Print this pagePlio-Pleistocene evolution of the Belize margin: strike-oriented depositional sequence model in a carbonate-siliciclastic system
FERRO, C. ELMER, ANDRE W. DROXLER, DAVE A. MUCCIARONE, JOHN B. ANDERSON, and SUSAN MORRICE
Interpretation of high resolution single-channel seismic grids from behind and in front of the modem Belize Barrier Reef (BBR), coupled with analysis of several conventional Shell seismic profiles across the barrier reef, appears to show that the BBR (1) consists of thin late Quaternary neritic carbonate deposits that cover a Plio-Pleistocene essentially siliciclastic margin and (2) was established less than 0.5 Ma ago during late Quaternary brief intervals of sea level transgression and highstand (interglacial stages 11 to 1?).
The BBR system colonized a series of lowstand prograding siliciclastic paleo shorelines, which consisted of several deltas partially reworked by longshore currents into a series of sub parallel beach ridges. The exposed BBR system during subsequent sea level lowstands, acting as a physical barrier to the drainage system of the newly formed fluvial plain, influenced the implantation of a network of incised valleys parallel to the BBR clearly oriented along strike. Siliciclastic sediments bypassing the exposed BBR only at a couple locations (i.e. English Cay Channel) were deposited as lowstand deltas and then partially reworked by longshore currents in front of the exposed BBR system. The top of these strike-oriented lowstand deposits became surfaces on top of which the carbonate reefal facies grew during the following sea level transgression. The Plio-Pleistocene sedimentary sequences along the Belize margin are usually, therefore, deposited parallel to the modern coastline in another words along a strike direction. This observation contrasts with most published mixed siliciclastic carbonate system models, where the prevalent orientation of the depositional sequences is along a dip direction.