Print this pageAnalysis of Tectonic Subsidence in the Eastern Part of the Colombia Offshore Basin, Southern Caribbean, Applying Spectral Decomposition of 2D Seismic Data
The Colombian Basin is located in the Southern Caribbean Sea with different tectonic features; the Hess Escarpment, the Mono Rise, the South Caribbean Deformed Belt, the Aruba Gap and the Beata Ridge. The main sediment sources are the Nicaraguan Rise in the north and the Magdalena Delta in the south. In some areas a transtensive structural style has been proposed while in other areas the structural style is compressive. Interpretations of 2D Seismic data were used in this study. The interpretations were achieved using seismic analysis techniques as spectral decomposition, used for detecting low and high frequency shadows associated with different types of bedrock in frequency domain. Spectral decomposition provides a novel means of using seismic data and the Discrete Fourier Transform (DFT). By transforming the seismic data into the frequency domain via the DFT, the amplitude spectra delineate temporal bed thickness variability while the phase spectra indicate lateral and vertical geologic discontinuities. Interpretations of the rock units in the study area were aided with the seismic response of the amplitudes and frequencies where these properties suffer attenuation and reduction in the signal level, because near to the crystalline basement an energy level reduction occurs. Interpreted seismic reflectors are: Oceanic Floor; Top of the Pliocene-Pleistocene Sequence; Top of Late Miocene Carbonate sequence, these sediments are thin beds of sands and clays rich in carbonate, that conform the Early Eocene - Middle Miocene sequence; top of the Cretaceous sediments, principally limestones and carbonate rich cherts. Proposed reflectors were correlated with the seismic units of Bowland (1993), of the Western part of the South Caribbean. These horizons were used for the Subsidence Model (Back stripping 1D) applying seismic and well data. The proposed tectonic subsidence is associated with a passive margin regime. Two important tectonic subsidence stages were identified the first one from the Late Cretaceous to Eocence-Miocence time and the second is a reactivation of tectonic subsidence through Miocene-Holocene time.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil