Cross section through the Toa Baja drillsite: Evidence for northward change in Late Eocene deformation intensity

Journal Article · Fri Mar 01 04:00:00 EST 1991 · Geophysical Research Letters (American Geophysical Union); (United States)

DOI:https://doi.org/10.1029/91GL00404· OSTI ID:5399636

Larue, D K ^[1]; Berrong, B ^[2]

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1. Univ. of Puerto Rico, Mayaguez (Puerto Rico)
2. Berrong Enterprises, Golden, CO (United States)

A 55 km geologic cross section through the Toa Baja Drillsite, generated by integrating geologic mapping data from the foothills of the Central Mountains of Puerto Rico with onshore and offshore multichannel seismic reflection data, provides an opportunity to examine in profile from the arc interior northward to within 40 km of the current trench slope break. Three structural divisions are recognized. In the foothills of Puerto Rico, Cretaceous and Eocene rocks are separated by transpressional strike-slip faults. In the vicinity of the Toa Baja drillsite where both seismic reflection and borehole data are available, Eocene rocks, deformed by thrust faults, .ie above a lower unit, interpreted to be of Cretaceous age. Offshore, north of the drilling site, seismic reflections suggest Eocene rocks onlap structural basement, thought to be Cretaceous rocks, and both units appear only slightly deformed. All Eocene and Eocene ( ) rocks are overlain by little deformed Oligocene to Recent rocks. From south to north, or from the arc massif interior toward the present-day trench, there is an apparent decrease in amount of Late Eocene to Middle Oligocene strike-slip and shortening deformation. Deformation events occurred mostly in the arc-interior and were not directly associated with the plate boundary which was probably near the Puerto Rico Trench.

• OSTI ID: 5399636
• Journal Information: Geophysical Research Letters (American Geophysical Union); (United States), Journal Name: Geophysical Research Letters (American Geophysical Union); (United States) Vol. 18:3; ISSN 0094-8276; ISSN GPRLA
• Country of Publication: United States
• Language: English

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