摘要:

The 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.

ISSN:0028-8306    

DOI:10.1080/00288306.1991.9514433

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Upper Ordovician Arthur Marble and Oligocene Takaka Limestone contain extensive phreatic cave systems beneath the Takaka valley and Golden Bay. Half of all water flows in the Takaka valley pass through subterranean drainage conduits in carbonate rock. New Zealand's largest freshwater springs, the Waikoropupu Springs, are one surface expression of these karst systems. Other characteristics are dolines and submarine springs.

ISSN:0028-8306    

DOI:10.1080/00288306.1991.9514434

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Decapod crustaceans have been collected from concretions at four localities in the middle Eocene (Bortonian) Tapui Glauconitic Sandstone in North Otago, South Island, New Zealand. Of the five species recognised,Callianassasp.,Ctenochelessp.,Laeviranina perarmataGlaessner,Lyreidus waitakiensisGlaessner, andRhachiosoma granuliferum(Glaessner), onlyL. waitakiensis, the oldest known representative of that genus, has been reported from the unit previously. This decapod fauna is similar to that from the Bortonian rocks in Snowdrift Quarry, South Otago.

ISSN:0028-8306    

DOI:10.1080/00288306.1991.9514435

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Diverse, mappable, and variably mylonitised high‐grade gneisses and granitoids, and lamprophyre, trachyte, and basalt dikes comprise the Fraser Complex, which is a new name proposed to replace the existing Fraser Formation. Sillimanite‐bearing pelitic gneisses have an upper amphibolite facies metapelitic mineralogy, indicating temperatures >600°C. Quartzofeldspathic gneisses, lacking sillimanite, are migmatitic, and hornblende gneisses have a diverse epidote‐amphibolite mineralogy. The high‐grade gneisses form a metamorphic suite within the Fraser Complex. Granite, granodiorite, and tonalite are intrusive into the high‐grade gneiss suite, and may have been derived from partial melts of the high‐grade gneisses. Swarms of camptonite lamprophyre, trachyte, and basalt dikes intrude the high‐grade gneisses and the granitoids. Mylonite zones now envelop the gneisses, granitoids, and dikes, and mylonitic deformation occurred at mid‐greenschist facies conditions and resulted in some retrogressive alteration of the protoliths. The Fraser Complex forms part of a regional gneissic and granitic basement to the Greenland Group in Westland. The juxtapostion of the Fraser Complex, with Mesozoic high‐grade metamorphism, against the low‐grade Ordovician Greenland Group sediments can be explained by vertical movement along the Fraser Fault rather than by invoking large‐scale normal detachment faulting, as has been suggested in North Westland.

ISSN:0028-8306    

DOI:10.1080/00288306.1991.9514436

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Metamorphosed andesite flows and dacite/rhyolite‐dominated, lithic‐rich and crystal‐rich volcaniclastics of unknown thickness crop out north and east of Little Hellfire Beach on western Stewart Island, New Zealand. Andesite geochemistry is of calc‐alkaline affinity, and an active continental margin eruptive setting is inferred. Petrographic and geochemical similarities to adjacent Paterson Group metavolcanics suggest that the volcanogenic suite should be incorporated in the Paterson Group.

ISSN:0028-8306    

DOI:10.1080/00288306.1991.9514437

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Broad, sequential changes in sand mineralogy through the late Neogene (Pliocene‐Quaternary) formations comprising the coastal deposits of the Kaihu Group in South Auckland reveal a series of provenance transitions for the group. An initial late Pliocene, mainly silicic volcanic provenance, was superseded in the early Pleistocene by a predominantly Mesozoic basement sedimentary provenance. Subsequently, during the early late Pleistocene, a mixed andesitic volcanic and basement sedimentary provenance developed. In the later Quaternary the andesitic volcanic provenance became predominant. The observed provenance transitions are consistent with major tectono‐volcanic events associated with the evolution of the late Cenozoic volcanic arc‐backarc system in western North Island. Transitions include the initial supply of silicic volcanic material from inferred late phases of the Coromandel Volcanic Zone; the initiation of the Taupo Volcanic Zone and related development of horst and graben topography in the South Auckland region, with accelerated erosion and supply of basement‐derived elastics but diversion of Taupo‐derived silicic detritus; and the supply of behind‐arc andesitic volcanic detritus from Egmont Volcanics.

ISSN:0028-8306    

DOI:10.1080/00288306.1991.9514438

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Deformation of the Late Jurassic ‐Early Cretaceous Torlesse Complex in the southeastern Tararua Range is characterised by development of melange, several generations of folds, faults at both a low angle and high angle to bedding, shear foliation, and cleavage. The region has undergone the following deformational sequence: (1) Development of at least two fold generations; (2) Fragmentation and disruption by faulting. Faults at a low angle and high angle to bedding have disrupted the sequence, in places producing chaotically disrupted units (melange). The Tauherinikau Melange represents a probable along‐strike northern continuation of the Esk Head Melange from the South Island; (3) Post‐melange folding; (4) Holocene faulting. Overall, the deformation is consistent with accretion at a convergent plate margin, followed by the present strike‐slip dominant regime.

ISSN:0028-8306    

DOI:10.1080/00288306.1991.9514439

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

At the northern end of the Remarkables mountain range, Central Otago, New Zealand, psammitic schists of the Caples terrane pass downwards through a 300 m thick transitional zone into pelitic schists of the Aspiring terrane. Second generation mesoscopic structures vary in orientation and morphology with proximity to this shallow, southerly dipping terrane boundary: F2folds tighten, S2cleavage becomes more penetrative, and L2fold axis and intersection lineations show progressive change from southeasterly trending to northeasterly trending. L2stretching lineations have a constant northeast trend. Rotation of second generation structures occurred by progressive noncoaxial deformation, with a northeasterly shear direction. Analysis of L2lineations indicates a major strain gradient over the Remarkables, with maximum shear strains (> 100) immediately above the terrane boundary. The Caples terrane was thrust upon Aspiring terrane during ductile greenschist facies conditions of metamorphism by translation of a major F2nappe fold, the Remarkables Nappe, in a northeasterly direction. The transitional terrane boundary zone was the zone of high strain developed at the base of the Remarkables Nappe. Integration of calculated shear strains suggests a minimum horizontal displacement of 2 km and a maximum displacement in the order of 150 km.

ISSN:0028-8306    

DOI:10.1080/00288306.1991.9514440

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Codfish Granite, a variably altered biotite granite crosscut by volumetrically minor dike(s) of biotite‐garnet‐muscovite‐bearing granite makes up 70% of the bedrock of Codfish Island. This pluton is part of the Rakeahua Batholith which forms a large part of nearby Stewart Island. Paterson Group metavolcanogenic sediments form a 500 m wide strip along the east coast of Codfish Island. Paterson Group rocks are characterised by heterogeneous foliation development and metamorphism to the upper greenschist or lower amphibolite facies. Rakeahua Batholith and Paterson Group rocks are separated by a kilometre‐wide cataclasite zone.

ISSN:0028-8306    

DOI:10.1080/00288306.1991.9514441

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A glauconitic, sand‐filled, vertical clastic dike (>10 m high, base unexposed) and two associated sand‐filled sills in late Miocene mudstone (c. 6 Ma) near Annedale, Northern Wairarapa, New Zealand, pinches out upwards and thickens downwards. Relationships suggest that the mudstone remained solid while the glauconitic sand was fluidised during a penecontemporaneous earthquake event and was injected from below. After injection the margins of the clastic dike and sills were cemented by calcium carbonate. The cemented margins of the dike record at least two subsequent periods of shearing which are shown by subhorizontal and vertical slickensides on the dike walls.

ISSN:0028-8306    

DOI:10.1080/00288306.1991.9514442

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor