Investigations into the development of continent-ocean transform boundaries

Details Investigations into the development of continent-ocean transform boundaries Investigations into the development of continent-ocean transform boundaries

Jun 1991

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1991phdt........17l&link_type=abstract

Ph.D. Thesis Columbia Univ., New York, NY.

Mathematics

Logic

Conductive Heat Transfer, Continental Shelves, Earth Crust, Earth Mantle, Geological Faults, Plates (Tectonics), Seismology, Stratigraphy, Tectonics, Two Dimensional Models, Continental Drift, Gravitation, Igneous Rocks, Lithology, Mathematical Models, Planetary Evolution, Plateaus

Scientific paper

A two-stage evolutionary model is proposed to explain the tectonic, stratigraphic, and igneous features observed along continent-ocean transform boundaries. New data sets are analyzed consisting of: (1) 14,000 km of multi-channel and single-channel seismic (MCS) reflection profiles for the Falkland/Malvinas Plateau (South Atlantic); and (2) a 200 km of deep penetration MSC profile, five expanded spread profiles (ESP's), physical property values from ODP Site 763, and shipboard gravity data for the Exmouth Plateau (N.W. Australia). Four major depositional sequences are defined and mapped for the Falkland Plateau. In the Exmouth, seismic reflectors are tied to lithological and age unit boundaries using ESP-derived physical properties. ESP models are shown comparable to in situ downhole derived measurements. During the first stage, at the time of rifting, extensional detachment surfaces develop at a high angle to the future transform and are later sheared by strike-slip faulting. Final transform rupture occurs within a 10-15 km region, attended by large fault block rotation and mafic intrusions in conditions of pure shear. During the second stage, the continental rim is underplated when the oceanic ridge abuts the continent. This has produced a 10 km thick, 7.3 km/s layer under the Exmouth margin, resulting in a permanent isostatic uplift of the crust and tilting of syn-rift sediments. Gravity modeling suggests this layer comprises a 3 g/cu cm mixture of mafic and felsic rocks. The thermal evolution for the transform is examined using a two-dimensional heat conduction model, and the results are presented.

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