geochemistry of a spring dense karst watershed located in a complex structural setting appalachian great valley west virginia usa the distribution and chemistry of the springs in the tuscarora creek watershed is controlled by both geologic structure and karst dissolution the watershed is located in eastern west virginia in the structurally complex great valley of the appalachian valley and ridge province the upper portion of the stream parallels strike along a mapped fault zone and is bordered by clastic rocks that comprise north mountain the lower reaches of the stream flow cross strike through cambro ordovician carbonates the controlling chemical signature in the spring water is carbonate dissolution little evidence was seen for the recharge from adjacent clastic rocks although differences in the ca mg molar ratio between springs indicated the presence of localized spring basins in headwater reaches na cl and ca generally increased from upstream to downstream in the cross strike reaches comparison of stream and cumulative spring discharge was consistent with significant groundwater base flow contribution directly to the creek particularly in the strike parallel region the largest spring in the watershed 162 l s was sampled during and after a large storm event along with the adjacent creek the creek displayed a typical dilution response with each flood pulse whereas the spring had only a limited or delayed response the overall chemical and thermal stability of the spring relative to the creek indicated the lack of significant direct hydraulic connection between the two the conceptual model for the area includes localized flowpaths in the headwater region where the stream flow is parallel to strike and a thrust fault in addition to the shallow localized flowpaths a deeper more regional flowpath likely exists for a large spring further downstream

accelerator mass spectrometer ages for the younger dryas event in atlantic canada abstract in atlantic canada bulk sediment dates for the onset of a late glacial cooling widely regarded as the younger dryas event are highly variable ranging from 14 300 270 to 10 800 100 yr b p we present the first accelerator mass spectrometer ams 14c dates from atlantic canada at or close to the boundaries of this event from six sites in new brunswick and nova scotia the mean of five dates places the onset of this cooling at ca 10 770 yr b p the inclusion of a sixth perhaps anomalously old date changes the mean to 10 880 yr b p the termination averages three dates ca 10 000 yr b p these dates place the timing of the younger dryas event in atlantic canada closer in line with the traditional chronozone boundaries of 11 000 and 10 000 yr b p in northwest europe

use of sinkhole and specific capacity distributions to assess vertical gradients in a karst aquifer the carbonate rock aquifer in the great valley west virginia usa was evaluated using a database of 687 sinkholes and 350 specific capacity tests to assess structural lithologic and topographic influences on the groundwater flow system the enhanced permeability of the aquifer is characterized in part by the many sinkholes springs and solutionally enlarged fractures throughout the valley yet vertical components of subsurface flow in this highly heterogeneous aquifer are currently not well understood to address this problem this study examines the apparent relation between geologic features of the aquifer and two spatial indices of enhanced permeability attributed to aquifer karstification 1 the distribution of sinkholes and 2 the occurrence of wells with relatively high specific capacity statistical results indicate that sinkholes funnel and collapse occur primarily along cleavage and bedding planes parallel to subparallel to strike where lateral or downward vertical gradients are highest conversely high specific capacity values are common along prominent joints perpendicular or oblique to strike the similarity of the latter distribution to that of springs suggests these fractures are areas of upward convergent flow these differences between sinkhole and high specific capacity distributions suggest vertical flow components are primarily controlled by the orientation of geologic structure and associated subsurface fracturing

factors influencing cavity detection in karst terrain on two dimensional 2 d direct current dc resistivity survey a case study from the western part of thailand to create a three dimensional 3 d cave and cavity network model in karst terrain from two dimensional 2 d direct current resistivity dcr profiles we first need to recognize their effects on the inversion results from a number of special cases 2 d and 3 d cavity models are created to demonstrate effects from 1 depth of the cavity 2 size and shape 3 distance to the edge of the cavity 4 orientations inclination and declination of the cavity and 5 several smaller cavities lying in an array for other complicated models combinations of these factors can be used to infer the results two parallel dcr profiles from the western part of thailand were first inverted with the 2 d inversion for interpretation knowledge gained from the numerical modeling on these special cases is helpful to constrain the interpretation and also to extend the interpretation to 3 d this gives us a picture of the 3 d cave and cavity networks beneath the area of study two main connected cavities between these two profiles can be inferred from the data along with several local cavities near the surface

central european vegetation response to abrupt climate change at 8 2 ka oxygen isotope records show a major climatic reversal at 8 2 ka in greenland and europe annually laminated sediments from two lakes in switzerland and germany were sampled contiguously to assess the response of european vegetation to climate change ca 8 2 ka with time resolution and precision comparable to those of the greenland ice cores the pollen assemblages show pronounced and immediate responses 0 20 yr of terrestrial vegetation to the climatic change at 8 2 ka a sudden collapse of corylus avellana hazel was accompanied by the rapid expansion of pinus pine betula birch and tilia linden and by the invasion of fagus silvatica beech and abies alba fir vegetational changes suggest that climatic cooling reduced drought stress allowing more drought sensitive and taller growing species to out compete corylus avellana by forming denser forest canopies climate cooling at 8 2 ka and the immediate reorganization of terrestrial ecosystems has gone unrecognized by previous pollen studies on the basis of our data we conclude that the early holocene high abundance of c avellana in europe was climatically caused and we question the conventional opinion that postglacial expansions of f silvatica and a alba were controlled by low migration rates rather than by climate the close connection between climatic change and vegetational response at a subcontinental scale implies that forecasted global warming may trigger rapid collapses expansions and invasions of tree species

early preboreal cooling in the nordic seas region triggered by meltwater at the younger dryas preboreal transition a high resolution core from the northeastern norwegian sea reveals a two step warming of sea surface temperatures dated at respectively 10 200 10 000 and 9700 9500 14 c yr b p 11 450 11 350 and 11 150 11 000 cal yr b p warming was interrupted by a period having stable temperatures and a reduction in sea surface salinity and we suggest that this pause in warming was triggered by an increase in freshwater supply that may have hampered the north atlantic heat conveyor the freshwater influx correlates to an atmospheric cooling over both the greenland ice sheet and northwest europe and to cooling of surface temperatures in the nordic seas freshwater may have been supplied from the waning fennoscandian ice sheet

subsurface cavity detection over patherdih colliery jharia coalfield india using electrical resistivity tomography the present study deals with delineation and mapping of subsurface voids which are very common around the patherdih colliery of jharia coal field india these are caused by coal fire and old unplanned illegal mining activity initially a conceptual model of void formation associated with coal fire has been proposed the burning of coal leads to the void formation due to volume reduction because of transformation of coal to ashes it is supposed to have significant resistivity contrasts between bedrock i e mainly sandstone clay stone shale etc and void space which are filled with ashes generated from burned coal seam field situations have been simulated through forward modeling and the data generated by gradient and dipole dipole arrays have been corrupted by 5 noise the simulations have been carried out for two voids with varied resistivity the inversions of the data for both the arrays bring up the dimension of the void within reasonable accuracy unlike its resistivity in fact the considered resistive void seems to be a conducting void in the present study data have been collected by a state of the art flashres universal electrical resistivity tomography ert instrument which have 61 channel and 64 electrode data acquisition capacity ert sections have been generated over two profiles using wenner schlumberger gradient dipole dipole and joint inversion of all combine arrays different resistive anomalous features with resistivity of about 300 200 m have been delineated in both profiles these are associated with voids at the depths of about 23 25 and 45 54 m generated by burning of coal seams xiva and xiv respectively the obtained results are in broad agreement with the available litholog and surface manifestation of coal fire the results prove the efficacy of the ert technique for detection of voids associated with coal fire

the amphi atlantic oscillation a proposed late glacial climatic event a contribution to the north atlantic seaboard programme of igcp 253 termination of the pleistocene abstract numerous palaeoclimatic records from europe greenland and the north atlantic ocean provide evidence for a short term cooling event which preceded the younger dryas stadial of ca 11 10 ka bp the discovery of a similar event in eastern north america the killarney oscillation ko raised the possibility of a single pre younger dryas cooling event that affected the entire north atlantic seaboard this paper reviews evidence for the ko and other pre younger dryas events and discusses the basis for their correlation the informal name amphi atlantic oscillation is proposed as a collective term for the ko and events that correlate with it

the younger dryas cold interval as viewed from central greenland abstract greenland ice core records provide an exceptionally clear picture of many aspects of abrupt climate changes and particularly of those associated with the younger dryas event as reviewed here well preserved annual layers can be counted confidently with only 1 errors for the age of the end of the younger dryas 11 500 years before present ice flow corrections allow reconstruction of snow accumulation rates over tens of thousands of years with little additional uncertainty glaciochemical and particulate data record atmospheric loading changes with little uncertainty introduced by changes in snow accumulation confident paleothermometry is provided by site specific calibrations using ice isotopic ratios borehole temperatures and gas isotopic ratios near simultaneous changes in ice core paleoclimatic indicators of local regional and more widespread climate conditions demonstrate that much of the earth experienced abrupt climate changes synchronous with greenland within thirty years or less post younger dryas changes have not duplicated the size extent and rapidity of these paleoclimatic changes

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

wisconsinan glacial and sea level history of maritime canada and the adjacent continental shelf a correlation of land and sea events the wisconsinan glacial history of maritime canada records the interaction of land based glaciers with the sea which dissects the region along the deep embayments of the bay of fundy and the laurentian channel ice centers collectively termed the appalachian ice complex shifted in a clockwise manner across the varied bedrock terranes of the region producing cross striated bedrock outcrops and compositionally distinct till sheets on land offshore glacial sediments can be correlated to their terrestrial counterparts on the basis of provenance thus establishing crucial land sea links in the glacial record five glacier flow events have been recognized during the caledonia phase in early to middle wisconsinan time ice from eastern appalachian upland sources crossed nova scotia and extended to the continental shelf edge where a calving margin was established slumping at this margin produced proximal wedge shaped bodies of diamicton that interfinger with glaciomarine sediments the caledonia phase glacier retreated during middle wisconsinan time to the inner scotian shelf during the escuminac phase in late wisconsinan time 22 19 ka an ice center formed over the magdalen shelf escuminac ice center and transported large quantities of local red bed material southward to the outer shelf slope margin this glacier retreated about 18 ka to a tidewater margin at sable island bank and banquereau sea level during this time was falling as a result of isostatic recovery from earlier escuminac phase maximum ice loads just after 18 ka ice wasted back across the midshelf basins to the tidewater margin of the scotian shelf end moraine complex and was stabilized by falling sea levels escuminac ice was reorganized into the scotian ice divide scotian phase over mainland nova scotia and the continental shelf south of cape breton island between 15 and 13 ka another period of glacier retreat ensued and the margin settled close to the present day land areas between 13 and 12 5 ka an ice margin was established from local terrestrial ice centers in northern nova scotia chignecto phase into the bay of fundy and just beyond the present day atlantic coast responding to increasing climatic warming these smaller glaciers dissipated and their margins retreated landward a sea level lowstand of 65 m on the inner shelf occurred ca 11 7 ka isolated terrestrial remnants of chignecto phase glaciers were reactivated as a result of cooling during the collins pond phase younger dryas ca 10 8 ka enhanced ice rafting evident in the north atlantic deep oceanic record appears to correlate with periods of glacier retreat in the appalachian ice complex during melting and sea level rise both the quantity and thickness of icebergs increased due to grounding line retreat within the magdalen shelf thereby increasing the net flux of hematite stained quartz to the north atlantic

a multi proxy lithostratigraphic record of late glacial and holocene climate variability from piper lake nova scotia a multi proxy lithostratigraphic record from piper lake nova scotia reveals environmental variability during the late glacial and holocene piper lake is a small shallow 3 m closed dystrophic basin located in the eastern nova scotia highlands the site was deglaciated about 14 5 cal calibrated ka bp and elevated loss on ignition values and relatively low carbon nitrogen c n isotope ratios indicate the establishment of a productive aquatic environment consistent with allerod warming the late glacial lake record is punctuated by two thin very fine grained clay layers that are correlative to the killarney and younger dryas yd oscillations they were deposited when perennial ice covered the lake the post yd lithostratigraphy indicates the rapid establishment of an increasingly productive and stable landscape this trend is reversed three times during the holocene by minerogenic units a complex 25 cm thick diamicton unique to piper lake was deposited ca 10 8 10 3 cal ka bp by slumping that was associated with periglacial slope processes and or lake level changes a direct correlation to early holocene preboreal cooling appears unlikely two thin minerogenic units deposited at ca 8 1 and ca 4 9 cal ka bp were likely the result of regional cooling and are broadly correlative with events noted in the gisp2 greenland ice sheet project 2 ice core record the holocene lithostratigraphic record from piper lake may be a consequence of unique limnological factors alternatively the strong lithostratigraphic response may be the result of the absence of a strong and persistent regional climate mechanism north atlantic oscillation which if present might have obscured the impact of hemispheric or larger scale climate forcing

late wisconsinan ice retreat from the scotian shelf the late middle to late wisconsinan laurentide ice sheet terminated at the edge of the scotian shelf ca 21 ka in close temporal agreement with the h 2 heinrich event of the north atlantic stratigraphy the ice began its recession along the western edge of the shelf prior to 20 ka by 15 ka the ice front had retreated in a northeastward direction exposing much of the western half of the shelf although ice appears to have remained on the inner shelf north of a morainal system for another 2 k y the retreat was probably controlled by an ice divide along the axis of the mainland until after 16 ka at which time an ice flow pattern began to emanate from local remnant ice centers on the mainland late wisconsinan ice seems to have remained on much of the eastern portion of the shelf as late as 12 14 5 ka and probably deposited several outer bank moraines younger dryas ice probably was present at isolated land and coastal areas for a short period ca 10 5 ka but its offshore influence appears to have been restricted to floating ice and storm related events

anomalously mild younger dryas summer conditions in southern greenland the first late glacial lake sediments found in greenland were analyzed with respect to a variety of environmental variables the analyzed sequence covers the time span between 14400 and 10500 calendar yr b p and the data imply that the conditions in southernmost greenland during the younger dryas stadial 12800 11550 calendar yr b p were characterized by an arid climate with cold winters and mild summers preceded by humid conditions with cooler summers climate models imply that such an anomaly may be explained by local climatic phenomenon caused by high insolation and fohn effects it shows that regional and local variations of younger dryas summer conditions in the north atlantic region may have been larger than previously found from proxy data and modeling experiments

late glacial allerod younger dryas buried organic deposits nova scotia canada a contribution to the north atlantic seaboard programme of igcp 253 termination of the pleistocene abstract numerous deposits of organic shallow pond sediments and wetland peat accumulations buried by minerogenic sediments have been discovered throughout nova scotia they are interpreted as representing a late glacial climatic oscillation correlative with the allerod younger dryas event of europe and the north atlantic ocean the organic deposits began forming during the warm or warming interval following deglaciation and often record a transition to colder conditions the climatic reversion recorded in many deposits began about 10 8 ka bp and continued or sustained cooling culminated in the burial of the organic deposits by minerogenic sediments indicative of solifluction and mass wasting processes some deposits provide strong evidence for regeneration or rejuvenation of local glaciers as the organic deposits are not as susceptible as lake sediments to contamination by old carbon they provide a more reliable chronological framework for deglaciation and late glacial vegetational history palynological evidence shows that pioneer herb tundra communities colonized some areas shortly after 13 ka bp willow and birch shrubs followed soon after spruce woodlands had migrated into the region prior to 10 8 ka bp but had not yet reached the northeast mainland and cape breton island cooling after 10 8 ka bp decimated tree populations and favoured a return to shrub and herb communities the record in the buried deposits was then truncated by deposition of minerogenic sediments and lake sediment sequences from deeper basins with continuous sedimentation are required to complete the record

abrupt climate oscillations during the last deglaciation in central north america evidence from stable isotopes and a variety of proxies from two ontario lakes demonstrate that many of the late glacial to early holocene events that are well known from the north atlantic seaboard such as the gerzensee killarney oscillation also known as the intra allerod cold period younger dryas and preboreal oscillation also occurred in central north america these results thus imply that climatic forcing acted in the same manner in both regions and that atmospheric circulation played an important role in the propagation of these events

exceptionally steep north south gradients in lake temperatures during the last deglaciation during the transition from the last glacial to the present interglacial climate late glacial period high summer insolation1 combined with the presence of the laurentide ice sheet is thought to have promoted the development of strong summer thermal gradients in north america south of the ice margin2 here we use palaeoecological methods to obtain quantitative evidence for the existence of these gradients our palaeoclimate reconstructions are based on water temperatures inferred from fossil assemblages of aquatic midge larvae in five lakes along a 240 km transect extending from central new brunswick canada to southeastern maine usa we show that the temperature gradient shifted during the killarney oscillation ko and younger dryas yd cooling events and that water temperature differences of 9 and 11 c existed over distances of 55 and 240 km respectively during parts of the late glacial period these gradients are much stronger than the current north south trends of lake summer surface water temperatures for these five lakes and for lakes across the northern tree line the rapid motion of such steep temperature gradients may have affected the progressive development of aquatic and terrestrial ecosystems in the region

a late glacial holocene palaeoecological record from pye lake on the eastern shore of nova scotia canadageological survey of canada contribution 20080395 pollen and chironomid analyses and radiocarbon dating at pye lake on the eastern shore of nova scotia are used to outline the vegetation and climatic history of the area the coast was deglaciated prior to 12 200 14c bp 14 300 cal bp and herbaceous tundra vegetation invaded the area midge inferred maximum summer surface water temperatures in the lake ranged between 9 and 11 c subsequent gradual warming to 18 c by 10 800 14c bp 12 725 cal bp favoured the migration of a variety of herbaceous and shrub taxa into the region rapid cooling to 10 c saw vegetation revert to herbaceous tundra communities this interval related to the younger dryas cold interval of the north atlantic and europe lasted until 10 000 14c bp 11 630 cal bp the climate then warmed again to conditions similar to those that prevailed immediately before onset of younger dryas cooling further warming saw successive tree species migrate into the area until by the mid holocene the forests contained most of the taxa preva

sinkholes related to discontinuous pumping susceptibility mapping based on geophysical studies the case of crestatx majorca spain the crestatx aquifer is the main source of water supply to the bay of alcudia one of the largest resorts on the island of majorca spain this water has been used since the 1970s using several pumping wells which draw an annual volume of 1 5 hm3 the seasonal exploitation of this karstic aquifer causes a substantial cone of depression with great variations in the piezometric level up to 120 m and dynamic water levels of down to 87 m below sea level at the end of the 1990s several sinkholes and subsidence depressions started being detected in a highly karstified area twenty subsidence and sinkhole morphologies have been inventoried in an area measuring 70 000 m2 with diameters up to 23 m and depth more than 15 m the intense and continuous rainfall during recent years 2008 2010 has considerably accelerated the process increasing the dimensions of existing sinkholes and the appearance of new morphologies by means of electrical tomography techniques a ground study was carried out numerous cavities have been identified in the upper 30 m using a map of the surface morphologies and the geophysical profiles we can determine that the propagation and orientation of the sinkholes lie along three main directions n30 e n130 e and n60 e the first is the most relevant which is parallel to the main tectonic structures in the area the interpretation of the electrical profiles has enabled us to identify the potentially most unstable areas which is an effective tool to assess risk in the area as there are roads and a housing development nearby the high but discontinuous exploitation of the aquifer is considered the main trigger for these sinkholes and subsidence depressions as it causes large variations of pressure and accelerates the dissolution process in the underlying rock

wisconsinan late glacial environmental change in nova scotia a regional synthesis a synthesis of the interpreted vegetational and climatic history of nova scotia during the wisconsinan late glacial period 14 9 ka bp is presented and described in 500 year intervals the concomitant regional deglaciation history of the region is also described a synthesis chart is provided which includes a qualitative curve of temperature reconstructions for the late glacial period

imaging the movement of toxic pollutants with 2d electrical resistivity tomography ert in the geological environment of the hoa khanh industrial park da nang vietnam this study presents the results of a geophysical survey undertaken by 2d electrical resistivity tomography ert along two traverses the study was conducted between an industrial park ip and a residential area bounding the hoa khanh industrial park da nang vietnam the first traverse 300 m long which is at the boundary between the industrial park and bau tram lake includes 504 measured data points the second traverse which includes 189 measured data points is 200 m in length and runs alongside the boundary between bau tram lake and the residential area bau tram lake is located between the ip and the residential area and acts as a natural boundary after discarding noisy data points the data were processed using the commercial software res2dinv which creates a 2d visual section of the resistivity distribution below surface using a finite difference algorithm and the method of least squares inversion the result of an inversion which is a simulated 2d resistivity image of the subsurface or electrical resistivity tomogram ert showed the formation characteristics and geological structure along the first traverse from surface to 39 4 m in depth including two overlapping geological layers with indistinctive local boundaries the resulting image illustrates the amalgamation of anthropometric transported soil and rocks with local lake material brought into the lake from other areas to fill up the lake with rock and improve the engineering foundation for the construction of the industrial park buildings the research results show that the main components of the second geological layer on both sides of the survey area have the same electrical signature associated with black mud and sand and represent the natural lake sediments the inferred groundwater level identified in the electrical imagery and two boreholes corresponds approximately to the water level in bau tram lake at a depth of approximately 10 m along both traverses the groundwater in bau tram lake and the surrounding residential areas is contaminated by electrolytes and heavy metals furthermore the groundwater inside the industrial park contains a significant amount of industrial electrolytes with a high probability of chemicals such as kcl nacl and heavy metal contamination with a high probability of elements such as pb hg zn at a greater density than measured in the residential areas this suggests that bau tram lake acts as a filter to strongly reduce the movement of these toxic substances from seeping into the groundwater below the residential area

exploration for a cave by magnetic and electrical resistivity surveys ayvacik sinkhole example bozdag izmir western turkey abstractgeophysical survey techniques have been successfully applied to near surface cave detection in karstic terrains we used magnetic and electrical resistivity surveys to delineate the karstic structure of the ayvacik sinkhole which may be considered to be a vertical cave the magnetic total field anomaly map helped reveal the metamorphic and sedimentary units in the study area the total horizontal gradient map which was based on a calculated pseudogravity anomaly successfully identified the contact between the limestone unit and the cave system using these results we positioned and carried out a vertical electrical sounding ves survey with a schlumberger array along a line that consisted of 11 stations the ves data were then processed using a 1d global optimization technique which used a genetic algorithm and a 2d linearized least squares algorithm the results were generally in good agreement with each other and together they pointed out three geologic layers 1 an overburden layer 3

proposed younger dryas glaciation of the eastern scotian shelf a refined synthesis of the stratigraphy of the scotian shelf is presented based on recently published borehole and seismic reflection data and detailed correlation along high resolution seismic profiles between the outer banks and the central basins one of the new stratigraphic units of the outer bank region is of glacigenic origin and represents the last glacial event near the margin of the shelf these deposits appear to be part of a morainal bank complex formed at a tidewater front a younger dryas age is proposed for the glacial deposits and the ice may have been widely distributed across the eastern scotian shelf evidence for the late glaciation is expressed in the central shelf area by an unconformity which on the bank areas is associated with subglacial meltwater channels 14c dates for the basin sediments of this region provide the most reliable chronology for the shelf stratigraphy the origin of sable island is closely related to the depositional history of the moraine and its surface has be

a multiproxy investigation of late glacial climate and vegetation change at pine ridge pond southwest new brunswick canada abstract pollen plant macrofossil chironomid and lithological analyses of late glacial sediment from pine ridge pond all indicate that the warming following deglaciation was punctuated on two separate occasions by a return to colder climes initially by a brief and moderate cold episode the killarney oscillation followed shortly by the younger dryas the killarney oscillation ams 14 c dated at between 11 290 and 10 960 yr b p is characterized by abrupt and simultaneous increases in betula birch pollen and betula glandulosa dwarf birch macrofossils and a decline in tree pollen the younger dryas is distinguished by the reversion of a short lived closed picea spruce forest to a prolonged forest tundra stage ca 10 820 to 9500 yr b p during which macrofossils of arctic alpine plants such as salix herbaces cassiope hypnoides armeria maritima and thalictrum alpinum make their sole late glacial appearance chironomid inferred summer surface water temperatures indicate a cooling of approximately 8 and 12 c during the killarney oscillation and younger dryas respectively and coarse sand analysis indicates increased erosion on the landscape during these same intervals

rapid least squares inversion of apparent resistivity pseudosections by a quasi newton method1 a fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer this technique is based on the smoothness constrained least squares method and it produces a two dimensional subsurface model from the apparent resistivity pseudosection in the first iteration a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically for subsequent iterations a quasi newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times respectively compared to the conventional least squares method tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly this technique takes about one minute to invert a single data set on an 80486dx microcomputer

karst conduit hydro gradient nonlinear variation feature study case study of zhaidi karst underground river through the analysis of monitoring data with a time interval of 10 min during the rainy season of 2012 for three points of g37 zk8 and zk7 which are located on the main conduit of zhaidi karst underground river system the variation features of water level and hydraulic gradient are studied and the relations are established between gradient and water level or amplitude 1 it is first discovered that there are different function relations such as linear parabola and inverse parabola between the g37 s water level and the hydraulic gradients of different conduit part 2 the peak delay times for water level curves are 50 min and the maximum conducting speed of water press is faster than 13 020 m h 3 the upstream and downstream karst conduits have corresponding enlarging and shrinking amplitude function by the coefficients of 1 899 km and 0 125 km 4 the gradient i variation is still linear to the level difference h made by nine rainstorms the conclusion and the methods of this paper have significance on the study of the regulation and storage capacity and groundwater resources evaluation of karst underground river system

the preboreal oscillation around the nordic seas terrestrial and lacustrine responses the occurrence of an early preboreal climatic cooling oscillation pbo in lacustrine and glacial records from northwest europe iceland and greenland is reviewed and documented the often subtle response of the proxy records to this oscillation in combination with its short duration make it difficult to detect owing to its chronostratigraphic position between the 10 000 9900 and 9600 9500 14 c plateaux c 11 300 11 150 calendar yr bp it is also difficult to 14 c date with precision we find that the vegetation response to the pbo varies between sites and regions in contrast to the pioneer vegetation in iceland and southern sweden the expanding birch pine forest in germany denmark was more susceptible to deteriorating growing conditions the combined lacustrine tree ring and glacial records imply that the pbo was characterised by cool and humid conditions throughout northwestern and central europe this is documented by vegetation changes decreased aquatic production increased soil erosion increased 2 h and 13 c content in tree rings readvances or stillstands of the ice sheet in norway and finland and ingression of brackish water into the baltic icelandic proxy records from lake sediments and glacial moraines imply cooler conditions than during the previous preboreal period but not as extreme as during the younger dryas greenland records suggest that the early preboreal was characterised by ice readvances as an effect of cool climate and increased precipitation in relation to the younger dryas it was not until the end of the pbo that climate was warm enough to melt the land based ice sheet this preboreal oscillation found on both sides of the nordic seas is interpreted as an effect of increased freshwater forcing on the thermohaline circulation in the nordic seas which is implied by a simultaneous and distinct rise in the atmospheric 14 c 12 c ratio a slow down of the thermohaline circulation may tempor arily have pushed the polar front further south 1997 by john wiley sons ltd preboreal oscillation thermohaline circulation lacustrine records glacial records chronology

karst database implementation in minnesota analysis of sinkhole distribution this paper presents the overall sinkhole distributions and conducts hypothesis tests of sinkhole distributions and sinkhole formation using data stored in the karst feature database kfd of minnesota nearest neighbor analysis nna was extended to include different orders of nna different scales of concentrated zones of sinkholes and directions to the nearest sinkholes the statistical results along with the sinkhole density distribution indicate that sinkholes tend to form in highly concentrated zones instead of scattered individuals the pattern changes from clustered to random to regular as the scale of the analysis decreases from 10 100 km2 to 5 30 km2 to 2 10 km2 hypotheses that may explain this phenomenon are 1 areas in the highly concentrated zones of sinkholes have similar geologic and topographical settings that favor sinkhole formation 2 existing sinkholes change the hydraulic gradient in the surrounding area and increase the solution and erosional processes that eventually form more new sinkholes

the cold event 8200 years ago documented in oxygen isotope records of precipitation in europe and greenland stable oxygen isotope ratios of ostracod valves in late glacial and holocene sediments of core as 92 5 from deep lake ammersee southern germany reflect variations of mean oxygen isotope ratios in past atmospheric precipitation the record reconfirms the strong similarity of climate evolution in europe and greenland during the last deglaciation for the first time in europe we find a 200 year long negative 18o excursion which is contemporaneous with the strongest negative 18o excursion in the greenland ice around 8 2 ky before present the 8 2 ky isotopic event on both sides of the north atlantic ocean is interpreted as a cold period most probably induced by a perturbation of the north atlantic thermohaline circulation we discuss two possible triggering mechanisms 1 weak forcing as proposed by alley et al and 2 forcing by a strong and sudden freshwater pulse from the collapse of the hudson ice dome

determination of cave geometry by using a geoelectrical resistivity inverse model determination of the geometry and the dimensions of a cave is an important factor considered for planning geotechnical archeological speleological studies and quarrying activities in recent years researchers have raised an increasing number of questions related to the shape and size of cavities using 2d geoelectrical resistivity imaging techniques the inverse model is valuable in detecting the location and extent of subterranean cavities in this study a 2d geoelectrical resistivity imaging technique is employed to determine the geometry of a known subterranean cavity the results provided valuable information and demonstrated the effectiveness of the technique for exploring the size of cavities

allerod younger dryas lake temperatures from midge fossils in atlantic canada remains of freshwater midges are abundant in lake sediments and their species distributions are closely related to the surface water temperature of lakes their distributions thus provide a powerful tool for paleoclimatology the distribution of species in a core from splan pond in atlantic canada indicates that there were abrupt transitions in late glacial temperatures between warm and cold states the transitions are correlative with the well known warm allerod and cold younger dryas events in europe these data thus confirm the inference from palynological data that these events affected regions on both sides of the atlantic

a regional 8200 cal yr bp cooling event in northwest europe induced by final stages of the laurentide ice sheet deglaciation the most notable change in 18o in greenland ice cores during the holocene occurs at 8200 cal yr bp here we present a new high resolution marine record from the northern north sea along with tree ring data from germany which contain evidence of a pronounced temperature drop 2 c contemporaneous with that of the greenland ice core records the synchronous timing of the cooling event in the greenland ice cores marine record and tree ring data from northwest europe reflects a regional influence on the north atlantic ocean atmospheric system suggesting a prominent role of the north atlantic thermohaline circulation the operation of the north atlantic ocean circulation is sensitive to variation in the freshwater budget implying that any change in freshwater flux is capable of altering the north atlantic circulation system we hypothesise minor but long term freshwater fluxes in the final stages of the deglaciation of the laurentide ice sheet as a forcing mechanism 1998 john wiley sons ltd

georeferenced thermal infrared images from uav surveys as a potential tool to detect and characterize shallow cave ducts abstract caves are buried geological features of great scientific and engineering interest based on the well known thermal inertia of cave settings with respect to the surface we have tested the use of thermal infrared tir cameras carried by unmanned aerial vehicles uavs to identify and characterize shallow karstic conduits a pilot area was selected in a limestone rock massif from the betic cordillera southern spain at surface this area appears as a doline field with several explored shaft entrances the main and deepest shaft was thermally monitored at different depths showing two well defined seasonal stages i air and temperature stratification in summer and ii upward air flow and temperature homogenization in winter we carried out uav surveys at the expected maximum thermal contrast hours finding out that winter dawns yielded the most distinctive images these images show new warm air exits warm spots apart from the known cave entrances and emphasize some of the main entrances depicting large warmed areas around them which in turn can be related to shallow voids and conduits in the cave system furthermore tir images have been georeferenced using a network of identifiable points that can be transferred from visible orthoimages the resulting tir orthoimage mosaics have allowed us to define a number of quantitative parameters to characterize the warm spots the most important of these parameters are i the characteristic temperature which is the maximum significant temperature of the air escaping from cave openings ii the warmed area which is the area that appears on the tir orthoimage with a temperature greater than the surface temperature mode and iii the average temperature weighted to the affected area the georeferenced tir orthoimages and the derived parameters are a new and very valuable tool for both speleological exploration and engineering purposes

high resolution analyses of an early holocene climate event may imply decreased solar forcing as an important climate trigger early holocene lacustrine tree ring ice core and marine records reveal that the northern hemisphere underwent a short cooling event at 10 300 calendar yr b p 9100 14 c yr b p the records were compared on a common high resolution time scale and show that the event lasted less than 200 yr with a cooling peak of 50 yr and the event coincides with a distinct holocene thermohaline disturbance recognized in the north atlantic ocean in spite of wellknown freshwater forcings at the time of the event the negligible difference between the modeled d 14 c record based on the gisp2 greenland ice sheet project 2 10 be data and the measured values does not allow for detectable d 14 c changes related to global ocean ventilation we can however show that the onset of the cooling coincides with the onset of one of the largest holocene 10 be flux peaks this finding may imply that the climate system is more

wisconsinan late glacial environmental change in newfoundland a regional review the distribution of 75 lake and bog sites from which pollen stratigraphical evidence relevant to the late quaternary of newfoundland has been obtained is presented the detailed records of lithology pollen and diatoms supplemented by geochemical data are discussed for three of the sites southwest brook lake woody hill brook pond and leading tickles and interpretations made are based on vegetational history relative climatic changes and extent of ice cover radiocarbon data from 14 sites are summarised a summary chart of late glacial environmental changes including a qualitative palaeotemperature curve is provided

a 9600 year record of water table depth vegetation and fire inferred from a raised peat bog prince edward island canadian maritimes a 582 cm long peat core was collected from baltic bog an ombrotrophic peatland in north eastern prince edward island canada the core was studied for testate amoebae plant macrofossils macrocharcoal peat humification and organic matter content the results show that baltic bog first developed 9600 cal a bp as a minerotrophic peatland fen dominated by cyperaceae at 8200 cal a bp the fen transitioned into a peat bog dominated by sphagnum between 8200 and 4000 cal a bp water table depth wtd was generally low and the bog surface supported trees such as picea mariana from 4000 to 1700 cal a bp wtd rose and the bog became more open the macrocharcoal results show that the period 2000 1000 cal a bp was characterized by several fire events that may have occurred on the bog surface at the core site the results presented in this paper correspond closely with previous fossil pollen research done at baltic bog and suggest that regional climate change was a key factor in controlling long term wtd variability and vegetation change at the site

investigation of sinkholes spatial distribution using the weights of evidence method and gis in the vicinity of karapinar konya turkey abstract there are many sinkholes 182 in the vicinity of karapinar approximately 20 large sinkholes 10 m in diameter were formed within the obruk plateau between 1970 and 2012 the formation of sinkholes is the most important geological hazard in the study area because they can damage engineering structures settlements agricultural areas and eventually be a source of casualties to date no study has been conducted on the distribution of sinkholes in this region in this study the spatial distribution of the sinkholes and the factors controlling sinkhole development were studied through the use of geographical information systems using a sinkhole inventory and a spatial database containing information on the topography geology hydrogeology and land use initially 182 sinkholes were identified in the area by examining the digital elevation model produced for this study the sinkholes were verified in the field thirty two factor maps were produced to investigate their relationship with sinkholes using the weights of evidence method the sinkholes are mainly related to dissolution of the neogene age lacustrine insuyu formation consisting of limestone and clayey limestone sinkhole frequency increases in the vicinity of drainages 2000 3000 m and faults

susceptibility mapping of instability related to shallow mining cavities in a built up environment anthropogenic activities and urbanization frequently spread over areas underlain by unstable karst ground or man made cavities leading to potential risk situations for buildings infrastructure and population the roof of the cavities may rapidly propagate upwards eventually resulting in progressive ground settlement and or sudden collapse these processes are frequently accelerated or triggered by various human activities e g overloading water recharge water table decline in this paper the susceptibility to instability of artificial cavity networks under an urban area in apulia region southern italy was assessed and evaluated here there is dense network of underground quarries excavated for the extraction of massive calcarenite for building and ornamental stone that are currently affected by severe instability problems identifying the zones of the cavities most prone to instability is of great practical importance susceptibility models have been developed analyzing the statistical relationships between the cavity sections with evidence of instability and a number of predisposing factors mainly related to the 3d geometry of the voids roof thickness and the presence of overloads the models produced by the discriminant analysis and the logistic regression approaches were independently and quantitatively evaluated through the construction of roc curves although the two models are characterized by different input data treatment as the logistic regression allows using continuous and discrete variables or any combination of both types even if they do not have a normal distribution the roc curves highlighted for both methods a satisfactory congruence between the model results and the observed data consequently from the model performance analysis the two models were evaluated comparable in terms of result reliability the methodology should be considered as a general first level analysis for near surface underground cavities aimed at identifying critical cave sectors that can be the focus of more detailed analyses especially those associated with sensitive zone related to the presence of buildings roads and frequent presence of human activity

an image analysis technique to measure grain size variation in thin sections of soft clastic sediments this paper presents a simple and fast image analysis technique to measure grain size variation in thin sections of soft elastic sediments optical and backscattered electron microscope photographs are digitised from thin sections cut by freeze drying to avoid disturbing the sediments processing of the 256 grey scale images produces binary black and white images where white pixels represent the clay rich sedimentary matrix and black pixels represent elastic grains data measured include grain surface grain perimeter and centre of gravity two indices are defined to quantify grain size d 0 equivalent disk diameter and p phase percentages the technique is applied to silt and clay laminations attributed to the d division of a distal turbidite from lake baikal the data obtained using image analysis are similar to the conventional descriptions of such deposits indices calculated on very small samples e g on a single lamina allow for greater precision in interpretation of sedimentary processes compared to photomicrographs backscattered electron microscope images have better qualities and allow to quantify variations in the grain size along a sediment core the technique produces objective and quantified grain size observations in less time than conventional petrographic methods c 1998 elsevier science b v all rights reserved

multiproxy evidence of an early holocene 8 2 kyr climate oscillation in central nova scotia canada an early holocene lake sediment record from central nova scotia contains a minerogenic oscillation that is closely correlative with the 8 2 kyr event ca 8200 cal yr bp an event that has not been reported elsewhere in atlantic canada a variety of biological and sedimentological indicators have been examined to characterise autochthonous and allochthonous changes that occurred during this time the minerogenic upper oscillation uo ca 8400 cal yr bp is marked by an increase in the chrysophyte diatom ratio following the oscillation the diatom community reflects a shift to more productive less acidic conditions the pollen record shows no major response to this short lived event lithostratigraphic analyses indicates that the uo is characterised by an increase in clastic content magnetic susceptibility and mean sediment grain size all indicators of changing environmental conditions most likely the result of regional cooling the taylor lake record adds to a growing body of evidence for a widespread hemispheric climate oscillation at 8 2 kyr copyright 2002 john wiley sons ltd

preboreal oscillation caused by a glacial lake agassiz flood the preboreal oscillation pbo has been attributed to increased meltwater but the source of the meltwater and causative mechanism of the pbo has remained elusive here we attribute the source to a massive meltwater discharge event from an abrupt drainage of glacial lake agassiz canada via the mackenzie river into the arctic ocean a maximum volume of 21 000 km 3 was discharged over a 1 5 3 yr period with a peakdischarge of 0 500 sverdrups sv equivalent to a 6 m rise in the arctic ocean or 0 062 m rise in global sea level the flood occurred at about 11 335 cal yr bp and was followed by a b0 042 sv flow until 10 750 cal yr bp when the southern outlet of lake agassiz reopened and diverted drainage to the mississippi river system we estimate that only 2 4 of the flood water would have frozen into sea ice within the beaufort region but coupled with increased river ice production during winter and thicker pack ice growth throughout the arctic ocean a thicker longer lasting and more extensive packice may have been flushed through fram strait the thicker and more extensive packice and freshened sea surface may have triggered the pbo by increasing albedo and generating a low salinity anomaly upon melting in the north atlantic thus decreasing the formation of north atlantic deep water r 2002 elsevier science ltd all rights reserved