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261.
262.
The term ‘connectivity’ is increasingly being applied in hydrological and geomorphological studies. Relevant research encompasses aspects of landscape connectivity, hydrological connectivity and sedimentological connectivity. Unlike other disciplines, notably ecology, published studies show no consensus on a standard definition. This paper provides an overview of how existing research relates to the concept of connectivity in both ecology and hydrology by proposing and evaluating a conceptual model of hydrological connectivity that includes five major components: climate; hillslope runoff potential; landscape position; delivery pathway and lateral connectivity. We also evaluate a proposed measure of connectivity called the volume to breakthrough to quantify changing connectivity between different environments and catchments. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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264.
Simon Wills Emma Louise Bernard Philippa Brewer Charlie J. Underwood David J. Ward 《Proceedings of the Geologists' Association. Geologists' Association》2019,130(2):170-186
Woodeaton Quarry in Oxfordshire has previously yielded a number of large sauropod vertebrae and other (unpublished) dinosaur remains from a horizon in the Rutland Formation. No review of the wider terrestrial fauna from Woodeaton has been published to date. Here we present an overview of new material recovered from a microvertebrate site at the top of the White Limestone Formation (Middle Jurassic, Bathonian, Great Oolite Group, Retrocostatum Zone) and review the stratigraphy to provide a comprehensive local stratigraphic framework and place the quarry in the correct regional context. The terrestrial fauna is similar to that found from other UK Bathonian microvertebrate sites and includes probable dromaeosaurid theropods, ornithischians, tritylodontids and mammaliaforms such as amphitheriids, docodonts, ‘eutriconodonts’, ‘haramyids’ and multituberculates. Placement of the White Limestone Formation boundaries are clarified with respect to the Rutland and Forest Marble Formations. This indicates that the microvertebrate bed from Woodeaton is slightly older than that of the well-known mammal bed from nearby Kirtlington Quarry. 相似文献
265.
Louise Cromer John A. E. Gibson Sandra J. McInnes Janelle T. Agius 《Journal of Paleolimnology》2008,39(1):143-150
Remains of tardigrades have rarely been reported to preserve in sediments, resulting in the absence of important ecological
and biogeographic information that they could provide. However, a study of faunal microfossils in Antarctic lake sediment
cores has shown that tardigrade eggs and occasionally exuvia can be abundant. Eggs from at least five tardigrade species were
identified in sediment cores from six lakes from across the continent, with abundances up to 6,000 (g−1 dry wt.). It is likely that the cold temperatures and absence of benthic grazers in Antarctic lakes results in particularly
good preservation conditions, though it may also be a function of population density. The conservation of tardigrade eggs
and exuvia in lake sediments enables a better understanding of paleodistributions and effects of environmental changes for
this phylum that cannot otherwise be obtained. 相似文献
266.
The previously poorly documented 26–16.6 ka interval of pyroclastic volcanism from Tongariro Volcano is marked by three distal
lapilli fall units (Rt1-3) exposed in ring-plain deposits. The distal Rt1-3 units are tentatively correlated to proximal scoria
deposits on the upper slopes of North Crater based on their dispersal patterns, petrography and geochemistry. Lapilli in each
of the Rt1-3 deposits are characterised by variable groundmass crystallinity, vesicularity and colour within individual clasts.
Matrix glasses are mostly microlite-free, and compositionally diverse across the deposits (SiO2 = 62–75 wt%), with wide composition ranges occurring within single clasts. The glasses represent different melts that were
mingled and mixed shortly before eruption; a finding supported by widely variable Fe–Ti oxide equilibrium temperature estimates
(∼830–1,200°C). Ranges of 30–160°C (typically 70°C) occur within individual clasts. Some clinopyroxene crystals display Mg-rich
(∼Mg #88) rim zones around homogeneous low-Mg (∼Mg #68) cores, with abrupt transition zones. This zoning is interpreted as
resulting from the injection of a more mafic melt into a stagnating, resident magma. Crystal-melt equilibria indicate that
several episodes of mafic intrusion occurred, to produce hybrid melts with zoned crystals forming isolated ponds within the
resident magma. Variable mixing from the percolation of melts and the coalescence of melt ponds would explain the wide range
of melt compositions and equilibrium temperatures observed in the ejecta. The magma heterogeneity was preserved by quenching
on prompt eruption, with much of the short-duration chaotic mixing of melts and crystals occurring in the conduit. The Rt1-3
eruptions were from an open magmatic system consisting of one or more long-lived stagnant crystal mush zones, from which eruptions
were rapidly triggered by new injections of mafic magmas from greater depths. A similar pattern of magmatic dynamics was observed
in the much smaller 1995 eruptions of the neighbouring Ruapehu Volcano. 相似文献
267.
Using images and laser ranging data from the NEAR-Shoemaker mission, we map lineaments on the surface of Eros in order to investigate the relationship between surface morphology and interior structure. Several sets of lineations are clearly related to visible impact craters, while others suggest that different parts of the asteroid may have undergone different stress histories. Some of these sets infer internal structure, at least on a local level. This structure may derive from Eros' parent body and suggest, although largely coherent, Eros' interior may have portions that have not undergone a common history. 相似文献
268.
Anthony J. Parsons Louise Bracken Ronald E. Poeppl John Wainwright Saskia D. Keesstra 《地球表面变化过程与地形》2015,40(9):1275-1277
Connectivity has emerged in recent years as a significant conceptual framework within which to address the spatial and temporal variability in runoff and sediment transport. This special issue draws together several of the papers that were presented in the session “Connectivity in water and sediment dynamics: how do we move forwards?” at the 2012 General Assembly of the European Geosciences Union in Vienna, Austria. The papers submitted for this special issue fall into three groups: empirical studies, modelling studies, and conceptual development. Although it may be evident that the concept of connectivity helps us to express the complexity (in terms of water and sediment yields) of landscape responses to rainfall inputs, does it improve our ability to understand or predict those responses? There would still seem to be some way to go in connectivity research before this nagging concern can be assuaged. That it can be will undoubtedly be an important task for a number of ongoing research initiatives. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
269.
Vladimír Čermák Louise Bodri Jan Šafanda Milan Krešl Petr Dědeček 《Studia Geophysica et Geodaetica》2014,58(3):403-424
Long-term observations of air, near-surface (soil) and ground temperatures, collected between 1994 and 2011, monitored in the Geothermal Climate Change Observatory at Spo?ilov, Prague (GCCO) are analyzed to better understand the relationship between these quantities and to describe the mechanism of heat transport at the land-atmosphere boundary layer. The 17 years long monitoring series provided a surprisingly small mean ground-air temperature offset of only 0.31 K with no clear annual course and with the offset value changing irregularly even on a daily scale. Such value is substantially lower than similar values (1–2 K and more) found elsewhere, but it may be well characteristic for a mild temperate zones, when all so far available information referred rather to more southern locations. As many other observed geophysical data, temperature time series consist of a systematic pattern (usually a set of identifiable components) contaminated by random noise, which makes the identification of the proper pattern difficult. To identify the existing systematic patterns (cycles) of the temperature-time series at several depth levels in the investigated depth interval 0–40 m, the observed data were processed with the help of the Fast Fourier Transform (FFT) and Recurrence Quantification Interval (RQI) analysis. The latter represents recently developed powerful technique to uncover hidden periodicities in a noisy time environment. At low frequency band the RQI may provide far finer resolution than the conventional FFT technique. The results proved considerable similarity for all investigated depth levels. In addition to the annual wave all measured series proved to have a more complex pattern including predominantly 8-year and 11 years long periodicities. The results were compared with similar analysis of the meteorological air temperature series as well as with the results of other similar studies. The potential dynamics explaining the occurrence of the 8-year wave is briefly discussed. 相似文献
270.
Louise ProckterPeter Thomas Mark RobinsonJonathan Joseph Ashley MilneBen Bussey Joseph VeverkaAndrew Cheng 《Icarus》2002,155(1):75-93
NEAR Shoemaker imaging of the asteroid Eros has revealed a variety of surface forms that probably reflect underlying structures. They range from global to local in scale. The most prominent positive topographic feature is a long ridge, Rahe Dorsum, which extends over 18 km and has the morphology of a thrust fault. Two large, ancient trough systems are also present. Grooves are ubiquitous, commonly occur in suborthogonal sets, and have linear or scalloped outlines. The grooves on Eros are similar in morphology and scale to those on other small bodies such as Gaspra, Ida, and Phobos and are likely to have a similar mode of origin, namely drainage of regolith into underlying fractures. Models that use groove dimensions as indicators of regolith thickness imply depths of up to several tens of meters. Many craters have been subjected to structural control, resulting in squared outlines. We find no evidence that specific groove sets are associated with individual impact events; however, evidence exists that preexisting structures have been reactivated by later impact activity. The large scale of Rahe Dorsum and many grooves on Eros's surface suggests that the asteroid is a largely coherent, but fractured body. 相似文献