ISSN:0028-8306    

DOI:10.1080/00288306.1969.10420223

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

ISSN:0028-8306    

DOI:10.1080/00288306.1969.10420224

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The turbidity current hypothesis has met with much support as well as severe criticism. Dogmatic statements in support of this hypothesis are not uncommon in the literature and a clear distinction between fact and inference is not always made. First developed as an explanation for the origin of submarine canyons, the turbidity current hypothesis was later applied to explain the deposition of ancient flysch-type sediments as well as recent deep-sea deposits of alternating coarse and fine layers. Though a turbidity current origin for these two facies has not yet been demonstrated beyond reasonable doubt, diagnostic features of the one are commonly used to prove such an origin for the other. Such circular reasoning is unwarranted and data from both facies should be kept strictly separated. Evidence to support the turbidity current hypothesis comes from three areas: ancient flysch-type sediments; Recent deep-sea deposits; and experimental turbidity currents. Careful study of this evidence shows so many exceptions, irregularities, and inconsistencies in the general turbidity current concept, that serious doubt as to its general validity must be expressed. More consideration should be given to alternative theories, such as ocean bottom currents and tectonically controlled sedimentation. The ocean bottom current theory provides a good explanation for Recent deep-sea sedimentation, but cannot explain flysch-type deposits. Tectonically controlled sedimentation under relatively shallow water conditions provides a promising working hypothesis for the origin of flysch-type sediments.

ISSN:0028-8306    

DOI:10.1080/00288306.1969.10420225

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Muddy marine sediments in the New Zealand region show a considerable range of colour. Thirty-five representative samples were selected, and divided by the writer into seven groups, lettered A to G. Simple chemical tests were applied to these samples in order to obtain information regarding the nature of the chemical compounds which control the colour of these sediments.

ISSN:0028-8306    

DOI:10.1080/00288306.1969.10420226

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Alternating bands of hard and soft limestone in a 14-ft (4 m)-thick lens at the base of the marine Waikawau Sandstone (Lower Miocene), West Auckland, are clearly secondary in origin since in places they cut across primary sedimentary structures such as current bedding. The only significant differences between the two lithologies are the calcium carbonate content, the development of glauconite, and the packing of bioclasts. It is inferred that segregation of calcium carbonate from an initially homogeneous, sandy biocalcarenite (62% CaCO3), to form hard bands with an average of 75% CaCO3and soft bands with an average of 42% CaCO3, took place in early diagenesis, penecontemporaneously with the development of glauconite. No other elements appear to have migrated with the calcium carbonate. Calcite was deposited as spar cement in hard bands, whereas calcareous bioclasts in soft bands were partially dissolved and pore space was drastically reduced. Segregation probably occurred because the pH in the interstitial fluids fluctuated above and below 7.8, in a mildly reducing environment. It is inferred that the differential cementation occurred no more than 6 ft (2 m) below the sea bed.

ISSN:0028-8306    

DOI:10.1080/00288306.1969.10420227

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The Kahurangi Shoals, north-west of Kahurangi Point, Nelson, and the Westland and D'Urville Currents are the major factors influencing the sediment distribution and sedimentation processes on the north-western shelf of the South Island. The sediments are derived from two major sources, one the Kahurangi Shoals, the other the high Alpine region which supplies its erosion products to sea by steep mountain streams and rivers. The Westland and D'Urville Currents not only carry the Alpine detritus to the area but also largely control the sediment distribution pattern. Immediately south and north of Farewell Spit well sorted wind-blown sands derived from the Spit have accumulated, whereas further south in Golden Bay the sediments are mainly supplied by the Aorere and Takaka Rivers. Petrologically the shelf sands are mainly a quartz-feldspar association with magnetite, ilmenite, garnet, and hornblende as rnaior constituents in the heavy mineral assemblage. The gravels and boulders derived from the Kahurangi Shoals consist mainly of well rounded quartzites. Seismic reflection profiles give an indication of the depositional history during and since the Pleistocene and provide information on the rate of sedimentation.

ISSN:0028-8306    

DOI:10.1080/00288306.1969.10420228

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The Mahurangi Limestone (Oligocene) on Puketotara Peninsula, is a highly deformed, whitish grey, fine-grained rock that typically lacks distinct bedding and identifiable macrofossils. It is faulted against the Waitemata Group (Miocene) and is probably overlain by the Onerahi Chaos-breccia (Upper Tertiary — Quaternary?). The basal contact was not seen. Petrographically the rock is an argillaceous biomicrite containing both terrigenous and organic grains “floating” in an argillaceous, micritic matrix that is seen to be composed mainly of coccoliths under an electron microscope.

ISSN:0028-8306    

DOI:10.1080/00288306.1969.10420229

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Comparative study of five South Island beaches and a beach on the central Texas coast suggests a short list of features that are diagnostic of the coastal beach. Beach sediments are clean (no mud matrix) and are very well to moderately well sorted. Foreshore strata occur as even, internally laminated, thin beds that dip seaward at low angles. The angle of dip is directly related to the slope of the foreshore surface (especially the beach face), which in turn is largely dependent upon the mean size of the beach sediment, that is, the coarser the grain size the steeper the foreshore. Backshore strata occur as lens- and slightly wedge- shaped, internally laminated thin beds. Scour surfaces and cross-stratified lenses are characteristic. Dip of strata varies from 0° to 15°, and strata dip directly or obliquely landward. A transition zone (foreshore or above high tide level plus outer backshore) is characterised by mixed foreshore and backshore stratification, and some strata dip landward, others dip seaward.

ISSN:0028-8306    

DOI:10.1080/00288306.1969.10420230

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The variation of mean grain size (Mzφ), sorting (σI), and beach face slope over mixed-sand shingle beaches at two areas along the east coast, South Island, New Zealand, it analysed in order to determine the nature of the relationships between these three variables. The study is confined to mean grain sizes between 0.25 and 16.0 mm, and the sorting and slope values associated with this range of sizes. Trend analysis of the data has been performed by fitting curves with the aid of a computer.

ISSN:0028-8306    

DOI:10.1080/00288306.1969.10420231

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Thick slump breccias, interbedded with greywackes and argillites, are well exposed in shore platforms and cliffs at Halliday's Point, 230 km north of Sydney. They are unusual in two respects. Firstly, they were formed by submarine slumping of marine sediments initially deposited by turbidity currents and pelagic sedimentation. The slumping was initiated by minor tilting of the sea floor perhaps brought about by faulting or by volcanic activity. Secondly, it was the coarse sandy layers which proved the more unstable lithology and which failed by viscous fluid flow. The finer grained interbedded layers in the slump mass fractured and remained as blocks and slabs, some large in size, in a matrix of coarser sediment.

ISSN:0028-8306    

DOI:10.1080/00288306.1969.10420232

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor