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Crustal Structure of Jurassic Oceanic Crust and Thinned Continental Crust Separating the Conjugate, Rifted Margins of Eastern Florida and the Yucatan Peninsula


The extinct ridge-transform geometry in western Gulf of Mexico (GOM), and extinct spreading segments in eastern GOM, have been identified from vertical gravity gradient data. Our mapping of basement and Moho horizons using an extensive grid of industry deep-penetration seismic reflection data, reveals that the eastern Gulf of Mexico (EGOM) oceanic ridge system is characterized by 30-60-km-long segments that include 15-km-wide, 2-km-high axial volcanoes in their centers and nodal basins at their ends. The negative gravity anomalies over the extinct slow spreading center high support the long-lived low-density root underneath the slow spreading center. The central location of axial volcanoes on all the studied spreading segments suggests that magma supply decreases near the ends of the spreading segments, which is characteristic of slow-spreading centers. Basement faults in the oceanic crust are mainly parallel to the ridge segments which indicate a NE-SW opening. The flowlines through the fracture zone identified from this study fit well with potential field response, which also supports anticlockwise rotation of the Yucatan block about a single pole of rotation. Interpretation of oceanic Moho from seismic reflection data suggests that oceanic crust in northwestern EGOM is thicker (6.4 km) than in southeastern EGOM (5.5 km). Based on mapping 68,089 km of merged, industry, 2D seismic reflection data sets, we divide thinned, continental crust of the conjugate margins of Florida and Yucatan that flank the deepwater area of oceanic crust into three structural provinces: 1) the 220 km-long, northwestern segment of magmatic thinned crust along the Florida margin is characterized as volcanic rifts; overlying this area of thinned crust is salt varying from 1 to 2.5 km; 2) the central segment of crust along the Florida margin is 260 km long and forms a V-shape area from 70 km to 25 km wide; salt is present as isolated diapirs although the underlying source of the diapirs salt is not imaged; and 3) the southern segment of extended crust along South Florida is 110 km long and 20 km wide and shows no evidence for the presence of salt. We propose that the most promising hydrocarbon prospects include the northwestern and central segments based on the close relationship of thinned continental crust, salt and key reservoir units such as the Late Jurassic Norphlet formation.