RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 1, NO. 5, PAGES 423–443, doi:10.2205/1999ES000018, 1999

The history of South Atlantics spreading ridges development and time -- space position of Bouve triple connection

Abstract

[1]  Using the example of the evolution of spreading ridges, connected in the zone of the Bouve triple connection, it is shown that the evolution history of the South Atlantic Ocean included at least three time intervals, when its spreading ridges were connected with one another to form three Bouve triple connections (TC): the Bouve TC-1 existed 119-122 million years ago, TC-2, 93-105 million years ago, and TC-3 is a modern triple junction. Changes in the relative movements of the lithospheric plates resulted in the disturbances of the spreading ridge geological structure, and were accompanied by the further propagation and skipping of the rift valleys, as well as by the destruction and dying-off of the spreading ridges. The geodynamic environments included (1) the migration of the asthenospheric flows during the propagations of the continental rifts during the periods of the Gondwana continents break-ups and the formation of the Southwest Indian Ridge (SWIR) and the Southern Mid-Atlantic Ridge (SMAR); (2) the migration of the flows during the advance of the oceanic rifts (western SWIR segment) and the jumping over of the spreading ridges (SMAR), caused by changes in the relative directions of the crustal plate movements; (3) the disturbance of the asthenospheric flow by the continental "barrier" of the Falkland Plateau during the development of the Bouve-1 triple connection, which resulted in the huge displacement of the rift axis along the Agulhas-Falkland transform zone; (4) the interaction of the subaxial asthenospheric flows (possibly varying in depth, temperature, and viscosity) in the region of the large Bain-Prince Eduard transform displacements in the Southwest Indian Ridge, and (5) the outbreak of the asthenospheric flow along the channel between the two continental blocks, namely, the Antarctic Peninsula and the southern termination of South America, which resulted in the formation of a new plate (Scotia) and of a new transform-divergent boundary between the plates of the American-Antarctic Ridge.

Received 15 May 1999; published 20 June 1999.

Keywords: South Atlantics spreading ridges, evolution of spreading ridges, Bouve triple connection.