TECHNICAL PAPER Seismic geomorphology of Cenozoic slope deposits and deltaic clinoforms in the Great South Basin (GSB) offshore New Zealand Kamaldeen Olakunle Omosanya 1,2 & Dicky Harishidayat 3 Received: 30 September 2018 /Accepted: 18 December 2018 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract In this study, the Cenozoic sedimentation and infill history of the Great South Basin (GSB), New Zealand, is analysed from a seismic geomorphologic perspective. A suite of sediment types, including mass-transport deposits (MTDs), deltaic clinoforms, contourite-drifts and turbidites, are documented based on high-quality 3-D seismic reflection data and multiple regional 2-D seismic profiles. The MTDs include older, highly compacted and deeper Palaeocene deposits that are markers of late Neogene tectonic reactivation, while the younger MTDs were translated over slopes eroded by drifts. Possible trigger mechanisms for mass wasting may include oversteepened margins, prolonged fluid dissipation and weak geological layers. Sedimentation from the Eocene to Recent was contemporaneous with regional plate reorganisation and syn-orogenic activity. As a result, three distinct Eocene deltaic systems with variably oriented channels and depositional elements provide evidence for changing plate kinemat- ics during the Eocene. The Eocene deltaic systems are river-dominated and were deposited during relative rise in sea level under variable flow regimes. The passage of the Antarctic Circumpolar Current in the GSB from the Late Eocene to Oligocene led to the deposition of three elongate, detached contourite drifts. In a final phase of basin infill, hemipelagic sedimentation and deposition by turbidity currents dominated late Neogene sedimentation in the GSB. The analyses presented here demonstrate the importance of geomorphology in understanding the sediment infill history, their interactions and temporal organisation, which have wider implications for numerous geoscience disciplines. Introduction Seismic geomorphology in the last few decades has revolutionised our understanding of sedimentary processes and has enhanced several related disciplines, such as seismic stratig- raphy, paleoenvironment, paleoclimatology and hydrocarbon ex- ploration (Zeng et al. 1998; Davies et al. 2004; Posamentier 2005; Posamentier et al. 2007; Alves et al. 2014). Perhaps the most significant contribution of seismic geomorphology to date is the illumination of the interconnection between sedimentary processes and elements operative in continental to transitional and deep-water environments (Alfaro and Holz 2014; Bourget et al. 2014). The co-existence of several sedimentary deposition- al elements during the geodynamic evolution of many basins has been studied in detail using a seismic geomorphologic approach (e.g. Scarselli et al. 2016; Liu et al. 2016). Seismic geomorphology, in simple terms, is the application of analytical techniques to the study of landforms and ancient geomorphological features imaged by 3-D seismic data (Posamentier et al. 2007). At the heart of such an application lies high-quality three-dimensional (3-D) seismic reflection data, which have led to not only a compendium of sediment types to be identified but also their morphological divisions to be bookmarked. In addition, 2-D seismic data is also benefi- cial to see geomorphological features from a regional point of view. Mass-transport deposits (Ward et al. 2018; Dalla Valle et al. 2013), contourites (Gong et al. 2017), turbidites and carbonates (Dong et al. 2015; Rankey 2017), channels and canyons (Harishidayat et al. 2015; Li et al. 2013), gullies (Harishidayat et al. 2018; Lonergan et al. 2013) and other * Kamaldeen Olakunle Omosanya kamaldeen.o.omosanya@ntnu.no 1 The Research Centre for Arctic Petroleum Exploration, Norwegian University of Science and Technology, Trondheim, Norway 2 Oasis Geoconsulting Limited, Abeokuta, Ogun State, Nigeria 3 Department of Geoscience and Petroleum, Norwegian University of Science and Technology, Trondheim, Norway Geo-Marine Letters https://doi.org/10.1007/s00367-018-00558-8