Mass transport deposit or complex channel system? A case study of the 3D Nimitz seismic survey, Taranaki Basin, New Zealand

Abstract

The Taranaki Basin is well known for studies examining the seismic stratigraphy, depositional and erosional features, and tectonic frameworks linked to the New Zealand (NZ) continent. We have examined a “funny looking thing” (FLT) that we associate to be consistent with that of a braided channelized system. We observe this feature within the 3D Nimitz survey, located in the northern Taranaki Basin, off the western continental coast of North Island, NZ. The FLT occurs within Quaternary deposits of the Whenuakura Formation, which are interpreted to reflect shelfal topset sediments. It is underlain by the Giant Foresets Formation of Pliocene to Pleistocene age, which are described as large-scale progradational and aggradational continental successions that migrated west to northwest in a basinward direction. It comprises a shelf-to-slope succession of claystone to siltstone with argillaceous sandstone intervals defining an overall coarsening-upward succession. The FLT within the Whenuakura Formation is characterized by chaotic facies in cross section, which shares characteristics with potential mass-wasting events. However, further analysis using seismic attributes improved the spatial and stratigraphic architecture of the FLT, which favored a complex channelized system interpretation over a mass transport deposit complex. Geological feature: Braided channel system Seismic appearance: Splayed structurally controlled feature, with internally abundant, continuously lineated patterns on horizon slice Alternative interpretations: Erosional scour Features with similar appearance: Mass transport deposit Formation: Whenuakura Age: Pleistocene–Recent Location: Offshore Taranaki Basin, North Island, New Zealand Seismic data: Nimitz 3D seismic survey; obtained by Origin Energy Ltd. Analysis tools: Variance and curvature attributes