Paleoenvironmental analysis of the Mangere Formation, Mangere Island, Chatham Islands, New Zealand : a thesis submitted in Earth Science for the degree of Master of Science at Massey University

Mangere Island consists almost entirely of alkali basalt of the late Miocene early Pliocene Rangiauria Formation (Campbell et al., 1993) with outcrops of the sedimentary Tupuangi Formation on the east coast and the Mangere Formation (Campbell, et al., 1993), a sedimentary remnant, mainly lacustrine but also partly marine, lying between the northeastern and southwestern groups of volcanic vents of Mangere Island: As a result of the present work the sedimentary Mangere Formation of Campbell et al. (1993) has been divided into two formations, Mangere Formation and the overlying Parakeet Formation. Mangere Formation consists of (1) a Basal member (32m of mudstone), and (2) a Cyclic member (12.6m of alternating sandstones and mudstones). Parakeet Formation has (1) a Carbonaceous member (0.6m Of organic rich mudstones), (2) a Skua member (16.8m of tuffaceous siltstone), and (3) a capping rhyolitic tephra. The Basal member of the Mangere Formation is underlain by a breccia that is texturally extremely variable (Bag End breccia). A sedimentary outcrop on the eastern coast of Mangere Island is lithologically and mineralogically identical to Tupuangi Formation on Pitt Island as well as having the same Cretaceous pollen suite. Thus it is inferred that, at the time of Rangiauria volcanism, Tupuangi Formation and its overlying Tertiary strata extended from Pitt Island at least as far as Mangere Island. An arm of the sea between two Mangere Island volcanic centres extended towards Waihere Bay, Pitt Island. At some time in the late Pliocene, volcanic debris avalanches from the northeast and southwest groups of vents formed a debris dam that blocked off the seaward side of the sea arm, resulting in the formation an oligotrophic fresh water lake. As a result of a low energy regime and vegetated slopes, the lake filled to ca. 30m with very fine sediment (the Basal member) from both the volcanics of Mangere Island and the quartzofelspathic Tupuangi Formation of Pitt/Mangere Island. Following this a debris dam, formed by volcanic debris avalanches, was breached by a rising sea. Local marine influence in storms destablised the slopes surrounding the then shallow lake resulting in the influx of coarse sands which alternated with mudstones deposited during quieter periods (the Cyclic Member). At the end of this period there was a eustatic fall of sea level or tectonic uplift or both, probably resulting in subaerial erosion and an unconformity between the Cyclic and Carbonaceous Members. A second shallow fresh water lake (the Carbonaceous member) was established on the top of the Cyclic member. This lake was later overwhelmed by wind-blown material derived from a deposit of Paleocene Red Bluff Tuff exposed probably by a falling sea level or marine erosion. The reworked Red Bluff Tuff was later covered by a layer of rhyolitic tephra probably from the Taupo Volcanic Zone (TVZ), North Island, New Zealand. The distinctive jointing pattern seen in the sandstone units of the Cyclic member resulted from doming with a principal stress directed northwest-southeast. This probably correlates with tectonic uplift in the Castlecliffian. The lack of any positive time markers makes dating the formation rather indeterminate, but the Basal and Cyclic members (Mangere Formation) are probably upper Mangapanian and the Skua member probably Quaternary. The sequence is generally lacking in fossils, except for palynomorphs which occur throughout, and ostracods which occur only in the Cyclic member. Neither proved useful for dating the sequence. The pollen diagrams show a consistent coastal plant association of small trees, shrubs, herbs and ferns throughout the history of the sequence, with the implication that climate during this time did not vary greatly from a mild, moist, equable mean

Practical constraints on network architecture and signalling in the MSAT system

Telesat Mobile Inc. plans to provide mobile satellite communications services in Canada in 1993/4, in close cooperation with the American Mobile Satellite Consortium Inc., which will be providing services in the U.S.A. L-band frequencies will be used in multiple beams for communication with mobile terminals. Ku-band frequencies will be used for the feeder-links to fixed stations. The system will support voice and data communications. The baseline Canadian system will support approximately 450 assignable voice channels, some fraction of which will be the equivalent in data channels. The method of multiple access will be Frequency Division Multiple Access/Single Channel Per Carrier. The availability of frequencies, the availability of technology and the time scale for implementation all constrain the network architecture for the system. Further, it is important to have an open specification to encourage multiple equipment vendors. The interplay of these constraints is discussed

Remote photothermal actuation for calibration of in-phase and quadrature readout in a mechanically amplified Fabry-Pérot accelerometer

A mechanically amplified Fabry-Pérot optical accelerometer is reported in which photothermal actuation is used to calibrate the in-phase and quadrature (I&Q) readout. The Fabry-Pérot interferometer (FPI) is formed between a gold-coated silicon mirror, situated in the middle of a V-beam amplifier, and the end surface of a cleaved optical fiber. On the opposite side of the silicon mirror, a further cleaved optical fiber transmits near-infrared laser light (λ = 785 nm), which is absorbed by the uncoated silicon causing heating. The thermal expansion of the V-beam is translated into an amplified change in cavity length of the FPI, large enough for the 2π-phase variation necessary for I&Q calibration. A simple 1D thermal analysis of the structure has been developed to predict the relationship between laser power and change in cavity length. A device having a V-beam of length 1.8 mm, width 20 μm, and angle 2 ° was found to undergo a cavity length change of 785 nm at 30 mW input power. The device response was approximately linear for input accelerations from 0.01 to 15 g. The noise was measured to be ~ 60 μg/√Hz from 100 Hz to 3.0 kHz, whereas the limit of detection was 47.7 mg from dc to 3.0 kHz

Complexity of and Algorithms for Borda Manipulation

We prove that it is NP-hard for a coalition of two manipulators to compute how to manipulate the Borda voting rule. This resolves one of the last open problems in the computational complexity of manipulating common voting rules. Because of this NP-hardness, we treat computing a manipulation as an approximation problem where we try to minimize the number of manipulators. Based on ideas from bin packing and multiprocessor scheduling, we propose two new approximation methods to compute manipulations of the Borda rule. Experiments show that these methods significantly outperform the previous best known %existing approximation method. We are able to find optimal manipulations in almost all the randomly generated elections tested. Our results suggest that, whilst computing a manipulation of the Borda rule by a coalition is NP-hard, computational complexity may provide only a weak barrier against manipulation in practice

Determining the Nature of Late Gunn-Peterson Troughs with Galaxy Surveys

Recent observations have discovered long (up to ~110 Mpc/h), opaque Gunn-Peterson troughs in the z ~ 5.5 Lyman-alpha forest, which are challenging to explain with conventional models of the post-reionization intergalactic medium. Here we demonstrate that observations of the galaxy populations in the vicinity of the deepest troughs can distinguish two competing models for these features: deep voids where the ionizing background is weak due to fluctuations in the mean free path of ionizing photons would show a deficit of galaxies, while residual temperature variations from extended, inhomogeneous reionization would show an overdensity of galaxies. We use large (~550 Mpc/h) semi-numerical simulations of these competing explanations to predict the galaxy populations in the largest of the known troughs at z ~ 5.7. We quantify the strong correlation of Lyman-alpha effective optical depth and galaxy surface density in both models and estimate the degree to which realistic surveys can measure such a correlation. While a spectroscopic galaxy survey is ideal, we also show that a relatively inexpensive narrowband survey of Lyman-alpha-emitting galaxies is ~90% likely to distinguish between the competing models.Comment: 12 pages, 16 figures. Submitted to Ap

Appraising weak and strong sustainability: searching for a middle ground

This paper seeks to address the ongoing issue of weak and strong sustainability, searching for a middle ground. It discusses the differences between weak and strong sustainability arguing for equality and equity between nature and humankind though movement towards an eco-socio-feminist perspective as an idealist point of view. Through this, full equality and balance may be attained