L' and M' standard stars for the Mauna Kea Observatories Near-Infrared system

We present L ' and M ' photometry, obtained at the United Kingdom Infrared Telescope (UKIRT) using the Mauna Kea Observatories Near-Infrared (MKO-NIR) filter set, for 46 and 31 standard stars, respectively. The L ' standards include 25 from the in-house 'UKIRT Bright Standards' with magnitudes deriving from Elias et al. and observations at the Infrared Telescope Facility in the early 1980s, and 21 fainter stars. The M ' magnitudes derive from the results of Sinton and Tittemore. We estimate the average external error to be 0.015 mag for the bright L ' standards and 0.025 mag for the fainter L ' standards, and 0.026 mag for the M ' standards. The new results provide a network of homogeneously observed standards, and establish reference stars for the MKO system, in these bands. They also extend the available standards to magnitudes which should be faint enough to be accessible for observations with modern detectors on large and very large telescopes.     

Geomagnetic line spectra-2 to 70 years

Application of a new data adaptive approach to power spectrum estimation has yielded greatly improved knowledge of the geomagnetic spectrum in the range 2 to 70 yr. The first successful line spectrum detection of the solar and double solar cycle variations in absolute geomagnetic element data are presented; also detected are the first four harmonics of the solar cycle and, excepting one, the first nine harmonics of the double solar cycle. Finally, evidence is found for a 60 yr line. The implications of these results for a variety of problems in planetary and space physics are discussed.     

Stratigraphy and architecture of the Upper Triassic Ischigualasto Formation,Ischigualasto Provincial Park,San Juan,Argentina

The Ischigualasto Formation in northwestern Argentina contains abundant fluvial channel sandstones, overbank mudstones, and paleosols that were deposited in a northwest-trending continental-rift basin during Late Triassic time. In the study area the formation progressively thins from ～700 m in the west to ～400 m in the east, over a distance of 7 km. This thinning is accompanied by a relative decrease in the abundance of fluvial channel sandstones and an increase in mud-rich overbank deposits and paleosols. While preserved channel deposits in the formation are highly variable in terms of their size and stratigraphic distribution, four general channel forms can be recognized based on their overall cross sectional geometry and internal sedimentary structures. Of these, the dominant channel-body types are interpreted as the deposits of sandy multi-channel fluvial systems. The internal stratigraphic architecture of the Ischigualasto Formation indicates that during deposition, the central part of the basin was the location of a long-lived, north flowing, fluvial channel belt that received relatively continuous channel and proximal overbank deposition. To the east, however, channel-related deposition was more infrequent, resulting in enhanced pedogenic modification of alluvial deposits. The overall thickness and facies trends observed in the Ischigualasto Formation most likely correspond to variations in fault-related accommodation development within the basin during the time of deposition.     

Periodic 18.6-year and cyclic 11-year induced drought and flood in northeastern China and some global implications

The general patterns of climatic evolution in China during the Holocene are reviewed, and following the postglacial eustatic rise of sea-level and the institution of the East Asian Monsoon, the systems and principal fluctuations are found to be concordant with those operating elsewhere in the globe. China's unique wealth of written history provides an abundance of proxy data on the climatic record and that record now furnishes a basis for analysing both long-term and short-term fluctuations, as well as sunspot behavior, that together provide an insight into extraterrestrial forcing. Recent Chinese work suggests a solar forcing, but our own studies suggest rather that a lunar tidal component, reinforced at times by the solar element may prove more important.Analysis of a drought-flood index for Peking (Beijing) in northeastern China since A.D. 1470 supports evidence (Hameed et al., 1983) for both periodic lunar nodal 18.6-year and solar cyclic 11-year induced drought-flood in the region. The nodal term exhibits bistable phasing with respect to epochs of tidal maxima (for our century epochs occurred at 1917.5, 1936.1, 1954.7 and 1973.3), a phenomenon previously found in drought-flood proxy data for South America (Currie, 1983), India (Currie, 1984a), North America (Currie, 1984d), and Africa (Hameed and Currie, 1985; Currie and Hameed, 1985). Solar cycle epochs of drought-flood are tabulated for the past two centuries, and compared with those from North America and Africa.     

Recognition and palaeohydrologic significance of fossil black fly larvae,with a key to the Nearctic genera (Diptera: Simuliidae)

Fossil black fly larvae of late Pleistocene and Holocene ages are reported from lacustrine deposits of coastal British Columbia, including the first record of the genus Parasimulium Malloch from Canada. Features that distinguish fossil larvae from the remains of other organisms are reviewed, and a key to the Nearctic genera based on features of the hypostoma presented. Fossil black fly larvae have potential for providing information about changes in fluvial conditions, and provide direct evidence about the composition of past faunas. The palaeohydrologic significance of late Quaternary assemblages from coastal British Columbia is discussed.     

The Topsails igneous terrane,Western Newfoundland: evidence for magma mixing

The Topsails igneous terrane of Western Newfoundland contains a diverse suite of igneous rocks, but consists mainly of Silurian alkaline to peralkaline granites and rhyolites. The terrane exhibits evidence for the coexistence of mafic and salic magmas in the form of composite dykes and flows, sinuous, boudined mafic dykes cutting granites and net vein complexes. Field data and major and trace element chemical data suggest that these magmas mixed to produce limited volumes of more or less homogeneous hydrids.Magma mixing, a process which has received recent prominence in petrogenetic models for calc-alkaline volcanic suites, has elicited less attention than restite separation and fractional crystallization as a cause of chemical dispersion in granites. Evidence from the Topsails igneous terrane suggests the possible importance of magma mixing to granite petrogenesis and a major role for transcurrent faulting in the origin and evolution of peralkaline magmas.     

Impact of exploratory offshore drilling on benthic communities in the Minerva gas field, Port Campbell, Australia

Changes to benthic infauna caused by exploratory gas drilling operations in the Minerva field were examined experimentally using a BACI (before, after, control, impact) design. Analysis of 72 x 0.1 m2 Smith-McIntyre grab samples obtained from one pre-drilling and three post-drilling periods yielded a diverse fauna consisting of 196 invertebrate species and 5035 individuals. Changes to benthic community structure were assessed using ANOVA and nonmetric multidimensional scaling (MDS). The abundances of two common species (Apseudes sp. 1 and Prionospio coorilla) decreased significantly at the well-head site immediately after drilling. The size of these reductions in abundance ranged between 71% and 88%, and persisted for less than 4 months after drilling. A third common species (Katlysia sp. 1) increased in abundance 200 m east of the well-head following drilling. Most species occurred at densities too low to be analysed individually and so were pooled at higher taxonomic levels. Changes in the abundance of species aggregated by phylum varied, but significant declines in the most abundant phyla (Crustaceans and Polychaetes) of 45-73% were observed at all sites within a 100 m radius of the well-head following drilling. In most cases these changes became undetectable four months after drilling following species recruitments. MDS ordinations confirm that drilling related changes to benthic community structure are most pronounced at stations located closest to the well-head. Additionally, the ordinations indicate that modified communities persist at the well-head for more than 11 months following exploratory drilling.     

Ocean acidification in New Zealand waters: trends and impacts

The threat posed by ocean acidification (OA) to the diversity and productivity of New Zealand marine ecosystems is assessed in a synthesis of published trends and impacts. A 20-year time series in Subantarctic water, and a national coastal monitoring programme, provide insight into pH variability, and context for experimental design, modelling and projections. A review of the potential impact of changes in the carbonate system on the major phyla in New Zealand waters confirms international observations that calcifying organisms, and particularly their early life-history stages, are vulnerable. The synthesis considers ecosystem and socio-economic impacts, and identifies current knowledge gaps and future research directions, including mechanistic studies of OA sensitivity. Advanced ecosystem models of OA, that incorporate the indirect effects of OA and interactions with other climate stressors, are required for robust projection of the future status of New Zealand marine ecosystems.