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. This particular study examines a “funny looking thing” (FLT) which we associate to be consistent with that of a braided channelized system. We observe this feature within the 3D Nimitz Survey (See Figure 1), located in the Northern Taranaki Basin (NTB) 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 (O’Leary et al., 2010). It is underlain by the Giant Foresets Formation (GFF) of Pliocene to Pleistocene age, which are described as large-scale progradational and aggradational continental successions that migrated west to northwest in basinward direction (Anell and Midtkandal, 2017; Clairmont et al., 2020; Hansen and Kamp, 2002; Shumaker et al., 2017) (Figure 2). It comprises a shelf-to-slope succession of claystone to siltstone with argillaceous sandstone intervals defining an overall coarsening upward succession (O’Leary et al., 2010). The FLT within the Whenuakura Formation is characterized by chaotic facies in cross section, which shares characteristics with potential mass wasting events (Figure 3a). 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.