Structure and tectonics along the inner edge of a foreland basin: The Hunter Coalfield in the northern Sydney Basin,New South Wales

From the early Late Permian onwards, the northeastern part of the Sydney Basin, New South Wales, (encompassing the Hunter Coalfield) developed as a foreland basin to the rising New England Orogen lying to the east and northeast. Structurally, Permian rocks in the Hunter Coalfield lie in the frontal part of a foreland fold‐thrust belt that propagated westwards from the adjacent New England Orogen. Thrust faults and folds are common in the inner part of the Sydney Basin. Small‐scale thrusts are restricted to individual stratigraphic units (with a major ‘upper decollement horizon’ occurring in the mechanically weak Mulbring Siltstone), but major thrusts are inferred to sole into a floor thrust at a poorly constrained depth of approximately 3 km. Folds appear to have formed mainly as hangingwall anticlines above these splaying thrust faults. Other folds formed as flat‐topped anticlines developed above ramps in that floor thrust, as intervening synclines ahead of such ramp anticlines, or as decollement folds. These contractional structures were overprinted by extensional faults developed during compressional deformation or afterwards during post‐thrusting relaxation and/or subsequent extension. The southern part of the Hunter Coalfield (and the Newcastle Coalfield to the east) occupies a structural recess in the western margin of the New England Orogen and its offshore continuation, the Currarong Orogen. Rocks in this recess underwent a two‐stage deformation history. West‐northwest‐trending stage one structures such as the southern part of the Hunter Thrust and the Hunter River Transverse Zone (a reactivated syndepositional transfer fault) developed in response to maximum regional compression from the east‐northeast. These were followed by stage two folds and thrusts oriented north‐south and developed from maximum compression oriented east‐west. The Hunter Thrust itself was folded by these later folds, and the Hunter River Transverse Zone underwent strike‐slip reactivation.     

Instability of the Kuroshio in Luzon Strait: Effects of ridge topography and stratification

The spectral analyses of moored current velocities in the central Luzon Strait reveal northward (i.e., downstream of the Kuroshio) propagation of a frontal wave with a five-day period, with wave amplitude increasing northward. Estimated from both curve fitting and frequency domain Empirical Orthogonal Function methods, the characteristics of five-day variations have wave speeds ranging from 32 to 40 cm s⁻¹, wavelengths ranging from 130 to 150 km, and e-folding time scales for growth ranging from 0.8 to 3 days. An analytical two-layer model used to explore linear stability characteristics indicates that bottom topography (two meridional ridges) is important for the Kuroshio stability characteristics in the Luzon Strait. In the two-layer model with the two ridges, the flow is stabilized for the long-wave mode but destabilized for the short-wave mode (due to increasing vertical shear in the horizontal velocity). The analytical model produces wavelengths and phase speeds for the most unstable mode which is similar to the observation, but the growth rate is underestimated. However, a spectral numerical model applied with a more realistic stratification and velocity structure does obtain faster growth rates comparable to the observations. Parameter sensitivity tests were conducted using the analytical model. The characteristics of the most unstable mode are most sensitive to the surface front location relative to the bottom topography but not sensitive to varying the density difference and thickness of the upper layer.     

Holocene Treeline History and Climate Change Across Northern Eurasia

Radiocarbon-dated macrofossils are used to document Holocene treeline history across northern Russia (including Siberia). Boreal forest development in this region commenced by 10,000 yr B.P. Over most of Russia, forest advanced to or near the current arctic coastline between 9000 and 7000 yr B.P. and retreated to its present position by between 4000 and 3000 yr B.P. Forest establishment and retreat was roughly synchronous across most of northern Russia. Treeline advance on the Kola Peninsula, however, appears to have occurred later than in other regions. During the period of maximum forest extension, the mean July temperatures along the northern coastline of Russia may have been 2.5° to 7.0°C warmer than modern. The development of forest and expansion of treeline likely reflects a number of complimentary environmental conditions, including heightened summer insolation, the demise of Eurasian ice sheets, reduced sea-ice cover, greater continentality with eustatically lower sea level, and extreme Arctic penetration of warm North Atlantic waters. The late Holocene retreat of Eurasian treeline coincides with declining summer insolation, cooling arctic waters, and neoglaciation.     

Promising signs of regeneration of blue cod and oyster habitat changed by dredging in Foveaux Strait,southern New Zealand

Epifaunal reefs in Foveaux Strait are oyster (Ostrea chilensis Philippi, 1845) habitat. One hundred and thirty years of oyster dredging has diminished the complexity and distribution of these reefs. Commercial densities of blue cod (Parapercis colias (Forster in Bloch and Schneider, 1801)) were discovered on epifaunal reef habitat in 1989 and became the focus of a major blue cod fishery. We document habitat changes that followed the closing of the oyster fishery in 1993 and interactions between the blue cod and oyster fisheries after the oyster fishery was reopened in 1996. Evidence from blue cod fishers and oyster surveys suggests that the benthic habitat of some oyster beds regenerated in the absence of dredging and that the relative density of blue cod, and then oysters, rebuilt to commercial levels. Benthic habitat was modified once more when oyster dredging restarted and the relative density of blue cod on oyster beds fell again. The observations suggest that rotational fishing of oysters could mitigate the effects of dredging on habitat and that marine protected areas could expedite habitat recovery. Increasing habitat complexity and blue cod density on a reef of oyster shells formed by an oyster fisher suggests that habitat enhancement might remedy effects of dredging. The questions raised by the observations could be answered by management experiments on the scale of the fisheries.     

Nature of late‐Early to Middle Devonian tectonism in the Buckambool area,Cobar, New South Wales

In the Buckambool area, Cobar, New South Wales, the boundary between dominantly shallow‐water, shelf sediments of the Winduck Group and fluviatile sediments of the Mulga Downs Group has been established as a small hiatus not resolvable by available fossil age data. Although dips are parallel over much of the area, disconformable and locally angular unconformable relations are present. This hiatus, late‐Early to Middle Devonian in age, marks a period of uplift, localised folding and erosion. These reflect movement of basement blocks along major fractures that are now revealed as lineaments.

Terminal deformation in the area, reflected by folding and re‐activation of lineaments, postdated deposition of the Mulga Downs Group, and is probably Carboniferous in age.     

Magnetic fabrics of Paleozoic rocks across the Lachlan Transverse Zone from eastern New South Wales ∗

The anisotropy of magnetic susceptibility (AMS) was systematically measured for samples collected across the Lachlan Transverse Zone in the Eastern Subprovince of the Lachlan Orogen, New South Wales. Although the degree of anisotropy is usually moderate to low, it can be shown that the origin of the magnetic fabric is generally composite. Many localities are witness to a tectonic influence in addition to a magnetic foliation preserved from the time of rock formation (compaction). Furthermore, some localities indicate the presence of superimposed magnetic fabrics, potentially associated with a Silurian east–west direction of shortening, and a younger north–south (?) direction of shortening. Finally, the progressive southwards change in orientation of the magnetic lineation in the Molong area from north–south to east–west and then back to north–south again south of the Lyndhurst–Neville Fault suggests that the Lachlan Transverse Zone coincides with, and reflects, a major cross-structure in the Eastern Subprovince. AMS is thus a powerful tool to help map the fabric of Paleozoic rocks in the Tasmanides. Additional data will be required to help obtain a comprehensive picture of the tectonic history of the region.     

Climate projections of future extreme events accounting for modelling uncertainties and historical simulation biases

A methodology is presented for providing projections of absolute future values of extreme weather events that takes into account key uncertainties in predicting future climate. This is achieved by characterising both observed and modelled extremes with a single form of non-stationary extreme value (EV) distribution that depends on global mean temperature and which includes terms that account for model bias. Such a distribution allows the prediction of future “observed” extremes for any period in the twenty-first century. Uncertainty in modelling future climate, arising from a wide range of atmospheric, oceanic, sulphur cycle and carbon cycle processes, is accounted for by using probabilistic distributions of future global temperature and EV parameters. These distributions are generated by Bayesian sampling of emulators with samples weighted by their likelihood with respect to a set of observational constraints. The emulators are trained on a large perturbed parameter ensemble of global simulations of the recent past, and the equilibrium response to doubled CO₂. Emulated global EV parameters are converted to the relevant regional scale through downscaling relationships derived from a smaller perturbed parameter regional climate model ensemble. The simultaneous fitting of the EV model to regional model data and observations allows the characterisation of how observed extremes may change in the future irrespective of biases that may be present in the regional models simulation of the recent past climate. The clearest impact of a parameter perturbation in this ensemble was found to be the depth to which plants can access water. Members with shallow soils tend to be biased hot and dry in summer for the observational period. These biases also appear to have an impact on the potential future response for summer temperatures with some members with shallow soils having increases for extremes that reduce with extreme severity. We apply this methodology for London, using the A1B future emissions scenario to obtain projections of the 50 year return values for the 20 year period centred on 2050. We obtain 10th to 90th percentile ranges of 35.9–42.1 °C for summer daily maximum temperature, 35.5–52.4 mm for summer daily rainfall and 79.2, 97.0 mm for autumn 5 day total rainfall, compared to observed estimates for 1961–1990 of 35.7 °C, 42.1 and 78.4 mm respectively.