Obrist-Farner, J, Ball, PJ, McGilvery, TAM and Rogers, RR (2018) A prograding margin during global sea-level maxima: an example from Mahajanga Basin, northwest Madagascar. Basin Research, 30 (4). 671 - 687. ISSN 0950-091X

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The Mesozoic shelf margin in the Mahajanga Basin, northwest Madagascar, provides an example where inherited palaeobathymetry, coupled with sea‐level changes, high sediment supply and fluctuations in accommodation influenced the stacking patterns and geometry of clinoforms that accreted onto a passive rifted margin. Two‐dimensional (2D) seismic profiles are integrated with existing field data and geological maps to study the evolution of the margin. The basin contains complete records of transgression, highstand, regression and lowstand phases that took place from Jurassic to Cretaceous. Of particular interest is the Cretaceous, Albian to Turonian (ca. 113‐93 Ma), siliciclastic shelf margin that prograded above a drowned Middle Jurassic carbonate platform. The siliciclastic phase of the shelf margin advanced ca. 70 km within ca. 20 My, and contains 10 distinct clinoforms mapped along a 2D seismic reflection data set. The clinoforms show a progressive decrease in height and slope length, and a fairly constant slope gradient through time. The successive shelf edges begin with a persistent flat to slightly downward‐directed shelf‐edge trajectory that changes to an ascending trajectory at the end of clinoform progradation. The progressive decrease in clinoform height and slope length is attributed to a decrease in accommodation. The prograding margin is interpreted to have formed when siliciclastic input increased as eastern Madagascar was uplifted. This work highlights the importance of sediment supply and inherited palaeobathymetry as controls on the evolution of shelf margins and it provides a new understanding of the evolution of the Mahajanga Basin during the Mesozoic.

Item Type: Article
Subjects: G Geography. Anthropology. Recreation > GB Physical geography
Divisions: Faculty of Natural Sciences > School of Geography, Geology and the Environment
Related URLs:
Depositing User: Symplectic
Date Deposited: 30 Sep 2019 09:02
Last Modified: 30 Sep 2019 09:02
URI: https://eprints.keele.ac.uk/id/eprint/6619

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