摘要:

The five previously reported fossil calcified hydroids from the New Zealand region are discussed, resulting in: a change of generic placement of two species(Stylastersensu Jones, 1970 toCalyptopora;andParaerrinasensu Squires, 1962 toLepidopora),and a query of the identification ofSporadopora mortensenisensu Squires, 1962. Several records of bryozoans reported as stylasterids are also rectified. Four additional fossil stylasterids are reported from the region: indeterminate species ofInferiolabiataandConoporafrom the early Miocene (Otaian) of Pakaurangi Point; a species ofErrinafrom the early to middle Eocene (Waipawan‐Bortonian) of Chatham Island; and a new species,Stylaster gigas,from the early Pliocene (Opoitian) of Kaawa Beach, North Island.S. gigashas one of the most massive coralla of any known stylasterid. The nine fossil stylasterids now known from the New Zealand region range from the early Eocene to the late Pliocene and are found from both North and South Islands as well as Chatham and Pitt Islands.

ISSN:0028-8306    

DOI:10.1080/00288306.1993.9514549

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The dominantly micritic Amuri Limestone Group of eastern Marlborough, New Zealand, consists of six regionally extensive units: the Mead Hill Formation, Teredo Limestone Formation, Lower Limestone Formation, Middle Limestone Formation, and the Lower and Upper Marl Formations, which were deposited in a northwest‐trending trough. Six separate diagenetic zones (I‐VI) are recognised, based on visually estimated proportions of chert, dolomite, or limestone. Zones I‐V occur in the Mead Hill to Lower Limestone Formations, and Zone VI occurs in the Middle Limestone Formation. There is no chert or dolomite in the two Marl formations. The bulk of the chert and dolomite occurs in the basin centre (mainly in the Mead Hill Formation) where the limestone is thickest, but decreases in abundance stratigraphically upwards and towards the basin margins. Zone I consists almost entirely of chert which is either detrital rich or detrital poor. Zones II and IV consist of chert and dolomite in approximately equal proportions. Zones III and VI contain varying proportions of chert and limestone. Zone V is a thin, chertified, fine sandstone‐mudstone of limited extent. Sulphide nodules, usually <10 mm in diameter, are common in all zones. Chert usually forms discontinuous nodular beds or nodules. Some elongated chert nodules which may be in excess of 2 m (chert bands) are found near the top of the chert sequence. Dolomite occurs as <1 mm diameter rhombohedra in discontinuous chert‐cemented beds and lenses. The common pinch and swell morphology displayed throughout most zones results from differential compaction of relatively chert‐free limestone, or dolomite, around chert nodules. Stylolites are generally absent, but where present they are deflected around chert nodules, indicating chert formation prior to stylolitisation.

ISSN:0028-8306    

DOI:10.1080/00288306.1993.9514550

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The Warder Formation of Ngaterian (late Albian‐Cenomanian) age crops out in southern Marlborough, New Zealand. Outcrops are characterised by fining‐upward alluvial cycles deposited by easterly flowing rivers on a coastal plain. Within‐channel deposits include clast‐supported conglomerate and trough cross‐bedded sandstone, overlain by alternating sandstone and siltstone, lateral accretion (inclined heterolithic stratification) beds, in turn overlain by siltstone and claystone. The fine‐grained units are interpreted as lacustrine sediments deposited in ox‐bow lakes through meander loop cut‐off. All outcrops are fault bounded, so a complete pattern of fluvial reconstruction cannot be made. The rivers which deposited the Warder Formation had a mean sinuosity of 1.5 and a discharge of 72–102 m3/s. Sedimentation was terminated by the eruption of alkaline basalts related to regional sea‐floor spreading.

ISSN:0028-8306    

DOI:10.1080/00288306.1993.9514551

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

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.

ISSN:0028-8306    

DOI:10.1080/00288306.1993.9514552

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Tests have been carried out on the simple precursory swarm hypothesis, which proposes a one‐to‐one relation between swarms and mainshock events, and tests are in progress on the generalised hypothesis, which allows for clustering.

ISSN:0028-8306    

DOI:10.1080/00288306.1993.9514553

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The 1987 January Tokaanu earthquake sequence occurred at a shallow depth near the southern shore of Lake Taupo. Sixty‐four earthquakes, in seven separate periods of activity were recorded over a 7 h interval; 26 earthquakes were located, with the largest ofML3.6occurring near the end of the sequence. The sequence had the characteristics of an earthquake swarm. Within the sequence, two adjacent clusters of epicentres were distinguished on the basis of waveform similarity and homogeneous station locations. Activity switched from one cluster to the other and back again, with both clusters sometimes active. Fluid overpressure may account for the switching by facilitating the rapid transfer of small stress changes between the two source regions. The sequence probably occurred where a northeast‐southwest‐trending fault was offset or sharply bent.

ISSN:0028-8306    

DOI:10.1080/00288306.1993.9514554

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Acquisition of seismic reflection data designed to image the lower crust is usually an expensive operation. By taking advantage of current petroleum industry surveying, however, and with only slight changes to the acquisition parameters, 51 km of reflection profiles, capable of being processed as deep crustal seismic sections, have been recorded in east Taranaki at negligible additional acquisition cost. The quality of the processed sections is encouraging, and the data show a zone of marked reflectivity between 10 and 12 s two‐way time with a north‐trending apparent dip of between 5 and 10°. Two factors make interpretation of the data difficult: the short length of the profiles prevents them from being adequately migrated; and their orientation subparallel to the strike of a major fault may be giving rise to spurious, out‐of‐plane events on the seismic sections.

ISSN:0028-8306    

DOI:10.1080/00288306.1993.9514555

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

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.

ISSN:0028-8306    

DOI:10.1080/00288306.1993.9514556

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The Murchison Basin lies close to the Alpine Fault and has an evolution that is intimately related to the development of the New Zealand plate boundary during the Tertiary. Faults in the Murchison Basin follow a regional NNE structural grain which is inherited from Paleozoic sutures that were zones of weakness prior to the late Eocene inception of the basin. The Tainui Fault may be the southern extension of the Paleozoic Anatoki Thrust that was reactivated during late Cenozoic compression. The Matin and Maunga Faults, which mark the western margin to the basin and the junction with a structurally high Karamea Batholith, are late Eocene normal faults that have similarly been reactivated and overturned. The eastern boundary is formed by the Tutaki Fault, a southeast‐dipping thrust fault which delineates the Rotoroa Complex basement block. Folds within the basin reach a depth of 8 km, whereas, on the basin margins, they have formed as gentle drape folds over a warped basement surface. The dominant structural control for the Murchison Basin is WNW‐oriented compression and reactivation of basement block‐faults, rather than dextral or sinistral transpression associated with Alpine Fault movement. This has resulted in the basin being the deepest and most intensely deformed of the West Coast region.

ISSN:0028-8306    

DOI:10.1080/00288306.1993.9514557

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The Bannockburn basin is the southern extension of the Upper Clutha basin, one of a series of prominent northeast‐trending structural and topographic basins in Central Otago. Post‐Miocene structure within the Bannockburn basin is shown up by deformation of an unconformity cut into schist basement beneath Miocene terrestrial sediments. The post‐Miocene deformation has been accommodated largely by flexure, and the structure consists of broad north‐trending synforms and antiforms in schistosity, mimicked by folds in the overlying sediments. The northwestern margin of the basin trends northeast, and the unconformity is steeply dipping or locally overturned, but there is no major fault separating the basin from the range immediately to the west. Minor faults in this area have normal, reverse, or strike‐slip senses of movement. The southwestern margin of the basin trends northwest and is marked by distinct faults which offset the unconformity.

ISSN:0028-8306    

DOI:10.1080/00288306.1993.9514558

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor