Modelling plate kinematics in the Scotia sea

• Main Author: Eagles, Graeme
• Format: Thesis
• Language: English
• Published: University of Leeds 2000
• Subjects: Antarctic; Scotia Sea; Antarc*; Tierra del Fuego
• Online Access: https://etheses.whiterose.ac.uk/258/; https://etheses.whiterose.ac.uk/258/1/uk_bl_ethos_492383.pdf; https://etheses.whiterose.ac.uk/258/2/uk_bl_ethos_492383_pullouts.pdf

A new model of plate kinematics in the Scotia Sea region is presented in which continental crustal blocks and the signatures of seafloor spreading are defined semi-automatically using gravity and total field magnetic anomalies and some of their residuals, transformations and derivatives. This study is the first of the region to integrate gridded magnetic and gravity data in order to make reconstructions, and one of the first anywhere to make full use of gridded magnetic data in an inverse procedure. The context provided by the quantitative reconstructions allows qualitative assessment of visually-derived reconstructions of small movements in the region. The Scotia Sea floor consists of three large oceanic magnetic provinces: the west,central and east Scotia seas, and four smaller sub-basins, all enclosed within the elevated submarine and emergent Scotia Arc. The Scotia Arc consists of Mesozoic continental and Cenozoic island-arc fragments. Only the east Scotia Sea remains active; the west and central parts are the products of extinct spreading centres. West Scotia sea spreading is reasonably well described by tectonic flowlines expressed in satellite free-air gravity anomalies and magnetic reversal isochrons in total field anomalies. These data are combined in an inversion to reconstruct the west Scotia Sea's margins between its inception at thron C8 (- 26.5 Ma) and extinction at chron C3a (- 6 Ma). The results suggest strongly, and for the first time, that the west Scotia Sea formed as a small ocean basin whose passive margins were Tierra del Fuego and the central Scotia Sea, and not as a back-arc basin in the strict sense. During its growth the kinematics of the west Scotia Sea's margins approximated those of the South American and Antarctic plates. The small kinematic differences are suggested to be due to convergence at the `proto-South Sandwich-Discovery' subduction zone, to the east of the central Scotia Sea, and to dextral strike-slip (pre-C6 (N 20 Ma)) and oblique convergence (post-C6) at the North ...