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 which has well defined yet complex Miocene deepwater sedimentary systems. This paper analyzes 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. Modern analogues from Snedden (2013) 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 resulting from turbulent flows that eroded the base of the channel. One alternative interpretation is that this is not a channel but rather a scar left behind from a small-scale mass trasnport deposit (MTD) where sediment later ponded and filled in the rugose topography left by the MTD. This process has also been observed by Kremer et al. (2018) within the Molasse Basin in southern Germany. However, these scours could also be interpreted as pockmarks resulting from channel abandonment and fluid escape due to compaction. Jobe et al. (2011) described this process within submarine canyon systems, offshore Equatorial Guinea. Within all possible interpretations, there is evidence of differential compaction as sediment fills the accommodation space and creates a concave down expression immediately above the interpreted scours.

Evolution of a Late Miocene Deep-Water Depositional System in the Southern Taranaki Basin, New Zealand

“…Sediment waves are significantly less common as inter-channel regions show high ERS values. In the western edge, a discontinuous scalloped feature is present and interpreted to be an erosional channel feature [33]. When viewed in vertical section, the scalloped feature exhibits an undulating reflection pattern, along with onlapping reflectors.…”