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(d) The Triple Junction area s.s.

Multibeam data show that the southernmost segment of MAR axis bifurcates approximately at the Triple Junction location as suggested by SCLATER1976, forming a sort of reversed Y. These two southern axial branches are elongated depressions oriented NW-SE and N-S, respectively. Recent accretionary activity in both branches is suggested by high acoustic reflectivity in back-scatter data, (indicating the absence of sedimentary cover within these throughs), and by a positive magnetic anomaly associated with each branch. A possible interpretation is that the Triple Junction is presently at the point of bifurcation of the southernmost MAR segment (Figs. 3 and 4). If we accept this interpretation, the Bouvet Triple Junction is presently of RRR type. An alternative interpretation, discussed by LIGI1997, suggests that the NW-SE branch became inactive roughly l my ago when the Spiess segment started to propagate NW, disrupting the previous geometry of the plate boundaries converging towards the Triple Junction.



2011-12-13