Geology and landforms of Two Peoples Bay Nature Reserve, Western Australia

Abstract

Context Underlying geology strongly influences landforms, soil composition, and hydrogeology in Two Peoples Bay Nature Reserve, Western Australia, which was mapped by P. E. Playford in 1982. Aims To review the mapping of the Reserve, with the aim to better understand the geological history and landforms of the area. Methods In 2024, I. M. Tyler and K. A. Evans reviewed P. E. Playford’s mapping in the field, viewed aerial photography and geophysical imagery, and reviewed research published since 1984. Key results The oldest rocks are 1290 Ma granitic gneiss and an 1180 Ma granite intrusion. Amalgamation of the Meso- to Neoproterozoic Rodinian Supercontinent put the Albany−Fraser Orogen at the heart of east Gondwana for ~1.0 billion years. At 165 Ma, that plate configuration began to break up, and from 83 Ma, the Eucla Basin opened. Cenozoic landforms and surficial deposits record northward plate movement and collision with south-east Asia at around 23 Ma, causing tectonic uplift, sea-level change, and climate change. The middle to upper Eocene Plantagenet Group was deposited in a shallow marine embayment with Maardjitup Gurlin/Mount Gardner, forming an island. The uplifted Eocene sea floor was lateritized in the Miocene and is presently covered by Holocene eolian sand dunes, peaty swamps and lakes. Maardjitup Gurlin/Mount Gardner was connected to the mainland by Pleistocene eolianite deposits. Conclusions The influence of plate tectonics on the geological evolution of an area is profound, from the origin and composition of the oldest rocks to the present landscape and the youngest surficial deposits. Implications Understanding the geological history of an area is essential to understanding landscape evolution and the natural history of the flora and fauna that inhabit it.