Stratigraphic subdivision of the Velkerri Formation, Roper Group, McArthur Basin, Northern Territory

Abstract

The Mesoproterozoic Velkerri Formation (Roper Group, McArthur Basin) is formally subdivided into three new members. They are, in ascending stratigraphic order, the Kalala, Amungee and Wyworrie members, which correspond respectively to the lower, middle and upper Velkerri Formation of previous usage. Subdivision of the Velkerri Formation into recognisable members is complicated by poor exposures and subtle lithological differences; the three members are therefore most readily distinguished in the subsurface by a combination of methods, including lithology, organic geochemistry, chemostratigraphy, wireline (gamma ray and resistivity) logs, hyperspectral data (HyLogger), and palynology. These methods collectively provide robust, high-resolution definitions that are consistent throughout the known subsurface distribution of the formation.