The effects of burrowing activity on archaeological sites: Ndondondwane,South Africa     

Kent D. Fowler  Haskel J. Greenfield  Leonard O. van Schalkwyk 《Geoarchaeology》2004,19(5):441-470

Burrowing activity is a widely recognized source of site modification. Most taphonomic studies of burrowers emphasize their destructive aspects on the archaeological record. Excavations at Ndondondwane, South Africa, suggest burrowing activity is destructive in some ways, but may also preserve cultural behavior. Drawing on both direct and indirect sources of evidence, we discuss how burrowing activity by rodents, earthworms, and termites can inform about pedogenic and depositional processes at archaeological sites and both preserve and destroy evidence of intra‐settlement patterns and early African cultigens. Specifically, we demonstrate the limited effect of earthworms on site stratigraphy, how the localized activity of termites have preserved casts of early African cultigens, and how the ability of archaeologists to distinguish the devastating effects of rodent burrowing from remains of architectural features have permitted important inferences about social and ritual life in early African farming communities. © 2004 Wiley Periodicals, Inc.  相似文献   

Paleoecology and geochronology of glacial Lake Hind during the Pleistocene–Holocene transition: A context for Folsom surface finds on the Canadian Prairies     

Matthew Boyd  Garry Leonard Running  Karen Havholm 《Geoarchaeology》2003,18(6):583-607

Stratigraphic and paleoecologic (palynomorph, macrobotanical) data obtained from a cutbank of the Souris River in southwestern Manitoba establish some fundamental parameters of Folsom land‐use in association with a proglacial lake on the Canadian Prairies. By dating the regression of glacial Lake Hind, we observed that recorded Folsom sites are restricted to areas of the Hind basin drained shortly before 10,400 yr B.P. This pattern may therefore record the interception of seasonal resources on recently‐drained proglacial lake surfaces. Based on paleovegetation reconstructions, we note that these surfaces were rapidly colonized by emergent and aquatic vegetation following regression, generating a viable resource base for Folsom hunter‐gatherers. However, low plant productivity and diversity may have greatly limited the extent to which this locale was exploited, in contrast to nonperiglacial regions on the Plains. We also suggest that wetland plant succession during the Pleistocene‐Holocene transition was due, at least locally, to climate‐forced fluctuations in groundwater levels. © 2003 Wiley Periodicals, Inc.  相似文献   

Cryptic metasomatic agent measured in situ in Variscan mantle rocks: Melt inclusions in garnet of eclogite,Granulitgebirge, Germany     

Alessia Borghini  Silvio Ferrero  Patrick J. O’Brien  Oscar Laurent  Christina Günter  Martin A. Ziemann 《Journal of Metamorphic Geology》2020,38(3):207-234

Garnet of eclogite (formerly termed garnet clinopyroxenite) hosted in lenses of orogenic garnet peridotite from the Granulitgebirge, NW Bohemian Massif, contains unique inclusions of granitic melt, now either glassy or crystallized. Analysed glasses and re-homogenized inclusions are hydrous, peraluminous, and enriched in highly incompatible elements characteristic of the continental crust such as Cs, Li, B, Pb, Rb, Th, and U. The original melt thus represents a pristine, chemically evolved metasomatic agent, which infiltrated the mantle via deep continental subduction during the Variscan orogeny. The bulk chemical composition of the studied eclogites is similar to that of Fe-rich basalt and the enrichment in LILE and U suggest a subduction-related component. All these geochemical features confirm metasomatism. In comparison with many other garnet+clinopyroxene-bearing lenses in peridotites of the Bohemian Massif, the studied samples from Rubinberg and Klatschmühle are more akin to eclogite than pyroxenites, as reflected in high jadeite content in clinopyroxene, relatively low Mg, Cr, and Ni but relatively high Ti. However, trace elements of both bulk rock and individual mineral phases show also important differences making these samples rather unique. Metasomatism involving a melt requiring a trace element pattern very similar to the composition reported here has been suggested for the source region of rocks of the so-called durbachite suite, that is, ultrapotassic melanosyenites, which are found throughout the high-grade Variscan basement. Moreover, the Th, U, Pb, Nb, Ta, and Ti patterns of these newly studied melt inclusions (MI) strongly resemble those observed for peridotite and its enclosed pyroxenite from the T-7 borehole (Staré, České Středhoři Mountains) in N Bohemia. This suggests that a similar kind of crustal-derived melt also occurred here. This study of granitic MI in eclogites from peridotites has provided the first direct characterization of a preserved metasomatic melt, possibly responsible for the metasomatism of several parts of the mantle in the Variscides.  相似文献   

A stochastic framework for modeling random-sized batch arrivals of sediment particles into open channel flows     

Christina?W.?TsaiEmail authorView author&#;s OrcID profile  Serena?Y.?Hung  Jungsun?Oh 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(7):1939-1954

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Stochastic sediment transport: anomalous diffusions and random movement     

Tsai  Christina W.  Hung  Serena Y.  Wu  Tsung-Han 《Stochastic Environmental Research and Risk Assessment (SERRA)》2020,34(2):397-413

Stochastic Environmental Research and Risk Assessment - A sediment particle in a flow not only follows the flow direction but also randomly diffuses through the surrounding fluid, because of the...  相似文献   

Connectivity as an emergent property of geomorphic systems     

Ellen Wohl  Gary Brierley  Daniel Cadol  Tom J. Coulthard  Tim Covino  Kirstie A. Fryirs  Gordon Grant  Robert G. Hilton  Stuart N. Lane  Francis J. Magilligan  Kimberly M. Meitzen  Paola Passalacqua  Ronald E. Poeppl  Sara L. Rathburn  Leonard S. Sklar 《地球表面变化过程与地形》2019,44(1):4-26

Connectivity describes the efficiency of material transfer between geomorphic system components such as hillslopes and rivers or longitudinal segments within a river network. Representations of geomorphic systems as networks should recognize that the compartments, links, and nodes exhibit connectivity at differing scales. The historical underpinnings of connectivity in geomorphology involve management of geomorphic systems and observations linking surface processes to landform dynamics. Current work in geomorphic connectivity emphasizes hydrological, sediment, or landscape connectivity. Signatures of connectivity can be detected using diverse indicators that vary from contemporary processes to stratigraphic records or a spatial metric such as sediment yield that encompasses geomorphic processes operating over diverse time and space scales. One approach to measuring connectivity is to determine the fundamental temporal and spatial scales for the phenomenon of interest and to make measurements at a sufficiently large multiple of the fundamental scales to capture reliably a representative sample. Another approach seeks to characterize how connectivity varies with scale, by applying the same metric over a wide range of scales or using statistical measures that characterize the frequency distributions of connectivity across scales. Identifying and measuring connectivity is useful in basic and applied geomorphic research and we explore the implications of connectivity for river management. Common themes and ideas that merit further research include; increased understanding of the importance of capturing landscape heterogeneity and connectivity patterns; the potential to use graph and network theory metrics in analyzing connectivity; the need to understand which metrics best represent the physical system and its connectivity pathways, and to apply these metrics to the validation of numerical models; and the need to recognize the importance of low levels of connectivity in some situations. We emphasize the value in evaluating boundaries between components of geomorphic systems as transition zones and examining the fluxes across them to understand landscape functioning. © 2018 John Wiley & Sons, Ltd.  相似文献   

Relationships between snowpack,low flows and stream temperature in mountain watersheds of the US west coast     

Gabrielle Boisramé  Adrian Harpold  Christina Tague 《水文研究》2024,38(5):e15157

Water temperatures in mountain streams are likely to rise under future climate change, with negative impacts on ecosystems and water quality. However, it is difficult to predict which streams are most vulnerable due to sparse historical records of mountain stream temperatures as well as complex interactions between snowpack, groundwater, streamflow and water temperature. Minimum flow volumes are a potentially useful proxy for stream temperature, since daily streamflow records are much more common. We confirmed that there is a strong inverse relationship between annual low flows and peak water temperature using observed data from unimpaired streams throughout the montane regions of the United States' west coast. We then used linear models to explore the relationships between snowpack, potential evapotranspiration and other climate-related variables with annual low flow volumes and peak water temperatures. We also incorporated previous years' flow volumes into these models to account for groundwater carryover from year to year. We found that annual peak snowpack water storage is a strong predictor of summer low flows in the more arid watersheds studied. This relationship is mediated by atmospheric water demand and carryover subsurface water storage from previous years, such that multi-year droughts with high evapotranspiration lead to especially low flow volumes. We conclude that watershed management to help retain snow and increase baseflows may help counteract some of the streamflow temperature rises expected from a warming climate, especially in arid watersheds.  相似文献   

Middle Pleistocene environments,landscapes and tephrostratigraphy of the Armenian Highlands: evidence from Bird Farm 1, Hrazdan Valley     

Jenni E. Sherriff  Keith N. Wilkinson  Poppy Harding  Hayley Hawkins  Rhys G. O. Timms  Daniel S. Adler  Emily J. Beverly  Simon P. E. Blockley  Boris Gasparyan  Christina J. Manning  Darren Mark  Samvel Nahapetyan  Katie J. Preece 《第四纪科学杂志》2022,37(1):6-27

The significance of the southern Caucasus in understanding Pleistocene hominin expansions is well established. However, the palaeoenvironments in which Palaeolithic occupation of the region took place are presently poorly defined. The Hrazdan river valley, Armenian Highlands, contains a rich Palaeolithic record alongside Middle Pleistocene volcanic, fluvial and lacustrine strata, and thus offer exciting potential for palaeoenvironmental reconstruction. We present the first results of sedimentological, geochemical, tephrostratigraphical and biological (diatoms) study of the sequence of Bird Farm 1, located in the central part of the valley. These data show six phases of landscape development during the interval 440–200 ka. The sequence represents the first quantitative Pleistocene diatom record from the Armenian Highlands and the southern Caucasus, and indicates the persistence of a deep, stratified lacustrine system, with evidence for changing lake productivity that is tentatively linked to climate. Furthermore, major element chemical characterization of visible and crypto-tephra horizons in the sequence enables the first stages of the development of a regional tephrostratigraphy. Together, the evidence from Bird Farm 1 demonstrates the importance of lacustrine archives in the region for palaeoenvironmental reconstruction and highlights the potential for linkages between archives on both a local and regional scale.  相似文献