Revised stratigraphy for NTGS stratigraphic drillholes LA05DD01 and BR05DD01, western Amadeus Basin, Northern Territory

Abstract

A revised stratigraphy is presented in this Record for two Northern Territory Geological Survey stratigraphic drillholes,LA05DD01 and BR05DD01, located in the western Amadeus Basin in the Northern Territory. The revisions include new boundary picks and updates to stratigraphic nomenclature to align with amended stratigraphy of the Neoproterozoic succession in the Amadeus Basin. Revisions have also been made to the Palaeozoic stratigraphy based on the authors' field observations.

Drillhole LA05DD01 now includes the Stairway and Illara sandstones, Horn Valley Siltstone and Julie Formation, and revised thicknesses of the Pacoota, Petermann and Arumbera sandstones, and the Tempe Formation. The Stairway Sandstone and Horn Valley Siltstone were identified in previously unlogged drill cuttings. Intervals now recognised as the Illara Sandstone and probable Julie Formation were previously included as part of the Petermann Sandstone and Arumbera Sandstone respectively.

Drillhole BR05DD01 now includes an equivalent to the Pertatataka Formation and the Aralka Formation and an equivalent to its constituent Ringwood Member, as well as the Areyonga, Wallara, Johnnys Creek and Loves Creek formations. The succession originally identified as the Pertatataka Formation is now included in the Pertatataka Formation equivalent and the Aralka Formation. The interval originally identified as the Bitter Springs Formation now includes the Wallara Formation, and the Johnnys Creek and Loves Creek formations of the Bitter Springs Group.

Biostratigraphic evidence supports the stratigraphic revisions. In BR05DD01, stromatolite taxa typical of the Aralka, Wallara, and Loves Creek formations are present. In addition, rare palynomorphs are present but are currently of limited use for biostratigraphy.