The Cainozoic geology of Flinders Island, Bass Strait

Abstract

Cainozoic sediments and volcanic rocks superficially overlie the mountainous Palaeozoic basement of Flinders island and mainly form the coastal plains. Marine deposits include Middle Pliocene to Recent near-shore and littoral coquinoid beds, and some Quaternary beds appear related to old marine stands at about 15-18 m., 4.5-6 m. and 0.6-1.5 m. above MHWS. Quaternary dune deposits afe predominantly calcareous on the west coast and predominantly siliceous on the east coast, and show varying degrees of consolidation and soil development generally related to age. A Recent beach ridge and coastal barrier system is developed and lagoonal deposits include Pleistocene limestone and Recent peat. Non-marine gravel and grit deposits (including st.anniferous and sub-basaltic deposits) were sometimes reworked by later marine incursions. Scattered volcanic rocks include tuffs, alkali olivinebasalts and olivine-nephelinites, erupted from several centres roughly aligned along a north westerly trend. The volcanism was largely Tertiary in age and some lavas are lateritised. The Cainozoic history was initiated by faulting, tilting and uplifting of the Flinders Island block by early Tertiary time, with subsequent volcanism. During the Cainozoic, alternations of predominantly terrestrial or marine erosion and deposition on Flinders Island were related to fluctuating sea-levels, which influenced some faunal movements.