and Theses. 428.
https://orb.binghamton.edu/dissertation_and_theses/428