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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 intergranular voids is generally primary or secondarily enhanced voids within rocks, with average dimensions of 0.00l to 0.lmm. such voids, or pores, may provide interconnected porosity in many karst rocks and allow early water movement under laminar flow conditions [9].?

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Your search for sequence stratigraphy (Keyword) returned 14 results for the whole karstbase:
KIMMERIDGIAN TITHONIAN EUSTACY AND ITS IMPRINTS ON CARBONATE ROCKS FROM THE DINARIC AND THE JURA CARBONATE PLATFORMS, 1991, Strohmenger C. , Deville Q. , Fookes E. ,
The Upper Jurassic stratigraphy and the facies development of the Dinaric carbonate platform of Slovenia (northwest Yugoslavia) are compared with the Jura carbonate platform of southern Jura (southeast France). The similar facies development between the two platforms during the Kimmeridgian and the Tithonian, as well as a pronounced discontinuity in the same stratigraphical position (controlled by dasycladacean algae and/or ammonites), made it reasonable to correlate the two regions. This discontinuity is marked by a bauxite horizon and a karst breccia in south Slovenia (inner platform), and by a black-pebble conglomerate (inner platform) and a reef breccia (outer platform) in the southern Jura. These features are interpreted as type 1 sequence boundaries related to a global fall of sea level. In southern Jura, biostratigraphical elements situate the sequence boundary between the Eudoxus and the <> ( = Elegans) zones, most probably at the end of the Beckeri ( = Autissiodorensis) zone. Integrating this discontinuity into the eustatic sea level curve proposed by the Exxon group (version 3.1) is difficult because the only suitable sequence boundaries, SB 139 and SB 142, are respectively too young (younger than the <> zone) or too old (older than the Eudoxus zone). We therefore suggest to introduce a new sequence boundary within the upper part of the Beckeri zone which would correspond to a <> sequence boundary SB 140. The investigations further show that Clypeina jurassica FAVRE and Campbelliella striata (CAROZZI) BERNIER most likely appear in the Beckeri zone in the realm of the Jura carbonate platform. The same dasycladacean algae assemblage defines a cenozone identified as <> in Slovenia. It therefore seems possible to correlate the stratigraphic limit between <> and <> of the Dinaric carbonate platform with the beginning of the Beckeri zone

THE EVOLUTION OF THE MIDDLE TRIASSIC (MUSCHELKALK) CARBONATE RAMP IN THE SE IBERIAN RANGES, EASTERN SPAIN - SEQUENCE STRATIGRAPHY, DOLOMITIZATION PROCESSES AND DYNAMIC CONTROLS, 1993, Lopezgomez J. , Mas R. , Arche A. ,
The Upper Permian-Triassic strata of the SE Iberian Ranges, eastern Spain, display the classic Germanic-type facies of Buntsandstein, Muschelkalk and Keuper. The Muschelkalk is represented by two carbonate units with a siliciclastic-evaporitic unit in between. Their ages range from Anisian to basal Carnian (Middle Triassic to base of the Upper Triassic). The carbonate units represent ramps that evolved during the early thermal subsidence period which succeeded the first rift phase. Seven facies have been distinguished, representing shoals, tidal flats, organic buildups and lagoons, as well as a karst horizon in the lower carbonatic unit. Most of the carbonates were dolomitised. Three processes of dolomitization are invoked: mixing waters, penecontemporaneous seepage refluxion, and deep burial. The top of the Buntsandstein and the Muschelkalk facies are subdivided into two depositional sequences, including lowstand, transgressive and highstand systems tracts, with superimposed tectonic and eustatic controls

Isolated carbonate platform of Caniego, Spain: A test of the latest Albian worldwide sea-level changes, 1997, Fernandezmendiola Pa, Garciamondejar J,
The upper Albian Caniego carbonate platform consists of a 20-m-thick unit of rudist- and coral-bearing limestones that crops out at the northern margin of the Mena diapir in northern Spain, The limestones were deposited on top of a slowly subsiding area, the Mena paleohigh, a diapiric-induced horst bounded by synsedimentary faults, The Caniego limestones originated in shallow warm tropical waters following a widespread marine transgression at the base of the foraminifera Rotalipora appenninica zone (ammonite Stoliczkaia dispar zone), Around the middle part of the appenninica zone the Caniego limestones underwent subaerial exposure and karst development, Fibrous calcite cements filled the bulk of the fissure-dike and dissolution cavities, Field, petrological, and geochemical data indicate that the fibrous calcites are meteoric flowstones, delta(18)O values in these cements range from -3 parts per thousand to -4.5 parts per thousand and delta(13)C values range from -7 parts per thousand to -14 parts per thousand (relative to the Peedee belemnite [PDB] standard), Thick wedges of nearshore shallow-marine siliciclastic sediments were deposited in paleotrough areas surrounding the Caniego paleohigh while the platform was subaerially exposed, The carbonate platform was drowned in early Cenomanian time and hardground-condensed facies developed during this period (Rotalipora brotzeni zone), Deeper water noncondensed marry sedimentation was reestablished in the mid-Cenomanian (Rotalipora reicheli zone), Comparison of the Iberian Caniego limestones with worldwide successions suggests a coincidence in the timing of platform formation emergence and drowning in several basins of different lithospheric plates, Nevertheless, an overall lack of coordination of sea-level histories from different basins may be related to tectonic movements of the lithospheric plates, Plate rearrangement is invoked as the primary control on relative sea-level changes and sequence development

Visualizing exploration targets through carbonate sequence stratigraphy, 1998, Handford C. Robertson,

Facies differentiation and sequence stratigraphy in ancient evaporite basins - An example from the basal Zechstein (Upper Permian of Germany), 1999, Steinhoff I. , Strohmenger C. ,
Due to excellent preservation, the Werra Anhydrite (Al), the upper member of the Upper Permian Zechstein cycle I (Ist cycle, Z1), is readily studied in terms of the distribution of sulfate facies and sequence stratigraphy that can be interpreted from these facies. In this study cores taken from seven wells in the Southern Zechstein Basin were examined for their sedimentary structures and various petrographic features. Facies interpretation and depositional sequences are based on detailed examination of core material. Four main facies environments have been identified: (I) supratidal (II) intertidal (III) shallow subtidal, and (IV) deeper (hypersaline) subtidal. These are further subdivided into 10 subfacies types: (1) karst and (2) sabkha within the supratidal environment (I), (3) algal tidal-flat, (4) tidal flat and (5) beach deposit within the intertidal environment (II), (6) salina, and (7) sulfate arenites within the shallow subtidal enviromnent (III). The (8) slope subfacies type commonly associated with (9) turbidites and the (10) basin subfacies type subdivide the deeper subtidal environment (IV). Vertical stacking patterns of these facies and subfacies types reveal the sequence stratigraphic development of the sulfate cycles in response to sea-level and salinity fluctuations. The lower Werra Anhydrite (belonging to Zechstein Sequence ZS2) is characterized by a transgressive systems tract (IST) overlying the transgressive surface of Zechstein Sequence ZS2 within the Al-underlying upper Zechstein Limestone (Cal). The TST of the AT is several tens of meters thick in platform areas, where it is built up by sulfate arenites and swallow-tail anhydrite-after-gypsum, and thins out to a few meters of thickness toward the condensed basinal section, where laminites ('Linien-Anhydrit') are predominant. Most of the Al succession consists of three relatively thick parasequences belonging to the highstand systems tract (HST) that shows typical prograding sets. Enhanced platform Buildup, including sulfate arenites, salina deposits, intertidal sediments, and sabkha precipitation as well as turbidite shedding off the platforms produced marginal ''sulfate walls' up to 400 m thick as platform to slope portions of the Werra Anhydrite. Seaward, the Al thins to a few tens of meters of laminated sulfate basin muds. Increasingly pronounced Al topography during highstand narrowed the slope subfacies belt parallel to the platform margin This contrasts with the broad but considerably thinner slope deposits of transgressive times with much shallower slopes. The ensuing sea-level lowstand is reflected by a sequence boundary on top of the karstified Al-platform and a lowstand wedge (Zechstein Sequence ZS3) overlying portions of the slope and basinal subfacies of the Al highstand systems tract Beyond the lateral limits of the lowstand wedge, the sequence boundary merges with the transgressive surface of ZS3, shown by the lithologic change from the Al anhydrites to the overlying carbonates of the Stassfurt Carbonates ('Haupt Dolomit' Main Dolomite, Ca2). The Basal Anhydrite (A2), which overlies and seals the carbonate reservoir of the Ca2, can also be subdivided into systems tracts by means of facies analysis. It is, however, much less complex than the Al and is comprised almost exclusively of a transgressive systems tract of Zechstein Sequence ZS4

Sequence stratigraphy of the type Dinantian of Belgium and its correlation with northern France (Boulonnais, Avesnois), 2001, Hance L. , Poty E. , Devuyst F. X. ,
The relative influences of local tectonics and global eustasy in the architecture of the sedimentary units of the Namur-Dinant Basin (southern Belgium) are determined. Nine third-order sequences are recognised. During the Lower Tournaisian (Hastarian and lower Ivorian) a homoclinal ramp extended from southern Belgium through southern England (Mendips) and into southern Ireland. From the upper Ivorian to the lower Visean rapid facies changes occurred due to progradation and increasing prominence of Waulsortian mudmounds. Progradation gradually produced a situation in which inner shelf facies covered the Namur (NSA), Condroz (CSA) and southern Avesnes (ASA) sedimentation areas, whereas outer shelf facies were restricted to the Dinant sedimentation area (DSA). During the middle and late Viscan a broad shelf was established from western Germany to southern Ireland. Because the shelf built up mainly by aggradation, parasequences can be followed over a large area. An early phase of Variscan shortening is perceptible during the Livian. The stratigraphic gap between the first Namurian sediments (E2 Goniatite Zone) and the underlying Visean varies from place to place, but is more important in the north. Sequence 1 straddles the Devonian-Carboniferous boundary. It starts with a transgressive system tract (TST) corresponding to the Etroeungt Formation (Fm.) and its lateral equivalent (the upper part of the Comb lain-au-Pont Fin.), and to the lower member of the Hastiere Fin. The highstand system tract (HST) is represented by the middle member of the Hastiere Fin. which directly overlies Famennian silicielastics in the northern part of the NSA. Sequence 2 starts abruptly, in the DSA and CSA, with the upper member of the Hastiere Fin. as the TST. The maximum flooding surface (MFS) lies within the shales of the Pont d'Arcole Fin., whereas the thick-bedded crinoidal limestones of the Landelies Fm. form the HST. Sequence 3 can clearly be recognised in the DSA and CSA. Its TST is formed by the Maurenne Fm. and the Yvoir Fm. in the northern part of the DSA and by the Maurenne Fm. and the Bayard Fin. in the southern part of the DSA. The Ourthe Fin. represents the HST. Growth of the Waulsortian mudmounds started during the TST. Sequence 4 shows a significant change of architecture. The TST is represented by the Martinrive Fm. in the CSA and the lower part of the Leffe Fin. in the DSA. The HST is marked by the crinoidal rudstones of the Flemalle Member (Mbr.) and the overlying oolitic limestones of the Avins Mbr. (respectively lower and upper parts of the Longpre Fin.). These latter units prograded far southwards, producing a clinoform profile. Sequence 5 is only present in the DSA and in the Vise sedimentation area (VSA). The TST and the HST form most of the Sovet Fm. and its equivalents to the south, namely, the upper part of the Leffe Fm. and the overlying Molignee Fm. In the VSA, the HST is locally represented by massive grainstones. Sequence 6 filled the topographic irregularities inherited from previous sedimentation. In the CSA, NSA and ASA the TST is formed by the peritidal limestones of the Terwagne Fm. which rests abruptly on the underlying Avins Nibr. (sequence 4) with local karst development. In the DSA, the TST corresponds to the Salet Fin. and, further south, to the black limestones of the strongly diachronous Molignee Fin. Over the whole Namur-Dinant Basin, the sequence ends with the thick-bedded packstones and grainstones of the Neffe Frn. as the HST. Sequence 7 includes the Lives Fm. and the lower part of the Grands-Malades Fm. (Seilles Mbr. and its lateral equivalents), corresponding respectively to the TST and HST. Sequence 8 corresponds to the Bay-Bonnet Mbr. (TST), characterised by stromatolitic limestones. The HST corresponds to the Thon-Samson Mbr. Sequence 9 is the youngest sequence of the Belgian Dinantian in the CSA and DSA. It includes the Poilvache Nibr. (TST, Bonne Fm.) and the Anhee Fm. (HST). These units are composed of shallowing-upward parasequences. The uppermost Visean and basal Namurian are lacking in southern Belgium where sequence 9 is directly capped by Namurian E2 silicielastics. In the VSA, sequence 9 is well developed

The sequence stratigraphy, sedimentology, and economic importance of evaporite-carbonate transitions: a review, 2001, Sarg J. F. ,
World-class hydrocarbon accumulations occur in many ancient evaporite-related basins. Seals and traps of such accumulations are, in many cases, controlled by the stratigraphic distribution of carbonate-evaporite facies transitions. Evaporites may occur in each of the systems tracts within depositional sequences. Thick evaporite successions are best developed during sea level lowstands due to evaporative drawdown. Type 1 lowstand evaporite systems are characterized by thick wedges that fill basin centers, and onlap basin margins. Very thick successions (i.e. saline giants) represent 2nd-order supersequence set (20-50 m.y.) lowstand systems that cap basin fills, and provide the ultimate top seals for the hydrocarbons contained within such basins.Where slope carbonate buildups occur, lowstand evaporites that onlap and overlap these buildups show a lateral facies mosaic directly related to the paleo-relief of the buildups. This facies mosaic, as exemplified in the Silurian of the Michigan basin, ranges from nodular mosaic anhydrite of supratidal sabkha origin deposited over the crests of the buildups, to downslope subaqueous facies of bedded massive/mosaic anhydrite and allochthonous dolomite-anhydrite breccias. Facies transitions near the updip onlap edges of evaporite wedges can provide lateral seals to hydrocarbons. Porous dolomites at the updip edges of lowstand evaporites will trap hydrocarbons where they onlap nonporous platform slope deposits. The Desert Creek Member of the Paradox Formation illustrates this transition. On the margins of the giant Aneth oil field in southeastern Utah, separate downdip oil pools have accumulated where dolomudstones and dolowackestones with microcrystalline porosity onlap the underlying highstand platform slope.Where lowstand carbonate units exist in arid basins, the updip facies change from carbonates to evaporite-rich facies can also provide traps for hydrocarbons. The change from porous dolomites composed of high-energy, shallow water grainstones and packstones to nonporous evaporitic lagoonal dolomite and sabkha anhydrite occurs in the Upper Permian San Andres/Grayburg sequences of the Permian basin. This facies change provides the trap for secondary oil pools on the basinward flanks of fields that are productive from highstand facies identical to the lowstand dolograinstones. Type 2 lowstand systems, like the Smackover Limestone of the Gulf of Mexico, show a similar relationship. Commonly, these evaporite systems are a facies mosaic of salina and sabkha evaporites admixed with wadi siliciclastics. They overlie and seal highstand carbonate platforms containing reservoir facies of shoalwater nonskeletal and skeletal grainstones. Further basinward these evaporites change facies into similar porous platform facies, and contain separate hydrocarbon traps.Transgressions in arid settings over underfilled platforms (e.g. Zechstein (Permian) of Europe; Ferry Lake Anhydrite (Cretaceous), Gulf of Mexico) can result in deposition of alternating cyclic carbonates and evaporites in broad, shallow subaqueous hypersaline environments. Evaporites include bedded and palmate gypsum layers. Mudstones and wackestones are deposited in mesosaline, shallow subtidal to low intertidal environments during periodic flooding of the platform interior.Highstand systems tracts are characterized by thick successions of m-scale, brining upward parasequences in platform interior settings. The Seven Rivers Formation (Guadalupian) of the Permian basin typifies this transition. An intertonguing of carbonate and sulfates is interpreted to occur in a broad, shallow subaqueous hypersaline shelf lagoon behind the main restricting shelf-edge carbonate complex. Underlying paleodepositional highs appear to control the position of the initial facies transition. Periodic flooding of the shelf interior results in widespread carbonate deposition comprised of mesosaline, skeletal-poor peloid dolowackestones/mudstones. Progressive restriction due to active carbonate deposition and/or an environment of net evaporation causes brining upward and deposition of lagoonal gypsum. Condensed sections of organic-rich black lime mudstones occur in basinal areas seaward of the transgressive and highstand carbonate platforms and have sourced significant quantities of hydrocarbons

Sequence Stratigraphy of the Neoproterozoic Infra Krol Formation and Krol Group, Lesser Himalaya, India, 2002, Jiang Ganqing, Christieblick Nicholas, Kaufman Alan J. , Banerjee Dhiraj M. , Rai Vibhuti,
A sequence stratigraphic study of terrigenous and carbonate rocks of the Infra Krol Formation and Krol Group in the Lesser Himalaya fold and thrust belt of northern India was undertaken as part of a broader investigation of the significance of carbon isotope data in Neoproterozoic successions. Eight regional stratigraphic discontinuities were traced over a distance of nearly 300 km, and interpretations were anchored in a series of local studies involving the mapping of key beds and the measurement of closely spaced sections. Three of the regional surfaces are interpreted as sequence boundaries on the basis of (1) locally developed incised valleys < 60 m deep; (2) paleokarstic depressions with < 50 m of mappable relief; (3) subaerial dissolution and weathering products (breccias and calcrete) filling vertical fissures, dikes, cavities, and shallow depressions in underlying carbonate rocks; and (4) small-scale evidence for subaerial exposure at an erosion surface. The remaining five discontinuities are regional flooding surfaces identified on the basis of either facies changes with an abrupt upward deepening across the surface or transitions in facies stacking patterns, typically from forestepping to backstepping. A glacio-eustatic origin is permitted, although not required, for the three sequence boundaries, but no evidence has been found for marked lowering of sea level at other horizons. A mismatch between the stratigraphic location of sequence boundaries and carbon isotope minima suggests that local diagenetic alteration or oceanographic phenomena unrelated to glaciation may be in part responsible for observed isotopic variation, and that small ice sheets may have existed during apparently nonglacial times without producing either cap carbonates or negative carbon isotope excursions

Seismic stratigraphy of Late Quaternary deposits from the southwestern Black Sea shelf: evidence for non-catastrophic variations in sea-level during the last ~10[punctuation space]000 yr, 2002, Aksu Ae, Hiscott Rn, Yasar D, Isler Fi, Marsh S,
Detailed interpretation of single channel seismic reflection and Huntec deep-tow boomer and sparker profiles demonstrates that the southwestern Black Sea shelf formed by a protracted shelf-edge progradation since the Miocene-Pliocene. Five seismic-stratigraphic units are recognized. Unit 1 represents the last phase of the progradational history, and was deposited during the last glacial lowstand and Holocene. It is divided into four subunits: Subunit 1A is interpreted as a lowstand systems tract, 1B and 1C are interpreted as a transgressive systems tract, and Subunit 1D is interpreted as a highstand systems tract. The lowstand systems tract deposits consist of overlapping and seaward-prograding shelf-edge wedges deposited during the lowstand and the subsequent initial rise of sea level. These shelf-edge wedges are best developed along the westernmost and easternmost segments of the study area, off the mouths of rivers. The transgressive systems tract deposits consist of a set of shingled, shore-parallel, back-stepping parasequences, deposited during a phase of relatively rapid sea-level rise, and include a number of prograded sediment bodies (including barrier islands, beach deposits) and thin veneers of seismically transparent muds showing onlap onto the flanks of older sedimentary features. A number of radiocarbon dates from gravity cores show that the sedimentary architecture of Unit 1 contain a detailed sedimentary record for the post-glacial sea-level rise along the southwestern Black Sea shelf. These data do not support the catastrophic refilling of the Black Sea by waters from the Mediterranean Sea at 7.1 ka postulated by [Ryan, Pitman, Major, Shimkus, Maskalenko, Jones, Dimitrov, Gorur, Sakinc, Yuce, Mar. Geol. 138 (1997) 119-126], [Ryan, Pitman, Touchstone Book (1999) 319 pp.], and [Ballard, Coleman, Rosenberg, Mar. Geol. 170 (2000) 253-261]

Late Quaternary history of the Marmara Sea and Black Sea from high-resolution seismic and gravity-core studies, 2002, Hiscott R. N. , Aksu A. E. ,
Lithologic and multi-proxy paleoenvironmental data from 21 dated cores have been used to define three allostratigraphic units (allounits) within the late Quaternary successions of the Marmara Sea and Black Sea. Allounits are bounded by unconformities and their correlative conformities. In both regions, Allounit A extends from the seafloor downward to a ~12-11-ka sequence boundary, which is a major shelf-crossing unconformity in water depths less than ~100-110 m. In deep basins of the Marmara Sea, the lower part of Allounit A, designated Subunit A2, is a laminated sapropel, M1. On the shelf, Subunit A2 consists of backstepping delta lobes and early-transgressive barrier islands and sand sheets. Allounit B has only been recovered in Marmara Sea cores collected at water depths greater than ~90 m, and represents basinal or prodeltaic deposition during the 23-12-ka late Pleistocene lowstand. During the last glacial maximum, the shelves surrounding the Marmara Sea were subaerially exposed, and deltas of Allounit B accumulated along the present-day shelf edge. Following the post-glacial rise of global sea level to -75 m at ~12 ka, the Marmara Sea quickly became inundated and thereafter rose in synchroneity with the Mediterranean. By ~10 ka, the Black Sea rose to start spilling into the Marmara Sea, leading to establishment of a brackish-water lid that has persisted to the modern day. The strongest Black Sea outflow began at ~10 ka and persisted to ~6 ka, promoting the accumulation of sapropel M1 in the deep Marmara Sea, and progradation of an overflow delta just south of the exit from the Bosphorus Strait. Allounit C is a laminated sapropel (M2) in basinal cores, dated at ~30-23 ka. Like M1, it is believed that M2 accumulated during a period of increased brackish-water input into the Marmara Sea mainly from the Black Sea. In the Black Sea, wave erosion kept the shelf stripped of unconsolidated sediments during the falling sea level associated with the last glaciation and subsequent early stages of the post-glacial Holocene transgression. This erosion created a major unconformity, [alpha]. Shelf-edge deltas of Allounit B received their sediment during the last lowstand from small rivers that likely coalesced into a single system toward the shelf edge, at modern water depths of -100 to -110 m. These deltas were active until ~11-10.5 ka. Subsequently, sea level in the Black Sea rose to -40 m by ~10 ka, and a set of backstepping barrier islands developed on the shelf as part of the associated transgressive systems tract. Once water level reached -40 m, continued sea-level rise stalled until ~9 ka as the Black Sea began to spill across the Bosphorus Strait into the Marmara Sea

Palaeokarst, pseudokarst sequence stratigraphy in Devonian reef complexes of the Canning Basin, Western Australia,, 2002, Playford P.

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

Heterogeneity in Fill and Properties of Karst-Modified Syndepositional Faults and Fractures: Upper Permian Capitan Platform, New Mexico, U.S.A, 2006, Kosa Eduard, Hunt David W. ,
This study examines the heterogeneity in properties of syndepositional faults and fractures found in the Upper Permian Capitan carbonate platform, Guadalupe Mountains, New Mexico. Syndepositional faults and fractures grew incrementally, and were repeatedly exploited by early karst as the platform developed. Primary fault and fracture rocks were preferentially dissolved to form structure-controlled paleocaverns, which were subsequently filled with platform-derived sediments. These are divided here into three groups: (i) carbonate-dominated, (ii) siliciclastic-dominated, and (iii) mixed carbonate-siliciclastic lithologies. The affinity of the paleocavern-filling deposits to platform strata permits linking of the different fill types to different stages of sea-level cycle. Consequently, periods of dissolution and deposition within paleocaverns can be tied to the platform's sequence stratigraphy. Paleocavern-filling sediments have a distinct vertical stratigraphy, and are observed to vary with distance from the platform margin over a distance of 2.6 km. Their distribution is thus to some extent predictable. Vertical and lateral variability in paleocavern fill is chiefly related to siliciclastic-filled karstic chimneys that narrow downwards and tend to become more frequent and laterally extensive upwards. This is because upper structural levels of fault and fracture zones were more frequently opened by early karst, and also because siliciclastics are not prone to dissolution, whereas carbonates are. Across platform, karst-modified faults and fractures located close to the platform margin are dominated by carbonate lithologies. The proportion and vertical penetration of siliciclastics increases with distance from platform margin. These patterns appear to reflect variations in the frequency and duration of subaerial exposure events across the basinward-inclined Capitan platform. The results of this study have implications for understanding properties of early faults and fractures in carbonate strata. Faults and fractures presented here are heterogeneous, and the heterogeneity is related principally to distribution of sedimentary rocks within paleocaverns developed along them. As a consequence, their properties are not related to dimensions or throw, as is the case for faults and fractures within siliciclastic rocks. Data and interpretations presented here have implications for Capitan hydrocarbon reservoirs, and can be applied to characterization of faults and fractures in other carbonate platforms subjected to early deformation

Palustrine Deposits on a Late Devonian Coastal Plain--Sedimentary Attributes and Implications for Concepts of Carbonate Sequence Stratigraphy, 2006, Macneil Alex J. , Jones Brian,
Palustrine deposits in coastal environments can cover thousands of square kilometers and are stratigraphically important. Palustrine deposits that originated in supratidal marshes can be used to track shifts in the shoreline position, whereas palustrine deposits that formed in marshes above the peritidal realm are indicative of subaerial unconformities. Despite the importance of these deposits, there are few documented examples of ancient coastal palustrine deposits, and their sedimentary attributes remain poorly understood. Misinterpretation of coastal palustrine deposits as marine deposits, or calcrete, may partly explain this situation. The Upper Devonian Alexandra Formation, exposed in the Northwest Territories of Canada, is formed of two reef complexes that are separated by a Type I sequence boundary. At the landward part of the platform, this boundary is marked by a succession of coastal-plain deposits that is ~ 50 cm thick. The most distinct aspect of this succession are palustrine deposits characterized by charophytes, skeletal (Rivularia) stromatolites, and various pedogenic features including complex crack networks, root traces, and authigenic kaolinite. Karst features and calcrete, generally regarded as typical indicators of subaerial exposure, are not found. This study highlights the sedimentary attributes that can be used to identify ancient palustrine deposits in marine coastal regions, distinguish these deposits from calcrete, and demonstrates their sequence stratigraphic significance, when found in marine limestone successions. It clearly demonstrates that palustrine deposits, like those found in the Alexandra Formation, should be considered indicative of subaerial unconformities and sequence boundaries, in the same manner as karst and calcrete

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