Publication: Consideraciones teóricas sobre el análisis de la subsidencia:aplicación a un caso real en el borde de la cuenca triásica ibérica
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1992
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Sociedad Geológica de España
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Abstract
Las variaciones de espesor y las discordancias internas que presenta el Buntsandstein en algunos sectores de la Cordillera Ibérica, demuestran la estrecha relación que existe entre estos sedimentos y la tectónica extensional a la que estuvo sometida la cuenca triásica. La geometría de las distintas unidades que lo componen y la evolución de los medios sedimentarios en que se depositaron, sólo pueden ser bien entendidas, si se analiza cómo ha evolucionado la subsidencia de la cuenca en el tiempo y en el espacio.
Después de revisar los métodos que existen actualmente para cuantificar la subsidencia y discutir sus limitaciones,
se han calculado las curvas de subsidencia total y tectónica, para un sector de borde de cuenca y para otros donde no existen discordancias angulares. Asumiendo un modelo de compensación isostática local, se ha analizado con mayor detalle el área de borde, donde hay cambios importantes en el espesor de los sedimentos y geometrías claramente ligadas a la tectónica extensiva mesozoica. El carácter asimétrico de la cuenca, se refleja en la notable variabilidad de los valores del factor de extensión (13) obtenidos, sobre todo para el área de borde de la misma.
Triassic red beds (Buntsandstein) in central Spain (Cordillera Ibérica-Sistema Central connection área) display significant thickness changes and local unconformities that are related to extensional tectonics that luled the evolution of the Triassic basin. The tectonic movements during the sedimentation resulted in a series of discontinuities in sedimentation together with sorne local unconforrnities. A detailed study of the subsidence evolution is necessary to fully understand the paleogeography and geometries of these deposits. A revision of the existing theories about quantitative analysis of subsidence rates and their limitations has been carried out. Tectonic subsidence and total subsidence plots have been constructed for several stratigraphic columns. Some of these columns are located in the border of the basin, but sorne others come from more central areas, where tectonic movements did not generate unconformities. The border of the basin, where tectonics generated a series of tilted fault blocks that gave way to significant thickness and geometries changes, has been detailed studied assuming a local isostatic compensation. The amount of lithospheric stretching (Beta) displays a great variability, mainly the values related to the border of the basin.
Triassic red beds (Buntsandstein) in central Spain (Cordillera Ibérica-Sistema Central connection área) display significant thickness changes and local unconformities that are related to extensional tectonics that luled the evolution of the Triassic basin. The tectonic movements during the sedimentation resulted in a series of discontinuities in sedimentation together with sorne local unconforrnities. A detailed study of the subsidence evolution is necessary to fully understand the paleogeography and geometries of these deposits. A revision of the existing theories about quantitative analysis of subsidence rates and their limitations has been carried out. Tectonic subsidence and total subsidence plots have been constructed for several stratigraphic columns. Some of these columns are located in the border of the basin, but sorne others come from more central areas, where tectonic movements did not generate unconformities. The border of the basin, where tectonics generated a series of tilted fault blocks that gave way to significant thickness and geometries changes, has been detailed studied assuming a local isostatic compensation. The amount of lithospheric stretching (Beta) displays a great variability, mainly the values related to the border of the basin.