Three‐dimensional Euler deconvolution and tectonic interpretation of marine magnetic anomaly data in the Puerto Rico Trench

Abstract

During the summer of 1996 single‐channel‐seismic, magnetic, gravity, Hydrosweep bathymetric and HMR1 sidescan data were collected north of the island of Puerto Rico to constrain the geologic and tectonic setting of the Puerto Rico trench. Magnetic data from this cruise are merged with other available data, then processed and interpreted with the aid of the Euler deconvolution method. The area north of the island of Puerto Rico is divided into three magnetic anomaly zones. Zone 1 is dominated by northwest to southeast trending magnetic anomalies. Zone 2 consists of an east‐west region of relatively low amplitude anomalies and occurs south of zone 1. Zone 3 is dominated by the highest magnetic values in the study area and the source region is roughly centered under the island of Puerto Rico. Respectively, these zones approximate three geologic provinces of the Puerto Rico trench composed of Early Cretaceous ocean crust with sedimentary cover, a blueschist belt and an Oligocene‐Cretaceous island arc with a limestone cap. Also mapped are the Main Ridge fracture zone and the Fourth of July fracture zone, both on the North American plate, which correlate with the Main Ridge and Fourth of July Ridge on the Caribbean plate. The 3‐D Euler deconvolution facilitates the identification of new faults as well as the mapping of known faults also evident in the seismic and bathymetric data. A model concerning the formation of the Puerto Rico trench is proposed that incorporates the existence of strike‐slip faults and the fracture zones associated with the subduction of the North America Plate. Evidence from this study support a tectonic interpretation of subduction followed by more recent strike‐slip faulting that is accompanied by only a minimal amount of subduction.