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| Format: | Artículo científico |
| Language: | en |
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ECOPETROL S.A.
2007
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| Online Access: | https://www.redalyc.org/articulo.oa?id=46530302 |
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| _version_ | 1866585453994442752 |
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| author | Germán Y. Ojeda |
| author_facet | Germán Y. Ojeda |
| contents | Basement configuration of the northwestern south America -Caribbean margin from recent geophysical data Germán Y. Ojeda John F. Cerón James N. Kellogg Ingeniería crust flexure Colombia basement tectonics The oceanic nature of the crust in northern Colombia (underlying the Lower Magdalena Basins) has beenpostulated by different authors as a northern extension of the Cretaceous, mafic and ultramafic rocks accretedto the western margin of northwest Colombia (in the Western Cordillera and Baudo range). Localized, smalloutcrops of oceanic affinity rocks seem to support this hypothesis. However, geophysical data do not support thisnorthern extension, but clearly mark the boundary between the collisional Panamá terrane with northern SouthAmerica and the over thrusting of the latter on top of the obliquely convergent Caribbean plate.We produced maps to basement and Moho topography by integrated modeling of gravity, magnetics, seismicreflection surveys and well data from northwest Colombia and the southwestern Caribbean. In areas withgood seismic coverage, the basement under the Lower Magdalena Basins (LMB) is represented by a clearreflector. In areas where seismic data shows poor imaging or is absent, we use a back stripping methodologyto model first the sedimentary section, with known densities, composition and geometry controlled byoil wells and high quality seismic data, and then the deeper section. 2,5D gravity and magnetics modelingresults in an initial Moho that can be extended to the entire region based on the control of available seismicrefraction points. This controlled Moho provides the basis for basement modeling for the whole area andthis sequence is iterated for several sections across the region.Our results indicate that the crust under northern Colombia is continental to thinned continental (transitional)in nature, with densities between 2,6 and 2,7 g/cm3. Our model also requires a dense wedge of sediments(density 2,5 g/cm3) at the base of the modern fold belt, which may represent a fossil sedimentary wedge attachedto the continental margin. This wedge may have served as a backstop for the modern fold belt. Thegravity modeling does not require oceanic crust to form the basement in the Sinú and San Jacinto fold beltsas previously suggested. Discrete layers and thin slivers of oceanic sediments and basement could have beenscrapped off the incoming plate and thrusted into an accretionary mélange, and eventually exposed at thesurface, as seen in the Mulatos, Chalan and Cansona locations.The shape of the continental wedge / oceanic crust boundary resembles that of a very low angle/flat subductionzone (β angle between 2º to 3º), and is interpreted here as a low angle over thrusting of northern SouthAmerica riding in a highly oblique direction over the underlying Caribbean plate. The map to basement depthobtained during this study forms the basis for basin analysis, oil maturation and evolutionary studies of theregion. As an example, we apply our map to a flexural analysis of the LMB. 2007 artículo científico 0122-5383 https://www.redalyc.org/articulo.oa?id=46530302 en http://www.redalyc.org/revista.oa?id=465 CT&F Ciencia, Tecnología y Futuro application/pdf ECOPETROL S.A. CT&F Ciencia, Tecnología y Futuro (Colombia) Num.3 Vol.3 |
| format | Artículo científico |
| id | redalyc_46530302 |
| language | en |
| publishDate | 2007 |
| publisher | ECOPETROL S.A. |
| spellingShingle | Basement configuration of the northwestern south America -Caribbean margin from recent geophysical data Germán Y. Ojeda Ingeniería crust flexure Colombia basement tectonics Basement configuration of the northwestern south America -Caribbean margin from recent geophysical data Germán Y. Ojeda John F. Cerón James N. Kellogg Ingeniería crust flexure Colombia basement tectonics The oceanic nature of the crust in northern Colombia (underlying the Lower Magdalena Basins) has beenpostulated by different authors as a northern extension of the Cretaceous, mafic and ultramafic rocks accretedto the western margin of northwest Colombia (in the Western Cordillera and Baudo range). Localized, smalloutcrops of oceanic affinity rocks seem to support this hypothesis. However, geophysical data do not support thisnorthern extension, but clearly mark the boundary between the collisional Panamá terrane with northern SouthAmerica and the over thrusting of the latter on top of the obliquely convergent Caribbean plate.We produced maps to basement and Moho topography by integrated modeling of gravity, magnetics, seismicreflection surveys and well data from northwest Colombia and the southwestern Caribbean. In areas withgood seismic coverage, the basement under the Lower Magdalena Basins (LMB) is represented by a clearreflector. In areas where seismic data shows poor imaging or is absent, we use a back stripping methodologyto model first the sedimentary section, with known densities, composition and geometry controlled byoil wells and high quality seismic data, and then the deeper section. 2,5D gravity and magnetics modelingresults in an initial Moho that can be extended to the entire region based on the control of available seismicrefraction points. This controlled Moho provides the basis for basement modeling for the whole area andthis sequence is iterated for several sections across the region.Our results indicate that the crust under northern Colombia is continental to thinned continental (transitional)in nature, with densities between 2,6 and 2,7 g/cm3. Our model also requires a dense wedge of sediments(density 2,5 g/cm3) at the base of the modern fold belt, which may represent a fossil sedimentary wedge attachedto the continental margin. This wedge may have served as a backstop for the modern fold belt. Thegravity modeling does not require oceanic crust to form the basement in the Sinú and San Jacinto fold beltsas previously suggested. Discrete layers and thin slivers of oceanic sediments and basement could have beenscrapped off the incoming plate and thrusted into an accretionary mélange, and eventually exposed at thesurface, as seen in the Mulatos, Chalan and Cansona locations.The shape of the continental wedge / oceanic crust boundary resembles that of a very low angle/flat subductionzone (β angle between 2º to 3º), and is interpreted here as a low angle over thrusting of northern SouthAmerica riding in a highly oblique direction over the underlying Caribbean plate. The map to basement depthobtained during this study forms the basis for basin analysis, oil maturation and evolutionary studies of theregion. As an example, we apply our map to a flexural analysis of the LMB. 2007 artículo científico 0122-5383 https://www.redalyc.org/articulo.oa?id=46530302 en http://www.redalyc.org/revista.oa?id=465 CT&F Ciencia, Tecnología y Futuro application/pdf ECOPETROL S.A. CT&F Ciencia, Tecnología y Futuro (Colombia) Num.3 Vol.3 |
| title | Basement configuration of the northwestern south America -Caribbean margin from recent geophysical data |
| topic | Ingeniería crust flexure Colombia basement tectonics |
| url | https://www.redalyc.org/articulo.oa?id=46530302 |