e-VLBI observations of GHz-peaked spectrum radio sources in nearby galaxies from the AT20G survey     

Paul J. Hancock  Steven J. Tingay  Elaine M. Sadler  Chris Phillips  Adam T. Deller 《Monthly notices of the Royal Astronomical Society》2009,397(4):2030-2036

Gigahertz-peaked spectrum (GPS) radio sources are thought to be young objects which later evolve into Fanaro–Riley type I (FR I) and FR II radio galaxies. We have used the Australia Telescope 20 GHz (AT20G) survey catalogue to select a uniform sample of GPS sources with spectral peaks above 5 GHz, which should represent the youngest members of this class. In this paper, we present e-VLBI observations of 10 such objects which are associated with nearby  ( z < 0.15)  galaxies and so represent a new population of local, low-power GPS sources. Our e-VLBI observations were carried out at 4.8 GHz with the Australia Telescope Long Baseline Array (LBA) using a real-time software correlator. All 10 sources were detected, and were unresolved on scales of ∼100 mas, implying that they are typically less than 100 pc in linear size.  相似文献   

Normal fault zone evolution and fault scarp degradation in the Aegean region   总被引：1，自引：0，他引：1  

IAIN S. Stewart  PAUL L. Hancock 《Basin Research》1988,1(3):139-153

Abstract The initial stages of rift-basin evolution are periods of great landform change. Fault scarps are newly created axes of erosion which, along with footwall uplands, act as sediment sources for subsiding hanging wall basins. Scarps formed during neotectonic normal faulting of Mesozoic carbonates in mainland Greece and western Turkey display a varied pattern of degradation related to the history of fault development and variations in fault zone architecture. Alternating zone-parallel compact breccia sheets and incohesive breccia belts, of contrasting resistance to erosion, underlie scarps. Meso-scale slip-plane phenomena, such as corrugations, gutters, comb fractures, and pluck holes, together with geomorphological features, such as subsurface solution pipes, and vegetation result in initial variations in the denudability of erosionally resistant compact breccia sheets. Migration with time of slip-plane activity within a fault zone into its hanging wall (i.e. intrafault-zone hanging wall collapse) adds to the structural heterogeneity of fault scarp footwalls. Quaternary talus, whether offset across a fault, banked unconformably against a slip plane, or faulted against a reactivated slip plane, has a dampening effect on degradation. The complexities of fault zone architecture combined with a history of hanging wall collapse lead, in the Aegean region, to non-uniform degradation and scarps which are commonly stepped and occasionally cavitated.  相似文献   

The geological evolution of the British Isles: T.R. Owen. Pergamon, Oxford, 1976, 161 pp., hardback £5.50, softback £2.50     

P.L. Hancock 《Tectonophysics》1977,40(3-4):386-387

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Predicting earthquakes: Bolt B. (author of introductory passages) 1980. Earthquakes and Volcanoes. (Readings from Scientific American), Freeman, San Francisco. 154 pp, 89 colour illustrations, 36 black & white figures. Price: hard-cover £8.90; soft-cover £4.30.     

P.L. Hancock 《Journal of Structural Geology》1980,2(4)

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Tectonic significance of mesofracture systems associated with the Lebanese segment of the Dead Sea transform fault     

P.L. Hancock  M.S. Atiya 《Journal of Structural Geology》1979,1(2):143-153

A 3000 m Jurassic-Cretaceous-Palaeogene succession dominated by carbonates is deformed by NNE trending open folds of Palaeogene age. Conjugate wrench faults and a system of normal faults extend the fold belt axially and probably evolved during anticlockwise rotation in a transpressive regime related to the oblique convergence of the African and Arabian plates across the Lebanese segment of the Dead Sea transform fault. Three sets and four systems of conjugate mesoscopic fractures, symmetrically orientated with reference to bedding and the plunge of the fold in which they are contained, resulted in minor axial elongation. Pressure solution on surfaces striking parallel to the fold belt locally achieved up to 50% shortening.The N30°E vertical Yammouné Fault Zone, which connects with the principal rift faults to the north and south, is accompanied by mesostructures which indicate that displacements were dominantly left-lateral and that the 1–2 km Zone is younger than the folds, possibly of Neogene age.  相似文献   

New constraints on the late Cenozoic incision history of the New River, Virginia     

Dylan J. Ward  James A. Spotila  Gregory S. Hancock  John M. Galbraith   《Geomorphology》2005,72(1-4):54-72

The New River crosses three physiogeologic provinces of the ancient, tectonically quiescent Appalachian orogen and is ideally situated to record variability in fluvial erosion rates over the late Cenozoic. Active erosion features on resistant bedrock that floors the river at prominent knickpoints demonstrate that the river is currently incising toward base level. However, thick sequences of alluvial fill and fluvial terraces cut into this fill record an incision history for the river that includes several periods of stalled downcutting and aggradation. We used cosmogenic ¹⁰Be exposure dating, aided by mapping and sedimentological examination of terrace deposits, to constrain the timing of events in this history. ¹⁰Be concentration depth profiles were used to help account for variables such as cosmogenic inheritance and terrace bioturbation. Fill-cut and strath terraces at elevations 10, 20, and 50 m above the modern river yield model cosmogenic exposure ages of 130, 600, and 600–950 ka, respectively, but uncertainties on these ages are not well constrained. These results provide the first direct constraint on the history of alluvial aggradation and incision events recorded by New River terrace deposits. The exposure ages yield a long-term average incision rate of 43 m/my, which is comparable to rates measured elsewhere in the Appalachians. During specific intervals over the last 1 Ma, however, the New River's incision rate reached 100 m/my. Modern erosion rates on bedrock at a prominent knickpoint are between 28 and 87 m/my, in good agreement with rates calculated between terrace abandonment events and significantly faster than 2 m/my rates of surface erosion from ancient terrace remnants. Fluctuations between aggradation and rapid incision operate on timescales of 10⁴− 10⁵ year, similar to those of late Cenozoic climate variations, though uncertainties in model ages preclude direct correlation of these fluctuations to specific climate change events. These second-order fluctuations appear within a longer-term signal of dominant aggradation (until 2 Ma) followed by dominant incision. A similar signal is observed on other Appalachian rivers and may be the result of sediment supply fluctuations driven by the increased frequency of climate changes in the late Cenozoic.  相似文献   

Tectonics of an early Proterozoic geosuture: The Halls Creek orogenic sub-province, northern Australia     

S.L. Hancock  R.W.R. Rutland 《Journal of Geodynamics》1984,1(3-5)

The exposed elements of the Lower Proterozoic orogenic belts of the Halls Creek sub-province, Northern Australia, lie in fault zones which have suffered repeated tectonic activity at various times through the Proterozoic and Phanerozoic. The Halls Creek and King Leopold orogenic domains subtend an angle of 80° and are characterized by linear late tectonic batholithic complexes several hundred kilometres long but only a few tens of kilometres wide, reminiscent of those in Phanerozoic Cordilleran orogenies. The associated superposed folding and high temperature metamorphism are more akin to those in Phanerozoic collision orogenies.The sub-province is analyzed in the wider context of the North Australian orogenic province which was deformed, metamorphosed and intruded by granitic plutons approximately 1900-1800 Ma ago. In this province the Archaen basement was extended and broken into a mosaic of blocks, some of which (now largely concealed by younger Kimberley and McArthur basin sediments) retained a more positive character and fed sediment to intervening regions (such as the Pine Creek Geosyncline) which suffered greater extension and subsidence, but which retained a thinned Archaean basement.The Halls Creek Group was deposited in a trough to the south-east of the Kimberley island continent, and deposition was probably broadly contemporaneous with, and continuous with, that in the Pine Creek geosyncline. A volcanic—fine grained clastic—carbonate phase of marine deposition, following basin formation, is represented by the Biscay Formation. During the later phase of basin evolution widespread flysch facies (Olympio Formation), partly derived from the island continent, was deposited and is now preserved in low grade zones on both sides of the main belt of high strain and upper amphibolite to lower granulite facies metamorphism which displays recumbent folding and nappe tectonics with fold axes oblique to the major faults.No island arc compex or paired metamorphic belts are present in the orogenic belts, and it is concluded that the lithospheric extension and subsequent convergence did not involve the generation of oceanic crust or B-subduction.In the Halls Creek domain vergence is south-easterly across all zones and is related to oblique convergence leading to limited A-subduction of the basinal area in the south-east beneath the island continent to the north-west, accompanied by left-lateral strike-slip or transform fault movements on the north-trending major faults. The convergence generated the associated high temperature metamorphism and plutonism on the leading edge of the lower plate.A phase of upright folding (with trends varying continuously form E-W in the King Leopold belt to NNE-SSW in the Halls Creek belt) intervenes between the main recumbent deformation and metamorphism (ca 1920 Ma ago) and the emplacement of the late tectonic granite batholiths (ca 1840 Ma ago) which are fault controlled.The province represents a distinctive type of linear Proterozoic ensialic orogeny, not explicitly identified previously, and it needs to be distinguished both from true collision orogenies of the Phanerozoic, involving a Wilson Cycle, and from the areally extensive Proterozoic orogenies with which it is associated. Its essential characteristics are due to convergence between a small continent and an ‘oceanic’ area underlain by thin continental crust, resulting in limited A-subduction of the latter prior to crustal shortening.  相似文献   

Referees for volume 5     

Paul Hancock  Tony Barber  Susan Treagus  Peter Hudleston  John Platt 《Journal of Structural Geology》1983,5(6):633

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A comparison of SRTM and high‐resolution digital elevation models and their use in catchment geomorphology and hydrology: Australian examples     

G. R. Hancock  C. Martinez  K. G. Evans  D. R. Moliere 《地球表面变化过程与地形》2006,31(11):1394-1412

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Revisiting the hypsometric curve as an indicator of form and process in transport-limited catchment     

Garry Willgoose  Greg Hancock 《地球表面变化过程与地形》1998,23(7):611-623

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