Pre-Tertiary Infrabasins (1:1,000,000)

The pre-Tertiary infrabasins are a series of north-northeast and northwest trending structures that underlie the Murray Basin, and comprise a sequence of Late Silurian through to Early Cretaceous sediments. Tectonic movements initiated the structural development of these infrabasins during the Devonian or very late Silurian, based on interpretation of the Bouguer anomaly and aeromagnetic trends, as few wells have been drilled and seismic data is limited. The resultant uplift of basement highs led to development of essentially north-south trending troughs as ‘infolds’ in the basement. Deposition of shallow marine and turbiditic sequences prevailed, which continued until the Middle Devonian Tabberabberan Orogeny. During the Upper Carboniferous to Lower Permian a sequence of marine and diamictite sediments were deposited within the infrabasins, suggesting deposition took place in a glacial environment.