Tumblagooda Sandstone

At Red Bluff, the Tumblagooda Sandstone in this section is different to the Tumblagooda Sandstone found at Natures Window, and thus, the deposition environment is different. Red Bluff was most likely deposited in a fluvial-intertidal environment (shallow waters) as indicated by the high abundance of skolithos trace fossils, skolithos generally reside in shallow waters (refer to notebook, page 58). The higher abundance of trace fossils in the upper section of the sandstone than the lower section suggests a change in environment. The lower sections of the Tumblagooda Sandstone represent a high energy braided fluvial environment. Evidence to support this include trough cross-bedding, which requires a flow medium, generally medium-grained and large
Literature suggests it could be a potential reservoir (Lasky & Mory 1999). The Tumblagooda has poor porosity at shallower depths, because of infilling of pore space, at greater depths the Tumblagooda has retained excellent reservoir characteristics. The Tumblagooda is around 1500m thick, has a porosity around 23% and permeability between 1280mD. The potential seal could be the Dirk Hartog Group lying underneath the Tumblagooda Sandstone, however, research suggests it is unlikely (Lasky & Mory 1999). The Gneudna Formation could act as a potential top seal for this
As well as this a map completed during this section of the trip will be included for visualisation of the geological history. The Gneudna Formation and associated unite are found in the Merlinleigh Sub- basin of the Southern Carnarvon Bain. The formations range from Mid to Late Devonian in age and consists of limestones, siltstone, sandstone and horizons of dolomite. The Gnuedna Formation can be divided into 3 facies types, based on the varying type of fossils found in each section, this will be discussed