The use of the slope–area function to analyse process domains in complex badland landscapes     

Francesca Vergari  Francesco Troiani  Hazel Faulkner  Maurizio Del Monte  Marta Della Seta  Sirio Ciccacci  Paola Fredi 《地球表面变化过程与地形》2019,44(1):273-286

This paper explores the effectiveness of the widely-used functional relationship between drainage area (A in m²) and slope (S in m/m) to identify local process domains and aid interpretation of process interactions in a complex badland landscape. In order to perform this investigation, a series of sub-basins tributary to the Formone River in the Orcia catchment (central Italy) were selected as a suitable study area within which to explore our questions, given these basins' general representativeness of local terrain, the availability of a high resolution digital terrain model and previous extensive geomorphological research. Eroding basins containing both calanchi and landslides are common in the sub-humid badland landscape of central Italy, where field observation identifies a complex pattern of erosive processes associated with a history of uplift, despite which parts of the local landscape appear disconnected. Results reveal that the shape of all S–A curves (plotted using S data binned on log A) is comparable with that described in the literature, although sub-basins containing calanchi generally plot with higher S values than non-calanchi ones, except in the ‘fluvial’ section of the plots. Second, when viewed on total data (non-binned) S–A plots, landslide source area domains and calanchi domains are entirely coincident in all basins, supporting a cause–effect relationship. Additional plotting of the frequency characteristics of the raw data in a new way supports the interpretation that calanchi frequently initiate in landslide scars. In general though, although the S–A plots can contribute to the disentanglement of geomorphological behaviour in some complex erosional landscapes, it became apparent that in this landscape, process domains do not separate out with clarity along the A axis as suggested by theory. Despite this, an alternative, broader-scale morphoevolutive model can be proposed for the development of within-landslide calanchi, driven by changes to basin connectivity to the base channel. © 2018 John Wiley & Sons, Ltd.  相似文献   

The Kansas University meteorit     

D. m. Schneider  P. h. Benoit  D. w. g. Sears  A. j. t. Jull 《Meteoritics & planetary science》1997,32(Z4):A149-A150

Abstract— A new 2.8 kg meteorite find from the United States, Kansas University, is classified as an L6 (S3) chondrite based on optical microscopy and electron microprobe analysis of mafic minerals. Natural thermo-luminescence (TL) and ¹⁴C measurements suggest that the Kansas University meteorite has a short terrestrial age compared to other meteorite finds from this area and is not paired with the other local meteorite finds, Densmore (1879), Lawrence, Kansas and Long Island, Kansas.  相似文献   

Editorial ethics     

Derek Sears 《Meteoritics & planetary science》1997,32(2):153-153

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“The Evolution of igneous asteroids: Focus on Vesta and the HED meteorites” Houston,Texas, 1996 October 16–18     

Derek Sears 《Meteoritics & planetary science》1997,32(1):3-3

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SKETCHES IN THE HISTORY OF METEORITICS 2: THE EARLY CHEMICAL AND MINERALOGICAL WORK     

D.W Sears  H. Sears 《Meteoritics & planetary science》1977,12(1):27-46

The chemical and mineralogical work on meteorites over the period 1800 to 1840 is reviewed. The number of elements known to be present in meteorites rose from six to 19. Chemical techniques advanced rapidly so that by 1815 the procedure was essentially that of modern wet chemical analysts: removal of the magnetic material, dissolution of the acid-soluble portion and fusion of the remainder with alkali. After Bournon's work in 1802 much mineralogical progress was made during the 1820's, notably by G. Rose. Berzelius made important contributions by his own analyses and synthesis of the work of others. By 1840 ordinary chondrites, carbonaceous chondrites, plagioclase-pyroxene achondrites, Chassigny, pallasites and octahedrites could all be distinguished  相似文献   

METAL OF HIGH Co CONTENT IN LL CHONDRITES     

D.W. Sears  H.J. Axon 《Meteoritics & planetary science》1976,11(2):97-100

Measurements on the metal of the LL chondrites Appley Bridge, Jelica, Olivenza, and Khanpur have shown that the Co: Ni ratio of the metal is near 1.24 and that Prior's law appears to be followed to some extent within the LL group.  相似文献   

THERMOLUMINESCENCE AND THE TERRESTRIAL AGE OF METEORITES     

D. W. Sears  A. A. Mills 《Meteoritics & planetary science》1974,9(1):47-67

The use of thermoluminescence (TL) to determine the terrestrial age of meteorites is investigated. It is found that meteorites can be divided into two groups. One group, in which members lose their low temperature TL rather rapidly (the “low retentivity” group), may be dated up to about 100 years after fall, although with little accuracy. The other (the “high” group) is more retentive, and may still be dated several hundred years after fall. A meteorite of unknown date of fall may be assigned to the high or low group by laboratory determination of the rate of decay of the low temperature TL. Weathering coats the grains with limonite and lowers the intensity of the TL. The percentage reduction is constant for various intensities, but the peak height ratio is changed. Therefore, for weathered specimens, a method which examines the decrease in the intensity of a single peak is preferred to one which depends upon peak height ratios: this is made possible by artificially irradiating the meteorites. The following terrestrial ages for finds were obtained: Plainview 225–300 years; Dimmitt 280–330 years; Calliham 350–400 years. Bluff, Etter, Potter, Shields and Wellman (c) proved to be too old to be dated by our methods (≥ 500 years). None of the low group finds available to us proved to be young enough to be dated precisely. Terrestrial ages indicate an extremely low efficiency of recovery (≤ 1%) for meteorites that are not seen to fall. Artificially irradiating the meteorites also revealed the fact that 9 of our 19 meteorites were saturated with respect to thermoluminescence when they entered the atmosphere, and therefore that a technique based on this phenomenon would not be applicable to such specimens to obtain their cosmic ray exposure age.  相似文献   

ARTIFICIALLY-INDUCED THERMOLUMINESCENCE GRADIENTS IN STONY METEORITES     

J. E. Vaz  D. W. Sears 《Meteoritics & planetary science》1977,12(1):47-60

Several meteorites show variations in natural thermoluminescence intensity with depth. To investigate this, the gamma-ray induced thermoluminescence of the Plainview, Ucera, and Lost City meteorites has been analyzed. The results show that the thermoluminescence gradients in the meteorites are related to the concentration of electron traps, probably as a result of some of them being produced by cosmic ray bombardment.  相似文献   

The exploration of Mars,martian meteorites,and the search for life     

Derek Sears 《Meteoritics & planetary science》2000,35(5):891-892

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The tight‐lipped chondrites     

Derek Sears 《Meteoritics & planetary science》2000,35(3):443-443

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