Chapter 3 Jurassic—early cretaceous tectono-paleogeographic evolution of the southeastern gulf of Mexico basin

Abstract

A new opening model for the Gulf of Mexico basin provides a framework in which the Jurassic-Early Cretaceous tectono-paleogeographic evolution of the southeastern Gulf of Mexico and surrounding regions can be discussed. A detailed analysis of available seismic data and the results of DSDP Leg 77 define four major tectono-stratigraphic sequences bounded by major unconformity surfaces: crystalline basement, Paleozoic(?) pre-rift rocks, a Late Jurassic syn-rift sequence, and an Early Cretaceous post-rift sequence. The pre-rift rocks are interpreted to represent a pre-Mesozoic (Late Paleozoic?) sedimentary cycle. The Late Jurassic syn-rift sequence in the central continental domain of the southeastern Gulf of Mexico occurs in grabens or half-grabens and is interpreted to consist of two units, a lower non-marine unit overlain by a marine carbonate unit consisting of carbonate buildups (platforms) and adjacent deeper marine sediments. Jurassic rocks are absent over high-standing blocks as well as the adjacent Yucatán and Florida blocks. The Lower Cretaceous post-rift sequence drapes the entire area and consists of deep-water carbonate sediments in the central basin flanked by shallow-water platforms on the adjacent Yucatán and Florida blocks. Six tectono-paleogeographic maps covering the eastern Gulf of Mexico and northwestern Cuba (palinspastically restored to the southeastern margin of Yucatán) document the evolution of the area. During the late Middle Jurassic (Callovian) the southeastern Gulf was a bridge between Yucatán and Florida, separating an area of widespread extension and salt deposition to the north in the Gulf of Mexico from another area of extension and clastic sedimentation to the south between Yucatán and northern South America. By Oxfordian time Yucatán had rotated 11° counter-clockwise and major continental rifting and non-marine sedimentation in rift basins had begun all along the southeastern Gulf. To the north salt deposition had ceased and a major marine transgression culminated in deposition of Smackover carbonates. South of Yucatán shallow-water carbonate sedimentation also prevailed. During Kimmeridgian, Tithonian and into earliest Cretaceous time, rifting continued in the southeastern Gulf as Yucatán continued to rotate counter-clockwise. As the basin subsided a marine seaway, characterized by shallow-water carbonate platforms on high-standing blocks, became established, connecting the Gulf of Mexico with the proto-Caribbean. In the northeastern Gulf the mixed clastic/carbonate Haynesville and Cotton Valley sequences were deposited, while to the south of Yucatán shallow-water carbonate sedimentation gave way to deeper water sedimentation as the margin subsided. In late Berriasian spreading ceased in the Gulf of Mexico, Yucatán reached its present-day position, and rifting stopped in the southeastern Gulf. Carbonate platforms atop rift blocks drowned as the basin subsided and sea level rose, and the southeastern Gulf became the deep-water seaway that it is today. The marine transgression reached the Yucatán and Florida blocks, where extensive carbonate platforms became established and flourished throughout the Early Cretaceous. To the south of Yucatán, deep-water pelagic sedimentation continued throughout the Early Cretaceous.