Title

Tectonics and sedimentation in transtensional and extensional settings: Examples from offshore Belize, Central America, and the Marajo Basin, northern Brazil

Date of Award

1993

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Marine Geology and Geophysics

First Committee Member

Bruce R. Rosendahl, Committee Chair

Second Committee Member

Gregor P. Eberli, Committee Member

Abstract

Analyses of multichannel seismic data in the Belize Southern Lagoon and in the Marajo Rift show that tectonics exercised a major control on sedimentation throughout the evolution of both basins. The Belize Southern Lagoon was first affected by transtensional stresses during the Paleocene, as Cuba swept past the eastern coast of the Yucatan peninsula moving along a left-lateral transform boundary. This tectonic event produced a series of southwest-northeast-trending en echelon normal faults, which created a topographic relief of ridges and troughs. The second transtensional event occurred during the Pliocene and/or later, revealing very recent activity along the Caribbean/North American left-lateral transform boundary. Southwest-northeast-trending high-angle normal faults characterize the style. Structure ultimately controlled sediment distribution in the Southern Lagoon throughout the Tertiary: ridges acted as a template for reef development, whereas topographic lows served as channels for land-derived siliciclastics.The Marajo "passive" intracontinental rift underwent extensional stresses from Early/Middle Jurassic to Cenomanian times, first, related to the southward propagation of the southern North Atlantic and second, to the transform rifting of the Equatorial Atlantic. Basin architecture is defined by asymmetric half-grabens bounded by listric/growth normal faults, which seem to sole out at a detachment surface located at mid-crustal levels. Rifting geometries were predominantly controlled by the pre-existing structural fabrics of the Trans-Amazonian Maroni-Itacaiunas mobile belt. The development of the Equatorial fracture zones during the Cretaceous gradually shifted eastward the locus of main extension, terminating the connection between the Marajo Rift and the North Atlantic and preventing further opening. The northern end of the rift "failed" just prior to the development of true oceanic crust, whereas the southern end of the rift never evolved beyond a "juvenile" stage of rifting. The northward "progression" in rifting caused an early northward tilt of the basin, resulting in the development of an axial fluvio-deltaic system fed not only from the rift flanks, but also from external sedimentary sources located at the southern end of the rift.

Keywords

Geology; Geophysics

Link to Full Text

http://access.library.miami.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9412943