Kinematic and paleobathymetric evolution of the South Atlantic basin. / Perez Diaz, Lucia.

2017. 237 p.

Research output: ThesisDoctoral Thesis

Unpublished

Documents

Abstract

The opening of the South Atlantic ocean is one of the most extensively researched problems in plate kinematics. An accurate representation of the plate motions that led to the growth of this ocean basin is crucial to understanding the dynamics of its margins, the formation of petroleum systems and the driving mechanisms behind present and past water circulation patterns. General agreement exists about ocean opening being the result of the diachronous separation of two major plates (South American and African), having involved a certain degree of intracontinental deformation. However, for a fuller understanding, the bathymetric evolution also needs to be considered.

I model oceanic growth as depicted by seafloor spreading data (fracture zone traces and magnetic anomalies). I present the results of this model as an animated tectonic reconstruction. Spreading started at 138 Ma, with movement along intracontinental accommodation zones leading to the assembly of South America by 123 Ma and Africa by 106 Ma. The model also provides an explanation for the inception and evolution of the Malvinas plate and its connection with the formation of a LIP south of the Falkland-Agulhas Fracture Zone. I challenge the view of narrow deformation belts as the sole sites of stress accommodation during continental separation and discuss the implications of the kinematic model in terms of the distribution of intracontinental strain.

Subsequently, I use a high-resolution seafloor age grid, derived from the plate kinematic model presented, to model the subsidence of oceanic lithosphere as a function of its age by applying plate-cooling theory. Then, I refine this thermal surface to account for other factors that affect bathymetry at smaller scales or amplitudes, both within the ocean and the continent-ocean transition zones (here sedimentation, variable crustal thickness and mantle fluctuations). Despite of the uncertainties that
this workflow introduces in the resulting model, which I describe and quantify, the paleobathymetric reconstructions are a big step forward (both in resolution and accuracy) from previous attempts at modelling the changes in seafloor depth through time in the South Atlantic.

The final products are a series of paleobathymetric reconstructions of the South Atlantic, which, together with the plate kinematic model provide a complete picture of its evolution from Cretaceous times to present.
Original languageEnglish
QualificationPh.D.
Awarding Institution
Supervisors/Advisors
Thesis sponsors
  • Reid scholarship, Royal Holloway
  • Helen Shackleton Fund for Travel Expenses
Award date1 Mar 2017
Publication statusUnpublished - 2017

Research outputs

This open access research output is licenced under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

ID: 27708788