Factors affecting trans-Tasman air services

International civil aviation is circumscribed by a plethora of bilateral air service agreements between sovereign nations. In recent years there has been a marked trend to liberalise these agreements as well as moves to create multilateral common markets as appear to be emerging in Europe. Airline managements are being given opportunities to implement operational strategies once severely proscribed in confidential memoranda of understanding lying behind the public bilateral documents. In keeping with the philosophy of extending the Closer Economic Relations (CER) agreement, Australia and New Zealand have been exploring the ramifications of bringing trade in air services within the ambit of CER. This paper examines some of the factors affecting the trans Tasman civil aviation environment and discusses the implications of modifications to air services in and between Australia and New Zealand.     

14C dating and palaeoenvironment of the historic ‘little ice age’ glacier advance of Nigardsbreen Southwest Norway

Moss and grass remains associated with a well-developed in situ palaeosol buried beneath a moraine ridge in front of Nigardsbreen (Jostedalsbreen ice cap, southern Norway) have been ¹⁴C-dated. Pollen preserved with the plant remains suggests the existence of an agricultural landscape prior to the deposition of the moraine. The calibrated dates and the pollen spectra are in close accord with historically-documented evidence for the timing and palaeoenvironment of the ‘Little Ice Age’ advance of the glacier. Considerable potential is indicated for estimating the maximum ages of moraine ridges and for palaeoenvironmental reconstruction where such documentary evidence does not exist.     

The linkage between velocity patterns and sediment entrainment in a forced‐pool and riffle unit

A field‐based project was initiated in order to characterize velocities and sediment entrainment in a forced‐pool and riffle sequence. Three‐dimensional velocities and turbulence intensities were measured with an acoustic Doppler velocimeter at 222 different points at three similar flows that averaged approximately 4·35 m³ s⁻¹ within a large pool–riffle unit on North Saint Vrain Creek, Colorado. Sediment‐sorting patterns were observed with the introduction of 500 tracer particles painted according to initial seeding location. Tracer particles moved sporadically during a 113 day period in response to the annual snowmelt peak flow, which reached a maximum level of 14·8 m³ s⁻¹. Velocity data indicate high instantaneous velocities and turbulence levels in the centre of pools. Patterns of sediment deposition support the notion that stream competence is higher in the pool than the downstream riffle. Flow convergence around a large channel constriction appears to play a major role in multiple processes that include helical flow development and sediment routing, and backwater development with low velocities and turbulence levels above the constriction that may locally limit sediment supply. Jet flow, flow separation, vortex scour and turbulence generation enhance scour in the centre of pools. Ultimately, multiple processes appear to play some role in maintenance of this forced pool and the associated riffle. Copyright © 2008 John Wiley & Sons, Ltd.     

Organized Subsurface Flows near Active Regions

Local helioseismic techniques, such as ring analysis and time-distance helioseismology, have already shown that large-scale flows near the surface converge towards major active regions. Ring analysis has further demonstrated that at greater depths some active regions exhibit strong outflows. A critique leveled at the ring-analysis results is that the Regularized Least Squares (RLS) inversion kernels on which they are based have negative sidelobes near the surface. Such sidelobes could result in a surface inflow being misidentified as a diverging outflow at depth. In this paper we show that the Optimally Located Averages (OLA) inversion technique, which produces kernels without significant sidelobes, generates flows markedly similar to the RLS results. Active regions are universally zones of convergence near the surface, while large complexes evince strong outflows deeper down.     

LA‐ICP‐MS Pb isotope test of meteorite provenance: A terrestrial origin for Lovina

Lovina, classified as an ungrouped ataxite, is controversial and its identity as a meteorite has been questioned. In this work, we use Pb isotopes on targeted troilite nodules in Lovina as a test of its antiquity and provenance. Although precise ages cannot be obtained, LA‐ICP‐MS offers a rapid, straightforward procedure to establish the source of lead, whether ancient (meteoritic) or modern (terrestrial). For nine pristine, unweathered nodules in Lovina, we find a lead isotopic composition of: ²⁰⁶Pb/²⁰⁸Pb = 0.492 ± 0.003 (2σ, MSWD 0.79; 95%) and ²⁰⁷Pb/²⁰⁶Pb = 0.852 ± 0.003 (2σ, MSWD 1.09; 95%) with no detectable uranium. All lead compositions of the troilite fall in the range expected for modern environmental and mantle lead and are distinctly different from the primordial Canyon Diablo Troilite (CDT) composition of ancient meteoritic troilite. Although the origin of Lovina remains unknown, we conclude that lead in the Lovina troilite is unsupported by U decay and originated from a terrestrial source.     

Magnetospheric accretion and pre-main-sequence stellar masses

We present a method of determining lower limits on the masses of pre-main-sequence (PMS) stars and so constraining the PMS evolutionary tracks. This method uses the redshifted absorption feature observed in some emission-line profiles of T Tauri stars, indicative of infall. The maximum velocity of the accreting material measures the potential energy at the stellar surface, which, combined with an observational determination of the stellar radius, yields the stellar mass. This estimate is a lower limit owing to uncertainties in the geometry and projection effects. Using available data, we show that the computed lower limits can be larger than the masses derived from PMS evolutionary tracks for M   0.5 M. Our analysis also supports the notion that accretion streams do not impact near the stellar poles but probably hit the stellar surface at moderate latitudes.     

Testing variations within the Tagish Lake meteorite—I: Mineralogy and petrology of pristine samples

Four samples (TL5b, TL11h, TL11i, and TL11v) from the pristine collection of the Tagish Lake meteorite, an ungrouped C2 chondrite, were studied to characterize and understand its alteration history using EPMA, XRD, and TEM. We determined that samples TL11h and TL11i have a relatively smaller proportion of amorphous silicate material than sample TL5b, which experienced low‐temperature hydrous parent‐body alteration conditions to preserve this indigenous material. The data suggest that lithic fragments of TL11i experienced higher degrees of aqueous alteration than the rest of the matrix, based on its low porosity and high abundance of coarse‐ and fine‐grained sheet silicates, suggesting that TL11i was present in an area of the parent body where alteration and brecciation were more extensive. We identified a coronal, “flower”‐like, microstructure consisting of a fine‐grained serpentine core and coarse‐grained saponite‐serpentine radial arrays, suggesting varied fluid chemistry and crystallization time scales. We also observed pentlandite with different morphologies: an exsolved morphology formed under nebular conditions; a nonexsolved pentlandite along grain boundaries; a “bulls‐eye” sulfide morphology and rims around highly altered chondrules that probably formed by multiple precipitation episodes during low‐temperature aqueous alteration (≥100 °C) on the parent body. On the basis of petrologic and mineralogic observations, we conclude that the Tagish Lake parent body initially contained a heterogeneous mixture of anhydrous precursor minerals of nebular and presolar origin. These materials were subjected to secondary, nonpervasive parent‐body alteration, and the samples studied herein represent different stages of that hydrous alteration, i.e., TL5b (the least altered) < TL11h < TL11i (the most altered). Sample TL11v encompasses the petrologic characteristics of the other three specimens.