Details

Autor(en) / Beteiligte

• Ruellan, Etienne
• Huchon, Philippe
• Auzende, Jean-Marie
• Gràcia, Eulàlia

Titel

Propagating rift and overlapping spreading center in the North Fiji Basin

Ist Teil von

• Marine geology, 1994, Vol.116 (1), p.37-56

Ort / Verlag

Amsterdam: Elsevier B.V

Erscheinungsjahr

1994

Link zum Volltext

Quelle

Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)

Beschreibungen/Notizen

• The present day geometry of the North Fiji marginal basin, at the Pacific and Indo-Australian plate boundary, results from a polyphased tectonic evolution. Since the beginning of the opening, spreading occurred along several ridge axes that are characterized by highly variable trends. From 15°S to 21°40′S, the present day trends of the axis are mainly N20°W, N20°E and N-N5°E. The structural analysis of multi-beam echo sounder and seismic data combined with submersible observations (18 dives in this area) allow a precise study of relationships between the N-N5°E and N20°E axes near 18°30′S. Two main oceanic features occur in this area. The most striking one consists in a broad northward propagating rift of the N-N5°E spreading ridge. The northern tip of the propagator is located at 18°10′S, on 173°30′E and is characterized by a northern V-shaped end and a slight camber. The diving observations corroborate the present day magmatic and tectonic activities along the N-N5°E spreading axis located between 18°10′S and 20°30′S and its northward propagation to the detriment of the N20°E axis which is less active at its southern end. Moreover, the youngest axis trends, inside the N20°E axial domain, confirms this northward propagation of the N-N5°E structural trends. The N-N5°E spreading axis shows very close similarities with those of an intermediate to fast-spreading ridge, either in its morphology or in its spreading rate. On the other hand, the N20°E axis displays a large tectonically active overlapping arm, that is counterposed to the northern end of the N-N5°E propagating system. The transform zone between the two overlapping arms is characterized by typical oblique and curved structural patterns in the sea floor. The whole tectonic system constitutes thus a typical large overlapping spreading center. The average propagating rate is calculated at 5.7 cm/yr that is compatible with backward migration of the N20°E overlapping arm. This study confirms the high instability of the North Fiji Basin spreading system through time and space, due to the regional tectonic stress produced by the plate convergence and the double sphenochasmic opening of the basin.