Post‐excavation deterioration of the Copney Bronze Age Stone Circle Complex: A geomorphological perspective     

Patricia A. Warke  Joanne M. Curran  Bernard J. Smith  Mark Gardiner  Claire Foley 《Geoarchaeology》2010,25(5):541-571

Post‐excavation deterioration of stones from under blanket peat at the Copney Bronze Age Stone Circle Complex in County Tyrone, Northern Ireland, proceeded through widespread scaling, flaking, and splitting of stones. Investigation showed that prior to burial the porphyritic stones already possessed a complex legacy of geological weaknesses derived from hydrothermal alteration and tectonic deformation. Analysis indicated that significant alteration occurred during approximately 2000 years of burial under acidic peat cover, with development of a secondary porosity, alteration of primary minerals, and the opening of preexisting lines of weakness within the stones. Burial under peat also resulted in “bleaching” the stones so that they appeared white in color following excavation. These alterations during burial left the stones in a significantly weakened state and particularly susceptible to the effects of subaerial weathering processes. Data underline the potential fragility of excavated stonework and highlight the need to plan for its aftercare before complete excavation is undertaken. © 2010 Wiley Periodicals, Inc.  相似文献   

Impacts of temperature and nutrients on coastal lagoon plant communities     

Joanne?C.?Bintz  Scott?W.?NixonEmail author  Betty?A.?Buckley  Stephen?L.?Granger 《Estuaries and Coasts》2003,26(3):765-776

We investigated the independent and interactive effects of nutrient loading and summer water temperature on phytoplankton, drift macroalgae, and eelgrass (Zostera marina) in a coastal lagoon mesocosm experiment conducted from May through August 1999. Temperature treatments consisted of controls that approximated the 9-yr mean daily temperatures for Ninigret and Point Judith Lagoons in Rhode Island (United States) and treatments approximately 4°C above and 4°C below the controls. Nutrient treatments consisted of the addition of 6 mmol N m⁻²d⁻¹ and 0.5 mmol P m⁻² d⁻¹ to mesocosms 4°C above and 4°C below the 9-yr daily mean. Nutrient enrichment produced marked phytoplankton blooms in both cool and warm treatments during early summer. These were replaced after midsummer by dramatic growths of macroalgal mats ofEnteromorpha flexuosa and, to a lesser degree,Cladophora sericea. No phytoplankton blooms were observed in the cool unenriched treatments, but blooms did develop in the mean temperature and warm mesocosms during the second half of the summer that were similar in intensity, though of shorter duration, than those observed earlier in the enriched systems. Macroalgal blooms did not occur in the unenriched mesocosms. Sustained warm water temperatures markedly decreased eelgrass density and belowground production and increased the time interval between the initiation of new leaves, particuarly when the biomass of macroalgae was high. The negative effect of elevated water temperature on eelgrass was significantly increased under conditions of elevated inorganic nutrient input. By the end of summer, virtually all of the measures of eelgrass health declined in rank order from cool, to mean, to cool enriched, to warm, to warm enriched treatments. It is likely that the marked declines in eelgrass abundance observed during recent decades in the Northeast have resulted from an interaction of increasing nutrient enrichment combined with increasing summer water temperatures.  相似文献   

Preface     

Joanne E. Norris  Erik Cammeraat  Alexia Stokes  Ioannis Spanos 《Geotechnical and Geological Engineering》2006,24(3):427-428

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The response of circulation and salinity in a micro-tidal estuary to sub-tidal oscillations in coastal sea surface elevation     

Joanne O’Callaghan  Charitha Pattiaratchi  David Hamilton 《Continental Shelf Research》2007

Conceptual models of circulation theorise that the dominant forces controlling estuarine circulation are freshwater discharge from the riverine section (landward), tidal forcing from the ocean boundary, and gravitational circulation resulting from along-estuary gradients in density. In micro-tidal estuaries, sub-tidal water level changes (classified as those with periods between 3 and 10 days) with amplitudes comparable to the spring tidal range can significantly influence the circulation and distribution of water properties. Field measurements obtained from the Swan River Estuary, a diurnal, micro-tidal estuary in south-western Australia, indicated that sub-tidal water level changes at the ocean boundary were predominantly from remotely forced continental shelf waves (CSWs). The sub-tidal water levels had maximum amplitudes of 0.8 m, were comparable to the maximum tidal range of 0.6 m, propagated into the estuary to its tidal limit, and modified water levels in the whole estuary over several days. These oscillations dominated the circulation and distribution of water properties in the estuary through changing the salt wedge location and increasing the bottom water salinity by 7 units over 3 days. The observed salt wedge excursion forced by CSW was up to 5 km, whereas the maximum tidal excursion was 1.2 km. The response of the residual currents and the salinity distribution lagged behind the water level changes by ∼24 h. It was proposed that the sub-tidal forcing at the ocean boundary, which changed the circulation, salinity, and dissolved oxygen in the upper estuary, was due to a combination of two processes: (1) a gravity current generated by a process similar to a lock exchange mechanism and (2) amplified along-estuary density gradients in the upper estuary, which enhanced the gravitational circulation in the estuary. The salt intrusions under the sub-tidal forcing caused the rapid movement of anoxic water upstream, with significant implications for water quality and estuarine health.  相似文献   

A magnetic survey of Explorer Seamount— Recent spreading at the Explorer trench     

Wu Mingxian  Patrick J. C. Ryall  Joanne Bryan 《中国海洋湖沼学报》1986,4(2):183-195

In 1981 a magnetic and bathymetric survey was carried out over Explorer Seamount located approximately between 48°50′ and 49°30′N and 130°40′ and 131°30′W. During the cruise four pillow fragments were dredged from peaks in this area. Based on the observed magnetic data, it was identified that the main peak of Explorer Seamount should be of the Bruhnes age while the magnetic high in the NW of study area would be Gauss. This would yield a spreading rate of about 2 cm per year for the Matuyama epoch. The results of intensities of remanence measured from the pillow fragments indicate that the ages are less than 10⁶ years. Similarly the Curie temperature is consistent with ages of around 10⁶ years. An attempt was made to model the observed magnetic field using a series of uniformly magnetized NE-SW trending blocks of alternating polarity. Agreement between the model and observed results is satisfied. Oxidation ratios calculated from measured samples suggest that the main peak of Explorer Seamount is not far from the present day ridge axis, which agrees with the younger interpretation from the magnetic profiles. The results mentioned above strongly, but not conclusively, favour an interpretation in which the southeastern peak of Explorer Seamount is of the Bruhnes age and the recent spreading is at Explorer trench, then the Sovanco Fracture Zone should be thought of as a complex triangular area between the northern end of Juan de Fuca Ridge and Explorer Seamount rather than as a simple transform fault as defined conventionally.  相似文献   

Source Parameters of Seven Large Australian Earthquakes Determined By Body Waveform Inversion     

Joanne Fredrich  Robert Mccaffrey  David Denham 《Geophysical Journal International》1988,95(1):1-13

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Periglacial microjointing and faulting in Weichselian fluvio-aeolian deposits     

Joanne Mol  Jef Vandenberghe  Kees Kasse  Harry Stel 《第四纪科学杂志》1993,8(1):15-30

A Weichselian Late Pleniglacial fluvio-aeolian deposit has been investigated in the southern Netherlands. Three main structural lineaments have been distinguished: (1) very small, vertical platy structures (microjoints), in a parallel and a columnar configuration; (2) large joints and normal faults with minor displacement (‘Grubbenvorst type’), arranged in a conjugate fault-system; (3) large joints and normal faults (‘wedge-type’), located adjacent to ice-wedge casts. Since clay is absent, the occurrence of the vertical platy structures cannot be attributed to desiccation cracking. The vertical platy structures are interpreted as the result of thermal contraction cracking of a relatively thin layer, due to a sudden temperature drop. The large joints and normal faults of the Grubbenvorst type are the result of failure of the sediment due to the melting of the permafrost in the Late Pleniglacial, just before the formation of the Beuningen Gravel Bed. In other areas large periglacial convolutions have been formed during the same period. The normal faults and joints of the wedge type are more generally known. They are the result of failure of the sediment adjacent to a melting ice wedge.  相似文献   

Depositional sedimentary environments : H.-E. Reineck and I. B. Singh. Springer-Verlag, Berlin/New York, 1980. 2nd, rev. and updated ed., 549 pp., 683 figs., paperback $29.80     

Joanne Bourgeois 《Quaternary Research》1981,16(3):426-427

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On cumulus mergers   总被引：1，自引：0，他引：1  

Dr. Joanne Simpson  Nancy E. Westcott  R. J. Clerman  R. A. Pielke 《Meteorology and Atmospheric Physics》1980,29(1-2):1-40

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Importance of inherited rift margin structures in the early North Alpine Foreland Basin, Switzerland   总被引：1，自引：0，他引：1  

Joanne C. Lihou  & Philip A. Allen 《Basin Research》1996,8(4):425-442

The earliest evolution of the North Alpine Foreland Basin in Switzerland was characterized by deposition in small, structurally partitioned sub-basins during the Late Cretaceous and Early Tertiary, rather than in a single, large foredeep. These sub-basins, which were probably located between old rift margin fault-blocks reactivated during Alpine compression, were incorporated into the thrust wedge during thin-skinned deformation. In eastern Switzerland, the most external sub-basins with respect to the orogenic wedge (North Helvetic Flysch and Blattengrat units) have at their base an unconformity attributed to flexural forebulge erosion. More internal sub-basins (Sardona and Prättigau units) contain a conformable succession from the underlying passive margin stage and are dominated by deep-water sedimentation. In western Switzerland, both external sub-basins, now found in the Helvetic Diablerets and Wildhorn nappes, and deep-water internal sub-basins (Höchst-Meilleret Flysch, Neisen Flysch, Tarentaise Flysch) preserve a well-developed basal unconformity. Comparison of the eastern and western Swiss transects shows important intrabasinal lateral variations to be present. The western Swiss area was a topographic high for much of the Late Cretaceous and Early Tertiary; this is demonstrated by the increased chronostratigraphic gap at the karstified basal unconformity surface in western Switzerland. The strata onlapping this unconformity young to the west, suggesting that drowning of the emergent area was delayed compared with the east. In addition, reactivation and uplift of the rift margin structures occurred earlier in western Switzerland compared with eastern Switzerland. There is therefore strong evidence for lateral topographic gradients in the early foreland basin caused by differential amounts of tectonic reactivation of rift margin structures. In the early foreland basin-fill, these lateral variations are as important in determining depositional patterns as strike-normal changes across the basin.  相似文献