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Kinematic evolution of a regional-scale gravity-driven deepwater fold-and-thrust belt: The Lamu Basin case-history (East Africa)
Univ Perugia, Dept Phys & Geol, I-06123 Perugia, Italy..
Univ Perugia, Dept Phys & Geol, I-06123 Perugia, Italy..
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
Univ Perugia, Dept Phys & Geol, I-06123 Perugia, Italy..
2017 (English)In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 712-713, 30-44 p.Article in journal (Refereed) Published
Abstract [en]

The deepwater fold-and-thrust belts (DWFTBs) are geological structures recently explored thanks to advances in offshore seismic imaging by oil industry. In this study we present a kinematic analysis based on three balanced cross-sections of depth-converted, 2-D seismic profiles along the offshore Lamu Basin (East African passive margin). This margin is characterized by a regional-scale DWFTB (>450 km long), which is the product of gravity-driven contraction on the shelf that exhibits complex structural styles and differing amount of shortening along strike. Net shortening is up to 48 km in the northern wider part of the fold-and-thrust belt (approximate to 180 km), diminishing to <15 km toward the south, where the belt is markedly narrower (approximate to 50 km). The three balanced profiles show a shortening percentage around 20% (comparable with the maximum values documented in other gravity-driven DWFTBs), with a significant variability along dip: higher values are achieved in the outer (i.e. down-dip) portion of the system, dominated by basinward-verging, imbricate thrust sheets. Fold wavelength increases landward, where doubly-verging structures and symmetric detachment folds accommodate a lower amount of shortening. Similar to other cases, a linear and systematic relationship between sedimentary thickness and fold wavelength is observed. Reconstruction of the rate of shortening through time within a fold-and-thrust belt shows that after an early phase of slow activation (Late Cretaceous), >95% of net shortening was produced in <10 Myr (during Paleocene). During this acme phase, which followed a period of high sedimentation rate, thrusts were largely synchronous and the shortening rate reached a maximum value of 5 mm/yr. The kinematic evolution reconstructed in this study suggests that the structural evolution of gravity-driven fold-and-thrust belts differs from the accretionary wedges and the collisional fold-and-thrust belts, where thrusts propagate in-sequence and shortening is uniformly accommodated along dip.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV , 2017. Vol. 712-713, 30-44 p.
Keyword [en]
Deepwater fold-and-thrust belt, Restoration, Rate of shortening, Lamu Basin, East Africa
National Category
Other Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:uu:diva-335711DOI: 10.1016/j.tecto.2017.05.002ISI: 000409284500003OAI: oai:DiVA.org:uu-335711DiVA: diva2:1164231
Funder
Swedish Research Council
Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2017-12-11Bibliographically approved

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Koyi, Hemin

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