Early Cretaceous microfossils from the type Wallumbilla Formation, Surat Basin, Queensland

Abstract

Foraminiferids, radiolarians, ostracods, diatoms, dinoflagellates, acritarchs, spores, and pollen are recorded from the type outcrop section of the Wallumbilla Formation in the Surat Basin, southern Queensland. The microfossils were recovered from calcareous mudstone nodules at two locations in the Doncaster Member. The foraminiferids belong to the Bigenerina pitmani Zone; the dinoflagellates to the Odontochitina operculata Zone; and the spores and pollen to the Osmundacidites dubius Zone (middle and upper part of Cyclosporites hughesii Subzone). The microfossils are associated with a predominantly molluscan megafauna typical of the Maccoyella barklyi Zone. The fossil association probably inhabited a slightly hyposaline, shallow sea. The microfossils themselves offer no definitive evidence regarding their precise age; they are broadly determined as late Early Cretaceous. Ammonites associated with the Maccoyella barklyi Zone, however, indicate that the microfossils are probably oflate Aptian age.