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Northern New Zealand (northern + new_zealand)
Selected AbstractsA reconstruction of the history of a Holocene sand dune on Great Barrier Island, northern New Zealand, using pollen and phytolith analysesJOURNAL OF BIOGEOGRAPHY, Issue 6 2000M. Horrocks Abstract Aim, To reconstruct the history of a Holocene sand dune using pollen and phytolith analyses, and to identify the strengths, weaknesses and compatibility of these two methods in the interpretation of Quaternary coastal environments. Location, Great Barrier Island, northern New Zealand. Methods, Pollen and phytolith analyses were carried out on a sequence through a Holocene sand dune containing a palaeosol. Results, Phytoliths were present throughout the sequence. Grass phytoliths increased at the expense of tree phytoliths following fire disturbance. Pollen (and spores) was preserved only in the palaeosol part of the profile. Pteridium fern spores increased at the expense of tall tree pollen following the fire disturbance. Main conclusions, Lack of phytolith production by many species and problems of taxonomic specificity in many others restricts the usefulness of phytolith analysis to defining only broad vegetation types. In New Zealand, gymnosperms are invisible in the phytolith record and ferns are extremely under-represented. In contrast, pollen analysis usually provides a great deal of information regarding the composition of a particular vegetation type. The loss of microscopic charcoal fragments during the phytolith extraction process is a disadvantage in the reconstruction of environments where fires have occurred. The greater durability of phytoliths compared with pollen means that phytoliths may be found in sediments where pollen has not been preserved. The phytolith record may also provide evidence of wetter environments that are not apparent in the pollen record. Unlike grass pollen, which is widely dispersed and therefore blurs the spatial record, the presence of grass phytoliths in sediments indicates a local source. The simultaneous application of both methods potentially provides a powerful tool in ecological interpretation and the reconstruction of Quaternary coastal environments. [source] Optimizing intertidal Pacific oyster (Thunberg) culture, Houhora Harbour, northern New ZealandAQUACULTURE RESEARCH, Issue 13 2002S J Handley Abstract Experiments were designed to determine the optimum intertidal rack height and growing density for producing Pacific oysters free of mudworm infestations and flatworm predators in the Houhora Harbour, northern New Zealand. At the same level, oysters grew to a larger size in the front of the farm (seaward) compared with those towards the rear (shoreward). Two experimental ,step racks' were constructed to test for the optimum oyster growth rates, oyster condition, shell density and degree of mudworm shell blistering. When experimental results were ranked for each rack level, extreme low water neap (ELWN) was the optimum growing level for the back of the farm, and 0.25 m above ELWN was the optimum growing level for the front of the farm. An efficient kill of flatworm predators was not achieved by any of the control methods tried, so avoidance of infestations is advised. The optimum density of oysters on a 1.2-m stick required to achieve maximum condition, shell density and ideal shell shape was 4,5 dozen. [source] Superposed deformation in turbidites and syn-sedimentary slides of the tectonically active Miocene Waitemata Basin, northern New ZealandBASIN RESEARCH, Issue 2 2007K. B. Spörli ABSTRACT The Miocene Waitemata Basin was deposited on a moving base provided by the Northland Allochthon, which was emplaced in the Late Oligocene, as a new convergent plate boundary was established in northern New Zealand. The basin experienced complex interaction between tectonic and gravity-driven shallow deformation. Spectacular examples of the resulting structures exposed on eastern Whangaparaoa Peninsula 50 km north of Auckland provide a world-class example of weak rock deformation, the neglected domain between soft-sediment and hard rock deformation. Quartz-poor turbidite sequences display a protracted sequence of deformations: D1, synsedimentary slumping; D2, large scale deeper-seated sliding and extensional low-angle shearing, associated with generation of boudinage and broken formation; D3, thrusting and folding, indicating transport mostly to the SE; D4, thrusting and folding in the opposite direction; D5, further folding, including sinistral shear; D6, steep faults. The deformation sequence suggests continuous or intermittent southeastward transport of units with increasing sedimentary and structural burial. By phase D3, the rocks had passed from the soft-sediment state to low levels of consolidation. However, with a compressive strength of ,5 MPa they are weak rocks even today. Such weak-rock deformation must be important in other sedimentary basins, especially those associated with active convergent plate boundaries and with immature source areas for their sediments. [source] | ||||||||||