Use of fallout tracers 7Be, 210Pb and 137Cs to distinguish the form of sub‐surface soil erosion delivering sediment to rivers in large catchments          下载免费PDF全文

Gary J. Hancock  Scott N. Wilkinson  Aaron A. Hawdon  Rex J. Keen 《水文研究》2014,28(12):3855-3874

Fallout radionuclides (FRNs) ¹³⁷Cs and ²¹⁰Pb are well established as tracers of surface and sub‐surface soil erosion contributing sediment to river systems. However, without additional information, it has not been possible to distinguish sub‐surface soil erosion sources. Here, we use the FRN ⁷Be (half‐life 53 days) in combination with ¹³⁷Cs and excess ²¹⁰Pb to trace the form of erosion contributing sediment in three large river catchments in eastern Australia; the Logan River (area 3700 km²), Bowen River (9400 km²) and Mitchell River (4700 km²). We show that the combination of ¹³⁷Cs, excess ²¹⁰Pb and ⁷Be can discriminate horizontally aligned sub‐surface erosion sources (rilled and scalded hillslopes and the floors of incised drainage lines and gully ‘badland’ areas) from vertical erosion sources (channel banks and gully walls). Specifically, sub‐surface sources of sediment eroded during high rainfall and high river flow events have been distinguished by the ability of rainfall‐derived ⁷Be to label horizontal soil surfaces, but not vertical. Our results indicate that in the two northern catchments, erosion of horizontal sub‐surface soil sources contributed almost as much fine river sediment as vertical channel banks, and several times the contribution of hillslope topsoils. This result improves on source discrimination provided previously and indicates that in some areas erosion of hillslope soils may contribute significantly to sediment yield, but not as topsoil loss. We find that in north‐eastern Australia, scalded areas on hillslopes and incising drainage lines may be sediment sources of comparable importance to vertical channel banks. Previous studies have used the combination of ¹³⁷Cs, excess ²¹⁰Pb and ⁷Be to estimate soils losses at the hillslope scale. Here, we show that with timely and judicious sampling of soil and sediment during and immediately after high flow events ⁷Be measurements can augment fallout ¹³⁷Cs and ²¹⁰Pb to provide important erosion source information over large catchments. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Tectonic interpretations of enigmatic structures in the North Anatolian fault zone     

P.L Hancock  A.A Barka 《Journal of Structural Geology》1983,5(2):217-220

Two geometrically distinct groups of syn-sedimentary and post-depositional mesofaults and joints cut Neogene-Quaternary sediments in basins situated along the convex-northwards arc of the North Anatolian fault zone between Çerkes and Erbaa. One group comprises second-order fractures interpreted as having developed during episodes of right-lateral shear along the fault zone, while the morphologically identical fractures in the other group have been interpreted as secondary products of left-lateral shear; thus apparently implying one or more former episodes of eastwards motion of the Anatolian scholle. Because such a reversal of motion would be counter to the well-established westward escape of Anatolia the structures have been called anomalous or incompatible.Alternative hypotheses which have been advanced to explain the development of the anomalous mesofractures include: localized reversals related to displacements of rigid blocks acting as buttresses within basins; selective operation of intra-pull-apart strike-slip faults; stress release; the coincidence of the present western sector of the fault with an older left-lateral fault zone; and the influence of a North Turkish neotectonic stress regime.  相似文献   

Opposed shear senses inferred from neotectonic mesofracture systems in the North Anatolian fault zone     

P.L. Hancock  A.A. Barka 《Journal of Structural Geology》1981,3(4):383-392

The 1200-km long North Anatolian fault zone is a right-lateral, intracontinental transform boundary which was initiated in the Late Neogene. Sediments of Pliocene to Holocene age in basins between Cerkes and Erbaa, within the convex-northwards arc of the fault zone, are deformed by syn-sedimentary and post-depositional mesoscopic faults and joints. The mesofractures, which strike obliquely to the fault zone, include reverse faults, normal faults, normal shear joints, conjugate vertical joints and strike-slip faults. Each type of structure occurs in two geometrical groups, one comprises four systems of fractures, the other is made up of five systems. The directions of secondary compression and/or extension inferred from the first group of mesofractures, which are restricted to sediments of Pliocene to Early Pleistocene age, are interpreted as being related to left-lateral shear along the North Anatolian fault zone. The directions of compression and/or extension inferred from the second group of mesofractures, which cut sediments of Pliocene to late Holocene age, were generated during right-lateral shear.The presence of the second group of mesofractures is understandable because they are related to the shear sense which operates at the present-day, but those interpreted as being related to left-lateral shear are more puzzling: their development implies one or more reversals of the dominant sense of displacement. Several tentative models to explain such reversals are proposed, including regional and local influences, the latter related to mechanical constraints and/or the effects of other fault systems.  相似文献   

Searching behaviour and catch of horse mackerel (Trachurus murphyi) by industrial purse-seiners off south-central Chile   总被引：2，自引：0，他引：2  

Hancock  Jim; Hart  Paul J. B.; Antezana  Tarcisio 《ICES Journal of Marine Science》1995,52(6):991-1004

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Species diversity of the Okavango Delta, Botswana   总被引：4，自引：0，他引：4  

Lars Ramberg  Peter Hancock  Markus Lindholm  Thoralf Meyer  Susan Ringrose  Jan Sliva  Jo Van As  Cornelis Vander Post 《Aquatic Sciences - Research Across Boundaries》2006,68(3):310-337

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The Influence of Strong-Motion Duration on the Seismic Response of Masonry Structures   总被引：2，自引：3，他引：2  

Julian J. Bommer  Guido Magenes  Jonathan Hancock  Paola Penazzo 《Bulletin of Earthquake Engineering》2004,2(1):1-26

The influence of strong-motion duration on the response of saturated soils is clearly recognised and accounted for in the assessment of liquefaction potential. The degree to which duration of shaking influences damage to structures, however, remains a topic of debate, with resolution of the issue complicated by the variety of definitions of duration and the variety of structural behaviours, as well as the difficulty of decoupling the specific effect of duration from other features of the ground motion. A suite of seven structural models with strength and stiffness degrading characteristics, designed to reflect the seismic behaviour of masonry structures commonly encountered in many parts of Europe, are analysed using a suite of almost 500 strong-motion accelerograms. Correlations are explored between the damage, measured in terms of the strength degradation, and a range of strong-motion parameters, demonstrating that Arias intensity and spectral acceleration at the fundamental initial period of the structure are both reasonably good damage indicators for such structures. A significantly improved correlation is obtained by using the elastic spectral accelerations averaged over a period range from the initial period of the structure to a value approximately three times greater, reflecting the stiffness degradation as the shaking progresses. The scatter in the correlation is shown to be partially explained by differences in duration. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The use of a landscape simulator in the validation of the SIBERIA landscape evolution model: transient landforms     

G. R. Hancock  G. R. Willgoose 《地球表面变化过程与地形》2002,27(12):1321-1334

SIBERIA is a physically based model for the geomorphic evolution of landforms. It is essential that the SIBERIA model be tested or validated against controlled landform development. Previous studies have demonstrated that SIBERIA is able to simulate declining equilibrium landforms and in this paper we examine SIBERIA's ability to simulate landforms as they evolve to their declining equilibrium form. These landscapes are termed transient landforms. Landscapes generated by SIBERIA were compared to those produced by a physical model (experimental model landforms) at stages of evolution. Comparison of the experimental landscapes with the simulated landscapes using total mass, hypsometric curve, width function, cumulative area distribution and area–slope demonstrate that SIBERIA can simulate the experimental model landscape during development (i.e. transient landscapes). Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Geological Atlas of Alpine Europe and Adjoining Alpine Areas : Lemoine, M. (editor) 1978. Elsevier, Amsterdam. 584 pp. Price: hardcover US $170.75     

P. L. Hancock 《Journal of Structural Geology》1979,1(4):342-343

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The petrology of the Chalk     

Jake M. Hancock 《Proceedings of the Geologists' Association. Geologists' Association》1975,86(4):499-535

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Photometric calibration of the Swift ultraviolet/optical telescope     

T. S. Poole  A. A. Breeveld  M. J. Page  W. Landsman  S. T. Holland  P. Roming  N. P. M. Kuin  P. J. Brown  C. Gronwall  S. Hunsberger  S. Koch  K. O. Mason  P. Schady  D. Vanden Berk  A. J. Blustin  P. Boyd  P. Broos  M. Carter  M. M. Chester  A. Cucchiara  B. Hancock  H. Huckle  S. Immler  M. Ivanushkina  T. Kennedy  F. Marshall  A. Morgan  S. B. Pandey  M. de Pasquale  P. J. Smith  M. Still 《Monthly notices of the Royal Astronomical Society》2008,383(2):627-645

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