The purpose of this volume is to inform the reader of the detailed geology of the four “divergent margin basins” discussed herein and to establish for the reader a set of analog scenarios which can be used for future petroleum exploration.
The divergent margin basins selected for presentation in this volume by the American Association of Petroleum Geologists are the Campos basin of Brazil, the Gabon basin, the Niger delta, and the basins of the northwest shelf of Australia. These four petroleum basins present a wide range of stratigraphic sequences and structural styles that represent the diverse evolution of this large and important class of world petroleum basins. Members of the AAPG as well as all the government, academic, and company geologists who will benefit from this volume are indebted to the authors, contributing associates, reviewers, and editors of these World Petroleum Basin Series volumes.
All basins in the divergent margin class occur along continental margins near a midplate position, where they overlie and straddle rigid continental and oceanic crust. These basins are now essentially aseismic and non- volcanic. All extant divergent margins are post-Triassic and are related to the sequential breakup of Pangea. They represent the opening ocean portion of the Wilson cycle of earth history (Wilson, 1976). As Pangea split, continental plates moved away from the African center (von Gerhard Bischoff, 1985).
The inboard roots of divergent margin basins lie on attenuated, subsided continental crust beneath the coastal plain, continental shelf, and continental slope. Outboard, they
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Divergent/Passive Margin Basins
All basins in the Divergent Margin class occur along continental margins near a midplate position, where they overlie and straddle rigid continental and oceanic crust. These basins are now essentially aseismic and non-volcanic. All extant divergent margins are post-Traissic and are related to the sequential breakup of Pangea. They represent the opening ocean part of the Wilson cycle of earth history ? as Pangea split, continental plates moved away from the African center. The inboard roots of divergent margin basins lie on attenuated, subsided continental crust beneath the coastal plain, continental shelf, and continental slope. Outboard, they lie on subsided oceanic crust beneath the continental slope and rise. All phases of basin development are dominated by gravity-driven extension tectonics. Hence, they are called passive, pull-apart, Atlantic-type, or divergent continental margins. This publication was initiated by the AAPG Publications Committee in 1985 and contributors were invited to write. AAPG designed their ?World Petroleum Basins? series and sought to publish the definitive volume on each of several basin types. In this volume, “Divergent/Passive Margin Basins,” a detailed overview was written about the Campos Basin (Brazil) as representative of divergent margin basins. The key paper was followed by less detailed reviews of three other selected passive margin basins: 1. Northwest Shelf of Australia 2. Gabon basin and 3. Niger Delta area. Contributors undertook to provide useful geologic information on the regional setting, stratigraphy, structure, tectonics, basin evolution, and oil and gas systems of these four basins. The goal was to develop a better understanding of the basin-forming, basin-filling, and basin-modifying processes that control hydrocarbon plays and resultant oil and gas fields in this class of basin. The volumes in the AAPG Basin Series include: 1. Divergent/Passive Margin Basins (AAPG Memoir 48) 2. Interior/Cratonic Basins (AAPG Memoir 51) 3. Active Margin Basins (AAPG Memoir 52) 4. Foreland Basins and Foldbelts (AAPG Memoir 55) 5. Interior Rift Basins (AAPG Memoir 59).