Ebor Volcano and Crescent Complex, northeastern New South Wales: Age and geological development

Abstract

The Ebor Volcano in northeastern New South Wales is one of a number of central volcanoes formed during the period of extensive Tertiary intraplate volcanism in eastern Australia. Geochronological results indicate a Miocene age (ca 19–20 Ma) for the volcano, which was constructed on Late Palaeozoic to Early Mesozoic rocks of the New England Orogen. Its remnants are dominated by lava flow sequences up to 400 m thick and cover an area of 480 km2. In mid‐Miocene time, the Ebor Volcano was conservatively 45 km across and of low shield form, standing at least 800 m above basement. Subsequent erosional retreat of the Great Escarpment has removed about 90% of its volume. Flows of olivine‐ and quartz‐normative tholeiitic basalts grading to icelandite form the bulk of the volcano and were erupted between 19.6 and 19.2 Ma. An alkaline and transitional basaltic lava suite is locally associated, with the majority of occurrences towards the volcano's western margin. Many of the latter are basanite in composition and ar...