The Cainozoic geology of Flinders Island, Bass Strait

Abstract

Cainozoic sediments and volcanic rocks superficiallyoverlie the mountainous Palaeozoic basement of Flindersisland and mainly form the coastal plains.Marine deposits include Middle Pliocene to Recentnear-shore and littoral coquinoid beds, and someQuaternary beds appear related to old marine standsat about 15-18 m., 4.5-6 m. and 0.6-1.5 m. aboveMHWS. Quaternary dune deposits afe predominantlycalcareous on the west coast and predominantly siliceouson the east coast, and show varying degrees of consolidationand soil development generally related toage. A Recent beach ridge and coastal barrier systemis developed and lagoonal deposits include Pleistocenelimestone and Recent peat. Non-marine gravel and gritdeposits (including st.anniferous and sub-basaltic deposits)were sometimes reworked by later marine incursions.Scattered volcanic rocks include tuffs, alkali olivinebasaltsand olivine-nephelinites, erupted from severalcentres roughly aligned along a north westerly trend.The volcanism was largely Tertiary in age and somelavas are lateritised.The Cainozoic history was initiated by faulting, tiltingand uplifting of the Flinders Island block by earlyTertiary time, with subsequent volcanism. During theCainozoic, alternations of predominantly terrestrial ormarine erosion and deposition on Flinders Island wererelated to fluctuating sea-levels, which influenced somefaunal movements.