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Clinoform Variability within the Neogene Succession of the Campos Basin, Offshore SE Brazil

Gjelberg, Helge *1; Helland-Hansen, William 1; Hadler-Jacobsen, Frode 2; Olaussen, Snorre 3
(1) Depertment of Earth Science, University of Bergen, Bergen, Norway.
(2) R & D, Statoil ASA, Trondheim, Norway.
(3) Department of Arctic Geology, The University Centre in Svalbard, Longyearbyen, Norway.

The Neogene succession of the Campos Basin, Brazilian continental margin, contains a series of well developed east to southeast prograding clinoforms. On the basis of depth converted 3D seismic data, clinoform successions have been studied to assess geometrical differences and to interpret which factors have been instrumental in controlling this variability, both within and between different thickness scales. Quantitative data on clinoform parameters like relief, gradients, rugosity and rollover curvature have been collected. The studied clinoforms have been grouped according to a hierarchic classification scheme where reliefs of 10's of meters constitute shoreline clinoforms, reliefs of 100's of meters constitute shelf prism clinoforms, and reliefs of 1000's of meters constitute continental margin clinoforms. With clinoform reliefs ranging from 50m to approximately 1100m, all three classes are present in this study. The coexistence of different scales of clinoforms, as expressed by shoreline clinoforms prograding across shelf prism clinoforms, supports this hierarchic subdivision system of clinoforms.

The concept of 3D trajectory analysis, a new approach for evaluating 3D clinoform geometry responses to changes in relative sea level and sediment supply, has been applied in this study. By coupling a series of depositional dip oriented clinoform rollover trajectories along strike, a surface that decipher the clinoform rollover trajectory in 3D can be created. Trajectories vary along depositional strike as a result of differing distance from point source and differential subsidence. Tracking the rollover of individual clinoforms along strike shows distinct curvatures, expressing the lobate plan view geometries of studied clinoform systems. The curvatures of shelf prism clinoforms are less accentuated than those of the shoreline clinoforms. However, shoreline clinoforms positioned at the shelf edge adapts to the lobate curvature of the underlying shelf prism clinoforms.


AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California