摘要:

Calcium carbonate and other constituents of Upper Cretaceous and lower Tertiary rocks were determined at three localities in New Zealand where the Cretaceous/Tertiary boundary was believed to occur. The boundaries could be delineated by chemical means alone, thus reducing the time expenditure needed for the more usual paleontological techniques. This method might also be useful in locating the boundary where paleontological evidence is missing or inconclusive. Diagnostic elements were: arsenic, calcium, chromium, cobalt, iron, magnesium, manganese, nickel, phosphorus, and sulphur. In lacustrine sediments near Rewanui, a possible location of the K/T boundary was indicated by anomalous levels of calcium, iron; magnesium, and manganese. The principles enumerated should be of general application elsewhere in the world where searches continue for K/T boundary material.

ISSN:0028-8306    

DOI:10.1080/00288306.1986.10427518

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Numerous rodingite dikes and rodingitised tectonic blocks occur within serpentinised harzburgite of the Dun Mountain Ultramafics, D'Urville Island, New Zealand. The rodingites formed during progressive metasomatic alteration of a wide range of mafic to silicic ophiolitic rocks, including metavolcanics and argillite, as well as gabbro and plagiogranite. Petrographic, mineralogical, and geochemical data distinguish between two types of rodingite which represent different degrees of metasomatic alteration. These are (1) coarse-grained rodingites that often preserve mineralogical features of their parent rocks, and (2) intensely altered, fine-grained rodingite pods which are bordered by distinctive chloritised serpentinite reaction zones. The two rodingite types differ in their degree of Ca and Al enrichment, and Si, total Fe and alkali depletion, as well as in their extent of oxidation, hydration or dehydration, and abundances of incompatible elements and transition metals. These differences are related to progressively changing mineralogies in the rodingite reaction zones that were imposed by chemically evolved fluids associated with serpentinisation of the enclosing ultramafic rocks.

ISSN:0028-8306    

DOI:10.1080/00288306.1986.10427519

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Complexly deformed Torlesse terrane lithologies of Otaki Forks, North Island, New Zealand, are dominated by very thick bedded sandstone, thinly alternating sandstone and argillite, very thick bedded argillite, with locally important green argillite, rare limestone, and intraformational conglomerate, some of which are Upper Triassic. The strata generally strike north-east-southwest, dipping steeply, but there are significant variations from this trend. The area has been subdivided into geographically bounded structural domains characterised by combinations of the following types of structures: isoclinal folding; “ductile” and “brittle” broken formations; melange; chevron-like folding; pressure solution and veining; striation faulting; open, moderate plunge folding; sinistral and dextral verging, asymmetric, steep plunge folding; and fault brecciation. The structural succession established is: early isoclinal folding, ductile broken formation, chevron-like folding/thrusting, brittle broken formation, veining, striation faulting/folding, sinistral folding, dextral folding, and recent fault brecciation. TheMonotislocality at Pukehinau Stream is not within a melange — the structural complexity of this area is largely due to two interfering fold phases.

ISSN:0028-8306    

DOI:10.1080/00288306.1986.10427520

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The basement structure and sedimentary history of the continental shelf east of the northern section of North Island, New Zealand, is interpreted from geophysical data collected by petroleum companies. Interpretation of magnetic data shows the basement to be composed of both igneous and nonigneous rocks in the vicinity of the Coromandel Peninsula and Great Barrier Island; further north the basement is almost entirely nonigneous. From seismic reflection data, basement in the region can be seen to have undergone extension, being faulted into a series of fault-angle depressions and grabens. Sea-floor expression indicating continued development of the fault-angle depressions is found locally, especially in the Tauranga Harbour — Cuvier Island region.

ISSN:0028-8306    

DOI:10.1080/00288306.1986.10427521

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Possible origins of the igneous bodies off the west coast of the North Island, as revealed previously by geophysical surveys, are considered in the context of the wider Cenozoic geotectonic development of New Zealand. First it is suggested that the northwest-southeast-trending anomaly sources north of Manukau Harbour cannot be genetically related to the Miocene orogenic andesites and basalts onshore in western Northland, as earlier proposed, chiefy because the onshore subduction-related frontal arcs were oriented north-east-southwest. An alternative origin suggests that the offshore igneous bodies are of the correct age and position to be either rift volcanics or the products of early sea-floor spreading within the axial trough of the mid-Cenozoic Challenger Rift System. The geophysical character, and limited geologic data, of the anomaly sources in the southern field indicates that they may have a dual origin. At least some of these anomaly sources probably originated as frontal arc andesites as the subducted Pacific plate progressively extended to the southwest beneath northern New Zealand and concomitantly increased its dip; substantial intrabasement magnetic sources indicate that others have a rift or early sea-floor spreading origin.

ISSN:0028-8306    

DOI:10.1080/00288306.1986.10427522

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The stratigraphic and chronologic relationships of Hinemaiaia Tephra and Whakatane Ash are examined using distal tephras preserved in organic-rich deposits at five sites in eastern and northern North Island, New Zealand. A c. 10 mm thick, unnamed white rhyolitic ash layer described at two of the sites (Tiniroto and Poukawa), and previously of disputed stratigraphie significance, also occurs at the other three sites (Kaipo, Rotomanuka, and Okoroire) as a primary airfall tephra. The tephra is derived from the Taupo Volcanic Centre and is correlated with Hinemaiaia Tephra (definition of Froggatt) using similarity of stratigraphie position, composition (ferromagnesian mineralogy and glass chemistry), and radiocarbon age. It stratigraphically overlies Whakatane Ash. The tephra underlying Whakatane Ash, and previously identified as Hinemaiaia Ash (definition of Vucetich & Pullar), is probably Motutere Tephra.

ISSN:0028-8306    

DOI:10.1080/00288306.1986.10427523

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Excavations for drainage of Ahuriri Lagoon near Poraiti has exposed a sequence, up to 8 m thick, of peat containing remains of two separate human skeletons, overlying primary airfall Waimihia Lapilli, and overlain by estuarine sediments. Stratigraphy together with radiocarbon dating of peat, wood, human bone, and shell samples is interpreted to indicate tectonic subsidence of 8 m in the last 3500 years at the pre-A.D. 1931 western margin of Ahuriri Lagoon. Most of this subsidence occurred between 3500 years B.P. and 1750 years B.P. at an average rate of 4.6 m/1000 years and was probably matched by the similar rate of peat accumulation. A hiatus in peat growth between c. 1800 years B.P. and c. 500 years B.P. was possibly the result of tectonic uplift.

ISSN:0028-8306    

DOI:10.1080/00288306.1986.10427524

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Benmore is the largest artificial lake in New Zealand. The lake has two arms which have quite different inflows in terms of volume, temperature, and suspended particulate matter (SPM) loadings. The Ahuriri Arm is fed by natural runoff from unglaciated catchments, whereas the Waitaki Arm receives the outflow of three large glacial-fed lakes which filter out much of the SPM and restrict the temperature range of water entering Lake Benmore. Geographical isolation of the two arms allows each to develop its own annual cycle of lake/ river interactions. The Ahuriri water, which is more responsive to seasonal temperature changes, underflows the warmer Waitaki water in winter and overflows in summer.

ISSN:0028-8306    

DOI:10.1080/00288306.1986.10427525

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Mesoscale precipitation patterns around Wellington, New Zealand, are examined using the method of principal component analysis. Five distinct precipitation patterns emerge which are caused by six synoptic situations. Given the great variability in synoptic patterns that can occur in the New Zealand region, and the complexity of the terrain about Wellington, the similarity of synoptic analogues for each precipitation pattern is good. The results demonstrate the effects of orographic interaction on the amount and distribution of precipitation by synoptic-scale airflow in the Wellington region.

ISSN:0028-8306    

DOI:10.1080/00288306.1986.10427526

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

An extensive search of newspaper reports, archival material, and the literature has revealed that many more tsunamis have affected the New Zealand coast than hitherto realised. 32 tsunami events are listed, including their probability of occurrence, the maximum runup height, as well as the epicentre and Richter magnitude for those events associated with earthquakes. Most coastal regions of New Zealand are reported as experiencing tsunamis. Generally these events have been associated with earthquakes, although the tsunami source mechanisms have also been attributed to large rotational slumps, submarine slumping along the Chatham Rise, and submarine mud volcanism associated with diapiric intrusions on the continental shelf off Poverty Bay. Tsunami waves and seiching accompanying the Krakatoa eruption of 1883 appear to have been induced by pressure coupling between the atmosphere and oceans.

ISSN:0028-8306    

DOI:10.1080/00288306.1986.10427527

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor