摘要:

Geophysical data show that the southern part of the Hauraki Depression is a rift structure. In W—E cross section it is made up of a fault angle depression, a median horst, and a graben. A maximum thickness of about 3 km of Quaternary and Tertiary sediments fill the two depressions. The fault angle depression and the graben are bounded at the eastern side by major normal faults which dip about 70 ± 10° to the west, namely, the recently discovered Kerepehi Fault in the centre and the Hauraki Fault which forms the eastern boundary of the depression. A minor hinge fault (Firth of Thames Fault) probably runs along the western boundary. Transverse faults cross the depression causing horizontal offsets of the major normal faults of up to 3 km. Recent rifting of the southernmost part is indicated by active faulting and by shallow earthquake activity beneath the depression (focal depth ≤ 12 km). The chemistry of numerous hot springs implies that high temperatures (250–300°c) occur at depths of less than 5 km; these springs occur over the boundary faults and over the median basement ridge.

ISSN:0028-8306    

DOI:10.1080/00288306.1979.10422550

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Pleistocene deposits in the south Parengarenga-Te Kao area are predominantly medium to fine, highly mature sandstones. They are comprised of 90–96% quartz and subordinate feldspar and rock fragments. Mafic minerals generally comprise less than 1% of these rocks and are opaque dominated.

ISSN:0028-8306    

DOI:10.1080/00288306.1979.10422551

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The mineralogy and textures of specimens from a sulphide occurrence in a green schist at Waitahuna River are described, and their origin is discussed. The ore minerals are chalcopyrite, pyrite, marcasite, pyrrhotite, and minor sphalerite, and there is a small amount of supergene alteration. Marcasite, and the later of two main types of pyrite, are believed to have formed from pyrrhotite after the main stage of metamorphism, but are not supergene.

ISSN:0028-8306    

DOI:10.1080/00288306.1979.10422552

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Gold, silver, and base-metal bearing veins in the Maratoto—Wentworth region of the Hauraki Goldfield have many similarities: Host rocks are hydrothermally altered andesites (propylites) of the Beesons Island Group; all have sub-parallel strike directions and dip steeply; all are composed predominantly of quartz and carbonates. Within some veins, rich bonanza mineralisation occurs in fan-shaped bodies that taper with depth. This is associated with marked thickening of the vein and a change in strike direction. Very little mineralisation is present outside of these bodies. In fact, beyond the bonanza, the vein itself is often only weakly developed and passes into an intensely sheared zone. Near the bonanza, reverse faults, or well-defined veinlets, may transect the vein at near right angles.

ISSN:0028-8306    

DOI:10.1080/00288306.1979.10422553

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Most of the sedimentary rocks of Small Nggela are early Miocene in age. In the north, uniform volcaniclastic arenite (theSiota Beds) crops out. Much of the central, western, and eastern parts of the island contain diverse strata including pillow lava, calcarenite, volcaniclastic arenite, grit, and breccia (theGhumba Beds). The Siota and Ghumba Beds, which are separated by a 1–1.5 km wide, east-trending ophiolite wedge, are considered to have been deposited in a forearc basin. The ophiolite wedge arrested the northward transport of coarse sediment and was emergent during the late Oligocene and early Miocene. The sediment and the ophiolite wedge are considered to have overlain a southward-descending Benioff zone.

ISSN:0028-8306    

DOI:10.1080/00288306.1979.10422554

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

An analogue approach to the geology of the middle Paleozoic Hill End Trough of New South Wales suggests a close parallel between its latest Silurian-Early Devonian (Pridoli-Siegenian) configuration and that of the southern apex of the Havre Trough where it impinges on the North Island of New Zealand, that is, at the junction of a largely intraoceanic multiple arc system and a continental block. This analogy, rather than one with the interarc basins of wholly intraoceanic multiple arc systems adopted by other authors, is favoured by: dimensional comparability, the basinaxial location of silicic lava flows, the silica-intermediate to silica-rich character of magmatic products within and around the basin apex, the broad continental magmatic province immediately beyond the basin apex, the probable substantial epiclastic component of the basin fill, the probable lack of a truly oceanic basement to the basin fill, and by metallogenetic parallels.

ISSN:0028-8306    

DOI:10.1080/00288306.1979.10422555

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

More than 100 species of molluscs are listed from Nukumaruan (late Pliocene or early Pleistocene) siltstone on the summit of the first hill south of Oaro, Hundalee Hills, southern Marlborough. Most species are part of the living bathyal molluscan fauna of canyons off eastern South Island, and the siltstone evidently was deposited in 600–800 m of water.Falsilunatia, Penion benthicolusDell,P. fairfieldae(Powell),Cominella (Eucominia)alertae(Dell),C. mirabilis cantuariensis(Dell),Euthrenopsis otagoensisPowell, andVolutomitra(Latiromitra) are reported as fossils for the first time. The fauna is dominated by the buccinidsCominella nassoides otakauicaPowell, an abundant living taxon, andAeneator(Aeneator)elegans(Suter), a species only recently recognised in the living fauna. The locality is probably the type locality ofAeneator elegansand ofFalsilunatia ambigua(Suter), the latter an earlier name for the livingF. powelliDell. New species ofMesoginella(Sinugin ella),Paracomitas(Macrosinus),Splendrillia(two), andNeoguraleus(Fusiguraleus) are named.Splendrillia armataPowell,S. kingmaiMarwick,S. majorinan.sp.,S. zeobliquan.sp., andParacomitas(Macrosinus)haumurian.sp. are recorded living off eastern South Island.

ISSN:0028-8306    

DOI:10.1080/00288306.1979.10422556

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Three distinct species ofBelemnopsisare present in the Heterian stratotype. Two of them,Belemnopsis annaen. sp. andBelemnopsis maccrawin. sp., are described herein and the description of the third,Belemnopsis keariStevens, is emended.B. annaeis of lower Heterian age.B. maccrawiandB. keariappear in the upper Heterian and their zones are partially overlapping. A fourth illdefined population consisting of a heterogeneous assortment of several taxa is present in the middle Heterian. The three named species are present in restricted sets of beds and because their zones apparently represent short time intervals they are expected to be of stratigraphic value.

ISSN:0028-8306    

DOI:10.1080/00288306.1979.10422557

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A new genus,Ikamauius, is proposed forPristiophorus ensifer(Davis), a fossil sawshark taxon based on completely barbed rostral teeth. A neotype is proposed for the type speciesIkamauius ensifer. Ikamauiusis known only from New Zealand, where it ranges in age from late Eocene to early Pleistocene.

ISSN:0028-8306    

DOI:10.1080/00288306.1979.10422558

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Between 1 km and 3 km west of Te Araroa, closely spaced gravel beach ridges extend 2·3 km inland. Dated shell samples show a consistent progradation rate of 0·48m/yr for the first 320 m. Projection inland suggests an age of 3850 years for the oldest ridge, which compares with 3900 years for the oldest ridge in the more stable region of the Firth of Thames. Comparison of the Te Araroa and Firth of Thames beach-ridge systems suggests an uplift rate of 1·5 mm/yr for the Te Araroa region. This rate is comparable with other known rates of crustal uplift along the east coast of the North Island.

ISSN:0028-8306    

DOI:10.1080/00288306.1979.10422559

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor