West Australian Ridge (Indian Ocean): Microcontinent or Large Igneous Province?

Abstract

A comprehensive analysis of extensive primary (morphological, geological, geophysical, and geochemical—including deep-sea drilling) data provides deep insight into the morphostructure, geology, and evolution of the West Australian Ridge (WAR) (or Broken Ridge), which unambiguously testify to its continental origin. The northeastern slope was distinguished additionally to two previously known main morphostructural elements of the ridge: the northern and southern slopes. It is inclined towards the Naturaliste abyssal plain and structurally forms its northwestern framing. It has been established that the morphology of the slopes is caused by the peculiarities of the tectonic development of the adjacent basins. It is determined that the sedimentary cover of the central part of the northern slope contains a lower (basal) seismoacoustic complex, which has not been exposed by deep-sea drilling and formed no later than the Early Cretaceous. The final subsidence of individual fragments of the ridge and the formation of its present-day morphostructure, as well as the structural-tectonic rearrangement of the adjacent areas, occurred at the youngest phase of tectonic activation in the Late Miocene–Pliocene.