Combining a computer simulation and eustatic events to date seismic sequence boundaries: a case study of the Neogene of the Bahamas

Abstract

This paper demonstrates that the principles of seismic sequence stratigraphy and the techniques of computer simulation can be combined to date the sedimentary section. As an example it uses the Neogene section of the western shelf of the Straits of Andros in the Bahamas. To this end, type I, second-order seismic sequence boundaries were identified on a seismic cross-section from the region. These were used as brackets to correlate enclosed third-order events with an eustatic sea-level curve. The interpreted section was then reproduced using a computer simulation program. The simulation successfully reproduced the onlapping geometries of the shelf margin identified on the seismic section. The early Neogene fill of the Straits of Andros is assumed to have had an uncomplicated and uniform tectonic setting. This simplified the inputs to the simulation, which focused on capturing the sedimentary response to the eustatic changes. Inputs included a constant rate of subsidence of 0.009 m/ka, a uniform linearly increasing rate of carbonate accumulation from 28.5 Ma to 11.5 Ma, and the sea-level cycle chart of Haq et al. (1987), updated for the Neogene with the absolute ages provided by Berggren et al. (1995). The subsequent graphical output shows a good match to the interpreted seismic. This suggests that the amplitude and ages of the sea-level changes as shown in the eustatic chart can be used to date the sequence boundaries for the Neogene of the Straits of Andros. It also establishes that for areas of known subsidence, simulation techniques can be used to date seismic sections where biostratigraphic data are poor.