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Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

New publications on hypogene speleogenesis

Klimchouk on 26 Mar, 2012
Dear Colleagues, This is to draw your attention to several recent publications added to KarstBase, relevant to hypogenic karst/speleogenesis: Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications Galdenzi,

The deepest terrestrial animal

Klimchouk on 23 Feb, 2012
A recent publication of Spanish researchers describes the biology of Krubera Cave, including the deepest terrestrial animal ever found: Jordana, Rafael; Baquero, Enrique; Reboleira, Sofía and Sendra, Alberto. ...

Caves - landscapes without light

akop on 05 Feb, 2012
Exhibition dedicated to caves is taking place in the Vienna Natural History Museum   The exhibition at the Natural History Museum presents the surprising variety of caves and cave formations such as stalactites and various crystals. ...

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That unconfined flow is ground-water flow displaying a free surface [16].?

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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
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Featured articles from other Geoscience Journals
Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
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Your search for sediment. (Keyword) returned 34 results for the whole karstbase:
Showing 1 to 15 of 34
The animal population of the hyporheic interstitial in a primary rock stream under the influence of the supply of allochthonous organic matter., 1976, Pieper Hansgerd
The Mettma, a mountain stream in the Black Forest, W. Germany, was investigated for effects of input of nutrients and energy by domestic waste water and effluent from a brewery introduced at one specific point. The investigation time ranged from May 1970 to February 1971. Initially, there is an impoverishment and structural changes of the biocoenosis in the hyporheic interstitial. There is an almost complete O2-depletion immediately after the waste water has been added. In winter, temperatures in the interstitial were higher than those in the current. No direct correlation between population densities and amount of organic matter were observed where allochthonous nutrients had been added. Population densities of multicellular animals were from 0 to 1.2 X 105 per 0.1 m3 of sediment. 4.1 km further downstream the fauna is similar to that above the waste water inlet, while at 7.35 km downstream of it is slightly less dense.

Structure et Fonctionnement des Ecosystmes do Haut-Rhone Franais; IX: Analyse des peuplements de deux stations phratiques alimentant des bras morts., 1981, Gibert J. , Ginet Rene, Mathieu J. , Reygrobellet Jean Luc
Two phreatic stations providing old meanders of the French river Rhone ("Lones") with interstitial water have been studied for three years. The samples (100 liters of water) have been collected by the Bou-Rouch method at 60 cm deep in the sediment. The analyses of populations show that the biocenoses of the two stations are quite different: The one (Station 2) is rather specialized; most of the species are troglobitic (80% of the whole biomass; the only Amphipod, Niphargopsis casparyi, represents 67% of this biomass). The other (Station 8) is very diversified; the seven dominant groups are all epigean animals. Population numbers have changed during the three years of sampling. Fluctuations have been observed in station 2, but the total numbers were quite similar in 1975 and 1977. On the contrary, station 8 shows an "exponential" type of growth generated by epigean organisms, while troglobitic species remained unchanged.

Three regolith-collapse sinkholes formed near the Dongola Unit School and the Pentecostal Church in the southern Illinois village of Dongola (Union County) during the spring of 1993. The sinkholes appeared over a three-month period that coincided with development of a new municipal well. The new well was drilled through clay-rich, valley-fill sediment into karstified limestone bedrock. The piezometric surface of the limestone aquifer is above land surface, indicating the presence of an upward hydraulic gradient in the valley and that the valley fill is acting as a confining unit. Pumping during development of the well lowered the piezometric surface of the limestone aquifer to an elevation below the base of the valley fill. It is hypothesized that drainage of water from the sediments, the resulting loss of hydrostatic pressure and buoyant force in overlying sediments, increased intergranular pressure, and the initiation of groundwater flow toward the well resulted in rapid sediment transport, subsurface erosion, and collapse of the valley-fill sediment. The sinkholes follow an approximately east west alignment, which is consistent with one of the two dominant alignments of passages of nearby joint-controlled caves. A constant electrode-separation resistivity survey of the school playground was conducted to locate areas that might contain incipient sinkholes. The survey revealed a positive resistivity anomaly trending N75E in the southern part of the study area. The anomaly is linear, between 5 and 10 m wide. and its trend either intersects or is immediately adjacent to the three sinkholes. The anomaly is interpreted to be a series of pumping-induced cavities in the valley-fill sediments that formed over a preexisting crevice in the karstified bedrock limestone

Diagenetic concretions from the cave clastic sediment, Cave in Tounj quarry, Croatia, 1998, Lackovič, Damir

Diagenetic concretions from Cave in Tounj quarry (central Croatia) are studied. Concretions are found in non-cemented unsorted clastic cave deposit. They consist of particles of different size (clay to pebble) and from different provenance. One part of calcite and clay minerals are coming from speleothems and cave walls limestone. Detrital particles: chert, quartz, muscovite, chlorite, ilmenite, magnetite and most of clay, are probable transported into the cave from Triassic and Pleistocene clastic sediments from the surface. Autochthonous constituents of concretions are limonitic pizoids and some calcite cement. Composition of concretion is similar to the composition of surrounding non-cemented sediment.

Non-invasive investigation of polygonal karst features: Yorkshire Dales National Park. MSc thesis (Exploration Geophysics), 1999, Gullen T.

Resistivity, refraction and resistivity tomography methods were used to ascertain the dimensions of any sediment body present within solution dolines. Fieldwork was undertaken at two sites within the Yorkshire Dales National Park: High Mark [SD920 679] northeast of Malham Tarn, and on Ingleborough, northeast of Clapham Bottoms [SD765 722].
Results of previous studies of doline fill have been inconclusive. It has been hypothesised (Howard, unpublished) that if dolines do contain significant amounts of sediment, the fill could provide a complete palaeoenvironmental record of the Quaternary.
Resistivity studies undertaken at High Mark used an Offset Wenner array, and field data were inverted to produce a 1-D image of the subsurface. The profiles were located at the base of the doline, in the area believed to contain the greatest sediment thickness. Results suggest that the fill comprises two layers. An upper layer approximately 1 m thick is composed of poorly consolidated clayey sand with an apparent resistivity of 166m. The second layer reaches a depth of 5.6m and is more clay-rich, with an apparent resistivity of 60m. These interpretations are supported by evidence from augering. The upper 10m of limestone below the sediment has been altered during doline formation, weathering and fracturing, and has a resistivity of 220m compared to 440m for the unaltered bedrock.
Refraction profiles were undertaken at High Mark, using the hammer and plate method with a 2m geophone spacing. Profiles were located on the base, flanks and interfluves of the doline. Ground conditions prevented the acquisition of very long offset shots (>10m), and lack of these data hindered interpretation. Profiles undertaken at Ingleborough used an explosive shot placed in a 45cm-deep hole, and a 5m geophone spacing was used. Profiles were located at the base of the dolines.
Results at High Mark suggest that the limestone is overlain by 4m of sediment. The upper layer has a velocity of approximately 0.50m/ms, whereas that of the second layer is 1.19m/ms. Alteration of the upper 6m of the bedrock is indicated by a velocity of 2.00m/ms, compared to 2.99m/ms for the unaltered limestone. The bedrock surface is undulatory, possibly indicating the effects of preferential dissolution or glacial activity.
Results of the refraction surveys at Ingleborough indicate that the limestone is overlain by a single 4m-thick layer of sediment with a velocity of 0.52m/ms. Beneath this, the upper 13m of limestone is altered, with a velocity of 2.45m/ms, which increases to 3.75m/ms in the unaltered limestone below. Velocities obtained are lower than expected, but reliable imaging of the limestone was ensured by siting the profiles close to observed rock exposures. Refraction interpretations indicate that the centre of the doline is not coincident with the position predicted from observation of the surface morphology.
Resistivity tomography profiles were undertaken at the base of the dolines at both sites. A fully automated system employing a Wenner array with 25 electrodes at 5m spacings was used, and six levels were recorded. The field data were inverted and the results suggest that there are about 12.5m of sediment in the High Mark doline. The sediment is underlain by 2m of altered limestone and the bedrock base of the doline is relatively smooth.
In contrast, the thickness of sediment fill in the Ingleborough dolines is 7.5m, but the depressions are bounded by a greater thickness of altered limestone (10m). In places the limestone imaged appears to reach the surface, but is not observed in the field, indicating that minimal sediment cover is not imaged. The surface of the limestone is pitted by smaller sediment-filled depressions, possibly a feature of glacial scour.
Two profiles were forward modelled to test the reliability of the inversion model. The models were similar, but features were displaced to the right of the true section. Synthetic models were constructed to test geological hypotheses concerning the composition of the dolines. The models suggested that the dolines are relatively shallow (<12m) and are underlain by significant thicknesses of altered limestone (~10m).
The combination of results obtained suggests that dolines are not filled by significant quantities of sediment and, consequently, they cannot be used as palaeoenvironmental indicators of the Quaternary.
Jobling A. 2000. Resistivity tomography survey over a topographic depression, West Yorkshire.
BSc thesis (Geophysical Sciences), School of Earth Sciences, University of Leeds, Leeds, LS2 9JT, UK.
Three resistivity profiles were completed across a topographic depression near Garforth, West Yorkshire. The depression is roughly circular, with a radius of approximately 20m. Two profiles ran through the centre of the depression, with a third profile lying outside it. Data from these three profiles were processed, and graphs and pseudosections were compiled. The data were also inverted.
The pseudosections and inversions both showed a large, negative resistivity anomaly centred approximately beneath the surface depression. This anomaly had a resistivity difference of between 600m and 700m compared to that of the surrounding rock.
The most likely reason for this anomaly is dissolution of limestone causing development of a doline or sinkhole. The chance of the depression being an old coal mine or sand mine working has been dismissed due to the location of the site and the nature of the resistivity anomaly.

The "unroofed cave" near the bunker (Laški Ravnik), 1999, Gerš, L Milan, Stepiš, Nik Uroš, , Š, Uš, Terš, Ič, Simona

Situated in the Laški Ravnik, about 4 km east of Planinsko polje (Slovenia), this unroofed cave is the longest of many found in the area. More than 200m of denuded passage has been traced at the surface. The cave's general trend is north - south. Three main "passages" making up the unroofed cave have been recognised, and each has been transformed in its own way. Disintegration of parts of the former cave roof is apparent, forming "false solution dolines", between which the ceiling is partly preserved, either in-situ or as isolated blocks lying on cave sediment. In the down-dip direction, passage sides have disintegrated almost completely, and detached blocks have slid down into washed-out portions of the former cave passages. All three passages developed along bedding planes, but in different directions, such that two of them now "emerge" above the surface whereas the third plunges down and is completely choked by loam. The unroofed cave passes southwards into a "normal" underground route, where a barely accessible, low and wide passage is accompanied by two "vertical" shafts, which are presumed to be former phreatic jumps. This part of the system is not considered in this paper.

Transport of free and particulate-associated bacteria in karst, 2000, Mahler B. J. , Personne J. C. , Lods G. F. , Drogue C. ,
Karst aquifers, because of their unique hydrogeologic characteristics, are extremely susceptible to contamination by pathogens. Here we present the results of an investigation of contamination of a karst aquifer by fecal indicator bacteria. Two wells intercepting zones with contrasting effective hydraulic conductivities, as determined by pump test, were monitored both during the dry season and in response to a rain event. Samples were also collected from the adjacent ephemeral surface stream, which is known to be impacted by an upstream wastewater treatment plant after rainfall. Whole water and suspended sediment samples were analyzed for fecal coliforms and enterococci. During the dry season, pumping over a 2-day period resulted in increases in concentrations of fecal coliforms to greater than 10,000 CFU/100 mi in the high-conductivity well; enterococci and total suspended solids also increased, to a lesser degree. Toward the end of the pumping period, as much as 50% of the fecal coliforms were associated with suspended sediment. Irrigation of an up-gradient pine plantation with primary-treated wastewater is the probable source of the bacterial contamination. Sampling after a rain event revealed the strong influence of water quality of the adjacent Terrieu Creek on the ground water. Bacterial concentrations in the wells showed a rapid response to increased concentrations in the surface water, with fecal coliform concentrations in ground water ultimately reaching 60,000 CFU/100 mi. Up to 100% of the bacteria in the ground water was associated with suspended sediment at Various times. The results of this investigation are evidence of the strong influence of surface water on ground water in karst terrain, including that of irrigation water. The large proportion of bacteria associated with particulates in the ground water has important implications for public health, as bacteria associated with particulates may be more persistent and more difficult to inactivate. The high bacterial concentrations found in both wells, despite the difference in hydraulic conductivity, demonstrates the difficulty of predicting vulnerability of individual wells to bacterial contamination in karst. The extreme temporal variability in bacterial concentrations underscores the importance of event-based monitoring of the bacterial quality of public water supplies in karst. (C) 2000 Elsevier Science B.V. All rights reserved

Diagenetic History of Pipe Creek Jr. Reef, Silurian, North-Central Indiana, U.S.A, 2000, Simo J. A. , Lehmann Patrick J. ,
Calcite cements in the Silurian (Ludlovian) Pipe Creek Jr. Reef, north-central Indiana, are compositionally zoned with characteristic minor-element concentrations and stable-isotope signatures, and were precipitated in different diagenetic environments. Superposition and crosscutting relationships allow us to group cement zones and to relate them to the sequence stratigraphic evolution of the reef. Pipe Creek Jr. Reef grew in normal marine waters, with the reef top high (greater than 50 m) above the platform floor. Flank facies are volumetrically important and are preserved largely as limestone, in contrast to most dolomitized Silurian reefs in the midcontinent. Syndepositional marine cements fill primary porosity and synsedimentary fractures and are interlayered with marine internal sediment. Now low-magnesium calcite, their isotopic compositions are similar to those of depositional grains and cements estimated to have precipitated from Ludlovian sea waters. Depositional porosity was reduced by 75% by the precipitation of these syndepositional cements, which stabilized the steeply dipping flank slope. Postdepositional, clear calcite cements are interpreted as shallow-phreatic and burial cements on the basis of their relationship to periods of karstification and fracturing. Shallow-phreatic cements, with concentric cathodoluminescent (CL) zonation, precipitated in primary pores and are postdated by fractures and caves filled with Middle Devonian sandstone. CL zonal boundaries are sharp, and some, near a major stratigraphic unconformity, show evidence of dissolution. The volumetric abundance of the individual CL zones varies in the reef, indicating a complex superposition of waters of varying chemistry and rock-water interaction that are probably related to relative sea-level changes. This important aspect of the reef stratigraphy is recorded only by the diagenetic succession, because evidence of earlier sea-level changes is removed by a major later regional unconformity. Burial cements are the youngest diagenetic feature recognized, and they rest conformably or unconformably over older cements. They exhibit both concentric CL zonation and sectoral zoning, they are ferroan to nonferroan, and they contain thin sulfide zones along growth-band boundaries. Their isotopic compositions do not overlap with shallow-phreatic or marine cement values. Degraded oil postdates burial cements, and is composed of the same sterane class as the Devonian-age Antrim Shale, the probable source rock. This source contrasts with that of reef reservoirs in the Michigan Basin, where Silurian strata are commonly the hydrocarbon source

Speleogenesis of the Black Hills Maze Caves, South Dakota, USA, 2000, Palmer A. N. , Palmer M. V.
Caves of the Black Hills of South Dakota, USA, are located in the Madison Limestone of Mississippian (early Carboniferous) age in a zone of diagenetic breccias and late-Mississippian paleokarst. Most of the caves are extremely complex networks with multiple stratigraphically controlled storeys. Today they are essentially hydrologic relics. Their history is as complex as the caves themselves: (1) The earliest cave openings were formed by diagenetic processes, mainly by the dissolution and reduction of sulfates. Oxidation of hydrogen sulfide produced many small and rather isolated voids lined by brecciated bedrock. (2) Late Mississippian exposure produced caves, dolines, and surface fissures, which were later filled with basal Pennsylvanian (late Carboniferous) sands and clays of the Minnelusa Formation. (3) Deposition of sedimentary strata buried these early karst features to depths of at least two kilometers. During this time, voids that had not been entirely filled by Pennsylvanian sediment were lined by a thin layer of scalenohedral calcite, and later by quartz. (4) Uplift of the Black Hills at the end of the Cretaceous Period exposed the Madison Limestone once again, allowing rapid groundwater flow through it. The earlier caves and solution pockets were enlarged at this time. (5) A thick layer of rhombohedral calcite precipitated on the cave walls, probably as the result of stagnation of groundwater caused by late Tertiary aggradation, which blocked spring openings. (6) Both before and after the calcite wall crust was deposited, deep subaerial weathering produced boxwork, with veins of calcite that had replaced earlier sulfates, as well as thick accumulations of carbonate sediment. The Tertiary cave enlargement probably involved mixing of at least two of the following water sources: artesian flow from recharge along the carbonate outcrop area, diffuse recharge through the overlying sandstone, and rising thermal water. There is evidence for all three sources, but the relative importance of each is still uncertain.

The fossilized tubes from the roofless cave - probably the oldest known remains of the cave worm Marifugia (Annelida: Polychaeta), 2000, Mihevc, Andrej

The paper is a report on the discovery of tubes of a fossilized cave serpulid in a roofless cave in the quarry above Črni Kal village. The site and shape of the fossilized tubes are described. The animals lived attached to the scallops in the wall of the passage. The passage was later filled with clay deposits, followed by a layer of flowstone several metres thick. The roof of the passage has been removed by karst denudation and flowstone now reaches to the surface. Fragments of tubes of animals of various sizes have been preserved, attached to the rock wall; those tubes which grew at a right angle to the wall have broken off but have been preserved in the sediment. In terms of their dimension and shape the tubes remind one of the tubes of the more recent cave serpulid Marifugia cavatica Absolon and Hrabe. The positions of the preserved tubes and the dating of the nearby sediments by palaeomagnetic method indicate that the remains of the serpulids are from the Pliocene epoch or older.

Dead carbon in stalagmites : limestone paleodissolution versus ageing of Soil Organic Matter - Implications for 13c variations in stalagmites, 2001, Genty D. , Baker A. , Massault M. , Procror Ch. , Gilmour M. , Ponsbranchu E. , Hamelin B

Dynamics of Cave development by Allogenic water, 2001, Palmer, Arthur N.

Streams that drain from non karstic surfaces tend to have great discharge fluctuations and low concentrations of dissolved solids. Where these streams encounter karstic rocks they can form caves with hydraulic and chemical dynamics quite different from those fed by autogenic recharge (e.g. through dolines). Caves in carbonate rocks that are fed by allogenic streams have a relatively short inception period, after which the mean annual rate of dissolutional wall retreat is typically about 0.01 cm/yr. Most of the annual growth takes place during a few major floods that occupy only a small fraction of the year. Local growth rates can be enhanced by abrasion from sediment. During floods, highly aggressive water is delivered rapidly to points deep within the karst aquifer. As flood discharge increases, cave streams become ponded by constrictions caused by detrital sediment, insoluble beds, or collapse material. Because the discharge during a flood rises by several orders of magnitude, the head loss across constrictions can increase enormously, causing water to fill parts of the cave under considerable pressure. This highly aggressive water is injected into all available openings in the surrounding bedrock, enlarging them at a rapid and nearly uniform rate. Depending on the structural nature of the bedrock, a dense array of blind fissures, pockets, anastomoses, or spongework is formed. Many such caves develop traversable mazes that serve either as bypass routes around constrictions, or as "karst annexes", which store and later release floodwaters. Many features that are sometimes attributed to slow phreatic flow or mixing corrosion are actually generated by ponded floodwaters. In caves that experience severe flooding, adjacent fissures or bypass routes with initial widths at least 0.01 cm can grow to traversable size within 10,000 years.

Les archives sdimentaires quaternaires de la grotte sous les Sangles (Bas-Bugey, Jura mridional, France). Indices palo-climatiques et sismo-tectoniques, 2002, Lignier Vincent, Desmet Marc
Quaternary sedimentary archives of the Sous les Sangles Cave (Lower Bugey, Southern Jura, France); paleo-climatic and sismo-tectonic evidences - The Sous les Sangles Cave is located in southern part of Jura mountain at the front part of the northwestern alpine tectonically active massifs. This region was covered by alpine and jurassian glaciers during the Last Glacial Maximum. An old gallery contains stratified fluvial and moraine injection, covered by a 3.5 meters thick deposit of finely laminated silty carbonate and clays. Sedimentological investigation reveals several periods of different water flow depending on glacial and inters glacial periods. The upper finely laminated sediments correspond to the end of the last glacial maximum according to the exokarstic equivalent of the Cerin lake and the U/Th ages obtained with speleothems. Spectral analysis (using Fourier methods and pass-band mapping techniques) on grey-level raw data have been used on the Sous les Sangles sediment. The main result shows evidence of a cyclic deposition according to the three main periodicities recognised through the 1.5-m top sequence. The laminated material is affected by plastic and brittle deformations. The entire deposit is characterised by (1) a vertical faulting without apparent dominant relative movement which can be interpreted as tension faults; (2) an associated soft and brittle deformation similar to thin skin tectonic at centimetre scale affecting the base of the deposit and testified to gravity reworking which could correspond to discrete sismotectonic activity; (3) brittle deformations associated with fluid escape patterns occurring at two specific levels along the vertical faults, emphasising the earth tremor existence according to several broken speleothems. These observations are highly supported by the geodynamic and tectonic frame of this part of Jura massif which reveal an actual uplift of several millimetre/year, especially in this part of the Cluse des Hpitaux cross valley. Numerous historical earthquakes have been documented in this area. The microtectonic study of the cave shows dominant inverse and strike-slip structures correlated to the general tectonic frame.

Assessing Humidity in an Upper Pleistocene Karst Environment: Palaeoclimates and Palaeomicroenvironments at the cave Divje babe I, Slovenia, 2002, Turk Ivan, Skaberne Dragomir, Blackwell Bonnie A. B. , Dirjec Janez

The article presents a new sedimentary-climatic model for explaining autochthonous clastic sediment in the Upper Pleistocene site, Divje babe I, Slovenia. The sediment analysed here was deposited during Oxygen Isotope Stages 1, 3 and 5 (OIS, OIS 3, OIS 5). The stress is on precipitation, which we explained on the basis of the quantity of authigenic structural aggregates in the sediment. We supported the results with quantitative analysis of clasts with etched surface, which represent corrosion of the cave ceiling, and etched bones, which represent corrosion on the cave ground. We also analysed the relation between climate and cave bears, and Neanderthals and climate, on the basis of mass fossil remains and finds of artefacts. All analyses were made on the basis of three-dimensional sampling, i.e., in horizontal and vertical directions. We sampled 65 profiles over an area of 65 m2. Each profile had 35 arbitrary stratigraphic units (splits) with data on aggregates, etched bones, fossil remains and artefacts. In explaining the sediment characteristics that point to climatic parameters, we consistently took into account the Holocene standards for the site. We found that the climate in OIS 3 was colder and damper than in OIS 1 and OIS 5. People and animals responded to the climatic changes in OIS 3 with more visits to the cave, but not at the same time. The climatic change was presumably reflected in the microlocation of the cave mainly by the longer duration of snow cover.

Sediment entrainment and transport in fluviokarst systems, 2004, Dogwiler T, Wicks Cm,
The primary geomorphic process active in the development of karst stream systems is generally regarded as bedrock dissolution. However, physical erosional processes may also be an important geomorphic agent in karst development. The objectives of this study were to determine the sediment transport threshold in two fluviokarst streams. The source of the sediment was internal to the karst basins. The approach used was to calculate basal and critical shear stresses from streams in two karst systems to determine if, and how frequently, storm-induced flows are capable of mobilizing stream sediment. The fluviokarst systems investigated as a part of this research are capable of transporting 50-85% of their stream substrates during bankfull discharge conditions. Based on the discharge and precipitation frequency, stream flows capable of entraining d(50) and d(85) particles occur at intervals of 2.4 and 11.7 months (0.98 yr), respectively. Thus, the sediment transport threshold in fluviokarst streams is exceeded by relatively common discharge events. (C) 2004 Elsevier B.V. All rights reserved

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