A facies model for a submarine volcaniclastic apron: the Miocene Manukau volcanic complex, Northland, New Zealand

Abstract

The Manukau Subgroup, New Zealand comprises a Miocene submarine volcaniclastic apron consisting of the products eroded and erupted from a large offshore partially emergent basaltic to andesitic volcanic complex. The submarine volcaniclastic apron is well exposed for over 30 km along the coast. The apron records the depositional history of a marine basin at bathyal water depths and the onset of fan progradation due to volcanism. The exceptional exposure, variation in fan architecture (distal, lobe, upper slope and channel), facies (e.g. sandstone, pumice breccias, conglomerates and pillow lavas) and origin (primary, resedimented or epiclastic), allows analysis of a facies model for submarine volcaniclastic fans. The facies analysis shows that submarine volcaniclastic fans differ from other clastic sedimentary fan models in the origin, supply and types of clasts.