Quaternary shelf structures SE of the South Island, imaged by high-resolution seismic profiling

Abstract

Along the south-eastern coast of New Zealand's South Island, observations and characterisations of shelf geology are complicated by numerous possibly active faults (e.g. the coast-parallel Akatore and coast-perpendicular Waihemo and Castle Hill faults), a Miocene-aged volcanic edifice (i.e. the Dunedin volcano) and incision from an extensive submarine canyon system. Conventional marine seismic data do not adequately image the basin beneath the shallow shelf here. However, six recently digitised high-frequency single-channel boomer seismic surveys have enabled the investigation of unique local geological structures and their relationships to the tectonic and sedimentary development of the region. These structures have significant control on active processes such as: (1) the localisation of sedimentation and submarine erosion; (2) the instigation of canyon channel incision; and (3) the distribution of fluid migration pathways on the shallow shelf. Future data acquisition will further constrain these processes and help to evaluate earthquake risk in this region.

Staying close to home: Marine habitat selection by foraging yellow-eyed penguins using spatial distribution models

“…Based on previous studies of the dive behaviour of yellow-eyed penguins, which demonstrated a consistent and specialised benthic foraging strategy (e.g., Mattern et al, 2007), we hypothesised that seafloor depth would have a major influence on yellow-eyed penguin marine space use. Although their eastward dispersal from the coast is bounded by the continental shelf and the shelf break, which occurs at approximate depths of 125-150 m (Carter et al, 1985;Sutton, 2003;Gorman et al, 2013;Stevens et al, 2019), bathymetry had low importance in most of the models. This is also contrary to previous baseline spatial modelling showed its significance to regional habitat suitability (Mattern, 2020).…”

“…Productive regions around current systems and frontal zones are important areas for many pelagic foraging seabird and penguin species (Hull et al, 1997;Boersma and Rebstock, 2009;Bost et al, 2009;Mattern et al, 2018b). In New Zealand, the northward flowing Southland Current is bounded by the Subtropical Front where Subtropical and Subantarctic waters meet (Gorman et al, 2013;Stevens et al, 2019;Stephenson et al, 2020). These currents and fronts extend to the seafloor during parts of the year due to the shallow (<150m) continental shelf around the South Island (Hopkins et al, 2010;Stevens et al, 2019), which could directly influence benthic foraging yellow-eyed penguins.…”

Marine heatwaves in shallow coastal ecosystems are coupled with the atmosphere: Insights from half a century of daily in situ temperature records

“…PML is a coastal station situated within the semi-enclosed Otago Harbor which has a mean depth of 4.5 m and is located on the southeast coastline of the South Island, New Zealand (Otago Regional Council and Dunedin City Council, 1991). PML is located 8 km from the entrance and 25 km inshore of the continental shelf break (Gorman et al, 2013). Circulation on the surrounding shelf is affected by an equatorward flowing WBC, known locally as the Southland Current (Sutton, 2003), which transports a combination of warmer subtropical shelf-water and cooler offshore subantarctic waters northeastward.…”