A thick sequence of Lower Cretaceous sediments outcrops in the Burrum Syncline, near Maryborough, southeast Queensland. The Aptian Maryborough Formation (ca 2 000 m, mostly marine), and the Albian Burrum Coal Measures (ca 2 400 m, mostly fluviatile and lacustrine), form the broad , asymmetrical, north-west-plunging Burrum Syncline. These units are compositionally alike, consisting of lithic greywacke, subgreywacke, arkosic sandstone, mudstone, and silty shale. The Burrum Coal Measures also contain carbonaceous shale and coal seams.
The Lower Cretaceous sediments were folded during the Late Cretaceous, with associated movement along the Electra Fault. These strata have subsequently undergone a complex alteration history, involving pedogenic silicification, followed by lateritization. The overlying Early Tertiary Takura Beds, a talus deposit of oligomictic breccia derived from the Maryborough Formation, and the Elliott Formation (fluviatile orthoquartzite) were extensively lateritized before extrusion of the first olivine basalt flow at Dundowran. Lateritization ceased before extrusion of the second flow. Geochemically these basalts belong to an alkali province, exhibiting some transitional characters. Geomorphological evidence indicates a Miocene age for the basalts, which has been confirmed by whole-rock K-Ar ages of 18 .4 m.y. (minimum age, lower altered flow), and 1 2 m.y. (upper fresh flow).
Specifically identifiable fossils are limited to the Lower Cretaceous units of the sequence. The Maryborough Formation contains abundant marine bivalves of Aptian age. The Burrum Coal Measures contain a microflora of limited diversity, which is dominated by fern spores of presumed gleicheniaceous and schizaeaceous affmity. This assemblage is typical of a coal-forming paludal environment. Biostratigraphically, the Burrum Coal Measures microflora belongs to the lower part of the Coptospora paradoxa Zone of Dettmann & Playford (1 969), of early to middle Albian age.