Crustal Structure, Tectonostratigraphy, and Hydrocarbon Potential of the Terranes Underlying the Caribbean Plate and the Camamu-Almada Rifted Passive Margin of Northeastern Brazil

This dissertation combines the results of two studies of the crustal structure and the late Cretaceous-Cenozoic tectonostratigraphy of the 3,300,000 km2 Caribbean plate and the 22,000 km2 Camamu-Almada passive segment of northeastern Brazil. In Chapter 2, the composite crustal structure of the Caribbean plate was described as including four terranes composed of island arc, continental, oceanic, and oceanic plateau crust. The terranes were characterized using seismic reflection, gravity, magnetics, and well data to demonstrate that the Late Cretaceous-Cenozoic basin size and depth were primarily controlled by the underlying terrane. Strongly flexed oceanic and oceanic plateau crust along zones at the edges of the Caribbean plate controlled the deepest sediment-filled basins. Areas of proven hydrocarbon source rocks were associated with continental and island arc crust, while organically-rich, Late Cretaceous source rocks may be widespread across the Caribbean plate interior. In Chapter 3, the rifted-passive margin of the Camamu-Almada basin in northeastern Brazil was investigated through 2D and 3D gravity modeling and interpretation of two, deep-penetration seismic lines. Integration of these data suggested that the 40–110 km-wide transition zone between continental and oceanic crust was structurally complex and composed of three crustal blocks: a 10–40 km-wide zone of hyperextended continental crust; a 20-km-wide zone of exhumed mantle, and a 40–60 km-wide zone of incipient oceanic crust, characteristic of a magma-poor rifted margin. In Chapter 4, two 200 km-long, seismic reflection profiles from the Camamu-Almada passive margin were structurally restored to understand Cretaceous-Cenozoic passive margin uplift events previously proposed for this area. Structural restorations showed that original Aptian salt thickness ranged from 1750-3500 m but largely evacuated to the southeast. Passive margin uplift was quantified and compared to far field and mantle causes. Given this more complex passive margin history, 1D basin modeling predicted deep-water potential for oil-generation in preserved synrift lacustrine source rocks. In Chapter 5, AI methods were applied to the structural interpretation of the Camamu rifted passive margin. Observations of evaporites, mini-basins, and salt detachments all supported an evaporitic influence on the post-salt evolution of the passive margin.