摘要:

The structure of the crust and upper mantle of the Central Volcanic Region, New Zealand, are deduced from long-range seismic refraction and wide-angle seismic reflection data. Three shots were detonated in the Bay of Plenty and one in Lake Taupo; seismographs were located at approximately 10 km intervals between these shots. The geometry of the experiment was such that there was a partially reversed coverage for the crustal phases, but correlatable upper mantle phases were only recorded from the Bay of Plenty shots. A nondipping, plane-layer model to account for the refraction observations consists of a 15 ± 2 km thick crust of seismic velocity 5.5–6.15 km/s, underlain by an upper mantle with an anomalously low velocity of 7.5 ± 0.2 km/s. Wide-angle upper mantle reflections were also recorded from the Lake Taupo shot; a simple T2versus X2analysis of these reflections gives a depth of about 16±1 km to the upper mantle with a root-mean-square (r.m.s.) velocity for the crust of 5.94 ± 0.2 km/s.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10552618

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The observed Bouguer anomalies on the volcanic islands in Western Samoa (Savai'i and Upolu) and American Samoa (Tutuila and the Manu'a Islands), and the free air anomalies at sea, are consistent with island platforms of density 2.4 Mg/m3(pyroclastic basaltic materials) containing cores of density 2.9 Mg/m3(basalt), and varying degrees of lithospheric depression. The maximum depression of about 2 km occurs below the western islands and is practically zero below the Manu'a Islands at the extreme eastern end of the island chain.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10552619

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The islands of the Lau Ridge in eastern Fiji have long been a focus for the attention of geologists owing to their spectacular sequences of preserved shorelines. A review of past work is given, and 107 shoreline levels are recognised across 32 Lau islands.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10552620

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Low sun angle Landsat imagery permits analysis of late Cenozoic deformation of Central Otago because of preservation of the deformed Tertiary peneplain developed on schist and greywacke together with the contrast in Landsat expression between basin sediments and older rocks. The degree of embayment of fault-controlled mountain fronts in Central Otago by erosion and alluvial-fan development permits determination of relative age of faulting using Landsat, but late Quaternary fault scarps within structural depressions are only rarely visible. Landsat shows that Cenozoic structures of Central Otago may be visualised on two scales. The smaller scale structures are individual northeast-or northwest-trending, fault-bounded ranges and basins, 5–20 km wide. Sets of ranges and basins are grouped into northwest-elongated structural provinces, 40–60 km wide. From northeast to southwest, starting at the Waitaki River, these include (1) a set of northwest-trending ranges with very few basins south to the Waihemo, Stranraer, and Hawkdun Faults; (2) a set of northeast-trending ranges and basins; and (3) step-faulted schist highlands with very few basins. Northwest elongation of these provinces is parallel to bedrock trends including fold axes in schist and the ophiolite belt. These provinces may represent different responses of crustal rocks to contractile strain across the plate boundary.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10552621

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Three phases of folding have been recognised in the greywacke-Alpine schist transition in the Torlesse terrane rocks of the Callery River headwaters, Westland. The first phase was synmetamorphic and isoclinal (F1). This deformation resulted in variable textural reconstitution of the rocks (textural zones 2 and 3). Subsequent deformation has disrupted the textural zone boundaries, so that the boundaries have been folded almost isoclinally (F2) and refolded by an upright antiformal structure (F3) correlated to Alpine Fault related structures.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10552622

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Detailed mapping of Fraser Formation has revealed a different relationship between mylonitic and gneissic rocks than found by previous workers. Mylonitic zones envelop areas of amphibolite facies gneisses and granitoid rocks, ranging up to several square kilometres, throughout the area. Mylonitisation does not increase in intensity towards either the Fraser Fault or the Alpine Fault. Numerous lamprophyric and trachytic dikes intrusive into Fraser Formation have not been observed to cut the foliation in the mylonite zones, and several of the dikes have been truncated by mylonitic fabric. These dikes therefore give a maximum age of mylonitisation, of probably middle Cretaceous, rather than a minimum age as previously believed. Structural data from the mylonites are consistent with dextral strike-slip movement.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10552623

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Sandstones from McKee Formation and near correlatives, are known only from cores in Taranaki, New Zealand, from depths >2130 m. Their heavy mineral suites consist dominantly of ilmenite, garnet, zircon, and tourmaline, with pyrite and barite of probable diagenetic origin. Hornblende, epidote, titanite, and kyanite are absent. Staurolite and garnet are absent through intrastratal solution below burial depths of about 3100 m and 3600 m respectively. This dissolution pattern is comparable to that observed in the North Sea Basin, although total dissolution of mineral species takes place somewhat deeper in the McKee Formation.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10552624

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The Kaiwera-Mimihau district, Southland, New Zealand, is partly mantled in loess a metre or more thick. Three soil series (Tuturau, Otaraia, and Rosemarkie) have been mapped in the loess. Tuturau soils, nearest the Mataura River, have similar sand-and silt-sized heavy minerals to Mataura River alluvium, indicating probable derivation from the Mataura River floodplain. Otaraia and Rosemarkie soils, which are further from the Mataura River, contain higher amounts of hornblende, similar to those in locally outcropping tuffaceous greywacke rocks, indicating that the local rocks were another source of loess.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10552625

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Aqueous solutions of the salt sodium polytungstate can be prepared with varying densities up to 3.1 g/cm3. The salt is nontoxic and it is recommended as a substitute for the hazardous halogenated hydrocarbons, tetrabromoethane and bromoform, customarily used in geological laboratories to perform light/heavy mineral separations.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10552626

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

An isolated edentulous dolphin mandible from the Tangahoe Mudstone (Waipipian Stage, Pliocene), Waihi Beach, probably represents a species ofDelphinusorSienella(Delphinidae). Other fossil dolphins have been reported from New Zealand, but this is the first specimen to be described formally.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10552627

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor