Three-dimensional sedimentary framework of the carbonate ramp slope of central west Florida: A sequential seismic stratigraphic perspective

摘要

The sequential post-Early Cretaceous stratigraphic evolution of the carbonate ramp slope of central west Florida has been determined via the integration of 1,500 km of seismic reflection profiles with drillcores, piston cores, and rock dredge hauls. Our goal has been to gain insight into, and increase our knowledge and understanding of, carbonate ramps in general, as well as to develop a model for potential application to the rock record. Our results, which focus on the Neogene, indicate that the three-dimensional sedimentary framework of the west Florida ramp slope has developed in response to the interplay of a number of processes, including (1) regional tectonic subsidence, (2) long-term sea-level change, (3) short-term sea-level oscillations, (4) large-scale gravity collapse, (5) a major paleoceanographic event, (6) fluctuating intensity of oceanic circulation, (7) lateral migration of ocean currents, and (8) open-ocean upwellang and pelagic carbonate production. During the Early Cretaceous (seismic sequence VI), the continental margin of west Florida was a large shallow-water carbonate/evaporate platform that had persisted since late stages of continental rifting in the Jurassic. During the mid-Cretaceous (seismic sequence V), terrigenous sedimentutrient influx terminated platform growth and deposited a layer of neritic marl. For the next 60 m.y., during a long-term eustatic highstand in the Late Cretaceous-Paleogene (seismic sequence IV), the present west Florida slope was an open-ocean, deep- water marginal plateau that accumulated pelagic carbonates. Following a eustatic lowstand in the late Oligocene (30 m.y. ago), the carbonate ramp slope of central west Florida began to take shape as a low-relief ramp margin built seaward into the early and middle Miocene (seismic sequences III and II). In the latest early Miocene, large-scale gravity collapse generated a slope basin that was rapidly filled by prograding clinoforms. In the middle Miocene, 12-15 m.y. ago, intensification of oceanic circulation truncated antecedent clinoforms, blocked off-shelf sediment transport, and stimulated pelagic carbonate production. This oceanographic event resulted in the succession of seaward-prograding clinoforms by a slope-front-fill pelagic depositional system that has survived numerous sea-level oscillations into the present (seismic sequence I).