Eocene to Miocene Chronostratigraphy of the Queensland Plateau: Control of Climate and Sea Level on Platform Evolution

Abstract

The Queensland Plateau carbonate platform (northeastern Australia) is characterized by a complex evolutionary history that has been punctuated by several interruptions in platform growth. The surface of the plateau (metamorphic rocks) was flooded during the middle Eocene marine transgression. For the first time, a carbonate platform was formed in the area. It was characterized by bryozoan-rich deposits, which originated in temperate-to-cool waters. However, some layers within this interval are rich in larger benthic foraminifers that point to warmer-water intrusions. A sea-level lowstand caused a regional unconformity (upper Eocene-lower Oligocene) and concomitant changes in surface-water temperatures. This was followed by a major rise of sea level, and during highstand conditions, a major subtropical-to-tropical buildup was established (upper Oligocene to middle Miocene). Several exposure surfaces within this interval document minor sea-level lowerings. In response to a major sea-level lowstand, the platform became exposed and eroded at the middle/upper Miocene boundary. Final drowning of most of the platform occurred during the late Miocene, initiated by rising sea level and increased subsidence of the basement.