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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. ...

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. ...

Speleology in Kazakhstan

Shakalov on 11 Jul, 2012
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 evaporation loss is the loss of precipitated water that is discharged to the atmosphere by evaporation [16].?

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Chemistry and Karst, White, William B.
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Geochemical and mineralogical fingerprints to distinguish the exploited ferruginous mineralisations of Grotta della Monaca (Calabria, Italy), Dimuccio, L.A.; Rodrigues, N.; Larocca, F.; Pratas, J.; Amado, A.M.; Batista de Carvalho, L.A.
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
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Your search for deformation (Keyword) returned 96 results for the whole karstbase:
Showing 1 to 15 of 96
Lattice Deformation and Curvature in Stalactitic Carbonate., 1983, Broughton Paul L.
The cause of lattice curvature is related to the nature of growth on a curved surface, peculiar to stalactites and stalagmites. Lattice curvature in stalactitic carbonate results from the coalescence of sub-parallel to divergent syntaxial overgrowth crystallites on the growing surface of stalactites and stalagmites. Moderate lattice mismatch results in an undulose extinction, or subcrystal domains, whereas more divergent growth favours marked lattice curvature recognized by its optical brush-extinction. Extreme lattice mismatch between the precursor crystallites results a columnar crystal boundary instead of lattice curvature.

Karsts alpins et notectonique, 1984, Julian, M.
ALPINE KARSTS AND NEOTECTONIC: A BRIEF OVERVIEW - Several problems are studied at the light of new investigations: 1) the deepening of the karstic network related to orogenic uplifts and the corresponding levels of the caves; 2) the tectonic deformations (faults) described upon some karstic surfaces or into some caves; 3) the pseudo-tectonic deformations like toppling failures and other tension-cracks parallel to the vertical cliff faces.

Exploitation d'une photo arienne pour la dtermination des coordonnes d'une cavit situe en terrain dcouvert, 1989, Lismonde, B.
Use of aerial view to determine geographic coordinates of caves located in bare area - A computation is presented to determine geographic coordinates from an air-photography with the correction of inclinations and reliefs deformations.

Origin of the cave in Trzy Kopce in the Silesian Beskidy Mts.. [in Polish], 1989, Puchejda, Wojciech

POST JURASSIC BRITTLE TECTONICS OF THE HAMMAM ZRIBA MINE (NORTHEASTERN TUNISIA) AND RELATED KARST AND FLUORINE, BARYTINE AND CELESTITE OCCURRENCES IN CARBONATE ENVIRONMENTS, 1991, Melki F. , Zargouni F. ,
The Hammam Zriba mine is located in a lenticular horst structure, of varying width (0.3 to 1 km) and NNW-SSE strike over about 3 kms. The mineralization is strata-bound at the top of massive Portlandian limestones and is overlain by embedded Middle to Upper Campanian limestones with marl intercalations. This horst has formed during the late Jurassic as an emerged block bound by major faults that were remobilized later during various deformation stages. These facts are clearly documented by field observations and tectonic analysis essentially along the N160-N180 trending faults in the Portlandian lithofacies. These fractures have also controlled the palaeomorphological framework of the uppermost part of the Portlandian massive facies. The overlying Campanian unit exhibits onlap structures that rest on the irregular eroded karstified and mineralized surface which forms a screen surface for the upward channelized fluids and mineral formations in karst and graben. Fluids were apparently channelized by faults trending N070-N090 and N160-180, a few hundred metres long, that have facilitated karst, dissolution and mineral deposition during tectonic events

Signification godynamique des rseaux karstiques tags du canyon de Baudinard (moyennes gorges du Verdon, 1992, Blanc, J. J.
GEODYNAMIC SIGNIFICATION OF LEVELLED KARSTIC NETWORKS IN THE BAUDINARD CANYON (VERDON CANYON, FRANCE) - An intense speleogenic activity can be observed in the Baudinard canyon: some levelled systems in relation to the lowering karstic water-table linked to the formation of the canyon, during Messinian, Pliocene and Quaternary periods. An active tectonic framework shows many deformations of the ante-vindobonian surface during the plio-quaternary burrowing canyon phases. Azimuth gallery direction analysis reveals several sorts of drainage network: linear, smoothed with loops, labyrinths and drainage-confluences. Networks are induced by local and successive tectonic actions. The gallery wall deformations are strongly marked by the shrinking stresses and interstrata shearing.

EVIDENCE FOR EXTENSIVE POST-CALEDONIAN KARST DEVELOPMENT IN SOUTHWESTERN SPITSBERGEN, 1992, Bjornerud M,
Proterozoic limestones at several localities in southwestern Spitsbergen contain karst-elated features (layered clastic infillings, collapse breccias, deeply weathered depressions) which overprint the Caledonian deformational fabric in the rocks. These features apparently developed between middle Devonian and mid-Carboniferous time when the Precambrian basement complex stood high above sea level. Recognition of these karst features may shed light on depositional and tectonic events in post-Caledonian Spitsbergen

Le palokarst littoral de Provence (Estaque, Calanques et zone de Bandol), 1993, Blanc, J. J.
The general features of coastal paleokarst in Provence are describes: suspended gallery sections and drain-pipes cut across by fracturations or fault reactivation. The types of deformations and breaking observed are tilting, stalactite fall, extension fault sealing, reactivation and speleothem shearing, coastal wall and karstic cleft collapse as well as network deformation. The influence of structural environment is represented by overlapping strata, coastal faults and crossed-fault systems. Emphasis has been laid on the tectonic inheritance as well as the geodynamic context. To conclude, the importance of provenal-ligurian rifting mechanisms and the transition to faulted and distorted margin is underlined.

DISLOCATION OF THE EVAPORITIC FORMATIONS UNDER TECTONIC AND DISSOLUTION CONTROLS - THE MODEL OF THE DINANTIAN EVAPORITES FROM VARISCAN AREA (NORTHERN FRANCE AND BELGIUM), 1993, Rouchy J. M. , Groessens E. , Laumondais A. ,
Within the Franco-Belgian segment of the Hercynian orogen, two thick Dinantian anhydritic formations are known, respectively in the Saint-Ghislain (765 m) and Epinoy 1 (904 m) wells. Nevertheless, occurrences of widespread extended breccias and of numerous pseudomorphs of gypsum/anhydrite in stratigraphically equivalent carbonate deposits (boreholes and outcrops), suggest a larger extent of the evaporitic conditions (fig. 1, 2). The present distribution of evaporites is controlled by palaeogeographical differentiation and post-depositional parameters such as tectonics and dissolution. These latter have dissected the deposits formerly present in all the structural units. By using depositional, diagenetic and deformational characters of these formations, the article provides a model for the reconstruction of a dislocated evaporitic basin. This segment of the Hercynian chain is schematically composed of two main units (fig. 1, 3) : (1) the autochthonous or parautochthonous deposits of the Namur synclinorium, (2) the Dinant nappe thrusted northward over the synclinorium of Namur. The major thrust surface is underlined by a complex fault bundle (faille du Midi) seismically recognized over more than 100 km. A complex system of thrust slices occurs at the Hercynian front. Except for local Cretaceous deposits, most of the studied area has been submitted to a long period of denudation since the Permian. Sedimentary, faunistic and geochemical data argue for a marine origin of the brines which have generated the evaporites interbedded with marine limestones. Sedimentary structures. - The thick evaporitic formations are composed of calcium-sulfates without any clear evidence of the former presence of more soluble salts (with the exception of a possible carbonate-sulfate breccia in the upper part of the Saint-Ghislain formation). As in all the deeply buried evaporitic formations, the anhydrite is the main sulfate component which displays all the usual facies : pseudomorphs after gypsum (fig. 4A, B), nodular and mosaic (fig. 4C), laminated. The gypsum was probably an important component during the depositional phase despite the predominant nodular pattern of the anhydrite. Early diagenetic nodular anhydrite may have grown during temporary emersion of the carbonates (sabkha environments), but this mechanism cannot explain the formation of the whole anhydrite. So, most of the anhydrite structures result from burial-controlled gypsum --> anhydrite conversion and from mechanical deformations. Moreover, a complex set of diagenetic processes leads to various authigenic minerals (celestite, fluorite, albite, native sulfur, quartz and fibrous silica) and to multistaged carbonate <> sulfate replacements (calcite and dolomite after sulfate, replacive anhydrite as idiomorphic poeciloblasts, veinlets, domino-like or stairstep monocrystals...). These mineral transformations observed ill boreholes and in outcrops have diversely been controlled during the complex evolution of the series as : depositional and diagenetic pore-fluid composition, pressure and temperature changes with burial, bacterial and thermochemical sulfate reduction, deep circulations favored by mechanical brecciation, mechanical stresses, role of groundwater during exhumation of the series. Deformational structures. - A great variety of deformational structures as rotational elongation, stretching, lamination, isoclinal microfolding, augen-like and mylonitic structures are generated by compressive tectonic stresses (fig. 4D to J). The similarities between tectonic-generated structures and sedimentary (lamination) or diagenetic (pseudo-nodules) features could lead lo misinterpretations. The calcareous interbeds have undergone brittle deformation the style and the importance of which depend of their relative thickness. Stretching, boudins, microfolds and augen structures F, H. I) affect the thin layers while thicker beds may be broken as large fractured blocks dragged within flown anhydrite leading to a mylonitic-like structure (fig, 4G). In such an inhomogeneous formation made of interlayered ductile (anhydrite) and brittle (carbonate) beds, the style and the intensity of the deformation vary with respect to the relative thickness of each of these components. Such deformational features of anhydrite may have an ubiquitous significance and can result either from compressive constraints or geostatic movements (halokinesis). Nevertheless, some data evidence a relation with regional tangential stresses: (1) increase of the deformation toward the bottom of the Saint-Ghislain Formation which is marked by a deep karst suggesting the presence of a mechanical discontinuity used as a drain for dissolving solutions (fig. 3, 4); (2) structural setting (reversed series, internal slidings) of the Epinoy 1 formation under the Midi thrust. However, tectonic stresses also induce flowing deformations which have contributed to cause their present discontinuity. It can be assumed that the evaporites played an active role for the buckling of the regional structure as detachment or gliding layers and more specifically for the genesis of duplex structures. Breccia genesis. - Great breccia horizons are widely distributed in outcrops as well as in the subsurface throughout the greater part of the Dinant and Namur units (fig. 2). The wide distribution of pseudomorphosed sulfates in outcrops and the stratigraphical correlation between breccia and Saint-Ghislain evaporitic masses (fig. 2) suggest that some breccia (although not all) have been originated from collapse after evaporites solution. Although some breccia may result from synsedimentary dissolution, studied occurrences show that most of dissolution processes started after the Hercynian deformation and, in some cases, were active until recently : elements made of lithified and fractured limestones (Llandelies quarries) (fig. 5A), preservation of pseudomorphs of late replacive anhydrite (Yves-Gomezee) (fig. 5B, C), deep karst associated with breccia (Douvrain, Saint Ghislain, Ghlin boreholes) (fig. 3, 4, 5D)). Locally, the final brecciation may have been favored by a mechanical fragmentation which controlled water circulations (fig. 5E). As postulated by De Magnee et al. [19861, the dissolution started mostly after the Permian denudation and continued until now in relation with deep circulations and surface weathering (fig. 6). So, the above-mentioned occurrences of the breccia are logically explained by collapse after dissolution of calcium-sulfates interbeds of significant thickness (the presence of salt is not yet demonstrated), but other Visean breccia may have a different origin (fig. 5F). So, these data prove the extension of thick evaporitic beds in all the structural units including the Dinant nappe, before dissolution and deformation. Implications. - Distribution of Visean evaporites in northern France and Belgium is inherited from a complicated paleogeographic, tectonic and post-tectonic history which has strongly modified their former facies, thicknesses and limits (fig. IA, 6). Diversified environments of deposition controlled by both a palaeogeographical differentiation and water level fluctuations led to the deposition of subaqueous (gypsum) or interstitial (gypsum, anhydrite) crystallization. Nevertheless, most of the anhydrite structures can be interpreted as resulting from burial conversion of gypsum to anhydrite rather than a generalized early diagenesis in sabkha-like conditions. Deformation of anhydrite caused by Hercynian tangential stresses and subsequent flow mechanisms, have completed the destruction of depositional and diagenetic features. The tectonic deformations allow us to consider the role of the evaporites in the Hercynian deformations. The evaporites supplied detachment and gliding planes as suggested for the base of the Saint-Ghislain Formation and demonstrated by the structural setting of Epinoy 1 evaporites in reverse position and in a multi-system of thrust-slices below the Midi overthrust (fig. 7). So, although the area in which evaporation and precipitation took place cannot be exactly delineated in geographic extent, all the data evidence that the isolated thick anhydritic deposits represent relics of more widespread evaporites extending more or less throughout the different structural units of this Hercynian segment (fig. 1B). Their present discontinuity results from the combination of a depositional differentiation, mechanical deformations and/or dissolution

HIGH-RESOLUTION SEISMIC EXPRESSION OF KARST EVOLUTION WITHIN THE UPPER FLORIDIAN AQUIFER SYSTEM - CROOKED LAKE, POLK COUNTY, FLORIDA, 1994, Evans Mw, Snyder Sw, Hine Ac,
We collected 43 km of high resolution seismic reflection profiles from a 14.5-hectare lake in the central Florida sinkhole district and data from three adjacent boreholes to determine the relationship between falling lake levels and the underlying karst stratigraphy. The lake is separated from karstified Paleogene to early Neogene carbonates by 65-80 m of siliciclastic sands and clays. The carbonate and clastic strata include three aquifer systems separated by clay-confining units: a surficial aquifer system (fine to medium quartz sand in the upper 20-30 m), the 25-35 m thick intermediate aquifer system (in Neogene siliciclastics), and the highly permeable upper Floridan aquifer system in Paleogene to early Neogene limestones. Hydraulic connection between these aquifer systems is indicated by superjacent karst structures throughout the section. Collapse zones of up to 1000 m in diameter and > 50 m depth extend downward from a prominent Middle Miocene unconformity into Oligocene and Upper Eocene limestones. Smaller sinkholes (30-100 m diameter, 10-25 m depth) are present in Middle to Late Neogene clays, sands, and carbonates and extend downward to or below the Middle Miocene unconformity. Filled and open shafts (30-40 m diameter; 10-25 m depth) ring the lake margin and overlie subsurface karst features. The large collapse zones are localized along a northeast-southwest line in the northern ponds and disrupt or deform Neogene to Quaternary strata and at least 50 m of the underlying Paleogene carbonate rocks. The timing and vertical distribution of karst structures are used to formulate a four-stage model that emphasizes stratigraphic and hydrogeologic co-evolution. (1) Fracture-selective shallow karst features formed on Paleogene/early Neogene carbonates. (2) Widespread karstification was limited by deposition of Middle Miocene clays, but vertical karst propagation continued and was focused because of the topographic effects of antecedent karst. (3) Groundwater heads, increase with the deposition of thick sequences of clastics over the semipermeable clays during Middle and Late Neogene time. The higher water table and groundwater heads allowed the accumulation of acidic, organic-rich soils and chemically aggressive waters that percolated down to Paleogene carbonates via localized karst features. (4) After sufficient subsurface dissolution, the Paleogene carbonates collapsed, causing disruption and deformation of overlying strata. The seismic profiles document an episodic, vertically progressive karst that allows localized vertical leakage through the clay-confining units. The spatial and temporal karst distribution is a result of deposition of sediments with different permeabilities during high sea levels and enhanced karst dissolution during low sea levels. Recent decreases in the potentiometric elevation of the Floridan Aquifer System simulates a sea-level lowstand, suggesting that karst dissolution will increase in frequency and magnitude

ASSOCIATION OF TEPEES AND PALEOKARST IN THE LADINIAN CALCARE-ROSSO (SOUTHERN ALPS, ITALY), 1994, Mutti M. ,
The Ladinian Calcare Rosso of the Southern Alps provides a rare opportunity to examine the temporal relationships between tepees and palaeokarst. This unit comprises peritidal strata pervasively deformed into tepees, repeatedly capped by palaeokarst surfaces mantled by terra rossa. Palaeokarsts, characterized by a regional distribution across the Southern Alps, occur at the base and at the top of the unit. Local palaeokarsts, confined to this part of the platform, occur within the Calcare Rosso and strongly affected depositional facies. Tepee deformation ranges from simple antiformal structures (peritidal tepecs) to composite breccias floating in synsedimentary cements and internal sediments (senile tepees). Peritidal tepees commonly occur at the top of one peritidal cycle, in association with subaerial exposure at the cycle top, while senile tepees affect several peritidal cycles, and are always capped by a palaeokarst surface. Cements and internal sediments form up to 80% of the total rock volume of senile tepees. The paragenesis of senile tepees is extremely complex and records several, superimposed episodes of dissolution, cement precipitation (fibrous cements, laminated crusts, mega-rays) and deposition of internal sediments (marine sediment and terra rossa). Petrographical observations and stable isotope geochemistry indicate that cements associated with senile tepees precipitated in a coastal karstic environment under frequently changing conditions, ranging from marine to meteoric, and were altered soon after precipitation in the presence of either meteoric or mixed marine/meteoric waters. Stable isotope data for the cements and the host rock show the influence of meteoric water (average deltaO-18 = - 5.8 parts per thousand), while strontium isotopes (average Sr-87/Sr-86 = 0.707891) indicate that cements were precipitated and altered in the presence of marine Triassic waters. Field relationships, sedimentological associations and paragenetic sequences document that formation of senile tepees was coeval with karsting. Senile tepees formed in a karst-dominated environment in the presence of extensive meteoric water circulation, in contrast to previous interpretations that tepees formed in arid environments, under the influence of vadose diagenesis. Tepees initiated in a peritidal setting when subaerial exposure led to the formation of sheet cracks and up-buckling of strata. This porosity acted as a later conduit for either meteoric or mixed marine/meteoric fluids, when a karst system developed in association with prolonged subaerial exposure. Relative sea level variations, inducing changes in the water table, played a key role in exposing the peritidal cycles to marine, mixed marine/meteoric and meteoric diagenetic environments leading to the formation of senile tepees. The formation and preservation in the stratigraphic record of vertically stacked senile tepees implies that they formed during an overall period of transgression, punctuated by different orders of sea level variations, which allowed formation and later freezing of the cave infills

Synsedimentary collapse of portions of the lower Blomidon Formation (Late Triassic), Fundy rift basin, Nova Scotia, 1995, Ackermann Rv, Schlische Pw, Olsen Pe,
A chaotic mudstone unit within the lower Blomidon Formation (Late Triassic) has been traced for 35 km in the Mesozoic Fundy rift basin of Nova Scotia. This unit is characterized by highly disrupted bedding that is commonly cut by small (<0.5 m) domino-style synsedimentary normal faults, downward movement of material, geopetal structures, variable thickness, and an irregular, partially faulted contact with the overlying unit. The chaotic unit is locally overlain by a fluvial sandstone, which is overlain conformably by mudstone. Although the thickness of the sandstone is highly variable, the overlying mudstone unit exhibits only gentle regional dip. The sandstone unit exhibits numerous soft-sediment deformation features, including dewatering structures, convoluted bedding, kink bands, and convergent fault fans. The frequency and intensity of these features increase dramatically above low points at the base of the sandstone unit. These stratigraphic relations suggest buried interstratal karst, the subsurface dissolution of evaporites bounded by insoluble sediments. We infer that the chaotic unit was formed by subsidence and collapse resulting from the dissolution of an evaporite bed or evaporite-rich unit by groundwater, producing dewatering and synsedimentary deformation structures in the overlying sandstone unit, which infilled surface depressions resulting from collapse. In coeval Moroccan rift basins, facies similar to the Blomidon Formation are associated with halite and gypsum beds. The regional extent of the chaotic unit indicates a marked period of desiccation of a playa lake of the appropriate water chemistry. The sedimentary features described here may be useful for inferring the former existence of evaporites or evaporite-rich units in predominantly elastic terrestrial environments

THE ORIGIN OF RAUHWACKES (CORNIEULES) BY THE KARSTIFICATION OF GYPSUM, 1995, Schaad W. ,
Rauhwackes (cornieules or cargneules) are breccias with a caicareous matrix and mainly dolomitic components that weather to form cavernous rocks. They are very often associated with tectonic contacts, e.g. detachment horizons. The origin of rauhwackes is still controversial, but has been attributed to the weathering and alteration of dolomite-bearing evaporites, the tectonisation of dolomites or other processes. New data based on field investigations show that the karstification of evaporites leads to the formation of rauhwackes. Two end member evaporitic protoliths can be distinguished: dolomite-bearing gypsum and gypsum-bearing dolomite. The karstification of the different protoliths leads to the formation of structurally distinct rauhwackes. Dolomite-bearing gypsum is associated with unstructured, often polymictic rauhwackes which reflect the shape of the karst cavities and which are interpreted as karst sediments. Gypsum-bearing dolomite occurs with stratiformal rauhwackes with fitting dolomite fragments that are arranged in layers. These rauhwackes can be regarded as collapse breccias. All investigated rauhwackes seem to have been formed after the alpine deformations and are probably of Quaternary age. In certain cases, the karstification of the evaporites and the formation of rauhwackes may have been favoured by fluvial or fluvioglacial processes at the surface. Therefore, these rauhwackes have nothing to do with alpine tectonics. Rather, it was the evaporitic protoliths of the rauhwackes that acted as detachment horizons and incompetent layers during folding

SHALLOW KARST EXPLORATION USING MT-VLF AND DC RESISTIVITY METHODS, 1995, Guerin R. , Benderitter Y. ,
A geophysical test was carried out over a well-located and fairly embedded karstic conduit. The MT-VLF method was selected because of its high resolution and its ability to provide a resistivity parameter sensitive to water and clay. This method was used together with DC resistivity methods which allow vertical adjustment of the VLF data and show consistency between the investigation and target depths. After correcting the deformations due to the polarization of the primary field, the MT-VLF data show clearly, in the central part of the site, that the conduit does not coincide with an anomaly axis but coincides with the boundary between a conductive area and a resistive area. 2D modelling confirms that direct detection of the conduit is not feasible and that the conduit is located close to a conductive zone corresponding to a completely clay-filled fractured zone. This situation was observed on the whole site and the conduit seemed systematically to thread its way between the conductive zones to join the outlet. The distribution of the conductive fractured zones and the direction of the hydraulic gradient were two important elements in predicting the location of the conduits. A 3D approach would increase the probability of finding the conduits in such a case

Yucatan karst features and the size of Chicxulub crater, 1996, Connors M, Hildebrand Ar, Pilkington M, Ortizaleman C, Chavez Re, Urrutiafucugauchi J, Granielcastro E, Camarazi A, Vasquez J, Halpenny Jf,
The buried Chicxulub impact structure is marked by a dramatic ring of sinkholes (called cenotes if containing water), and adjacent less prominent partial rings, which have been shown to coincide with maxima in horizontal gravity gradients and a topographic depression. These observations; along with the discreteness and spacing of the features, suggest a formation mechanism involving faulting in the outer slump zone of the crater, which would thus have a diameter of approximately 180 km, An opposing view, based primarily on the interpretation of gravity data, is that the crater is much larger than the cenote ring implies, Given the association of the known cenote ring with faults, we here examine northern Yucatan for similar rings in gravity, surface features and elevation, which we might expect to be associated with outer concentric faults in the case of a larger, possibly multiring, structure, No such outer rings have been found, although definite patterns are seen in the distribution of karst features outside the crater rim, We explain these patterns as resulting mainly from deformation related to the block fault zone that parallels the shelf edge of eastern Yucatan

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