An Overview of Taranaki Region Geology, New Zealand

Surveys conducted by the New Zealand Department of Scientific and Industrial Research in 1987 and1989 provided a high-quality data set which, when incorporated with older data, permits a detailed analysis of sedimentation, volcanism, and geologic evolution of the region. AbstractThe Challenger Basin is a newly discovered sedimentary basin beneath the western margin of the Challenger Plateau. Seismic and gravity data near the site of two Deep Sea Drilling Project holes (DSDP 284 and 593) show more than 2 km of sediment in the basin, probably formed in the early stages of Late Cretaceous rifting in the Tasman Sea. Thinning of about 5 km occurred before separation took place to the southwest and stranded this portion of the rift system. Regional subsidence ensued in the early Cenozoic, followed by a major phase of submarine basaltic volcanism about 38 Ma ago. This volcanism may have been related to the onset of spreading southwest of New Zealand. Subsequent sedimentation has been virtually entirely pelagic. The Oligocene unconformity commonly observed in the New Zealand region was not found in the wells, presumably because of either oceanographic changes induced by tectonic events, or redeposition from adjacent highs. Changes in ocean current patterns and biogenic productivity caused by paleogeographic changes such as the separation of Australia and Antarctica and uplift of the Southern Alps produced unconformities identifiable on seismic reflection data.

Section: 110mentioning

confidence: 87%

Section: 110mentioning

confidence: 99%

Structure and seismic stratigraphy of the western Challenger Plateau

Wood¹

1991

“…Regional paleogeographic reconstructions in the Taranaki Basin suggest that before coal measure deposition, the nearest coastline was at least 70 km to the northwest (King & Robinson 1988).…”

Section: Depositional Historymentioning

confidence: 99%

Brunner Coal Measures at Golden Bay, Nelson: An Eocene fluvial‐estuarine deposit

Leask¹

1993

Brunner Coal Measures (previously named Motupipi Coal Measures) of Bortonian to ?latest Runangan (Eocene) age, are preserved as three contrasting units in Golden Bay, Nelson, New Zealand.The lower Takaka valley contains up to 350 m of crossbedded medium to coarse grained sandstone (mainly of granitic provenance), interlaminated fine sandstone and siltstone, carbonaceous mudstone, and thin coal seams. These have been grouped into five facies associations: (1) a combination of the above lithologies with a dominance of mudstone and interlaminated sandstone-siltstone, interpreted as meandering river floodplain deposits; (2) mainly bioturbated muddy sandstone, interpreted as tidal flat deposits; (3) cross-bedded sandstone, interpreted as braided river or flood tidal delta deposits; (4) thickly bedded sandstone and conglomerate, interpreted as fluvial channel deposits; and (5) alternating sandstone, conglomerate, and mudstone with a distinctive metamorphic provenance, interpreted as aggradational sheetflood deposits.The Washbourn Limonite Member (new name) consists of blocky iron-ore which forms irregular masses up to 50 m thick on ridge crests west of Onekaka. It is interpreted as a bog iron deposit developed over a marble karst basement.The Quartz Wash Member (new name) consists of coarse quartzose conglomerate and sandstone with basal carbonaceous mudstone, as scattered remnants up to 40 m thick on the southeast flank of the Aorere and Parapara valleys. This is interpreted as a braided river deposit.In the Takaka valley, a NNW-oriented paleobasin is inferred from isopachs, north-trending paleocurrents, and the largely granitic source of the sediments. Sedimentation was controlled by subsidence on a northeast-striking normal fault, which is inferred to be the precursor of the reverse Pikikiruna Fault active during Miocene time. With increasing distance from the fault, and probably also towards the top of the formation, eustatic sea-level changes exerted greater influence. Most of the formation in the Takaka area reflects fluvial deposition succeeded by estuarine deposition. At the A paraconformity between the Brunner Coal Measures and the overlying Takaka Limestone indicates nondeposition during the entire Whaingaroan Stage. The Golden Bay area appears to have been a stable platform during Oligocene time, in contrast to rapidly subsiding areas to the south and east.

“…The geologic history of the Taranaki Basin and its structural, stratigraphic, and paleogeographic development have been discussed in detail by Pilaar & Wakefield (1978), Knox (1982), Palmer (1985), King & Robinson (1988), King (1990), and Thrasher (1990). The structural setting and depositional history of the Kupe Anticline, located in the southern, offshore part of the Manaia (= Manganui) Graben (Fig.…”

Section: Introductionmentioning

confidence: 99%

Structure and evolution of the Kapuni Anticline, Taranaki Basin, New Zealand: Evidence from the Kapuni 3D seismic survey

Voggenreiter¹

1993

Styles of deformation and timing of tectonic events documented by the Kapuni 3D seismic survey provide important constraints on models for the structural evolution of the Taranaki Basin. Two-way travel time and seismic attribute maps of this survey reveal a large degree of structural complexity and a pronounced vertical change in structural style. Taranaki Basin stratigraphy has, to a large extent, been controlled by distinct tectonic events resulting in discrete seismostratigraphic units being recognised in the Kapuni area.Seismic units 3 and 2 represent coals, shales, siltstones, and sandstones of the Eocene Kapuni Group and bathyal mudstones and turbidite sandstones of the Oligocene-middle Miocene Ngatoro and Wai-iti Groups, respectively. Their bulk strain can be described as triaxial oblate flattening in response to east-west-oriented compression during the late Eocene-late Miocene.The overlying seismic unit 1 represents sandstones, siltstones, and mudstones of the late Miocene-Pleistocene Rotokare Group. Its structure is dominated by a dense array of left-stepping oblique-slip normal faults that originated from Pliocene-Pleistocene oblique extension/dextral transtension and are possibly detached from seismic units 2 and 3 by an inclined detachment surface that cuts stratigraphically deeper from northeast to southwest.