ABSTRACT An extensive kame-terrace sequence in the middle Rangitata Valley reveals ice-volume fluctuations spanning the last (Otiran) glaciation. Stratigraphic and sedimentologic characteristics document lateral ice-marginal processes and provide context for luminescence dating. The sequence provides novel and complementary data on glacier ice thickness, which fluctuated substantially throughout the Otiran glaciation. Thick ice constructed one of the highest kame terraces (540 m above the valley floor) ca. 68 ka and thinned nearly 500 m to the valley floor by ca. 53 ka. Following an episode of ice thickening to an unknown elevation, ice again thinned to the valley floor by ca. 44 ka. Ice thickened to its greatest late marine oxygen isotope stage (MIS) 3 extent of 480 m by ca. 37 ka, and thinned to 230 m by ca. 31 ka. The final ice expansion, to 260 m, occurred by ca. 25.5 ka, and the ice fluctuated and thinned to 240 m at ca. 22–20 ka and to 170 m at ca. 21–17 ka. Published cosmogenic radionuclide (CRN) ages indicate surface stabilization near the valley floor (55 m) by ca. 18 ka. This ice-thickness chronology provides an independently derived ice-volume record that is consistent with local and regional glacial chronologies. The site, lying between the Mackenzie Basin and the northern Canterbury Plains drainages, displays a chronology with advances correlative in part with each of those regions. Maximum ice extent occurred 70–65 ka in the Rangitata Valley and the Mackenzie Basin, while the subsequent ice expansion ca. 37 ka is similar in timing to chronologies in both the Rakaia Valley to the north and the Mackenzie Basin to the south.

Abstract Lacustrine-tsunami risk from landslides can be significant yet for most locations globally the hazard remains unquantified. Lake Tekapo, in the tectonically active mountain belt of New Zealand's South Island, has been chosen to develop surveying and modelling techniques to assess the hazard from landslide tsunamis. Lake Tekapo is ideal for this study due to the high sedimentation rates, steep surrounds and the proximity to active faulting that indicate a high landslide potential. The shoreline tourist settlement and hydropower infrastructure mean the impact of any tsunami could be significant. In 2016 a survey was carried out to collect high-resolution (1 m grid) EM2040 multibeam bathymetry, high-resolution seismic reflection data (Boomer and chirp) and 6 m long sediment cores. These data reveal a diverse range of sedimentary processes in response to high sediment input and numerous landslides with varied styles of emplacement. For example, a one-off landslide initiated 40 m above the shoreline with debris deposits that have runout onto the lake floor to 100 m water depth contrasts with the Cass River delta on the western shore that has failed multiple times during the lake-basin infilling history. Landslide-generated tsunami scenarios are used to determine the relative hazard at different regions of the lake to guide development of a probabilistic tsunami model.

ABSTRACT We combined sand petrofacies with lithofacies to characterize sedimentation within unconformity-bounded sequences at Integrated Ocean Drilling Program (IODP) Expedition 317 sites drilled across the Canterbury shelf to the slope, located off the east coast of the South Island, New Zealand. Differentiation of the relative influence of along- and across-shelf sand supply in this system is made possible by the unique aspects of the onshore geology. Northern rivers draining mainly Torlesse composite terrane lithologies are dominated by lower-grade metamorphic lithic fragments, whereas central rivers, draining the Torlesse to schist (semi-schist) transition (Haast/Otago Schist), contain more higher-grade metamorphic lithic fragments, and the southern rivers contain sand that is quartzofeldspathic and mica rich, having been derived predominantly from coarse schist. Differences are documented in onshore river sand that allow for the provenance classification of 38 offshore sand samples from IODP Expedition 317 cores into four provenance groups based on their likely bedrock sources: (1) Torlesse, (2) Torlesse-schist transition, (3) schist, or (4) mixed. The distribution of sand composition in the 0–0.62 Ma sections of the shelf and slope sites indicates a dynamic system where shore-parallel and shore-perpendicular processes alternated on the shelf, and shore-perpendicular processes dominated at the slope site. When sand compositions are placed in a sequence-stratigraphic context, they indicate an evolving paleogeography through time. Significant sand provenance shifts are linked to falling sea level, with Torlesse-schist transition compositions characteristic of regressive systems tracts. Torlesse compositions are supplied to the sites during falling sea level and sea-level lowstands, when fluvial and coastal geomorphology promotes influx from the north. Mixed compositions characteristic of transgressive systems tracts are likely products of littoral- and shelf-current mixing and potential influx of schist detritus from the south.