Lithospheric magnetic mapping of the northern Caribbean region
TL;DR: A more complete view of the northernmost part of the Venezuela Basin is provided by data from an international public database processed with new geomagnetic models (CM4) together with data from aeromagnetic surveys and from a recent marine cruise in areas offshore Puerto Rico and the Dominican Republic as mentioned in this paper.
Abstract: A more complete crustal perspective of the northernmost part of the Venezuela Basin is provided by data from an international public database processed with new geomagnetic models (CM4) together with data from aeromagnetic surveys and from a recent marine cruise in areas offshore Puerto Rico and the Dominican Republic. The magnetic anomaly map set off three main domains: the North Atlantic plate, a narrow zone extending from the Dominican Republic to Puerto Rico-Virgin Islands, and the North Caribbean Plate. We focused mainly on the latter, applying the Euler deconvolution algorithm in the Venezuela Basin. Shallow and middle depth sources (located between 2km and 12km) are inferred to be the dominant sources (85%), while deep sources are located mostly in the Venezuela Basin, and scarcely appear in the Beata and Aves Ridges. We performed 2D+1/2 modeling on an eastwest transect, using Bouguer gravity and magnetic anomaly data to derive a more detailed crustal description of the northern part of the Venezuela Basin. The model suggests that in the Caribbean crust, long wavelengths (>200km) are controlled by variations in crustal thickness, whereas the intermediate ones (50-100km) are mainly controlled by variations in their magnetic properties. It also suggests the presence of a local anomalous body located in the east-west transect, between 487km and 560km, displaying a remarkable positive magnetization contrast (0.3 SI) with regard to the rest of the basin. This body shows a slight increase in density (3010kg/m3), and extends from the bottom of the UCL (Underplate Cumulate Layer) to a depth of 7.5km. We correlate it with the volcanic wedge reported by Driscoll and Diebold (1998).
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TL;DR: In this paper, wide-angle seismic data are analyzed along a WNW-ESE trending line in the northern flank of Beata Ridge, providing a complete tectonic view about shallow, middle and deep structures.
Abstract: The complex tectonic region of NE Caribbean, where Hispaniola and Puerto Rico are located, is bordered by subduction zone with oblique convergence in the north and by incipient subduction zone associated to Muertos Trough in the south. Central Caribbean basin is characterized by the presence of a prominent topographic structure known as Beata Ridge, whose oceanic crustal thickness is unusual. The northern part of Beata Ridge is colliding with the central part of Hispaniola along a transverse NE alignment, which constitutes a morphostructural limit, thus producing the interruption of the Cibao Valley and the divergence of the rivers and basins in opposite directions. The direction of this alignment coincides with the discontinuity that could explain the extreme difference between west and east seismicity of the island. Different studies have provided information about Beata Ridge, mainly about the shallow structure from MCS data. In this work, CARIBE NORTE (2009) wide-angle seismic data are analyzed along a WNW-ESE trending line in the northern flank of Beata Ridge, providing a complete tectonic view about shallow, middle and deep structures. The results show clear tectonic differences between west and east separated by Beata Island. In the Haiti Basin area, sedimentary cover is strongly influenced by the bathymetry and its thickness decreases toward to the island. In this area, the Upper Mantle reaches 20 km deep increasing up to 24 km below the island where the sedimentary cover disappears. To the east, the three seamounts of Beata Ridge provoke the appearance of a structure completely different where sedimentary cover reaches thicknesses of 4 km between seamounts and Moho rises up to 13 km deep. This study has allowed to determine the Moho topography and to characterize seismically the first upper mantle layers along the northern Beata Ridge, which had not been possible with previous MCS data.
13 citations
Cites background from "Lithospheric magnetic mapping of th..."
...north–southward magnetic anomalies (east of the Beata Ridge) can be found distributed over a negative terrace (CATALÁN and MARTÍN DÁVILA 2013)....
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TL;DR: In this paper, a grid of geomagnetic data was surveyed in an area close to the Island of San Andres in the north-west of the Colombian maritime territory, and the results showed negligible differences between the magnetic data obtained for the years 1970 and 2018 for all the variables measured, such as the inclination, declination, and total magnetic field.
Abstract: In recent years, the Oceanographic and Hydrographic Research Center (part of the General Maritime Directorate of Colombia (DIMAR) has made important efforts to advance research in the field of marine geophysics, in particular, the techniques of geomagnetism, sub-bottom profiling, and side-scan sonar, the first being the most developed at the present time. A method is presented for the acquisition of geomagnetic data in marine environments, as used by DIMAR in the Colombian maritime territory. The development of the geomagnetic method not only offers the opportunity to advance basic scientific knowledge, but it is also of great importance in support of national sovereignty issues. Among other applications, the most representative uses of the geomagnetic method are the location of pipelines and metal plates, detection of buried ordnance, identification of sites of archaeological interest, and the identification and characterization of geological structures. As a result of testing the method, a grid of geomagnetic data was surveyed in an area close to the Island of San Andres in the north-west of the Colombian maritime territory. The survey was prepared with a regional geometric arrangement, the result of which was compared with survey data obtained from the National Oceanic and Atmospheric Administration (NOAA) magnetic data repository and carried out in the same study area. Despite the long time interval between the two surveys, almost 50 years, no significant differences were observed in terms of the analyzed variables. Finally, results show negligible differences between the magnetic data obtained for the years 1970 and 2018 for all the variables measured, such as the inclination, declination, and total magnetic field. These differences may be attributable to a geological component or also to the acquisition and processing methods used in the 1970s.
2 citations
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TL;DR: In this paper, combined gravity and magnetic surveys were conducted over six diabase bodies in the Triassic Basin of Pennsylvania, and the results of these surveys indicate a resultant direction of magnetization given approximately by: declination 2° W, inclination 41 de...
Abstract: Recent studies have shown that many rocks of the earth’s crust have a substantial component of remanent magnetization. Extensive sampling is required to determine adequately the remanent vector from small samples. A field technique has been developed (and tested on model data) for the in‐situ determination of the resultant (induced+remanent) magnetic vector of bulk volumes of rock, using a combined analysis of the gravity and magnetic fields of a disturbing body (Poisson’s Theorem). The potential fields are sampled adequately at a limited expenditure of time and effort in the field by utilizing the geometry of two‐dimensional bodies. The major limitation to the analysis is the removal of regional gradients and the estimation of the base levels of anomalies. Combined gravity and magnetic surveys were conducted over six diabase bodies in the Triassic Basin of Pennsylvania. The results of these surveys indicate a resultant direction of magnetization given approximately by: declination 2° W, inclination 41 de...
9 citations
"Lithospheric magnetic mapping of th..." refers methods in this paper
...315 Poisson’s theorem has been used in the past to calculate single-source magnetization-density ratios (Garland 1951; Kanasewich and Agarwal, 1970) and the direction of source magnetization (Ross and Lavin, 1966; Cordell and Taylor, 1971)....
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...…V I L A Magnetic mapping of the Northern Caribbean region 315 Poisson’s theorem has been used in the past to calculate single-source magnetization-density ratios (Garland 1951; Kanasewich and Agarwal, 1970) and the direction of source magnetization (Ross and Lavin, 1966; Cordell and Taylor, 1971)....
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01 Jan 2004
TL;DR: The main rasgo del magnetismo de la Republica Dominicana is el de mostrar una clarisima estructuracion in bandas NO-SE, coincidentes con las provincias (terrenos) que configuran la geologia de la isla La Espanola as mentioned in this paper.
Abstract: El principal rasgo del magnetismo de la Republica Dominicana es el de mostrar una clarisima estructuracion en bandas NO-SE, coincidentes con las provincias (terrenos) que configuran la geologia de la isla La Espanola. Estas bandas se encuentran limitadas por accidentes magneticos mayores muy nitidos de esa direccion, segun las cizallas que limitan tales terrenos, En disposicion subparalela a la de estos ocurre un numeroso cortejo de directrices magneticas de menor entidad, Existe tambien un importante conjunto de discontinuidades de direccion NE-SO, complementarias de las anteriores. Adicionalmente, el campo magnetico se caracteriza por presentar fuertes anomalias debidas a un magmatismo ubicuo en toda la Isla. Desde el punto de vista de susceptibilidad magnetica se observa inmediatamente que se trata de un magmatismo bimodal con zonas magneticas y paramagneticas sobre cualquiera de las intrusiones y ejes volcanicos principales de la isla. La radiometria gamma natural, aun con el inconveniente de la excesiva altura de vuelo por la accidentada orografia de la isla, complemento la cartografia estructural magnetica, permitiendo establecer una macrozonacion radiometrica de la Republica Dominicana en los siguientes terminos: 1) Zonas de maximos radiometricos: corresponden a sedimentos lutiticos, cuaternarios o pertenecientes a las cuencas de flysch ante y trasera de arco, y a unidades volcano-detriticas del extremo oriental de la isla; 2) Zonas intermedias: respuestas tipicas de uranio y torio son las producidas por masas calcareas, mientras que las firmas de potasio son generadas por un amplio espectro de rocas intermedio-acidas, volcanicas e intrusivas; y 3) Zonas de minimos radiactivos: corresponden a rocas ultrabasicas, rocas basicas intrusivas (garbos) y extrusivas (basaltos. espilitas). y a rocas metamorficas de protolito igneo basico (esquistos y anfibolitas). Los datos geofisicos aeroportados, magneticos y radiometricos, ofrecen muy buenas posibilidades para apoyar la cartografia geologico-estructural general de la Republica Dominicana, de lo que existen numerosos ejemplos alguno de los cuales se presenta aqui.
6 citations
TL;DR: The corrected map is devoid of artifacts, and the contours became smooth, which can be utilized for meaningful geological interpretation as mentioned in this paper, and the corrected free-air gravity map indicates improvements from the original in resolution with clear isolated anomalies in high track density areas.
Abstract: Geophysical data (magnetic, gravity, and bathymetric) collected by international and national agencies along intersecting track lines in the Bay of Bengal show discrepancies that are analyzed and adjusted by crossover techniques The original magnetic anomaly map over this region exhibits high gradients over the entire region, which do not fit with the known geological framework The corrected map is devoid of artifacts, and the contours became smooth, which can be utilized for meaningful geological interpretation The corrected free-air gravity map indicates improvements from the original in resolution with clear isolated anomalies in high track density areas Corrected bathymetry does not show much improvement
6 citations
"Lithospheric magnetic mapping of th..." refers methods in this paper
...Crossover analyses were used to estimate the quality of the geophysical surveys, and to provide an effective technique to identify and correct systematic and non-systematic errors in geophysical data grids (Wessel and Watts, 1988; Thakur et al., 1999)....
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