Geological processes and site structure: Assessing integrity at a Late Paleolithic open‐air site in northern France     

James G. Enloe 《Geoarchaeology》2006,21(6):523-540

The difficulty of reading the archaeological record of caves and rock shelters is becoming increasingly obvious to Paleolithic researchers. Although some open‐air sites are thought to avoid such taphonomic complications, interpreting their archaeological record is less straightforward than assumed. Postdepositional processes may obscure structure in configurations of features and artifacts. Recently developed techniques for the excavation and analysis of Paleolithic cave sites can be applied to open‐air sites before spatial patterning is interpreted for inferences about prehistoric social organization. Analysis of the orientation of elongated artifacts on the occupation surface of the late Upper Paleolithic site of Verberie, France, is employed for evaluation of the integrity of site structure. Results indicate spatial structure largely undisturbed by geological processes. The lack of disturbance in the configuration of archaeological materials allows for a behavioral interpretation of those remains. The proposition that Verberie was a hunting campsite for initial carcass processing is supported. © 2006 Wiley Periodicals, Inc.  相似文献   

Marine cements in mid-Tertiary cool-water shelf limestones of New Zealand and southern Australia   总被引：1，自引：0，他引：1  

Campbell S. Nelson  & Noel P. James 《Sedimentology》2000,47(3):609-629

Large areas of southern Australia and New Zealand are covered by mid‐Tertiary limestones formed in cool‐water, shelf environments. The generally destructive character of sea‐floor diagenesis in such settings precludes ubiquitous inorganic precipitation of carbonates, yet these limestones include occasional units with marine cements: (1) within rare in situ biomounds; (2) within some stacked, cross‐bedded sand bodies; (3) at the top of metre‐scale, subtidal, carbonate cycles; and (4) most commonly, associated with certain unconformities. The marine cements are dominated by isopachous rinds of fibrous to bladed spar, interstitial homogeneous micrite and interstitial micropeloidal micrite, often precipitated sequentially in that order. Internal sedimentation of microbioclastic micrite may occur at any stage. The paradox of marine‐cemented limestone units in an overall destructive cool‐water diagenetic regime may be explained by the precipitation of cement as intermediate Mg‐calcite from marine waters undersaturated with respect to aragonite. In some of the marine‐cemented limestones, aragonite biomoulds may include marine cement/sediment internally, suggesting that dissolution of aragonite can at times be wholly marine and not always involve meteoric influences. We suggest that marine cementation occurred preferentially, but not exclusively, during periods of relatively lowered sea level, probably glacio‐eustatically driven in the mid‐Tertiary. At times of reduced sea level, there was a relative increase in both the temperature and the carbonate saturation state of the shelf waters, and the locus of carbonate sedimentation shifted towards formerly deeper shelf sites, which now experienced increased swell wave and/or tidal energy levels, fostering sediment abrasion and reworking, reduced sedimentation rates and freer exchange of sediment pore‐waters. Energy levels were probably also enhanced by increased upwelling of cold, deep waters onto the Southern Ocean margins of the Australasian carbonate platforms, where water‐mass mixing, warming and loss of CO₂ locally maintained critical levels of carbonate saturation for sea‐floor cement precipitation and promoted the phosphate‐glauconite mineralization associated with some of the marine‐cemented limestone units.  相似文献   

Disseminated ‘jigsaw piece’ dolomite in Upper Jurassic shelf sandstones,Central North Sea: an example of cement growth during bioturbation?     

James P. Hendry  Mark Wilkinson  Anthony E. Fallick  & Nigel H. Trewin 《Sedimentology》2000,47(3):631-644

Unusual textural and chemical characteristics of disseminated dolomite in Upper Jurassic shelf sediments of the North Sea have provided the basis for a proposed new interpretation of early diagenetic dolomite authigenesis in highly bioturbated marine sandstones. The dolomite is present throughout the Franklin Sandstone Formation of the Franklin and Elgin Fields as discrete, non‐ferroan, generally unzoned, subhedral to highly anhedral ‘jigsaw piece’ crystals. These are of a similar size to the detrital silicate grains and typically account for ≈5% of the rock volume. The dolomite crystals are never seen to form polycrystalline aggregates or concretions, or ever to envelop the adjacent silicate grains. They are uniformly dispersed throughout the sandstones, irrespective of detrital grain size or clay content. Dolomite authigenesis predated all the other significant diagenetic events visible in thin section. The dolomite is overgrown by late diagenetic ankerite, and bulk samples display stable isotope compositions that lie on a mixing trend between these components. Extrapolation of this trend suggests that the dolomite has near‐marine δ¹⁸O values and low, positive δ¹³C values. The unusual textural and chemical characteristics of this dolomite can all be reconciled if it formed in the near‐surface zone of active bioturbation. Sea water provided a plentiful reservoir of Mg and a pore fluid of regionally consistent δ¹⁸O. Labile bioclastic debris (e.g. aragonite, Mg‐calcite) supplied isotopically positive carbon to the pore fluids during shallow‐burial dissolution. Such dissolution took place in response to the ambient ‘calcite sea’ conditions, but may have been catalysed by organic matter oxidation reactions. Bioturbation not only ensured that the dissolving carbonate was dispersed throughout the sandstones, but also prohibited coalescence of the dolomite crystals and consequent cementation of the grain framework. Continued exchange of Mg²⁺ and Ca²⁺ with the sea‐water reservoir maintained a sufficient Mg/Ca ratio for dolomite (rather than calcite) to form. Irregular crystal shapes resulted from dissolution, of both the dolomite and the enclosed fine calcitic shell debris, before ankerite precipitation during deep‐burial diagenesis.  相似文献   

Determination of the REE in Geological Reference Materials DTS-1 (Dunite) and PCC-1 (Peridotite) by Ultrasonic and Microconcentric Desolvating Nebulisation ICP-MS     

Jinesh C. Jain  M. Paul Field  Clive R. Neal  James C. Ely  Robert M. Sherrell 《Geostandards and Geoanalytical Research》2000,24(1):65-72

Inductively coupled plasma-mass spectrometry is well suited for the precise, accurate and rapid determination of rare earth elements in most geological samples. However, determination of rare earth elements in certain mantle-derived materials, without applying preconcentration techniques, remains problematical due to low natural concentrations (generally < 1 ng g⁻¹). Consequently, USGS reference materials DTS-1 (a dunite) and PCC-1 (a partially serpentinized harzburgite) have only suggested rather than recommended values for the rare earth elements in reference material compilations. We compared results obtained using two ICP-MS instruments: a U-5000AT ultrasonic nebuliser coupled to a PQ2+ quadrupole ICP-MS and an ELEMENT sector field ICP-MS equipped with a MCN-6000 microconcentric desolvating nebuliser, with the suggested literature values for these two reference materials. Precision and accuracy of analytical methods employed by both instruments were demonstrated by excellent relative standard deviations (< 2%) and inter-laboratory agreement (< 5%) for numerous analyses of BHVO-1 and BIR-1, which are well established with rare earth elements contents at the μg g⁻¹ level. Repeat analyses of DTS-1 and PCC-1 at each laboratory indicate that each method is generally precise to better than 5% at sub-g g⁻¹ levels. Furthermore, values from both instruments generally agree to within 10%. Our DTS-1 and PCC-1 values agree reasonably well with selected data reported in the literature (except for Ce and Sm in DTS-1) but exhibit poorer agreement with reported compilation values. With the demonstrated level of precision and accuracy, we contend that these new values for DTS-1 and PCC-1, generated by two different instruments, are the best estimates of the true whole-rock composition of these samples reported to date.  相似文献   

A portable retractable ADCP boom-mount for small boats     

James L. Hench  Richard A. Luettich  James T. Bircher 《Estuaries and Coasts》2000,23(3):392-399

This paper describes the design, testing, and application of a portable and retractable shipboard acoustic Doppler current profiler (ADCP) boom-mount. The boom is specifically adapted for small fiberglass boats working with a minimal crew. The design permits the rapid collection of ADCP data on discontinuous transects which would be difficult or impossible using a large displacement hull vessel or with a towed vehicle. This capability is particularly useful in shallow wind-driven estuaries and in tidal channels where flow time scales are often on the order of several hours. Tests of the boom show that high quality ADCP data (as measured by percent good) can be obtained at boat speeds up to 4.0 m s⁻¹ and that data quality depends on transducer depth. The utility of the retractable design is demonstrated with an 8 m boat on two nearly synoptic ADCP surveys of a shallow estuary. With minor modifications to accommodate different vessel geometries, the design could be readily adapted for use on similar vessels.  相似文献   

社区可持续发展指标体系研究——以上海崇明为例   总被引：14，自引：1，他引：13  

袁雯  Philip JAMES  杨凯 《地理研究》2003,22(4):484-494

本文探索了在专业人员指导下的小组参与方法建立符合中国国情的社区可持续发展指标体系。研究以上海崇明为例,分析了不同社会群体对可持续发展的认识和需求,比较了不同经济发展水平、不同社会背景和不同决策层面对可持续发展的不同关注点,提出由4个核心指标、7个扩展指标和5个附加指标构成的社区可持续发展指标体系,为其他地区制订可持续发展指标体系提供了参考,并有利于实施社区发展可持续性的评估。  相似文献   

The refurbishment of Herschel House     

Debbie James 《Astronomy& Geophysics》2000,41(5):5.14-5.15

Curator Debbie James reports on developments at the Herschel House Museum in Bath, once the home of William and Caroline Herschel.  相似文献   

Deterministic and Stochastic Modeling of Aquifer Stratigraphy, South Carolina   总被引：3，自引：0，他引：3  

Russell B. Miller  James W. Castle  Tom J. Temples 《Ground water》2000,38(2):284-295

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Significance of ichnofossils to genetic stratigraphy--Examples from the Cretaceous of Alberta, Canada   总被引：1，自引：0，他引：1  

S. George Pemberton  James A. MacEachern  Murray K. Gingras  ZHANG Jianping 《中国科学D辑(英文版)》2000,43(5)

Trace fossils represent both sedimentological and paleontological entities, representing a unique blending of potential environmental indicators in the rock record. Trace fossils and trace fossil suites can be employed effectively to aid in the recognition of various discontinuity types and to assist in their genetic interpretation. Ichnology may be employed to resolve surfaces of stratigraphic significance in two main ways: 1) through the identification of discontinuities using substrate-controlled ichnofacies, and 2) through careful analysis of vertical softground (penecontemporaneous) ichnologic successions (analogous to facies successions). Ichnological analysis is a valuable tool in genetic stratigraphic studies. Integrating the data derived from substrate-controlled ichnofacies with paleoecological data from vertical ichnologic successions greatly enhances the recognition and interpretation of a wide variety of stratigraphic surfaces. When this is coupled with conventional facies analysis and sequence stratigraphy, a powerful approach to the interpretation of the rock record is generated.  相似文献   

Tracking the last sea-level cycle: seafloor morphology and shallow stratigraphy of the latest Quaternary New Jersey middle continental shelf     

Catherine Schuur Duncan  John A. Goff  James A. AustinJr.  Craig S. Fulthorpe 《Marine Geology》2000,170(3-4):395-421

Seafloor geomorphology and surficial stratigraphy of the New Jersey middle continental shelf provide a detailed record of sea-level change during the last advance and retreat of the Laurentide ice sheet (120 kyr B.P. to Present). A NW–SE-oriented corridor on the middle shelf between water depths of 40 m (the mid-shelf “paleo-shore”) and 100 m (the Franklin “paleo-shore”) encompasses 500 line-km of 2D Huntec boomer profiles (500–3500 Hz), an embedded 4.6 km² 3D volume, and a 490 km² swath bathymetry map. We use these data to develop a relative stratigraphy. Core samples from published studies also provide some chronological and sedimentological constraints on the upper <5 m of the stratigraphic succession.The following stratigraphic units and surfaces occur (from bottom to top): (1) “R”, a high-amplitude reflection that separates sediment >46.5 kyr old (by AMS ¹⁴C dating) from overlying sediment wedges; (2) the outer shelf wedge, a marine unit up to 50 m thick that onlaps “R”; (3) “Channels”, a reflection sub-parallel to the seafloor that incises “R”, and appears as a dendritic system of channels in map view; (4) “Channels” fill, the upper portion of which is sampled and known to represent deepening-upward marine sediments 12.3 kyr in age; (5) the “T” horizon, a seismically discontinuous surface that caps “Channels” fill; (6) oblique ridge deposits, coarse-grained shelly units comprised of km-scale, shallow shelf bedforms; and (7) ribbon-floored swales, bathymetric depressions parallel to modern shelf currents that truncate the oblique ridges and cut into surficial deposits.We interpret this succession of features in light of a global eustatic sea-level curve and the consequent migration of the coastline across the middle shelf during the last 120 kyr. The morphology of the New Jersey middle shelf shows a discrete sequence of stratigraphic elements, and reflects the pulsed episodicity of the last sea-level cycle. “R” is a complicated marine/non-marine erosional surface formed during the last regression, while the outer shelf wedge represents a shelf wedge emplaced during a minor glacial retreat before maximum Wisconsin lowstand (i.e., marine oxygen isotope stage 3.1). “Channels” is a widespread fluvial subarial erosion surface formed at the late Wisconsin glacial maximum 22 kyr B.P. The shoreline migrated back across the mid-shelf corridor non-uniformly during the period represented by “Channels” fill. Oblique ridges are relict features on the New Jersey middle shelf, while the ribbon-floored swales represent modern shelf erosion. There is no systematic relationship between modern seafloor morphology and the very shallowly buried stratigraphic succession.  相似文献