摘要:

The spatial distribution of microseismicity observed during a 16-day survey of the upper Clutha valley is broadly similar to that of the longterm seismicity, All but one of the microearthquakes were located within the crust, with the proportion of lower crustal events being greater than in the Lake Pukaki region to the northeast. The single subcrustal event, located at 73 km depth, exhibited a definite phase between the P- and S-phases, similar to the S to P conversion at the base of the crust recently identified in records of 2 subcrustal earthquakes west of Lake Pukaki. A composite focal mechanism for all the crustal microearthquakes indicates strike-slip faulting with a P-axis acting southeast-northwest. This mechanism is very similar to that found previously for crustal microearthquakes to the west and northeast of the study area.

ISSN:0028-8306    

DOI:10.1080/00288306.1983.10421517

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A study is made of the time-spacemagnitude dependence of upper crustal earthquakes through the ideas of conditional intensity and conditional expected magnitude. Strong clustering is found within short distances and times before and after a large event. Seismic gap of smaller earthquake activity prior to an impending large earthquake within jts vicinity and increase inb-value of shocks after a large event are also observed.

ISSN:0028-8306    

DOI:10.1080/00288306.1983.10421518

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The Glenham Porphyry is a suite of andesitic terrestrial flows and subvolcanic intrusions in an inlier of Murihiku Supergroup sediments in eastern Southland. Potassium-argon dating has been used to determine the age of the volcanics. Plagioclase ages are in the range 182–240 Ma, indicating a probable Late Triassic to Early Jurassic time of extrusion. Discordant younger ages of whole-rock samples indicate argon loss from the glassy matrix, possibly caused by low-grade regional metamorphism during the Rangitata Orogeny.

ISSN:0028-8306    

DOI:10.1080/00288306.1983.10421519

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Here we synthesise available data and present 22 new chemical analyses of dredged volcanic rocks, recovered by the USNSEltanin, from a wide variety of morphotectonic settings in the southern oceans. Generally, these samples have undergone the variable affects and styles of postmagmatic alteration.

ISSN:0028-8306    

DOI:10.1080/00288306.1983.10421520

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Karioi, Pirongia, Kakepuku, and Te Kawa which show a northwesterly (300°) alignment. Volcanism was predominantly basaltic and produced approximately 55 km3of lava, volcanic breccia, and scoria from at least 40 centres. A new formation is proposed within the Alexandra Volcanic Group, theOkete Volcanic Formation, which shows differences in form, petrography, petrochemistry, and eruptive mechanisms from the rest of the Alexandra Volcanics. The Okete Volcanics form numerous small partially eroded scoria cones and thin lava flows with occasional tuff rings, and are alkalic in nature, consisting of finegrained basanites, basalts, and rare hawaiites. The Pirongia, Karioi, Kakepuku, and Te Kawa Volcanics form large low-angle composite cones constructed of thick lava flows and volcanic breccias, with minor dikes, scoria, tuff and lahars. They are composed of tholeiitic or subalkaline coarse-grained basalts, basaltic andesites, with rare andesites. Volcanism in the Alexandra field is Plio-Pleistocene in age, spanning the interval between 3.79 m.y. and 1.80 m.y., although some volcanic centres may be considerably younger. Geomorphological evidence suggests the volcanoes of Karioi, Pirongia, Kakepuku, and Te Kawa become progressively younger to the southeast. The Okete Volcanics intercalate stratigraphically with lavas from Pirongia and Karioi, and show no distinct temporal relationships. The regional northwesterly alignment may be caused by rising magma which encountered a major northwesterly fracture at deeper crustal levels and was channelled in part along the system of north and northeast-striking faults at upper crustal levels.

ISSN:0028-8306    

DOI:10.1080/00288306.1983.10421521

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Interstratified matrix-rich colluvium and scree-like gravels form a regolith up to 5 m thick over a dissected bedrock surface of Moutere Gravel in the headwaters of Tadmor River, South Island, New Zealand. Drainage density of the paleolandscape was 2–4 times greater than at present, with substantially steeper lower-slope gradients. Several episodes of gully filling by scree-like gravels and matrix-rich colluvium are identifiable. Dissection of the paleolandscape is considered to have occurred prior to the last Otiran stadial or during the Oturian Interglacial, with the present regolith having accumulated either during late Otiran and Postglacial time or during the whole of the Otiran and Postglacial time. Inferred regolith accumulation rates during either time span are much larger than current sediment yield rates. The deposits studied are probably equivalent to other similar deposits in Nelson and Marlborough which are interstratified with Kawakawa Tephra (c. 20000 years old).

ISSN:0028-8306    

DOI:10.1080/00288306.1983.10421522

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Studies of aerial photographs show clear evidence of increased erosion, since 1943, concentrated at differing altitudes in different parts of the Kaimai Range, North Island, New Zealand. In the Te Rere area, the increase was greatest between 1943 and 1960, but in the other 2 areas (Mt Te Aroha and Te Hunga) the increase was greatest between 1960 and 1974. There is also a high normal erosion frequency at Te Hunga due to steep terrain. Landslides do not appear to be concentrated on slopes of any particular aspect, slope, soil type, or basement geology, but may be linked with areas of poor vegetation.

ISSN:0028-8306    

DOI:10.1080/00288306.1983.10421523

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Glacial and fluvioglaciallandforms and deposits preserved in the middle reaches of the Maruia valley, southeast Nelson, New Zealand, record the activity of the Maruia glacier during the late Pleistocene Otira Glaciation. Five advances are recognised, from oldest to youngest: Creighton 1, 2, 3, and the Reid Stream 1, 2 advances. !bere was an interstadial interval between the Creighton 3 and Reid Stream 1 advances. The Reid Stream 1 advance occurred shortly after 14 800 years B.P . (NZ536, old T½).

ISSN:0028-8306    

DOI:10.1080/00288306.1983.10421524

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Bohemiella cobbensisn. sp., the earliest articulate brachiopod yet found in New Zealand, andHaupiria tasmanin. gen. and n. sp., a kutorginide brachiopod, are described from late Middle Cambrian siltstones in northwest Nelson, New Zealand. The stratigraphic range of Kutorginida, hitherto known only from Lower Cambrian strata, is thus extended.

ISSN:0028-8306    

DOI:10.1080/00288306.1983.10421525

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Monotis (Inflatomonotis)cf.hemisphericaTrechmann,Hokonuia limaeformisTrechmann (Bivalvia), and unidentified woody plant fragments are recorded from Torlesse Supergroup rocks in the St Arnaud Range, Nelson. The fossils are of Warepan age (Norian; Late Triassic) and were probably redeposited by mass-flow processes. They are scattered throughout a 40 m thick zone of sandstone and siltstone which forms an integral part of a megascopically folded, largely overturned but coherent sequence.

ISSN:0028-8306    

DOI:10.1080/00288306.1983.10421526

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor