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dc.contributor.advisorChairperson, Graduate Committee: Michael H. Gardneren
dc.contributor.authorWolak, Jeannette Marieen
dc.contributor.otherMichael H. Gardner was a co-author of the article, 'A hierarchical approach to understanding reservoir property distribution (porosity and permeability) in the Isongo Formation, equatorial West Africa' in the journal 'Sedimentology' which is contained within this thesis.en
dc.contributor.otherMichael H. Gardner and W. Sebastian Bayer were co-authors of the article, 'Incipient structural growth and transient fan development in the Late Miocene Isongo Formation, Southeastern Niger Delta' in the journal 'AAPG bulletin' which is contained within this thesis.en
dc.description.abstractDeepwater clastic deposits of the Late Miocene Isongo Formation, located 50 km northwest of Bioko Island, characterize a sand-rich transient fan system developed in response to incipient structural growth on the continental slope. Approximately 1200 ft (366 m) of conventional core, 21 wells, 3-D seismic (maximum 40-60 Hz), biostratigraphy, chemostratigraphy and dynamic production data from the 100 km 2 study area are used to: (1) Define process-based sedimentological facies within the Isongo Fan; (2) Characterize porosity and permeability trends at three temporal and spatial scales; (3) Identify sedimentary bodies throughout cored and uncored intervals; and (4) Correlate stratigraphic sequences within a framework of adjustment, initiation, growth and retreat (AIGR). While the former two objectives capture small-scale geologic heterogeneities developed at the time of deposition, the latter two describe changes in fan geomorphology during coeval uplift and sedimentation. Fifteen core-defined sedimentological facies reflect subaqueous depositional processes including turbidity currents, debris flows and pelagic settling. Pore space generated during deposition is correlated to grain size; pore connectivity is correlated to sorting. Sedimentation units and facies assemblages, which characterize depositional processes operating during a single sedimentation event, show patterns of accumulative flow in the confined, narrow portion of the Isongo Fan; depletive flow in the unconfined, southwestern portion. Erosional slope channel-levee systems in the northeast demonstrate very large sedimentation events, likely due to eruptive activity and uplift of Mount Cameroon 50 km updip. Partly confined to unconfined distributary channel-lobe systems in the southwest characterize a change in fan geomorphology off the flank of a growing structure. Core-calibrated petrophysical facies and wireline log thicknesses allow identification of sedimentary bodies in uncored intervals throughout the Isongo Fan, a 2.3 million year episode of sand-rich deposition (3rd order sequence). High frequency 4th and 5th order sequences are used to describe changes in fan morphology over time relative to the growing anticline. A surface of adjustment marks the onset of syn-sedimentary growth, followed by 4th order phases of initial deposition that onlap the structure. Sandrich fan growth, however, is greatest during a period of minimal uplift, followed by retreat of the Isongo depocenter to the north. Post-Isongo deposits suggest that renewed anticline growth resulted in avulsion of the system to the northwest after 8.2 Ma.en
dc.publisherMontana State University - Bozeman, College of Letters & Scienceen
dc.subject.lcshSubmarine fansen
dc.subject.lcshTurbidity currentsen
dc.subject.lcshContinental slopesen
dc.subject.lcshGeology, Stratigraphic--Neogeneen
dc.titleSedimentology and stratigraphy of a deepwater transient fan on the continental slope : the Late Miocene Isongo Formation, equatorial West Africaen
dc.rights.holderCopyright 2011 by Jeannette Marie Wolaken
thesis.catalog.ckey1823734en, Graduate Committee: James G. Schmitt; David W. Bowen; David .W. Mogk; Michael Reidyen Sciences.en

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