Rifting of the Guinea Margin in the Equatorial Atlantic from 112 to 84 MA: Implications of Paleo-Reconstructions for Structure and Sea-Surface Circulation

Persistent Link:
http://hdl.handle.net/10150/321395
Title:
Rifting of the Guinea Margin in the Equatorial Atlantic from 112 to 84 MA: Implications of Paleo-Reconstructions for Structure and Sea-Surface Circulation
Author:
Edge, Russ
Issue Date:
2014
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Embargo:
Release 15-May-2016
Abstract:
The Guinea Plateau is a shallow-marine, flat-lying bathymetric province situated along the equatorial West African margin, offshore Republic of Guinea. The Guinea Plateau and the conjugate Demerara Plateau hold particular geologic significance, as they represent the final point of separation between the African and South American continents during Gondwana break-up. Recent interpretation of both 2-D and 3-D seismic surveys along the Guinean margin have illuminated subsurface features related to Early Cretaceous crustal extension. Seismic structural investigations on these datasets suggest that the majority of extension is accommodated along large-scale listric normal faults located on a relatively narrow (<50 km) continental slope (up to ~39% extension). Minimal faulting reveals that little upper-crustal extension has occurred on the Guinea Plateau. Additionally, multiple 2-D seismic profiles image the transition from continental crust on the plateau and slope, to oceanic crust in the deeper marine basin. This continent-ocean boundary is the most representative boundary when testing the accuracy of plate reconstructions. Mapping of both the continent-ocean boundary and fracture zones across the equatorial Atlantic suggests that the Demerara Plateau and the South American plate are too far south in previous pre-rift reconstructions. A revised model introduces 20 km of Early Cretaceous NNW-oriented contraction across the Amazon Basin; an area of relative weakness where both geologic and geophysical data support such accommodation. Sea-surface flow models, which used this revised reconstruction and interpreted paleo-bathymetric data, predict upwelling throughout the newly formed equatorial seaway, and later along the West African margin during periods of regional organic-rich black shale deposition. With reduced decomposition of organic matter strongly correlated to upwelling, being able to predict these zones is of particular significance to petroleum companies, who have recently started exploring both the equatorial South American and West African coastlines.
Type:
text; Electronic Dissertation
Keywords:
equatorial Atlantic; Guinea Plateau; plate reconstruction; reflection seismology; rifting; Geosciences; crustal structure
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Geosciences
Degree Grantor:
University of Arizona
Advisor:
Johnson, Roy A.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen
dc.titleRifting of the Guinea Margin in the Equatorial Atlantic from 112 to 84 MA: Implications of Paleo-Reconstructions for Structure and Sea-Surface Circulationen_US
dc.creatorEdge, Russen_US
dc.contributor.authorEdge, Russen_US
dc.date.issued2014-
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.releaseRelease 15-May-2016en_US
dc.description.abstractThe Guinea Plateau is a shallow-marine, flat-lying bathymetric province situated along the equatorial West African margin, offshore Republic of Guinea. The Guinea Plateau and the conjugate Demerara Plateau hold particular geologic significance, as they represent the final point of separation between the African and South American continents during Gondwana break-up. Recent interpretation of both 2-D and 3-D seismic surveys along the Guinean margin have illuminated subsurface features related to Early Cretaceous crustal extension. Seismic structural investigations on these datasets suggest that the majority of extension is accommodated along large-scale listric normal faults located on a relatively narrow (<50 km) continental slope (up to ~39% extension). Minimal faulting reveals that little upper-crustal extension has occurred on the Guinea Plateau. Additionally, multiple 2-D seismic profiles image the transition from continental crust on the plateau and slope, to oceanic crust in the deeper marine basin. This continent-ocean boundary is the most representative boundary when testing the accuracy of plate reconstructions. Mapping of both the continent-ocean boundary and fracture zones across the equatorial Atlantic suggests that the Demerara Plateau and the South American plate are too far south in previous pre-rift reconstructions. A revised model introduces 20 km of Early Cretaceous NNW-oriented contraction across the Amazon Basin; an area of relative weakness where both geologic and geophysical data support such accommodation. Sea-surface flow models, which used this revised reconstruction and interpreted paleo-bathymetric data, predict upwelling throughout the newly formed equatorial seaway, and later along the West African margin during periods of regional organic-rich black shale deposition. With reduced decomposition of organic matter strongly correlated to upwelling, being able to predict these zones is of particular significance to petroleum companies, who have recently started exploring both the equatorial South American and West African coastlines.en_US
dc.typetexten
dc.typeElectronic Dissertationen
dc.subjectequatorial Atlanticen_US
dc.subjectGuinea Plateauen_US
dc.subjectplate reconstructionen_US
dc.subjectreflection seismologyen_US
dc.subjectriftingen_US
dc.subjectGeosciencesen_US
dc.subjectcrustal structureen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorJohnson, Roy A.en_US
dc.contributor.committeememberJohnson, Roy A.en_US
dc.contributor.committeememberKapp, Paulen_US
dc.contributor.committeememberZandt, Georgeen_US
dc.contributor.committeememberBennett, Ricken_US
dc.contributor.committeememberSbar, Marcen_US
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