The fossil microfaunal assemblage in the Oodnadatta 1 petroleum wildcat well has been examined as a basis for correlation and possible zonation of the Lower Cretaceous sequence in the South Australian portion of the Great Artesian Basin. 112 samples of drill cores taken at 10-foot intervals in the well from 22 to 1297 feet depth KB were prepared and scrutinized. Foraminifera are abundant throughout almost the whole of the sequence downward from the Upper Albian to probably the base of the Aptian or Neocomian below 1200 feet. Although microfaunal transition is gradual on the whole, observed subdivisions are in agreement with the boundaries set by Dr Brunnschweiler (of Santos Ltd) on the evidence of the megafossils. Planktonic foraminifera are present which may later be used for zonation when systematic comparisons have been made. Suggested subdivisions are: - Upper Albian 22 to 250 feet depth; Middle Albian 250 to 390 feet depth; Lower Albian 390 to 460 feet depth; Aptian 460 to 960 feet depth; ?Aptian - Neocomian 960 to 1262 feet depth.