摘要:

We have studied the reorganisation of drainage patterns in response to the tectonically driven emergence of a small ridge (South Rough Ridge) along the flank of a larger ridge (Rough Ridge) as described by previous workers in the Central Otago region of New Zealand.

ISSN:0028-8306    

DOI:10.1080/00288306.1999.9514827

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Fifty‐eight distinct ridges are preserved on the Holocene progradation plain in Okains Bay, Banks Peninsula, Canterbury. Of these, 48 represent beach berm and foredune complexes and the remaining 10 are transverse dune ridges. Periods of rapid coastal progradation are marked by multiple beach berm preservation, whereas intervening periods of lower sediment accumulation result in a stable coastline and transverse dune formation.

ISSN:0028-8306    

DOI:10.1080/00288306.1999.9514828

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Bottom‐hole temperature data collected from 24 petroleum exploration wells have been used to calculate conductive heat flow through the West Coast, South Island. Steady‐state modelling suggests a mean heat flow of 76 ± 15 mW/m2(20%, 1 SD), a figure higher than those obtained previously by Funnell et al. and Funnell & Allis for the southern Taranaki and southwest South Island regions (65— 70 mW/m2and 60 ± 4 mW/m2, respectively). Pliocene‐Quaternary erosion over much of the West Coast has probably caused an increase in measured surface heat flow of 25–30 mW/m2.

ISSN:0028-8306    

DOI:10.1080/00288306.1999.9514829

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

K‐Ar and Rb‐Sr ages of Marlborough Schist and Pelorus Group metasediments show coherent regional metamorphic/cooling age patterns, irrespective of their terrane protolith, in which ages are primarily inversely related to metamorphic grade and, more locally, with distance from the Picton Fault Zone. The oldest ages, from the lowest grade (prehnite‐pumpellyite facies, textural grade 1'IIA) Pelorus Group are mainly in the range 175–200 Ma, indicating regional metamorphism occurred at least in earliest Jurassic or latest Triassic times. Progressive cooling of Marlborough Schist resulted in a spectrum of cooling ages, mainly 110–180 Ma, which reflects slow regional uplift during the Jurassic and Early Cretaceous. Some disruption of this pattern occurred at the Picton Fault Zone where post‐Early Cretaceous movement has juxtaposed high and low structural levels. Initial87Sr/86Sr isotopic ratios (i) at the time of metamorphism (t), derived from Rb‐Sr whole‐rock isochron data, further characterise terrane protoliths identified by field, petrographic, and geochemical evidence. The (t)‐(i) data largely confirm these prior regionalgroupingsbut do not entirely confirm the terrane identifications. A less radiogenic group, (i) < 0.7055, termed Western Marlborough Schist, comprises the Pelorus Group, and schist equivalents, west of a postulated suture/terrane boundary in the schists, and is correlated with Caples Terrane rocks in Otago. “Torlesse"‐type schists are more radiogenic, (i) > 0.7062, but do not match Torlesse (Rakaia) Terrane (t)‐(i) data from Wellington or Otago. They correlate better with Kaimanawa Schist of the central North Island. An intermediate group, (i) = 0.7042–0.7062, is separate from the “Torlesse” group, but partly overlaps the Caples Terrane group. This correlates well with Waipapa Terrane of the central North Island and Haast Schist of uncertain terrane affinity in Otago. The combined radiogenic and intermediate groups, termed Eastern Marlborough Schist, define alineagewhich thus includes Kaimanawa Schist, Pahau Subterrane rocks, and both Waipapa‐type and Torlesse‐type schists in Marlborough. It is possible that the Moonlight Fault Zone of Otago has a continuation in Eastern Marlborough Schist as the Picton Fault Zone.

ISSN:0028-8306    

DOI:10.1080/00288306.1999.9514830

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Late Cretaceous carbonaceous rocks have been dredged from two sites on the Norfolk Ridge system northwest of New Zealand. On the West Norfolk Ridge, Raukumara Series (late Cenomanian to late Coniacian, 95–86.5 Ma) coal measure sandstones and mudstones contain dispersed, immature #OPRO0.37%), terrestrial (type III) organic matter and have poor petroleum generative potential (TOC 2.2–2.8%, S2 1.2–1.6 mg HC/g rock). However, thein situcoal measure sequence may contain abundant coal seams with excellent generative potential, and thus constitutes a potential source rock formation for the adjacent New Caledonia and Reinga Basins that have thick sections of sediments. The coal measures probably formed in a coastal plain environment subjected to episodic marine incursions. At the second dredge site, near the junction of the Norfolk and Reinga Ridges, a late Piripauan to early Haumurian (Santonian‐Campanian, 85–75 Ma) marine shale contains sparse, mixed marine and terrestrial (type II/III) organic matter. Hopane and sterane parameters imply a maturity equivalent to at least 0.6% Ro, but the analysed shale has poor generative potential (TOC 0.9%, S2 1.4 mg HC/g rock). Biomarkers suggest that the terrestrial contribution to bitumen in the shale is minor compared with the marine, but kinetic parameters are more consistent with a type III kerogen than the type II/III kerogen identified. A likely explanation of the discrepancy is that early oil generation has occurred in the sample, possibly associated with sulphur incorporated into the kerogen during diagenesis. In addition, a high saturated: aromatic hydrocarbon ratio suggests that mature bitumen may have migrated into the shale. Given greater TOC contents and sufficient volume, the shale could be a potential source rock within the Reinga Basin and Norfolk and Three Kings Ridges. A simple thermal model at a pseudo‐well site in the Reinga Basin shows that at depths >4.5 km below seabed, potential source rocks with the kerogen kinetic parameters of the dredged rocks should be generating hydrocarbons and approaching the threshold of oil expulsion. The model does not explain the presence of migrated hydrocarbons in the shale sample unless similar source rocks are more deeply buried nearby or thermal conditions were greater than those modelled. In comparison, a predominantly marine unit like the Waipawa Shale would be in the oil window at 3.0 km. Maturity levels may well have been enhanced by increased heat flow associated with the latest Oligocene to early Miocene rifting and opening of the adjacent Norfolk Basin. If equivalent rocks with sufficient organic richness exist in the Northland Basin (part of the Reinga Basin adjacent to New Zealand), where sediment thickness commonly exceeds 5 km and locally exceeds 7 km, they will have generated and expelled hydrocarbons.

ISSN:0028-8306    

DOI:10.1080/00288306.1999.9514831

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The presence ofGlyphea christeyin. sp. in the Waihao Greensand, exposed along the Opihi River, South Canterbury, marks the geologically youngest occurrence of the genus in New Zealand and, perhaps, in the world. The only other Eocene report ofGlypheavon Meyer is from Antarctica, also a high latitude occurrence. This discovery reinforces our contention that the sole extant member of the family,Neoglyphea inopinataForest & de Saint Laurent, 1975, was derived from a speciesof Glypheain the South Pacific region.

ISSN:0028-8306    

DOI:10.1080/00288306.1999.9514832

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Conodonts of Early Permian age are described for the first time from New Zealand. Conodont elements have been obtained from siliceous pelagites in the Torlesse Terrane near Meyers Pass, South Canterbury, and from limestone blocks in the Caples Terrane, near Nokomai, northern Southland. Conodonts from both localities includeMesogondolellaPa elements,Xaniognathus,and associated ramiform elements, and have close affinities with cool‐water pelagic faunas from the Northern Hemisphere. These conodonts provide an excellent basis for stratigraphic correlation within and between New Zealand late Paleozoic‐Mesozoic terranes.

ISSN:0028-8306    

DOI:10.1080/00288306.1999.9514833

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The 160 m thick Castlecliff coast section was deposited during the middle Pleistocene (c. 1.07–0.35 Ma) and comprises 10 disconformity‐bound cyclothems or sequences. A typical sequence has three parts: (1) a basal suite of shore face and inner shelf sediments with intertidal and shallow subtidal molluscan faunas, and cross‐bedded, pebbly shell gravels (type A shellbeds); (2) a mid‐cycle shellbed, which containsin situoffshore molluscs in a matrix of muddy fine sandstone or fine sandy siltstone (type B shellbeds); and (3) an upper unit of terrigenous siltstone, either bedded and barren of fossils, or bioturbated and with a sparsely scatteredin situfauna similar to that of the subjacent shellbed. The three parts of each sequence correspond respectively to the transgressive systems tract, mid‐cycle shellbed, and highstand systems tract of the sequence stratigraphic model. Sequence 7 (Kupe Formation, Upper Kai‐Iwi Shellbed, Upper Kai‐Iwi Siltstone) is designated as the type example of the Castlecliff motif. A detailed measured section is presented of the Castlecliff section, with 30 formations designated which correspond to the most significant lithostratigraphic units and to the inferred systems tract interpretation. Where possible, the formational nomenclature follows that of Fleming (21 formations, six with adjusted boundaries). However, three formations represent newly observed units (Mowhanau Formation, Lower Kai‐Iwi Shellbed, Lower Castlecliff Siltstone), and seven other formations are erected on the basis of previously described beds, members or informal units (Rolled Concretion Conglomerate,Tiostrea‐DosinaBed,OphiomorphaSand, Lower Westmere Shellbed, Kaikokopu Formation, Upper Westmere Shellbed, Upper Kai‐Iwi Shellbed). The lithofacies and macrofaunal and microfaunal associations are documented across the section in terms of this lithostratigraphic framework.

ISSN:0028-8306    

DOI:10.1080/00288306.1999.9514834

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Northern Wairarapa, North Island, New Zealand, lies in the onland part of the forearc of the Hikurangi margin, which formed since early Neogene time when the Pacific plate commenced westward subduction beneath the Australian plate. The onland part of the forearc is now 75 km wide, and there are two dextral fault zones: the Wellington Fault and the Alfredton‐Pleckville Faults. However, in early Miocene time, a zone of dextral faulting lay adjacent to the inboard part of the trench slope break. At various times during its development, the onland part of the forearc comprised the following units: (1) Coastal Block (outboard); (2) Tawhero Basin; (3) Forearc Platform; (4) Mt Bowen Basin; (5) Mauriceville Ridge; (6) Eketahuna Basin, a successor basin with two subunits; and (7) Axial Ranges (Tararua Range) (inboard). However, currently only the Coastal Block, the widespread Eketahuna Basin (comprising units 2, 3, 4, 5 and 6), and the Axial Range units are developed. At various times the following NNE‐ and NE‐trending faults bounded the units: Tinui (outboard), Waihoki, Mauriceville, Pleckville‐Hastwells, and Wellington (inboard).

ISSN:0028-8306    

DOI:10.1080/00288306.1999.9514835

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor