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101.
Katy Mee Jennie S. Gilbert David W. McGarvie José A. Naranjo Malcolm S. Pringle 《Bulletin of Volcanology》2009,71(8):933-952
Nevados de Chillán Volcanic Complex, central Chile, has been active for at least 640 ka—a period spanning a number of glacial
and interglacial periods. Geologic mapping, radiometric dating and geochemical analysis have identified six new volcanic units
and produced four new 40Ar/39Ar ages for Cerro Blanco, the northern subcomplex of Nevados de Chillán volcano. Compositions range from dacite to basaltic-andesite
and a new geologic map is presented. Examination of lava fracture structures on both newly mapped lavas and those mapped during
previous studies has enabled interpretations of former eruptive environments. Palaeoenvironment reconstructions, combined
with 40Ar/39Ar ages and comparison with the marine oxygen isotope record, show that at least three phases of volcanic activity have occurred
during the evolution of Cerro Blanco: (1) a constructive, pre-caldera collapse period; (2) a period of caldera formation and
collapse; and (3) a constructive period of dome growth forming the modern day volcanic centre. This style of volcanic evolution,
whereby large-scale caldera collapse is followed by growth of a new stratocone is common at Andean volcanoes. 相似文献
102.
John W. Magee Gifford H. Miller Nigel A. Spooner Danielle G. Questiaux Malcolm T. McCulloch Peter A. Clark 《Quaternary Geochronology》2009,4(2):84-92
A whole emu egg, with infilling sediment believed to be coeval with egg laying and burial, was found in late Pleistocene lunette sediments near Lake Eyre, central Australia. The stratigraphic context and initial amino acid racemization (AAR) results suggested an age between 25 ka and 35 ka, ideal for a multiple cross-dating comparison. The sediment infilling the egg provided material for luminescence dating that minimized problems of association. Age estimations from AAR, 14C and U series methods were obtained from the eggshell and optically stimulated luminescence (OSL) of the infilling sediment. All methods agreed within their respective dating uncertainties confirming the utility of all four methods. They indicate an age for the emu egg of 31.24 ± 0.34 ka. 相似文献
103.
Marine Geophysical Research - We have estimated empirical relationships that associate the age of the Pacific oceanic lithosphere with the seismic energy released on both flanks of the East Pacific... 相似文献
104.
Modelling and extracting 3D geographical data presents numerous challenges that require continual research to attempt to evolve an efficient, reliable and accurate solution. LiDAR data capture and analysis has become a preferred acquisition choice for elevation data because the resulting quality and level of detail far exceeds traditional methods for large survey areas. As with any data collection system, LiDAR is prone to errors. Analysing these errors, ascertaining causes and producing error correction strategies is vital if accurate and confident results are to be obtained. Eight years of LiDAR datasets (from 1998 to 2005) have been closely analysed for a large coastal area of South Wales. This article provides a detailed and accurate summary of the identified LiDAR data issues and subsequent errors which affect the accuracy of end products such as Digital Surface Models (DSMs). 相似文献
105.
Faggioni Osvaldo Beverini Nicolò Carmisciano Cosmo Giori Italiano 《Marine Geophysical Researches》2001,22(2):63-79
We show the results obtained by means of a seabed reduction technique on the intensity of geomagnetic anomaly fields applied
to a synthetic case and then to the real case of a geomagnetic survey of eastern Ligurian Sea (Italy). The eastern Ligurian
Sea has very intense short waves anomaly fields and a sea bed that varies greatly in depth. As a result the geomagnetic space
signal is characterized by a very large spectral content; in these conditions it is not possible to obtain a full sampled
marine survey and vertical continuation analytic procedures and standard numerical bottom reduction based on a single vertical
incremental parameter, whichever is applicable, fails to give accurate results. The present technique, which has been fine-tuned
over 4 years of experimentation in environmental researchs, aims to provide a simple and efficient means to reduce the distortion
of geomagnetic anomalies field caused by the variation of distance between survey plane and magnetic outcrop source position.
The compensation procedure is based on evaluation, by comparison of two measurements carried out at different altitudes, of
the mean vertical increment typical of each anomaly field principal frequency component bands. The component anomaly fields
are then corrected by application of the corresponding vertical increments and lastly, the anomaly geomagnetic field reduced
to the sea-bed is computed as Inverse Fourier Transform of a spectrum built as synthesis of the component anomaly fields'
spectra. The results obtained have shown a notable increase in definition of anomaly field intensity without the production
of appreciable distortions or false geomagnetic echoes.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
106.
107.
Nicol Morton 《《幕》》2008,31(4):420-422
The Jurassic is traditionally famous for shallow marine sediments that are often very fossiliferous, notably in Europe, where the standard chronostratigraphic subdivisions were established and defined. However, widespread marginal and non-marine Jurassic sediments are also known, and are of great importance for the wellpreserved terrestrial biotas they contain, as well as for their hydrocarbon and coal reserves. IGCP Project 506 is directed towards finding means of correlation between marine and non-marine Jurassic rocks, as a foundation for a better understanding of the evolution of the Earth during the Jurassic Period. 相似文献
108.
Regional magma plumbing and emplacement mechanisms of the Faroe‐Shetland Sill Complex: implications for magma transport and petroleum systems within sedimentary basins 下载免费PDF全文
Nick Schofield Simon Holford John Millett David Brown David Jolley Simon R. Passey Dave Muirhead Clayton Grove Craig Magee Joanne Murray Malcolm Hole Christopher A.‐L. Jackson Carl Stevenson 《Basin Research》2017,29(1):41-63
The movement of magma through the shallow crust and the impact of subsurface sill complexes on the hydrocarbon systems of prospective sedimentary basins has long been an area of interest and debate. Based on 3D seismic reflection and well data, we present a regional analysis of the emplacement and magmatic plumbing system of the Palaeogene Faroe‐Shetland Sill Complex (FSSC), which is intruded into the Mesozoic and Cenozoic sequences of the Faroe‐Shetland Basin (FSB). Identification of magma flow directions through detailed seismic interpretation of approximately 100 sills indicates that the main magma input zones into the FSB were controlled primarily by the NE–SW basin structure that compartmentalise the FSB into its constituent sub‐basins. An analysis of well data shows that potentially up to 88% of sills in the FSSC are <40 m in thickness, and thus below the vertical resolution limit of seismic data at depths at which most sills occur. This resolution limitation suggests that caution needs to be exercised when interpreting magmatic systems from seismic data alone, as a large amount of intrusive material could potentially be missed. The interaction of the FSSC with the petroleum systems of the FSB is not well understood. Given the close association between the FSSC and potential petroleum migration routes into some of the oil/gas fields (e.g. Tormore), the role the intrusions may have played in compartmentalisation of basin fill needs to be taken fully into account to further unlock the future petroleum potential of the FSB. 相似文献
109.
Modelling landscape evolution on geological time scales: a new method based on irregular spatial discretization 总被引:5,自引:0,他引:5
We present simulations of large-scale landscape evolution on tectonic time scales obtained from a new numerical model which allows for arbitrary spatial discretization. The new method makes use of efficient algorithms from the field of computational geometry to compute the set of natural neighbours of any irregular distribution of points in a plane. The natural neighbours are used to solve geomorphic equations that include erosion/deposition by channelled flow and diffusion. The algorithm has great geometrical flexibility, which makes it possible to solve problems involving complex boundaries, radially symmetrical uplift functions and horizontal tectonic transport across strike-slip faults. The algorithm is also ideally suited for problems which require large variations in spatial discretization and/or self-adaptive meshing. We present a number of examples to illustrate the power of the new approach and its advantages over more 'classical' models based on regular (rectangular) discretization. We also demonstrate that the synthetic river networks and landscapes generated by the model obey the laws of network composition and have scaling properties similar to those of natural landscapes. Finally we explain how orographically controlled precipitation and flexural isostasy may be easily incorporated in the model without sacrificing efficiency.
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110.