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Community news

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 cycle is regular periodic occurrence of an event [16].?

Checkout all 2699 terms in the KarstBase Glossary of Karst and Cave Terms


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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
See all featured articles
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 fossil (Keyword) returned 243 results for the whole karstbase:
Showing 226 to 240 of 243
The Mammalian Fauna of Abismo Iguatemi, Southeastern Brazil, 2011,
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Castro Mariela C. , Langer Max C.

The Quaternary vertebrate fauna record of South America is characterized by the predominance of mammals, and the study of cave deposits can provide important information on their diversity and distribution. In Brazil, cave deposits have preserved remarkable fossil remains, including both large and small vertebrates, although the former have been the focus of most paleontological works. The fossils studied here came from Abismo Iguatemi, a karstic fissure located in the municipality of Apiaı´, upper Ribeira River valley, Sa˜o Paulo, Brazil. Blocks of sediment collected from its floor yielded a large sample of micro-remains, mainly composed of fragmentary small vertebrate specimens. Taphonomic parameters suggest that the fossil elements entered the cave either by entrapment or transported by rain runoff, as partially decayed carcasses or isolated elements. A total of 35 taxa were recorded in Abismo Iguatemi, four of which are extinct. The number of identified specimens per taxon (NISP index) is the best estimator of number of individuals at the burial site. The comparison of this fauna to that of other Quaternary deposits and to the present biodiversity of different areas reveals low similarity. The identification of fossil organisms with different ecological requirements (extinct savannah organisms and extant dense-forest organisms) suggests the existence of time averaging and may reflect environmental changes in the vicinity of the cave during the late Pleistocene and Holocene


Laltration de type "fantme de roche" : processus, volution et implications pour la karstification, 2011,
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Quinif Yves, Bruxelles Laurent

Depuis plusieurs années, de nombreux exemples de fantômes de roche ont été reconnus dans les karsts en Belgique, en France et en Italie. Ils correspondent à des poches ou à des couloirs de décalcification emplis d’altérite in situ. Leur genèse relève d’un cas spécial de karstification où, à l’inverse des phénomènes de karstification par enlèvement total, le résidu insoluble ou moins soluble reste en place et forme un squelette qui mime la structure initiale de la roche (fossiles, joints, lits de chailles, etc.). Cette altérite, qui peut également se développer sous une voûte calcaire, forme un vaste réseau interconnecté et calé sur la fracturation. De fait, elle constitue une discontinuité importante au sein des massifs karstiques. Lorsque le niveau de base s’abaisse, l’altérite s’effondre sur elle-même puis elle est érodée par des circulations souterraines qui se mettent en place à son toit. Des réseaux de galeries mais aussi des formes de surface se forment alors rapidement, essentiellement par évidement de l’altérite. Ce phénomène est maintenant reconnu dans le monde entier, affectant tous les types de roches, carbonatées ou non.

For several years, numerous examples of ghost rocks have been recognised in karst areas in Belgium, in France and in Italy. They correspond to decalcified pockets but also to decalcified corridors filled with in-situ alterite. It is a special case of karstification where a non-soluble skeleton remains and preserves the structures of the initial rock (fossils, joints, levels of cherts, etc.). This alterite, which can also be formed under a safe roof, draws a large maze following the tectonic patterns. It constitutes an important discontinuity inside the karstic areas. When the base level drops, the structure of the alterite collapses and a void is formed on his top. Then runoff can use this void and erode the soft alterite. Cave network but also surface features can develop quickly, mainly by the cleaning of the alterite. Now, some examples of this phenomenon have been recognised all around the world and occur in different sorts of rocks, carbonated or not.


Organic matter of fossil origin in the amberine speleothems from El Soplao Cave (Cantabria, Northern Spain), 2012,
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Gzquez Fernando, Jose Maria Calaforra, Fernando Rull, Paolo Forti, And Antonio Garcacasco.

Unusual amberine-coloured speleothems were recently found in El Soplao Cave (Cantabria, Spain). Chromophore elements such as Fe, Mn, Cd, Co or Ti were not present in significant quantities. Rather, our data show that their colour comes from leachates of fossilized organic material hosted in the carbonaceous Urgonian facies of the host rock. These leachates are related to the Cretaceous amber deposit that has been recently discovered in the vicinity of El Soplao Cave. The presence of humic and fulvic acids of fossil origin were confirmed by IR and Raman spectroscopic analysis of the carbonaceous strata and the speleothems. In addition, the mineralogy of the amberine speleothems was studied. Alternating bands made of calcite and aragonite reveal that periods of humidity and aridity occurred within the cave during the speleothem genesis.


OBSERVATIONS OF PLIOCENE KARSTS FOSSILIZED BY QUATERNARY EOLIAN SILTS IN THE MATMATA MOUNTAINS (SOUTH-EAST TUNISIA), 2012,
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Sghari, Abdeljalil

The submeridional Dahar chain in southeastern Tunisia is over 200 km long. It is separated from the Mediterranean Sea by the Jeffara plain with some tens of kilometers in width. This landscape continues to the South into Libya, but to the North, the chain ends with the Matmata mountains which form a plateau slightly inclined to the west and some 10 km wide. The eastern scarp shows a mainly calcareous geological stratigraphy from Upper Permian to the Senonian. The Dahar-Matmata structure belongs to the Sahara platform and shows a hiatus during the whole Tertiary, since it was emerged since Upper Cretaceous. The Tunisian Atlas nearby shows a completely different paleogeographic evolution, with a complete Tertiary series and a later Plio-Quaternary structuration. These two paleogeographic domains of Southern Tunisia, the Sahara Atlas and the NE border of the Sahara platform, were influenced by the Messinian crisis (5.9 Ma to 5.3 Ma). This was expressed by the collapse of the Mediterranean Sea level, profoundly modifying the fluvial dynamics with an inversion of the erosional system, from normal erosion to regressive erosion. It results a deepening of canyons in the downstream part and a deepening of the watercourses in the upstream part. The geological structures in the Messinian have been deeply affected by these large eustatic changes, with an incision of cluses in the Atlas and the deposition of a thick clayeysandy series that we could recently link to deltaic systems and Gilbert deltas. The re-establishment of seaways between the Atlantic and the Mediterranean, and the subsequent infill in the Lower Pliocene (Zanclean transgression), with an important inpact in Southern Tunisia, had multiple consequences in that region. The newly adjusted sealevel, together with a more humid climate that was confirmed by faunal and floral extension oof tropical plants in Northern Africa, stimulated an important karstification of the limestone areas. In the Dahar chain, caves, dolines, karstic depressions or karstic dry valleys emerged, the most spectacular ones being found in the Matmata Mountains. The karstic depressions are the forms that represent best this Pliocene karstification that surely was interrupted in an early stage, because localized endokarstic forms had not enough time to develop. So the karstification seems to have been active in Matmata from 5.4 to 4.0 million years, i.e. two times as long than the duration of the Messinian crisis. The interruption of karstification is due to an increase in temperature and dryness, which even gets more intense during the Pliocene, pulverizing the soils. Already at the beginning of the desertification, a calcareous crust forms by rapid cristallization of dirt. It is immediately transported from the karstic zones to the Jeffara plain. This transfer fo dissolved calcite was the origin of the resistant calcitic crust well known in the Jeffara plain. We now identified the same crust in a karstic depression in the Matmata Mountains, opening the way to new geomorphologic and tectonic interpretations, and a review of the eolian silts formerly attributed to the Upper Pleistocene. Later, during Upper Pliocene-Gelasian, we observe a general tectonic uplift of the Dahar chain and the Matmata Mountains as well as the subsidence of the Jeffara plain at the Medenine fault (NW-SE), prolonging the large Gafsa fault towards the East. The karstic paleoforms were thus uplifted more than 500 m, but nevertheless remain open on the Jeffara plain, as seen by large depressions. As a consequence, the karstic depressions of Matmata played the role of traps for eolian silts blown from the Jeffara plain during the extreme desertification in the Upper Pliocene-Gelasian. The morphological reconstruction since the Messinian shows a succession of important events during the Pliocene that profoundly influenced the Quaternary. All indications permit to reject the hypothesis that the Matmata silts came from the West (Eastern Erg).

 


OBSERVATIONS OF PLIOCENE KARSTS FOSSILIZED BY QUATERNARY EOLIAN SILTS IN THE MATMATA MOUNTAINS (SOUTH-EAST TUNISIA), 2012,
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Sghari, Abdeljalil

The submeridional Dahar chain in southeastern Tunisia is over 200 km long. It is separated from the Mediterranean Sea by the Jeffara plain with some tens of kilometers in width. This landscape continues to the South into Libya, but to the North, the chain ends with the Matmata mountains which form a plateau slightly inclined to the west and some 10 km wide. The eastern scarp shows a mainly calcareous geological stratigraphy from Upper Permian to the Senonian. The Dahar-Matmata structure belongs to the Sahara platform and shows a hiatus during the whole Tertiary, since it was emerged since Upper Cretaceous. The Tunisian Atlas nearby shows a completely different paleogeographic evolution, with a complete Tertiary series and a later Plio-Quaternary structuration. These two paleogeographic domains of Southern Tunisia, the Sahara Atlas and the NE border of the Sahara platform, were influenced by the Messinian crisis (5.9 Ma to 5.3 Ma). This was expressed by the collapse of the Mediterranean Sea level, profoundly modifying the fluvial dynamics with an inversion of the erosional system, from normal erosion to regressive erosion. It results a deepening of canyons in the downstream part and a deepening of the watercourses in the upstream part. The geological structures in the Messinian have been deeply affected by these large eustatic changes, with an incision of cluses in the Atlas and the deposition of a thick clayeysandy series that we could recently link to deltaic systems and Gilbert deltas. The re-establishment of seaways between the Atlantic and the Mediterranean, and the subsequent infill in the Lower Pliocene (Zanclean transgression), with an important inpact in Southern Tunisia, had multiple consequences in that region. The newly adjusted sealevel, together with a more humid climate that was confirmed by faunal and floral extension oof tropical plants in Northern Africa, stimulated an important karstification of the limestone areas. In the Dahar chain, caves, dolines, karstic depressions or karstic dry valleys emerged, the most spectacular ones being found in the Matmata Mountains. The karstic depressions are the forms that represent best this Pliocene karstification that surely was interrupted in an early stage, because localized endokarstic forms had not enough time to develop. So the karstification seems to have been active in Matmata from 5.4 to 4.0 million years, i.e. two times as long than the duration of the Messinian crisis. The interruption of karstification is due to an increase in temperature and dryness, which even gets more intense during the Pliocene, pulverizing the soils. Already at the beginning of the desertification, a calcareous crust forms by rapid cristallization of dirt. It is immediately transported from the karstic zones to the Jeffara plain. This transfer fo dissolved calcite was the origin of the resistant calcitic crust well known in the Jeffara plain. We now identified the same crust in a karstic depression in the Matmata Mountains, opening the way to new geomorphologic and tectonic interpretations, and a review of the eolian silts formerly attributed to the Upper Pleistocene. Later, during Upper Pliocene-Gelasian, we observe a general tectonic uplift of the Dahar chain and the Matmata Mountains as well as the subsidence of the Jeffara plain at the Medenine fault (NW-SE), prolonging the large Gafsa fault towards the East. The karstic paleoforms were thus uplifted more than 500 m, but nevertheless remain open on the Jeffara plain, as seen by large depressions. As a consequence, the karstic depressions of Matmata played the role of traps for eolian silts blown from the Jeffara plain during the extreme desertification in the Upper Pliocene-Gelasian. The morphological reconstruction since the Messinian shows a succession of important events during the Pliocene that profoundly influenced the Quaternary. All indications permit to reject the hypothesis that the Matmata silts came from the West (Eastern Erg).


MACROSCOPIC DIAGENETIC CHANGES IN LATE MIOCENE SPELEOTHEMS, WESTERN DESERT, EGYPT, 2012,
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Pickford, Martin

Understanding the diagenesis of speleothems is important on account of the fact that such deposits are often used for determining palaeoclimate parameters and for estimating the ages of speleothem growth. Impressive speleothem deposition of Vallesian age occurred in an immense palaeokarst network in the Western Desert, Egypt, the age of formation being determined on the basis of mammalian biochronology (fossils found in spelean clastic deposits intercalated between speleothems). Many of the Egyptian speleothems have been pervasively recrystallised internally, but their outer surfaces are usually well preserved except in the formations which were buried in clastic deposits, in which case the entire speleothem can be recrystallised. The recrystallisation results in large crystals (up to 20 cm diameter) growing radially outwards from the centre of stalagmites and stalactites, or at right angles to the outer surface of flowstone deposits. It is clear that crystal growth occurred without change of volume. Although the recrystallisation of speleothems in the Western Desert of Egypt resulted in the development of unusually large calcite crystals, it does indicate that diagenesis may be an important process that needs to be taken into account before speleothems in other karst systems can be used as raw material for unravelling palaeoclimatic and geochronological parameters. The gross morphology of the Egyptian speleothems is described in order to put on record the effects of diagenesis on them. The geochemistry of the speleothems remains to be studied.


THE UNDERGROUND KARST OF THE NEOPROTEROZOC SERIES OF NIARI-NYANGA (CONGO AND GABON). A KARSTOGENESIS CONTROLLED BY ENVIRONMENTAL CHANGES, 2012,
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Peyrot, Bernard

The area of Niari-Nyanga, divided between Congo-Brazzaville and Gabon, corresponds to a Neoproterozoic synclinal whose schisto-limestones and dolomitic layers shelter many caves as well as vast underground karst systems that are hardly known. In a sub-equatorial climate characterized by sparse rainfall with very variable intensity, a dry season of five months and a savanna environment, the endokarst presents a vast array of forms with sometimes large, sometimes small dimensions. The caves are mostly horizontal and oriented along tectonic lines. Old fossil perched caves contrast with epiphreatic caves and drowned inaccessible systems. In current bioclimatic conditions, corrosion seems not very effective and not in equilibrium with some vast morphologies. The stacked levels, the presence of fossil speleothems and detritic material suggest a polyphase genesis in link with important paleoclimatic changes, where humid and dry periods alternate. Recent age dating with 14C on stalagmites show that the speleothemes are holocene and grew during the important rainfalls of this time, before drying up at the general chlimate change 3000 years before present. Thus, the endokarst of Niari-Nyanga as well as its neighbours is an archive of large importance.


A large Cervidae Holocene accumulation in Eastern Brazil: an example of extreme taphonomical control in a cave environment, 2012,
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Hubbe Alex, Auler Augusto S.

A remarkable cervid bone accumulation occurs at a single passage (named Cervid Passage; CP) at Lapa Nova, a maze cave in eastern Brazil. CP lies away from cave entrances, is a typical pitfall passage and contains bone remains of at least 121 cervids, besides few bats, peccaries and rodents remains. There is no evidence of water (or sediment) flow at the site and in general bones lack post depositional alterations and display anatomical proximity, suggesting that the majority of the remains found inside CP (mainly cervids) are due to animals that after entering the cave got trapped in the site. Observations suggest that two entrances could have provided access to cervids (and the few other animals, besides bats), either by falling inside the cave or by entering by their own free will. Once inside the cave, the maze pattern would make route finding difficult, and of all passage intersections, only the one leading to CP would result in a non-return situation, starving the animal to death. Radiocarbon dates suggest that animal entrapment occurred during at least 5 thousand years, during the Holocene. The reasons why mainly cervids were found are unknown but they are probably related to the biology of this group coupled with the fact that caves provide several specific taphonomic processes that may account for a strong bias in bone accumulation. Indeed, the frequent occurrence of Cervidae in both the fossil and sub-fossil record in Brazilian caves may be related to an overall high faunal abundance or may suggest that these animals were especially prone to enter caves, perhaps in search of nutrients (as cave saltpetre) or water.


Bericht ber die Probegrabung (2011) in der Pendling-Brenhhle bei Kufstein (Nordtirol; 1266/21), 2012,
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Frischauf C. , Mazelis E. , Rabeder G.
A recent excavation in the Pendling cave (Rauberloch) has yielded identifiable remains of brown bears and cave bears. A radiometric dating attempt of a fossilized cave bear bone (Astragalus) failed due to the lack of collagen.

Emine-Bair-Khosar Cave in the Crimea, a huge bone accumulation of Late Pleistocene fauna, 2013,
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Ridush . , Stefaniak K. , Socha P. , Proskurnyak Y. , Marciszak A. , Vremir M. , Nadachowski A.

The Crimean Mountains are well known from the abundance of Middle and Late Palaeolithic sites and palaeontological remains recovered from cultural layers in caves and rockshelters. The fossil-bearing deposits of Emine-Bair-Khosar Cave, located at the elevation of 1000 m on the Chatyrdag Plateau, yielded a very diverse and numerous vertebrate remains that widen the knowledge of Late Pleistocene faunal diversity in the Crimea. The assemblage comprised in total almost 50 species of vertebrates. Studies included geomorphological, geological and stratigraphic analyses as well AMS 14C dating. Faunal remains were present in ten palaeontological sites. The main bone accumulation (section Ba2) was deposited during Middle Valdai or Vytachiv (MIS 3) interstadial, and including a long time gap, to the end of the Pleistocene and the Holocene. Comparison of the Emine-Bair-Khosar fauna with vertebrate faunas of other Crimean sites showed a remarkable stability in the faunal composition and frequency during the whole MIS 3 interstadial. Steppe and other open-country species dominated in the compared assemblages, while boreal-tundra species were far less numerous. Inhabitants of forests, including red deer and some rodents, were stable members of fossil assemblages.


Preservation and burial of ancient karst., 2013,
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Osborne, R. A. L.

Ancient karst features can be preserved by burial, filling, or by occurring in areas with extremely slow denudation. Although the terms ‘paleokarst’, ‘relict karst’,‘buried karst’, and ‘fossil karst’ have caused much confusion, paleokarst, buried karst, and relict karst can be defined in terms useful to karst geomorphologists and cave scientists. The term ‘fossil karst’ is best abandoned. Burial and paleokarstification are not necessarily the end of karst. Ancient features may be exhumed and reactivated. Karst ends with denudation at the Earth’s surface. Unroofed caves are a particular feature of karst denudation. Most ancient karst features may be preserved by filling, burial, and exhumation. In unusual conditions, karst features have survived at the surface since the Mesozoic. Burial, exhumation, and slow denudation may not be sufficient for extreme survival; relative vertical movement may be required. As caves and many other karst landforms are negative features, they are prone to filling by a range of materials, making cave sediments and paleokarst deposits quite diverse. Whole karst landscapes can be buried and evidence of burial can be recorded in the diagenesis of sediments. Although filled and unfilled caves can survive shallow burial, deep burial can crush caves, forming crackle breccia. Exhumation can occur from the surface following uplift or from below following hypogene speleogenesis. Preservation, burial, and exhumation of ancient karst have two unexpected consequences. Caves can be older than the landscapes in which they occur and stalagmites can be the longest surviving karst features


Late Quaternary Caviomorph Rodents (Rodentia: Hystricognathi) from Ceara State, Northern Brazil, 2013,
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De Oliviera P. V. , Ribeiro A. M. , Kerber L. , Lessa G. , Viana M. S.

In this paper we report the first remains of caviomorph rodents from the karst of the Parque Nacional de Ubajara, Ceara´ State, northeastern Brazil, collected with precise stratigraphic and radiometric control. The material is derived from levels with thermoluminescence dating of about 8,000 years BP, corresponding to the early Holocene. In these levels, we found remains of Kerodon rupestris Wied, 1820, cf. Dasyprocta Illiger, 1811 and Thrichomys Trouessart, 1880. The data here reported contribute to the knowledge of Brazilian Quaternary rodents and show the potential of the studied area for fossils.


Hypogene speleogenesis in Italy, 2013,
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Menichetti, M.

Through more than one century of speleological research in Italy, many hypogenic limestone caves have been explored, mapped and studied. These caves are characterized by a variety of patterns and morphological sizes including three-dimensional maze sys-tems and deep shafts, with both active endogenic CO2 and H2S vents.
An integrate approach taking in account geological, hydrological and geochemical set-tings permit to recognize the main hypogenic speleogenetic process. The H2S oxidation to sulfuric acid, by oxygen-rich groundwaters as well as in the atmosphere is actually the main active hypogenic cave-forming processes. Both phreatic and vadose corrosion reactions involve chemotropic microbial activity, with sulfur-redox bacterial communi-ties that generate sulfuric acid as metabolic product. The bedrock corrosion produce sulfate ions in the phreatic zone and gypsum replacement in the limestone walls of the vadose sectors of the caves. The caves are characterized by both fossil and active pas-sages in which water rich in H2S as well as endogenic CO2 plays a determinant role in speleogenesis. Although sulfuric acid-related speleogenesis typically produces gypsum deposits, in caves where the karstification processes are driven by subterranean CO2 sources, voids and speleothems are the only final products.
In Italy all the end-members of the karst processes can be found, from solution caves to outcrop of carbonate travertine. The hypogenic caves are concentrated for largest and both fossils and active systems in the Tuscany, Umbria, Marche and Latium regions (Menichetti, 2009). These consist of few tens of kilometers of solutional passages with galleries and shafts, which are characterized by large rooms, cupola and blind pits, anas-tomotic passages, bubble trails roof pendants, knife edges, and phreatic passages. Ac-tive smaller karst systems are known in Southern Italy in Apulia, Campania and Sicily, related to the geothermal anomaly associated with CO2 and H2S vents.


PLEISTOCENE SEA LEVEL CHANGES AS REVEALED BY FLANK MARGIN CAVES IN TELOGENETIC LIMESTONES IN SICILY AND SARDINIA (ITALY), 2013,
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Dangeli I. M. , Waele J. D. , Ruggieri R. , Sanna L.

Coastal karst areas often host many indices of past sea level changes, such as marine terraces, fossiliferous sediments, tidal notches and coastal caves. Tectonic movements can then displace these ancient coastlines vertically. The interplay between rising or falling sea level and uplifting or subsidence can be very complex and difficult to unravel. The combination of a detailed knowledge of marine terraces and the study of some flank margin caves located at various altitudes have allowed to reconstruct the speleogenetic history of the coastal plain of Cornino-Custonaci (NW Sicily). Along the centraleastern coast of Sardinia, instead, the detailed study of the Fico Cave has allowed to recognise it as a flank margin cave developed on five levels, related to Pleistocene sea level highstands. These studies show that this type of mixing corrosion caves is much more widespread than previously thought also in telogenetic limestones. These caves, being excellent sea level markers, might help coastal geomorphologists to understand more on both sea level rise and fall and tectonic movements in coastal areas.


BAHAMIAN CAVES AND BLUE HOLES: EXQUISITELY PRESERVED FOSSIL ASSEMBLAGES AND TAPHONOMIC INFLUENCES, 2014,
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Albury N. A. , Mylroie J. E.

In The Bahamas, caves and blue holes provide clues to the geologic and climatic history of archipelago but are now emerging as windows into the ecological and cultural past of islands. Cave environments in The Bahamas alternate cyclically between vadose and phreatic conditions with sea-level change, thereby providing unique but ephemeral fossil capture and preservation conditions.

A diverse assemblage of fossil plants and animals from Sawmill Sink, an inland blue hole on Abaco Island in the northern Bahamas, has revealed a prehistoric terrestrial ecosystem with exquisitely preserved fossil assemblages that result from an unusual depositional setting. The entrance is situated in the pine forest and opens into a flooded collapse chamber that intersects horizontal conduits at depths to 54 meters. The deepest passages are filled with sea water up to an anoxic mixing zone at depths of 14 to 9 meters and into the upper surface fresh-water layer. The collapse chamber is partially filled with a large talus pile that coincides with an anoxic halocline and direct sunlight for much of the day.

During glacioeustatic sea-level lowstands in the late Pleistocene, Sawmill Sink was a dry cave, providing roosting sites for bats and owls. Accumulations of bones deposited in depths of 25 to 30 meters were subsequently preserved by sea-level rise in the Holocene. The owl roost deposits are dominated by birds but also include numerous small vertebrate species that were actively transported by owls to the roost sites.

As sea levels rose in the Holocene, Sawmill Sink became a traditional passive pitfall trap. Significant quantities of surface derived organic material collected on the upper regions of the talus at the halocline where decaying plant material produced a dense layer of peat within an anoxic mixing zone enriched with hydrogen sulfide. Vertebrate species that drowned were entombed in the peat, where conditions inhibited large scavengers, microbial decomposition, and mechanical disarticulation, contributing to the superb preserva­tion of the fossil assemblage in the upper regions of the talus.


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