Seismic geomorphology anomalies within a Pliocene deepwater channel complex in the Taranaki Basin, offshore New Zealand

Abstract

The Taranaki Basin, located offshore New Zealand, is a Cretaceous rift basin that has well defined yet complex Miocene deepwater sedimentary systems. We analyze a pronounced anomalous seismic response in a Late Miocene to Early Pliocene deepwater channel within the 2005 Hector 3D survey located in the southern Taranaki Basin. Several seismic attributes were calculated to interpret the extent of these anomalous features. Analogues within both the Iron River reservoir in Albania, Canada and the East Breaks Basin Four, offshore Gulf of Mexico suggest that these anomalous seismic features are most likely channel-body basal scours. Another interpretation suggests that these scours were formed and later filled by mass transport deposits (MTDs) with sediment ponding as suggested from some studies within the Molasse Basin in southern Germany. Alternatively, these scours could also be interpreted as pockmarks resulting from channel abandonment and fluid escape due to compaction. Others describe this process within submarine canyon systems, offshore Equatorial Guinea. However, there is compelling evidence to suggest that these features are most likely channel-body basal scours rather than being related to MTDs or pockmarks. Within all of the interpretations, there is evidence of differential compaction, which is further supported by the reflectors displaying a slight doming immediately above where the scours are located. Geological feature: Seismic geomorphology anomalies within a Pliocene deepwater channel complex in the Taranaki Basin, offshore New Zealand Seismic appearance: Asymmetric bowl-shaped geometry with high-amplitude reflectors that are incised into underlying sediment Alternative interpretations: Pockmarks resulting from channel abandonment and fluid escape due to compaction Features with similar appearance: Channel scours or pockmarks Formation: Mount Messenger Formation, Taranaki Basin Age: Late Miocene to Early Pliocene Location: Southern Taranaki Basin, New Zealand Available data: Hector 3D data set, Kiwa-1, and Hector-1 wells Analysis tools: 3D seismic data, well logs, and seismic attributes