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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 cave development is the inception of cave development in carbonate rocks begins if water can move through the bedrock and commence dissolution. the earliest water movement may be due to mechanisms (including ground-water pumping and ionic diffusion effects) unrelated to those dominating later development. similarly, inception may include physical and chemical dissolution (involving removal of carbonates and mineral impurities by water and by strong acids), as well as by the carbonic acid dissolution that dominates later cave growth. initial water movement can be along primary pores in the rock (in coarse raffle limestones, oolites or chalk), along relatively thin non-carbonate beds within the succession, or along incipient or open fissures (joints, faults and bedding planes). these potential water routes are initially very narrow and water movement is severely restricted and laminar, allowing only very slow dissolutional growth (see gestation), until enlargement beyond the turbulent threshold (breakthrough) permits faster flow and accelerated cave growth. after establishment of turbulent flow conditions the effects of dissolution are augmented by mechanical abrasion and collapse, which expose new rock. during the early development stages a network of narrow openings is formed. subsequently, geological factors guide the preferential expansion of favorable routes, which capture more of the local flow and enlarge, at the expense of less favorable openings, to form caves. the less favorable fissures are relegated to a subordinate role in transmitting percolation water or, more rarely, in carrying elements of overflow water during floods. also during the early stages, all voids are water filled but as permeability increases and true hydraulic flow conditions are established, the upper voids drain freely, forming a water table. almost all caves therefore originate under phreatic conditions but the overall passage morphology is modified during later growth into vadose or phreatic caves, enlarged from the original phreatic imprint, above or below the water table. ultimately, cave development evolves towards efficient drainage close to the water table. passage enlargement then becomes regressive as collapse increases. the stage of a cavernous karst collapsing extensively is relatively rarely achieved, being overtaken at high latitudes and high altitudes by surface lowering, but such collapse can contribute to the chaotic land forms of tropical karst [9].?

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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 expansion (Keyword) returned 46 results for the whole karstbase:
Showing 16 to 30 of 46
Linear and nonlinear input/output models for karstic springflow and flood prediction at different time scales, 1999, Labat D. , Ababou R. , Mangin A. ,
Karstic formations function as three-dimensional (3D) hydrological basins, with both surface and subsurface flows through fissures, natural conduits, underground streams and reservoirs. The main characteristic of karstic formations is their significant 3D physical heterogeneity at all scales, from fine fissuration to large holes and conduits. This leads to dynamic and temporal variability, e.g, highly variable flow rates, due to several concurrent flow regimes with several distinct response times. The temporal hydrologic response of karstic basins is studied here from an input/output, systems analysis viewpoint. The hydraulic behaviour of the basins is approached via the relationship between hydrometeorological inputs and outputs. These processes are represented and modeled as random, self-correlated and cross-correlated, stationary time processes. More precisely, for each site-specific case presented here, the input process is the total rainfall on the basin and the output process is the discharge rate at the outlet of the basin (karstic spring). In the absence of other data, these time processes embody all the available information concerning a given karstic basin. In this paper, we first present a brief discussion of the physical structure of karstic systems. Then, we formulate linear and nonlinear models, i.e. functional relations between rainfall and runoff, and methods for identifying the kernel and coefficients of the functionals (deterministic vs. statistical; error minimisation vs. polynomial projection). These are based mostly on Volterra first order (linear) or second order (nonlinear) convolution. In addition, a new nonlinear threshold model is developed, based on the frequency distribution of interannual mean daily runoff. Finally, the different models and identification methods are applied to two karstic watersheds in the french Pyrenees mountains, using long sequences of rainfall and spring outflow data at two different sampling rates (daily and semi-hourly). The accuracy of nonlinear and linear rainfall-runoff models is tested at three time scales: long interannual scale (20 years of daily data), medium or seasonal scale (3 months of semi-hourly data), and short scale or 'flood scale' (2 days of semi-hourly data). The model predictions are analysed in terms of global statistical accuracy and in terms of accuracy with respect to high flow events (floods)

Why and how are caves "organized": does the past offer a key to the present, 1999, Lowe, David J.

Many caves within carbonate (and perhaps other) rock sequences display marked spatial organization, particularly a tendency to group within vertical clusters. Most past explanations of clustering involve "recent" effects and interactions. New ideas, based on study of "denuded" or "unroofed" caves, acknowledge but re-interpret features and relationships that were observed long ago and commonly dismissed as "atypical", "irrelevant" or "impossible". Some traditional explanations of vertical clustering must now be re-assessed. Assumptions that any stratigraphical (bedding plane) or joint/fault fissure in carbonate rock provides (or provided) a de facto route for fluid transfer, and hence a focus for void development, are not confirmed by observation. Primitive pre-cave, but potentially cavernous, carbonate masses are not inevitably active hydrologically; nor are they geologically homogeneous. New evidence, and re-evaluation of earlier observations, implies that dissolutional void "inception" is related to a minor subset of all stratigraphical partings, which dominate initially, imprinting incipient guidance for later cave development. Recognition of this fundamental role provides a possible key to understanding the organization of cave systems and necessitates acceptance of an expansion of speleogenetic timescales back to the time of diagenesis.

Views on cave Formation before 1900, 2000, Shaw T.
Nearly all present-day explanations for the formation of caves in limestone had been suggested before 1900, and some had been developed in considerable detail. Speleogenesis by erosion and the role of carbon dioxide in the solution of cave passages were understood in the first half of the 19th century, and by the end of it there already existed schools of thought which supported solution by vadose water and by phreatic water. The most important names in all this are those of Catcott who in 1756 recognized that caves resulted from water action (though he did attribute the water to the biblical Flood), Lyell and Thirria who independently in 1830 appreciated the importance of carbon dioxide in enabling water to dissolve caves in limestone, Evans who understood in 1870 that some caves were formed by solution in groundwater, Martel who from 1890 emphasized the solutional activity of vadose water and made it well known among speleologists, Posepny who described the movement of groundwater and its speleogenetic effect in 1893, and Dupont who developed that idea. There were also some distinctly primitive explanations, mostly in earlier times, including the creation of cavities when beds were folded and mountains formed, erosion of rock by water before it had become hard, expansion in the soft rock of gases from decomposing animal bodies drowned in the Flood, and the solution of salt inclusions having the same shape as the resulting caves. These catastrophic theories were often inspired by the need to explain the formation of caves, as of all landforms, in the relatively short period since the creation of the world, which was commonly believed to have happened 4000 years BC.

Speleogenesis in the Ljubljanica river drainage basin, 2000, Sustersic F.
The Ljubljanica is a typical sinking river, disappearing and reappearing on the surface seven times. Data from 1534 surveyed caves in the central part of the basin have been processed statistically. Fragments of horizontal caves are grouped in clearly expressed clusters. At least two of the clusters appear to have been separated apart along the Idrija strik-slip fault and displaced about 12 km. The spatial orientation of the clusters only vaguely fits the present hydrogeological situation, and it is suggested that the caves are relict or re-occupied voids that formed originally in circumstances different from those of today. Most of the caves have typical phreatic shapes, which are further modified into epiphreatic channels only where there has been considerable input of mechanically transported material. The general genetic pattern is: initiation along bedding planes; penetration into joints; expansion by collapse of crushed zones and along faults; filling of lower parts of the system with sediments and transformation into epiphreatic tunnels.

Gypsum-karst collapse in the Black Hills, South Dakota-Wyoming, USA, 2000, Epstein, Jack B.

Intrastratal dissolution of gypsum and anhydrite in four stratigraphic units of Pennsylvanian to Jurassic age in the Black Hills of South Dakota and Wyoming has resulted in many collapse features that have developed primarily in the non-soluble overlying rocks. Subsidence has affected several areas that are undergoing urban development. Subsurface intrastratal dissolution of anhydrite in the Minnelusa Formation has produced a regional collapse breccia, extensive disruption of bedding, many dolines, and breccia pipes and pinnacles, some of which extend upwards more than 300 m into overlying strata. Recent collapse is evidenced by steep-walled dolines more than 20 m deep, collapse in water wells and natural springs resulting in sediment disruption and contamination, and fresh circular scarps surrounding shallow depressions. Many beds of gypsum are contorted because of expansion due to its hydration from anhydrite, and many gypsum veinlets extend downward along random fractures from parent gypsum beds. Several dolines are sites of resurgent springs. As the anhydrite dissolution front in the subsurface Minnelusa moves downdip and radially away from the center of the Black Hills uplift, these resurgent springs will dry up and new ones will form as the geomorphology of the Black Hills evolves. Old dolines and breccia pipes, preserved in cross section on canyon walls, attest to the former position of the dissolution front. Mirror Lake, which is expanding northwestward in a downdip direction, is a local analog of a migrating dissolution front.

Hydrology, Hazards, and Geomorphic Development of Gypsum Karst in the Northern Black Hills, South Dakota and Wyoming, 2001, Epstein, J. B.

Dissolution of gypsum and anhydrite in four stratigraphic units in the Black Hills, South Dakota and Wyoming, has resulted in development of sinkholes and has affected formational hydrologic characteristics. Subsidence has caused damage to houses and water and sewage retention sites. Substratal anhydrite dissolution in the Minnelusa Formation (Pennsylvanian and Permian) has produced breccia pipes and pinnacles, a regional collapse breccia, sinkholes, and extensive disruption of bedding. Anhydrite removal in the Minnelusa probably dates back to the early Tertiary when the Black Hills was uplifted and continues today. Evidence of recent collapse includes fresh scarps surrounding shallow depressions, sinkholes more than 60 feet deep, and sediment disruption and contamination in water wells and springs. Proof of sinkhole development to 26,000 years ago includes the Vore Buffalo Jump, near Sundance, WY, and the Mammoth Site in Hot Springs, SD. Several sinkholes in the Spearfish Formation west of Spearfish, SD, which support fish hatcheries and are used for local agricultural water supply, probably originated 500 feet below in the Minnelusa Formation. As the anhydrite dissolution front in the subsurface Minnelusa moves down dip and radially away from the center of the Black Hills uplift, these resurgent springs will dry up and new ones will form as the geomorphology of the Black Hills evolves. Abandoned sinkholes and breccia pipes, preserved in cross section on canyon walls, attest to the former position of the dissolution front. The Spearfish Formation, mostly comprising red shale and siltstone, is generally considered to be a confining layer. However, secondary fracture porosity has developed in the lower Spearfish due to considerable expansion during the hydration of anhydrite to gypsum. Thus, the lower Spearfish yields water to wells and springs making it a respectable aquifer. Processes involved in the formation of gypsum ka 

Engineering approaches to conditions created by a combination of karst and faulting at a hospital in Birmingham, Alabama, 2002, Cooley T,
Foundations for a major expansion and modification of a multistory hospital in Birmingham, AL, were founded on faulted and karst-dissolutioned dolomite. The foundation approach had to accommodate a high degree of uncertainty concerning local conditions due to limited access for exploration and extremely variable rock conditions. The scope of the construction included excavation of a subbasement into rock with associated tiebacks to support adjacent foundations, installation of rock-bearing shear walls and rock anchors under the existing hospital, and installation of rock-bearing caissons and wall foundations outside the existing hospital. Local complications included areas of highly shattered rock, a generally pinnacled rock surface with average relief of 3-6 m (10-20 ft), locally very deep cutters and pits, areas where dolomite was weathered to sand or weak rock up to 3 m (10 ft) thick, and pockets of flowing sand and mud near the rock surface. Because of the complexity of site conditions and limited initial access to the site, on-site geotechnical services required innovative approaches to gather additional information on the highly variable and ambiguous rock conditions and adapt detailed foundation design and foundation approaches to the actual conditions encountered. These approaches included triple-tube coring of shattered rock at selected caisson locations; development of a technique for installation of rock anchors into shattered rock, determination of required undercut depths, and remediation at individual foundations where rock was shattered, disaggregated, or steeply pinnacled; characterization of individual cutters by airtrack probing for remediation information in wall foundations; low-angle coring for cutter characterization in the tieback area; change in foundations from walls to caissons or caissons to mat foundations in select areas; and above all, careful judgment-based design. Limitations of characterization methods are also discussed. A fundamental understanding of karst processes and three-dimensional conceptualization was an essential part of the engineering required for this project. (C) 2002 Elsevier Science B.V. All rights reserved

Rainfall-runoff relations for karstic springs: multifractal analyses, 2002, Labat D. , Mangin A. , Ababou R. ,
Karstic watersheds appear as highly as non-linear and non-stationary systems. The behaviour of karstic springs has been previously studied using non-linear simulation methods (Volterra expansion) and non-stationary analyses methods based on wavelet transforms. The main issue of karstic spring behaviour consists of the presence and the identification of characteristic time-scales. In order to highlight more precisely the scale-properties of the rainfall-runoff relations for karstic springs, the multifractal analysis is introduced. These methods are applied daily and half-hourly rainfall rates and runoffs measured on a three French karstic springs located in the Pyrenees Mountains (Ariege, France): Aliou, Baget and Fontestorbes. They are characterised by a variable development of the drainage systems. We have at our disposal long and uninterrupted series of data over period of several years, which constitute a high quality bank data. Multifractal analyses of both daily and half-hourly rainfall rates and runoffs give evident a scale-dependant behaviour. Effectively, it highlights the presence of different multifractal processes at each sampling rate. Using a universal class of multifractal models based on cascade multiplicative processes, the identified multifractal sub-processes are characterised by the classical parameters alpha and C-1. All these results should lead to several improvements in karstic springflow simulation models. (C) 2002 Elsevier Science B.V. All rights reserved

Using stable isotope analysis (delta D-delta O-18) to characterise the regional hydrology of the Sierra de Gador, south east Spain, 2002, Vandenschrick G. , Van Wesemael B. , Frot E. , Pulidobosch A. , Molina L. , Stievenard M. , Souchez R. ,
Water stress is rapidly increasing in many Mediterranean coastal zones mainly due to expansion in agriculture and tourism. In this paper, we focus on the Sierra de Gador-Campo de Dalias aquifer system (southeastern Spain) in order to assess the capability of water stable isotope analysis (deltaD-delta(18)O) to refine the understanding on recharge of this karstic aquifer system. Different types of surface and groundwater were sampled along an altitudinal gradient from the recharge zone in the mountains to the coastal plain. Surface water is restricted to local runoff, collected in closed reservoirs. Runoff amounts, collected in three of these reservoirs were monitored together with the precipitation in their catchments. Meteorological maps were used to detect the origin of the precipitation generating the majority of the runoff. The results were compared to literature data on local and regional precipitation. The use of oxygen and hydrogen isotopic composition has proved to be a useful tool to explain the origin of groundwater in a Mediterranean karstic system. Such studies are, however, not numerous and are often limited to local scale recharge for fast-reacting systems. This paper focuses on the delta(18)O-deltaD relationships of local precipitation to explain the isotopic variability of a large karstic aquifer system. The isotopic compositions of groundwater sampled along an altitudinal gradient from the recharge zone to the coastal plain are well displayed, in a deltaD-delta(18)O diagram, on a mixing line connecting a pole of Mediterranean waters to a pole of Atlantic waters. The Atlantic signature predominates in the shallow groundwater of natural springs, reflecting the rainfall which produced the local runoff sampled. The Mediterranean signature is mainly restricted to deep groundwater from boreholes in the coastal plain. The existence of a degree of spatial separation of groundwater types demonstrates that groundwater flow in a complex karstic system is not always continuous. The Mediterranean signature of deep groundwater could be due to past extreme rainfall events during which connectivity between recharge and reservoir exists, while at the same time the Atlantic signature of recent winter rains dominates in shallow groundwater. The assumption that an equilibrium in isotopic composition is established within a continuous aquifer and that therefore a slope lower than 8 in a deltaD-delta(18)O diagram indicates evaporation is not necessarily valid.

Human impact on Karst: the example of Lusaka (Zambia)., 2003, De Waele Jo, Follesa Roberto
Lusaka, the capital of Zambia with over 2,000,000 inhabitants, is built on an extensive plateau composed mainly of schists and dolomitic marbles, constituting a very important aquifer that provides the city with almost half of its drinking water needs. Recent demographic growth, leading to uncontrolled urban expansion, and mismanagement of the water resource and of urban waste has lead, in the past 20 years, to an overexploitation of the aquifer and to a generalised water quality depletion, putting in serious danger the future social and economical development of the capital. This third world city has, for these reasons, become a terrifying example of human impact on a vulnerable karst environment, and if no measures will be taken in the very near future, quality of life in the city will be at serious risk.

Solution and recrystallisation processes and associated landforms in gypsum outcrops of Sicily, 2003, Ferrarese F, Macaluso T, Madonia G, Palmeri A, Sauro U,
Four small areas of Messinian (Upper Miocene) age gypsum, outcropping in western Sicily, are described. Messinian age evaporites are found in Sicily over a 1000-km(2) area. Here, gypsum outcrops extensively as a consequence of soil erosion induced by human impact. Geomorphological maps show how the rocky surfaces are characterized by a wide range of forms. There are large, medium, small, and microsized forms, which can be identified as belonging to different morphotypes. The morphotypes can be classified into two main categories: those that originated by solution and those that originated through recrystallisation. Four areas, illustrated by geomorphological maps, were specifically chosen to describe a type of medium-sized form: dome-like hills. These medium-sized forms are covered by a mosaic of smaller forms, related to both the previous categories: different types of karren and of 'expansion' forms. The types of karren can be explained as the results of the solution process under different hydrodynamical behaviour; the dome-like hills and other related 'expansion' forms are more difficult to understand. These 'expansion' forms can be explained by the same process that leads to the development of gypsum tumuli. The outcrops of gypsum lacking soil cover and influenced by alternating seasonal water conditions of surplus and deficit are affected by both solution and recrystallisation processes. During the wet season, the water soaks into the rocky mass, filling all the fissures and pores of the outer rocky layer from a few centimetres to some metres below the surface. During the dry season, there is a capillary upward motion of the water solution. Near the surface, gypsum precipitates from the oversaturated solution, increasing the crystal size or forming new crystals. In this way, during the dry season, there is a pressure increase in the outer gypsum layers, which is responsible for the development of a 'gypsum weathering crust' and characterised by many different forms such as gypsum tumuli, pressure ridges, pressure humps, and other related small forms. The crust may also lead to the development of mega-tumuli and dome-like hills. From the morphostructural point of view, the dome-like hills do not seem to be controlled by the strike, dip, or fissuring of the gypsum beds. Their evolution seems to be linked to the fact that on most of the dome surfaces, the weathering crust is evolving through a nearly isotropic field of stresses, resulting in volume increase in the outer gypsum layer. (C) 2002 Elsevier Science B.V. All rights reserved

Sequence Stratigraphy and Carbonate-Siliciclastic Mixing in a Terminal Proterozoic Foreland Basin, Urusis Formation, Nama Group, Namibia, 2003, Saylor Beverly Z. ,
Superb three-dimensional exposures of mixed carbonate and siliciclastic strata of the terminal Proterozoic Urusis Formation in Namibia make it possible to reconstruct cross-basin facies relations and high-resolution sequence stratigraphic architecture in a tectonically active foreland basin. Six siliciclastic facies associations are represented: coastal plain; upper shoreface; middle shoreface; lower shoreface; storm-influenced shelf; and pebble conglomerate. Siliciclastic shoreface facies pass seaward into and interfinger with facies of an open carbonate shelf. Four carbonate facies associations are present: mid-shelf; shelf crest; outer shelf; and slope. Facies are arranged hierarchically into three scales of unconformity-bounded sequences. Small-scale sequences are one to tens of meters thick and span a few thousand years. They consist of shelf carbonate with or without shoreface siliciclastic facies near the bottom. Medium-scale sequences are tens of meters thick and span a few hundred thousand years. They consist of shoreface siliciclastic facies in their lower parts, which grade upward and pass seaward into shelf carbonate. Large-scale sequences are tens to hundreds of meters thick and span 1 to 2 million years. They are identified by widespread surfaces of exposure, abrupt seaward shifts in shoreface sandstone, patterns of facies progradation and retrogradation, and shoreline onlap by medium-scale sequences. Patterns of carbonate-siliciclastic mixing distinguish tectonic from eustatic controls on the evolution of large-scale sequences. Characteristics of eustatically controlled large-scale sequences include: (1) basal unconformities and shoreface sandstone that extend across the shelf to the seaward margin; (2) retrograde carbonate and siliciclastic facies belts that onlap the shoreline together, symmetrically, during transgression; and (3) upper shoreface sandstone that progrades seaward during highstand. In contrast, tectonically controlled sequences feature: (1) basal erosion surfaces and upper shoreface sandstone that are restricted to near the landward margin and pass seaward into zones of maximum flooding; and (2) asymmetric stratigraphic development characterized by landward progradation of carbonate from the seaward margin coincident with backstepping and onlap of the shoreline by siliciclastic facies. A two-phase tectonic model is proposed to account for the stratigraphic asymmetry of tectonically controlled sequences. Increased flexural bending during periods of active thrust loading caused submergence of the seaward margin and uplift of the landward margin. Rebound between thrusting episodes flattened the basin gradient and submerged the landward margin, causing expansion of carbonate facies from the seaward margin and simultaneous transgression of the landward margin. Although the two-phase model should apply to single-lithology successions deposited in active foreland basins, the mixing of carbonate and siliciclastic facies provides a particularly sensitive record of tectonic forcing. The sensitivity may be sufficient for medium- and small-scale sequences to record higher-frequency variations in flexural warping

Palaeoenvironments in semi-arid northeastern Brazil inferred from high precision mass spectrometric speleothem and travertine ages and the dynamics of South American rainforests, 2004, Auler A. S. , Wang X. , Edwards R. L. , Cheng H. , Cristalli P. S. , Smart P. L. , Richards D. A.

Understanding past environmental changes in tropical rainforests is extremely important in order to assess the response of such environments to present and future climatic changes and understand causes and the present patterns of biodiversity.
Earlier hypothesis on the origin of biodiversity have stressed the role of past climatic changes in promoting speciation. According to the “refuge hypothesis” (Haffer, 1982), dry periods could have led to forest fragmentation, isolating more humid forested zones (called refuges) within an environment largely dominated by savannas. The refuge hypothesis does not assign timescales for rainforest fragmentation, although recent studies have suggested that speciation could have occurred over timescales of millions of years (Knapp and Mallet, 2003). Although the focus of heavy criticism (Colinvaux, et a., 2000), the refuge hypothesis has generated a large amount of research. In general, pollen studies (Colinvaux, et a., 1996, Haberle and Maslin, 1999) tend to support a continuous forest cover throughout late Quaternary climatic shifts, although large variations in rainfall have also been demonstrated by other pollen and isotopic studies (van der Hammen and Absy, 1994; Maslin and Burns, 2000).
Amazon and Atlantic rainforests are the two major forested zones in South America. Amazon rainforest, the largest rainforest in the world, comprise a total original area of 4.1 million km2 and is renowned for hosting the large biodiversity in the world (30% of all the world’s known plant and animal species). Atlantic rainforest, also a biodiversity hotspot, occurs along the coast and has been subjected to heavy deforestation since European arrival. Nowadays only c. 7% of its original forested area of 1.3 million km2 remains. These two rainforests are separated by drought-prone semi-arid northeastern (NE) Brazil. Our study does not address the refuge hypothesis directly although it sheds new light on the dynamics of forest expansion in the past as well as indicates alternative ways of promoting speciation. It has long been hypothesized, due to botanical (Mori, 1989; Andrade-Lima, 1982) and faunistic (Costa, 2003) similarities, that the Amazon and Atlantic rainforests were once linked in the past. Although numerous connecting routes have been postulated (Bigarella, et al, 1975; Por, 1992; De Oliveira, et al, 1999), the timing of forest expansion and their possible recurrence have remained elusive.
The study area lies in the driest portion of NE Brazil “dry corridor”, close to the village of Laje dos Negros, northern state of Bahia. Mean annual precipitation is around 480 mm and potential evapotranspiration is in excess of 1,400 mm/year (Fig.1). Present vegetation comprises a low arbustive scrubland known locally as caatinga. The area contains a well-developed underground karst (Auler and Smart, 2003) with abundant secondary calcite precipitates, both underground (speleothems) and on the surface (travertines).

A pipe-based, first approach to modeling closed conduit flow in caves, 2004, Springer Gregory S. ,
A closed conduit model is constructed for a discrete cave segment using the energy equation and the assumption that energy losses in the segment are generated by large-scale flow separation associated with expansions and bends. As employed, the model uses paleostage indicators and passage geometry to estimate total head loss across the study reach. Channel roughness is estimated using pipe-based equations and a skin friction factor estimated from secondary means. Discharge is varied in the model until calculated head loss matches observed head loss. The model is employed to estimate discharge for a flood recorded in Buckeye Creek Cave, West Virginia as high water marks consisting of silt lines. Under varying assumptions, the model yields paleodischarges in the range of 22-29 m3 s-1. Shear stress values calculated using model output are in general agreement with the size distribution of gravel on the stream bed and shear stress values are relatively insensitive to changes in discharge. The apparent friction factor for the study reach is estimated to be in the range of 0.4-0.7, which is in general agreement with previous studies of large conduits. The model is applicable to similar cave reaches, but requires further testing and validation because so little is known about conduit flow in karst

The Danube submarine canyon (Black Sea): morphology and sedimentary processes, 2004, Popescu Irina, Lericolais Gilles, Panin Nicolae, Normand Alain, Dinu Cornel, Le Drezen Eliane,
The Danube Canyon is a large shelf-indenting canyon that has developed seaward of the late Pleistocene paleo-Danube valley. Mechanisms of canyon evolution and factors that controlled it are revealed by analyzing the morphology and the sedimentary structure of the canyon, as well as the main features of the continental margin around the canyon. This is based on investigation by swath bathymetry in the canyon area combined with different types of seismic data.The canyon is a major erosional trough with a flat bottom cut by an entrenched axial thalweg. The thalweg path varies from highly meandering to fairly straight in relation to the local gradient. Segments of the canyon are characterized by specific morphology, orientation and gradient along the axial thalweg. We interpret these segments in terms of canyon maturity. The sedimentary structure of the canyon documents an older phase of erosion followed by partial infilling, and thus attests for repeated cycles of canyon development.Canyon morphology is interpreted as a result of erosive sediment flows along the entrenched axial thalweg that caused downcutting into the canyon bottom and instability of the canyon walls, and hence enlargement of the canyon and expansion by headward erosion. During the last lowstand level of the Black Sea the canyon was located in an area of high sediment supply close to the paleo-Danube River mouths. This is indicated by buried fluvial channels on the shelf and by a wave-cut terrace associated with a water level situated about -90 m below the present level. We infer that erosive flows in the canyon resulted from hyperpycnal currents at the river mouths, probably favored by the low salinity environment that characterized the Black Sea during lowstand times. Other mechanisms could have contributed to trigger sediment failure along the canyon, such as instability related to the presence of shallow gas, or the effect of a deep fault

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