Palynology of drillhole Shenandoah 1a (Warramban 1:100 000 sheet; Tanumbirini 1:250 000 sheet) Beetaloo Basin, Northern Territory, Australia

Abstract

Four drill cuttings samples from drillhole Shenandoah 1A (drilled by Sweetpea in 2007 to a depth of 1555 m and deepened by Falcon Australia in 2009 to a total depth of 2714 m, and held in the NTGS core library in Darwin, Northern Territory) were collected as part of a reassessment of the hydrocarbon prospectivity of the Beetaloo Basin. Palynological samples were prepared using a modified technique. Initial examination of the prepared slides indicated abundant organic material in all four samples, but no identifiable palynomorphs in the upper two samples from the Kyalla Formation, and only sparse, poorly preserved palynomorphs in the lower two samples from the Lower Velkerri Formation. Despite the poor preservation, some of these taxa appear complex and similar to ones recorded previously from the upper Velkerri Formation in McManus 1. They appear to belong to new taxa that cannot readily be assigned to existing species or precisely dated. Because of the difficulties presented by these previously undescribed taxa, slides were set aside until time was available for a more detailed examination. Further work has now been carried out, but it still has not been possible to do more than document some of the more common species. A more extensive study is needed to define the taxa present and document their stratigraphic distribution. The general aspect of the assemblage indicates a Mesoproterozoic age. More detailed analyses should provide a biostratigraphic scheme covering much of the Mesoproterozoic Beetaloo Basin succession. Such a scheme would have considerable potential for correlation of hydrocarbon exploration drillholes in the Beetaloo Basin.