Sequence stratigraphy of Jurassic strata in the lower Surat Basin succession, Queensland

Abstract

The principles of non-marine sequence stratigraphy were applied to the Jurassic strata in the lower part of the Surat Basin, in order to better determine the depositional history of the basin and highlight potential reservoir and source rocks. The lithostratigraphic units in the Early-early Late Jurassic interval can be divided into three supersequences: J, K and L. Each supersequence consists of a basal sandstone-dominated unit generally exhibiting an unconformable, diachronous relationship with the underlying unit. This is the lowstand system tract, which potentially offers an extensive well-sorted sandstone reservoir with interconnected porosity. These amalgamated sandstone sheets are overlain by a fining-upward interval consisting of predominantly muddier carbonaceous lithologies including coal and lacustrine deposits. This upper sequence embraces the transgressive system tract and possibly the highstand system tract. Isolated meander-belt sandstone bodies may be preserved within these widespread finer deposits and provide reservoirs juxtaposed to source rocks. Vitrinite reflectance values indicate that these Jurassic units are immature to marginally mature and, hence, may only have limited hydrocarbon-generating prospects.