An integrated biostratigraphy and seismic stratigraphy for the late Neogene continental margin succession in northern Taranaki Basin, New Zealand

Our aim has been to develop an integrated biostratigraphy and seismic stratigraphy for the Pliocene and Pleistocene formations (Ariki, Mangaa, Giant Foresets) in northern Taranaki Basin to better understand the evolution of the modern continental margin offshore central-western North Island, New Zealand. Detailed mapping of seismic reflectors in part of the basin, when compared with correlations of late Neogene stage boundaries between 11 well sections, has highlighted crossover between the datasets. To help resolve this issue, the biostratigraphy of the Pliocene-Pleistocene parts of each of four well sections (Arawa-1, Ariki-1, Kora-1, and Wainui-1) has been re-examined using a dense suite of samples. In addition, the biostratigraphy of seven other well sections (Awatea-1, Kahawai-1, Mangaa-1, Taimana-1, Tangaroa-1, Te Kumi-1, and Turi-1) has been re-evaluated. The crossover is partly attributed to a combination of sampling resolution inherent in exploration well sections, the mixed nature of cuttings samples, and the general scarcity of age-diagnostic planktic foraminifera in the late Neogene formations. The achievement of seismic closure suggests that error in the mapping of the seismic reflectors is not a significant source of the uncertainty (crossover). We have developed a workable time-stratigraphic framework by qualitatively weighting the biostratigraphic data in each of the well sections, thereby identifying the parts of particular well sections with the highest resolution microfossil data and the optimal stratigraphic position of stage boundaries with respect to the mapped seismic horizons/seismic units. Hence, it is possible to assign the known numerical ages for these stage boundaries to reflection horizons/seismic units mapped within the basin. We have applied this information to produce a series of isopach maps for successive stage boundaries that help show the sedimentary evolution of the continental margin succession west of central North Island

Geomorphological and seismostratigraphic evidence for multidirectional polyphase glaciation of the northern Celtic Sea

High‐resolution seismic and bathymetric data offshore southeast Ireland and LIDaR data in CountyWaterford are presented that partially overlap previous studies. The observed Quaternary stratigraphic successionoffshore southeast Ireland (between Dungarvan and Kilmore Quay) records a sequence of depositional and erosionalevents that supports regional glacial models derived from nearby coastal sediment stratigraphies and landforms. Aregionally widespread, acoustically massive facies interpreted as the‘Irish Sea Till’infills an uneven, channelizedbedrock surface overlying irregular mounds and deposits in bedrock lows that are probably earlier Pleistocenediamicts. The till is truncated and overlain by a thin, stratified facies, suggesting the development of a regionalpalaeolake following ice recession of the Irish Sea Ice Stream. A north–south oriented seabed ridge to the north is interpreted as an esker, representing southward flowing subglacial drainage associated with a restricted ice sheet advance of the Irish Ice Sheet onto the Celtic Sea shelf. Onshore topographic data reveal streamlined bedforms that corroborate a southerly advance of ice onto the shelf across County Waterford. The combined evidence supports previous palaeo glaciological models. Significantly, for the first time, this study defines a southern limit for a Late Midlandian Irish Ice Sheet advance onto the Celtic Sea shelf