Aquagene volcanism in the Tasmanian Tertiary, in relation to coastal seas and river systems

Abstract

Tertiary aquagene volcanics at over forty localities in Tasmania concentrate in three main regions. The North West Coast - Bass Strait islands examples are mostly related to Miocene high seas. Phreatic tuffs and flow foot breccias erupted from emergent vents (Cape Grim, Trefoil Island, Steep Island, Redpa, Brittons Swamp, Temma, N. Robbins Island and possibly Wynyard. Pillowy lavas represent subaqueous phases of emerging volcanoes (Flat Topped Bluff, S. Robbins Island and Black Pyramid Island). The aquagene volcanics supplement data on levels and depositional depths of Niocene seas and suggest relative levels now up to 110m (early Niocene), l30-l40m (early-mid Miocene) and possibly 75m (late-mid Niocene?) above present sea level.