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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. ...

Did you know?

That vertical shaft is these are formed by underground water dripping of flowing straight downward through the limestone along vertical cracks. uniformly distributed dissolution of the rock results in a silo- or well-shaped passage so that most of them appear roughly circular in cross section when viewed straight up and down. they form above active tubular passages although they may intersect a limited number of passages along their length. at mammoth cave, they range in size from 30 feet across to 200 feet from top to bottom [15]. synonym: dome-pit. see also canyon passage; fissure cave; keyhole passage; passage; tubular passage; vadose shaft; vertical cave.?

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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 upper cretaceous (Keyword) returned 38 results for the whole karstbase:
Showing 16 to 30 of 38
Reconstitution morpho_lo_gique du Causse du Larzac (Aveyron, France), rle des formations superficielles dans la morphogense karstique, 2001, Bruxelles, Laurent
The study of post-Jurassic deposits, superficial formations which stay on the plateau or are preserved in caves permits us, together with the morphologies of landscape, to reconstitute the main steps of morphological evolution of this part of the Larzac. In particular, the discovery of numerous witnesses of cretaceous cover, marine and continental, let us know the first morphogenesis of the Grands Causses. After the bauxite episode, coniacian transgression fossilized a differentiated palaeotopography under one hundred meters of sandy limestone. After, the erosion of this deposits and the transit of various alterites, allogene or autochthonous, show further morphological steps. Theses formations can constitute a real cover and contribute to the development of karstic levellings. Residual formations, associated with levels of shelves, regulate lowering of karstic surface between Eocene and Miocene, before the canyon digging and the development of karstic recules. Then, between Miocene and Quaternary, karst declogging changes radically the evolution of the plateau surface and let appear poljes, dolines and underground network. Only some specific areas can keep their cover of alterites and maintain, temporally, an old functioning.

Karst characteristics of thrust contact limestone-dolomite near Predjama, 2001, Č, Ar Jož, E, Š, Ebela Stanka

With detailed lithological and tectonic-structural mapping at the scale 1:5000 we studied the area near Bukovje NE from Predjama. In the studied area and further towards the NE we can follow a strong thrust contact between Upper Cretaceous limestones of Snežnik thrust sheet over which Upper Triassic Norian-Rhaetian dolomite of Hrušica thrust sheet is overthrust. The thrust is cut by systems of dextral faults with expressed vertical component. Beneath the studied area underground passages of Predjama cave can be found; they are developed in limestones as in dolomites. Dolines in Upper Cretaceous limestone are uniformly arranged and are in structural-genetic view broken (D), near-fault (E) or fault (F). Along the thrust edge we have contact dolines (G) in dolomite. The rest of the dolines on dolomite are connected to differently broken rocks in fault zones and are called reproduced fault-broken dolines / HF(D)do /. For described karst features along thrust contact we suggest the name contact karst on dolomite along thrust.

Caves formed within Upper Cretaceous skarns at Baita, Bihor County, Romania: Mineral deposition and speleogenesis, 2002, Onac B. P. ,
The Baita metallogenic district, in Bihor County, Romania, is genetically connected to a deep-seated Upper Cretaceous granitic pluton. Within this district, several bodies of skarn host economic concentrations of Mo, W, Bi, Cu, Pb, Zn, B, wollastonite, and marble. During mining, numerous karst cavities were encountered. Minerals such as wittichenite, antimonian luzonite, natrolite, quartz, chalcanthite, rosasite, glaukosphaerite, aurichalcite, azurite, malachite, norsethite and, more commonly, calcite, aragonite, hydromagnesite, and goethite were found within these skarn-hosted caves as crusts, coralloids, minute crystals, aggregates, and earthy masses. Some of the minerals are of hydrothermal origin, whereas others are interpreted to have formed during episodes of hydrothermal or vadose alteration. A third group consists of minerals that were precipitated from low-temperature karstic waters. Although most skarn-hosted cavities exhibit the classical features of meteoric-water-induced cave, their mineralization, morphology, and position within the skarn support a hydrothermal or a mixed hydrothermal-vadose origin

Genesis of the Dogankuzu and Mortas Bauxite Deposits, Taurides, Turkey: Separation of Al, Fe, and Mn and Implications for Passive Margin Metallogeny, 2002, Ozturk Huseyin, Hein James R. , Hanilci Nurullah,
The Taurides region of Turkey is host to a number of important bauxite, Al-rich laterite, and Mn deposits. The most important bauxite deposits, Do[g]ankuzu and Morta[s], are karst-related, unconformity-type deposits in Upper Cretaceous limestone. The bottom contact of the bauxite ore is undulatory, and bauxite fills depressions and sinkholes in the footwall limestone, whereas its top surface is concordant with the hanging-wall limestone. The thickness of the bauxite varies from 1 to 40 m and consists of bohmite, hematite, pyrite, marcasite, anatase, diaspore, gypsum, kaolinite, and smectite. The strata-bound, sulfide- and sulfate-bearing, low-grade lower part of the bauxite ore bed contains pyrite pseudomorphs after hematite and is deep red in outcrop owing to supergene oxidation. The lower part of the bauxite body contains local intercalations of calcareous conglomerate that formed in fault-controlled depressions and sinkholes. Bauxite ore is overlain by fine-grained Fe sulfide-bearing and calcareous claystone and argillaceous limestone, which are in turn overlain by massive, compact limestone of Santonian age. That 50-m-thick limestone is in turn overlain by well-bedded bioclastic limestone of Campanian or Maastrichtian age, rich with rudist fossils. Fracture fillings in the bauxite orebody are up to 1 m thick and consist of bluish-gray-green pyrite and marcasite (20%) with bohmite, diaspore, and anatase. These sulfide veins crosscut and offset the strata-bound sulfide zones. Sulfur for the sulfides was derived from the bacterial reduction of seawater sulfate, and Fe was derived from alteration of oxides in the bauxite. Iron sulfides do not occur within either the immediately underlying or overlying limestone. The platform limestone and shale that host the bauxite deposits formed at a passive margin of the Tethys Ocean. Extensive vegetation developed on land as the result of a humid climate, thereby creating thick and acidic soils and enhancing the transport of large amounts of organic matter to the ocean. Alteration of the organic matter provided CO2 that contributed to formation of a relatively 12C-rich marine footwall limestone. Relative sea-level fall resulted from strike-slip faulting associated with closure of the ocean and local uplift of the passive margin. That uplift resulted in karstification and bauxite formation in topographic lows, as represented by the Do[g]ankuzu and Morta[s] deposits. During stage 1 of bauxite formation, Al, Fe, Mn, and Ti were mobilized from deeply weathered aluminosilicate parent rock under acidic conditions and accumulated as hydroxides at the limestone surface owing to an increase in pH. During stage 2, Al, Fe, and Ti oxides and clays from the incipient bauxite (bauxitic soil) were transported as detrital phases and accumulated in the fault-controlled depressions and sinkholes. During stage 3, the bauxitic material was concentrated by repeated desilicification, which resulted in the transport of Si and Mn to the ocean through a well-developed karst drainage system. The transported Mn was deposited in offshore muds as Mn carbonates. The sulfides also formed in stage 3 during early diagenesis. Transgression into the foreland basin resulted from shortening of the ocean basin and nappe emplacement during the latest Cretaceous. During that time bioclastic limestone was deposited on the nappe ramp, which overlapped bauxite accumulation

Concurrent tectonism and aquifer evolution > 100,000 years recorded in cave sediments, Dinaric karst, Slovenia, 2003, Sasowsky I. D. , Sebela S. , Harbert W. ,
A natural conduit that had formed along a fault was exposed in Upper Cretaceous limestones during construction of a tunnel near Postojna,. Slovenia. The conduit is filled with poorly indurated clastic sediments. Slickensides found on the margin of the sediment deposit show sinistral fault motion that is consistent with regional tectonism. Analysis of the sediments revealed reversed magnetic polarity. The minimum age for latest movement on the fault, origin of the cave, and deposition of these sediments is 780 ka. Present-day tectonic stresses are concordant with the fault movement, and it is likely that the fault has been continuously active throughout growth, infilling, and hydrologic abandonment of the conduit. Based upon known and modeled growth rates for conduits, this system is recording a period of growth and abandonment that exceeds 100,000 years. The role that rock discontinuities play in groundwater flow may vary over these timescales, and it may be important to account for tectonism when evaluating the long-term evolution of aquifers

Overview of the karst occurences in northern Cyprus, 2003, Necdet, Mehmet

Cyprus is at the easternmost part of the Mediterranean and is in the intersected zone bezween Eurasia, Africa and Arabic Plates. Karstification occurs as travertines or caves in Northern Cyprus in formation of different ages. Those formations are the dolomitic limestones of Kyrenia (Girne) Range of Jurassic - Upper Cretaceous; Gypsum Deposits of Messinian ages. Travertine terraces (Quaternary) are seen as characteristic at the northern edge of the Kyrenia Range. Secondary limestones of Holocene age were deposited on the older sediments and seen with some sort of karst features over the island. Karstic occurrences are seen as different size of open or sealed caves and the sinkholes in those formations mentioned above.

Geomorphological Conditions of the Genesis of the Ponor Jovac Cave (Croatia), 2004, Boč, Ić, Neven, Bać, Urin Ž, Eljko

The middle part of the Slunj karst plateau is built of permeable karstified upper Cretaceous limestone. The Miocene sandstones and marls lie over them in transgressive contact in the form of denudation remains. This area is impermeable and has characteristics of fluviodenudational relief. In a morphological sense, the blind valley of \edinovac periodical stream is remarkable. The \edinovac stream sinks underground in the contact zone of the Miocene and Cretaceous rocks and continues its flow through the main channel of the Ponor Jovac cave. The Ponor Jovac cave is 689 m long and has the function of a permanent percolating and periodical sinkhole cave. The area built of limestone is well karstified and without a surface fluvial network. But in continuation of the \edinovac stream blind valley a dry valley exists which is a morphological trace of the former surface flow of the \edinovac stream

Smoganica - a cave developed in upper Cretaceous breccia, 2005, Knez Martin, Slabe Tadej, Š, Ebela Stanka

On the Banjšice plateau (NW Slovenia) the longest spring cave is 492 m long Smoganica. The cave (505 m above sea level) is situated on the SW slope of Čukla (770 m) E from the Soča river (153 m above the sea level). Smoganica is developed in limestone breccia, which is 10 m thick and belongs to the Upper Cretaceous flysch rocks. On the territory around the cave, the green marls are included in breccias or breccias are included into the green marls. Clasts in coarse-grained breccia, in which the cave is located, vary from some cm to several dm in diameter. Clasts are mostly deriving from younger rudist limestones, Lower and Upper Cretaceous and Jurassic micritic and oolitic limestones. Smoganica is situated about 2 km south from Idrija fault and about 200 m north from Kobarid fault. There are two principal fissure orientations in the cave, N30-45_E and N120-135_E. Smoganica was formed from the system of smaller passages that have been developed inside the breccia in 3D. The cave was formed in phreatic conditions, later it was completely filled with cave sediments. In the next stage the above-sediment rock forms were developed. Cave sediments were later removed from the cave. Today the active water stream is cutting rock forms in the bottom of the cave passages. Higher water quantities are forming scallops and potholes and lower quantities floor channels. Smoganica can be described as polygenetic cave because the percolating water is reshaping the passages.

Lithostratigraphic characteristics of the intermittent Pivka lakes region and Matijeva jama cave estavelle, 2005, Knez Martin, Slabe Tadej

This article describes the typical characteristics of rock found in the area of the intermittent Pivka lakes. Two characteristic karstic caves formed in Upper Cretaceous limestone: Matijeva jama, which appears as an estavelle today, and Trnska jama, vvith several old and recent signs of frequent and plentiful fluctuation in groundwater level. Several new research results are presented.

Tectonic sights of the Pivka basin, 2005, Š, Ebela S.

The important regional thrust called Snežnik thrust, that divides the Snežnik thrust sheet from the parautochthon of the Komen thrust sheet, runs through the Pivka basin. A tectonic window near Knežak is proof of older thrusting deformations. The landscape is cut by numerous younger faults among which the most important are Raša, Predjama and Selce faults. The area of Upper Pivka is tectonically quite active, which is shown by earthquakes in recent years. It looks as if the most active is the Raša fault or one of its northern parallel faults, for example Šembije fault or maybe Selce fault. Karst intermittent lakes of Upper Pivka are developed in Upper Cretaceous limestones. The lakes are situated 0.5-4.0 km NE from the Snežnik thrust. Most of the lakes are situated along the Selce fault.

Al-Daher Cave (Bergish), Jordan, the first extensive Jordanian limestone cave: a convective Carlsbad-type cave?, 2006, Kempe S. , Almalabeh A. , Alshreideh A. , Henschel Hv.
In spite of the vast limestone area present in Jordan, no karstic caves to speak of were known there until 1995 when Al-Daher Cave was discovered. The cave is situated east of Bergish Reserve for Ecotourism in the mountains of Bergish at about 830 m above sea level. The cave formed in the Wadi As Sir Limestone Formation of Upper Cretaceous age. It is a maze developed along NW-SE and NE-SW striking joints which owe their existence to the Dead Sea Transform Fault situated a few kilometers to the west of the cave. Rooms, with a total area of 1750 m2, were formed within a square of 70 70 m. The cave is constrained to certain limestone strata, laminated and non-laminated, divided by four chert layers that form distinctive markers throughout the cave. Chert nodules occur also within the limestone layers. The cave formed phreatically exclusively by dissolution within a small body of rising and convecting water. It is suggested that the very localized solution capacity derived from the oxidation of either H2S, or possibly even CH4, by oxygen present near the former water table. Thus, Al-Daher Cave may have formed by a process similar to that which formed the Guadalupe Mountain caves, New Mexico, among them Carlsbad Cavern. The altitude of the cave suggests that it may be as old as upper Miocene. The cave contains several relict generations of speleothems but also active forms. The local government is hoping to develop the cave into a show cave; it would be the first in Jordan.

Continental France and Belgium during the early Cretaceous: paleoweatherings and paleolandforms, 2006, Thiry Medard, Quesnel Florence, Yans Johan, Wyns Robert, Vergari Anne, Theveniaut Herve, Simoncoincon Regine, Ricordel Caroline, Moreau Marie Gabrielle, Giot Denis, Dupuis Christian, Bruxelles Laurent, Barbarand
During the early Cretaceous, successive tectonic phases and several sea level falls resulted in the emersion of the main part of western Europe and the development of thick 'lateritic' weathering. This long period of continental evolution ended with the Upper Cretaceous transgressions. During this period, the exposed lands displayed a mosaic of diverse morphologies and weathered landscapes. Bauxites are the most spectacular paleoweathering features, known for long in southern France. Recently, new residual outcrops have been identified, trapped in the karstic depressions of the Grands Causses. Other bauxitic formations, containing gibbsite, have also been recognised, occurring with the Clay-with-Jurassic-cherts in the southeastern border of the Paris Basin. These bauxitic formations overlay Jurassic limestone and are buried beneath Upper Cretaceous marine deposits. The recognition of bauxites up north into the southern Paris Basin significantly widens the extension of the Lower Cretaceous bauxitic paleolandscapes. On the Hercynian basements thick kaolinitic weathering mantles occur. They have been classically ascribed to the Tertiary. The first datings of these in situ paleosoils, by means of paleomagnetism and/or radiogenic isotopes, record especially early Cretaceous ages. This is the case for the 'Siderolithic' formations on the edges of the French Massif Central, but also for the kaolinitic profiles in the Belgian Ardennes. In the Flanders, the Brabant basement is deeply kaolinised beneath the Upper Cretaceous cover. These paleosoils show polygenetic evolutions. The relief of these basement paleolandscapes may have been significant. There where probably high scarps (often of tectonic origin) reaching 200 m in elevation or beyond, as well as wide surfaces with inselbergs, as in the present day landscapes of tropical Africa and South America. On the Jurassic limestone platforms occur diverse kaolinitic and ferruginous weathering products. Around the Paris Basin they show various facies, ranging from kaolinitic saprolites to ferricretes. Due to the lack of sedimentary cover, the age of these ferruginous and kaolinitic weathering products has been debated for long, most often allocated to the Siderolithic sensu lato (Eocene-Oligocene). Recent datings by paleomagnetism have enabled to date them (Borne de Fer in eastern Paris Basin) back also to the early Cretaceous (130 {} 10 Ma). These wide limestone plateaus show karstified paleolandforms, such as vast closed and flat depressions broken by conical buttes, but also deep sinkholes in the higher areas of the plateaus and piedmonts. The depth of the karst hollows may be indicative of the range of relative paleoelevations. Dissolution holes display seldom contemporaneous karst fillings, thus implying that the karstland had not a thick weathering cover or that this cover had been stripped off before or by the late Cretaceous transgression. Nevertheless, some areas, especially above chert-bearing Jurassic limestone or marl, show weathering products trapped in the karst features or as a thick weathering mantle. In the Paris Basin, the Wealden gutter looked like a wide floodplain in which fluvio-deltaic sands and clays were deposited and on which paleosoils developed during times of non-deposition. The edges of the gutter were shaped as piedmonts linked up with the upstream basement areas. The rivers flowing down to the plain deposited lobes of coarse fluvial sands and conglomerates. The intensity of the weathering, the thickness of the profiles and their maturation are directly dependent on the duration of the emersion and the topographic location relative to the gutter. Near the axis of the gutter, where emersion was of limited duration, the paleoweathering features are restricted to rubefaction and argillization of the Lower Cretaceous marine formations. On the other hand, on the borders of the basin and on the Hercynian basement, where emersion was of longer duration, the weathering profiles are thicker and more intensively developed. The inventory of the Lower Cretaceous paleoweathering features shows the complexity of the continental history of this period. Moreover, the preserved weathering products are only a part of this long lasting period, all the aspects relative to erosion phases are still more difficult to prove and to quantify. In this domain, apatite fission tracks thermochronology (AFTT) can be helpful to estimate the order of magnitude of denudation. Residual testimonies and subsequent transgressions may enable to estimate relative elevations, but in return, we presently have no reliable tool to estimate absolute paleoelevations. In the work presented here, the inventory enabled to draw a continental paleogeographic map showing the nature of the weathering mantles and the paleolandscape features, just as paleoenvironments and paleobathymetry presently appear on marine paleogeographic maps. For the future, the challenge is to make progress in dating the paleoweathering profiles and especially in the resolution of these datings, in order to correlate precisely the continental records with the different events which trigger them (eustatism, climate, regional and global geodynamics). The final goal will be to build up a stratigraphic scale of the 'continental geodynamic and climatic events' in parallel with 'sequential stratigraphy' in the marine realm

Cretaceous Karstic Cave-Fill Manganese-Lead-Barium Deposits of Imini, Morocco, 2006, Gutzmer J. , Beukes N. J. , Rhalmi M. , Mukhopadhyay J. ,
The economically important high-grade manganese ores of the Imini district, Morocco, are exceptional because of their unusually high Mn/Fe ratios and exceptional enrichment in Ba and Pb. There is ample evidence that the three strata-bound manganese orebodies of the Imini district formed in a laterally extensive karst cave system, associated with internal sediment, and developed in a shallow marine dolostone succession of Cretaceous age. The manganese ores occur in dolostone breccias and ferruginous clays that represent the earliest phase of internal sediment in the cave system. Later phases of cave fill are ferruginous without manganese enrichment. Ore formation, karstification, and meteoric dolomitization are all related to an extended period of exposure and terrestrial weathering, prior to the deposition of terrestrial red beds and evaporites of Upper Cretaceous age that overlie the ore-bearing dolostone succession above an erosional unconformity. The manganese ores formed when warm, acidic Mn2?? meteoric water migrated from the elevated regions of the Anti Atlas region into the exposed carbonate succession. Alkali feldspar-rich igneous basement rocks were the source for Mn, Pb, and Ba. Metals were deposited in a zone of mixing between metal-bearing, reducing meteoric water and oxygenated ground water resident in the cave system

Genesis of the Neogene interstratal karst-type Pöhrenk fluorite?barite ( lead) deposit (Kırşehir, Central Anatolia, Turkey), 2006, Genç, Yurdal
The Pöhrenk fluorite?barite ( lead) deposit is located 200 km east of Ankara, Central Anatolia, Turkey. The ores are hosted by sedimentary rocks of the east?west trending Tertiary Çiçekdağı foreland basin. The Çiçekdağı Basin is bounded by Paleozoic metamorphic rocks of the Kırşehir Massif in the south, and Upper Cretaceous ophiolites and Paleocene granitoids in the north. The basin contains mainly Eocene and Upper Miocene?Pliocene sediments. The Eocene sediments consist of conglomerate, sandstone, marl and carbonate. These are covered unconformably by red conglomerate, mudstone, sandstone, siltstone and claystone of Late Miocene?Pliocene age. Mineralization occurs both in Eocene (Lutetian) limestones and Neogene detrital rocks. The distribution of ores is controlled by the unconformity surface between limestones and detrital rocks. The main ore types are replacements, open-space fillings, breccias and veins. The Pöhrenk deposit was emplaced epigenetically after the host rocks and shares some characteristics with the paleokarst- and Mississippi-Valley-type deposits. Fluid inclusion and stable isotope data indicate that ore fluids for the mineralization were mildly hot (58 to 154 C), highly saline (14 to 21 wt.% NaCl equivalent) formation waters and ore deposition occurred in a paleokarst environment. The driving force for fluid migration was both topographic gradients created by uplift and tectonic squeezing of basin sediments. The Paleocene granitoids in the north are considered as the potentially main source of F, Ba and Pb for the Pöhrenk deposit. Release of these elements from granitoids can be tied to erosion and leaching.

Barka depression, a denuded shaft in the area of Snez?nik Mountain, southwest Slovenia, 2007, Zupan Hajna N.
On the southern slope of Dedna gora, Slovenia, at an elevation of 1147 m, an interesting large closed depression referred to as Barka (Barge) is developed. It is about 40 m long, 25 m wide and 20 m deep, with smooth, almost polished precipitous walls. It is developed in Upper Cretaceous limestones and affected by several faults and fissure zones. The feature lies within a large karren field (about 104 m2) with many closed depressions of various dimensions. In the winter time, snow accumulates in the bottoms giving the appearance of snow-kettles, such as those found in the Alps. The size and especially the shape of the walls suggests that these features are the remains of shafts. After their primary genesis as the inner vadose shafts of one or more caves, their upper parts would have been denuded. Walls and bottoms were subsequently remodeled by snow and ice action during the last glaciations, and this continues today as winter snow accumulates at their bottoms. This is indicated by silt fragments (gelifraction) and frost rubble accumulated in portions of the depression, and the development of sorted and nonsorted polygons. Shafts that have been exposed at the surface are a potentially important morphological element of karst topography. They can represent a significant portion of closed depressions of different sizes, including many snow-kettles.

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