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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 outlet cave is a cave developed at the point of re-emergence of an underground karst watercourse [19].?

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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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Paleokarst - a Systematic and Regional Review, 1989,

Description
Prepared by some of the world's leading experts in the field, this book is the first summarizing work on the origin, importance and exploitation of paleokarst. It offers an extensive regional survey, mainly concerning the Northern Hemisphere, as well as a thorough analysis of the problems of research into paleokarst phenomena, with particular emphasis on theoretical contributions and practical exploitation. By concentrating on phenomena which have appeared in the course of geological history, the book represents a substantial development in the general theory of paleokarst and demonstrates the advantages of a comprehensive approach to the problem. Considerable emphasis is put on the economic importance of paleokarst phenomena, from the point of view of exploiting significant deposits of mineral raw materials, as well as from a civil engineering and hydrological point of view. Since the publication deals with a boundary scientific discipline, it is intended for specialists from various branches of science: geologists, paleontologists, economic geologists, geographers, mining engineers and hydrogeologists.

Contents
List of Contributors. Foreword.

Part I. Introduction.
Introduction (P. Bosák et al.). Paleokarst as a problem (J. Głazek, P. Bosák, D.C. Ford). Terminology (P. Bosák, D.C. Ford, J. Głazek).

Part II. Regional Review.
Paleokarst of Belgium (Y. Quinif). Paleokarst of Britain (T.D. Ford). Paleokarst of Norway (S.-E. Lauritzen). Paleokarst of Poland (J. Głazek). Paleokarst of Czechoslovakia (P. Bosák, I. Horáček, V. Panoš). Paleokarst of Hungary (G. Bárdossy, L. Kordos). Hydrothermal paleokarst of Hungary (P. Müller). Paleokarst of Italy. Selected examples from Cambrian to Miocene (M. Boni, B. D'Argenio). Paleokarst-related ore deposits of the Maghreb, North Africa (Y. Fuchs, B. Touahri). Paleokarst of Yugoslavia (D. Gavrilović). Paleokarst of Bulgaria (I. Stanev, S. Trashliev). Paleokarst of Romania (M. Bleahu). Paleokarst of the Union of Soviet Socialist Republics (R.A. Tsykin). Paleokarst of China (Zhang Shouyue). Paleokarst of Canada (D.C. Ford). Paleokarst of the United States (M.V. Palmer, A.N. Palmer).

Part III. Mineral Deposits Connected With Karst.
An introduction to karst-related mineral deposits (P. Bosák). Pb-Zn ores (S. Dżułyński, M. Sass-Gustkiewicz). Bauxites (G. Bárdossy). Iron ore deposits in paleokarst (G. Bárdossy, Y. Fuchs, J. Głazek). Clays and sands in paleokarst (P. Bosák). The oceanic karst: modern bauxite and phosphate ore deposits on the high carbonate islands (so-called ``Uplifted Atolls'') of the Pacific Ocean (F.G. Bourrouilh-le Jan). Paleokarst-related uranium deposits (Y. Fuchs).

Part IV. Hydrogeology and Engineering Hazards in Paleokarst Areas.
Paleokarst as an important hydrogeological factor (J. Zötl). Hydrogeological problems of opencast and underground mining of mineral deposits encountered during their exploration, development and exploitation stages (P. Bosák). Hydrogeological problems of the Cracow-Silesia Zn-Pb ore deposits (Z. Wilk). Hydrogeological problems of Hungarian bauxite and coal deposits (T. Böcker, B. Vizy). Paleokarst in civil engineering (A. Eraso). Interaction between engineering and environment in the presence of paleokarst: some case histories (J. Głazek).

Part V. Paleokarst as a Scientific Subject.
Special characteristics of paleokarst studies (I. Horáček, P. Bosák). Tectonic conditions for karst origin and preservation (J. Głazek). Problems of the origin and fossilization of karst forms (P. Bosák). Biostratigraphic investigations in paleokarst (I. Horáček, L. Kordos).

Part VI. Conclusions. Part VII. References. Part VIII. Indexes.
Author Index. Geographical Index. Subject Index.

Bibliographic & ordering Information
Hardbound, ISBN: 0-444-98874-2, 726 pages, publication date: 1989
Imprint: ELSEVIER


La karstification de l'le haute carbonate de Makatea (Polynsie franaise) et les cycles eustatiques et climatiques quaternaires, 1991, Dessay J. , Pouchan Y. , Girou A. , Humbert L. , Malezieux J.
THE KARST 0F MAKATEA ISLAND (FRENCH POLYNESIA) AND THE CLIMATIC AND GLACIO-EUSTATISM SETTING - Located in the Central Pacific, in the northwestern part of the Tuamotu Archipelago, Makatea island (148 15 W - 15 50 S) is an uplifted, karstic, carbonate construction of Early Miocene age, which reaches 113m in height. From 1906 to 1966, phosphate deposits were exploited on Makatea Island. These phosphate deposits (apatite) overlaid the Miocene series and filled the karstic cavities in the higher regions of the island. Several traces of ancient shorelines can be observed on Makatea: 1/ three different reef formations, which reach about +27m, +7m, +1m above the present mean sea level and respectively dated 400,000 100,000 yr BP, 140,000 30,000 yr BP, between 4,470 150 yr BP and 3,720 13O yr BP; 2/ four distinct marine notch lines on the Early Miocene cliff at about +1m, +7m, +27m and +56m (or +47m on the west coast caused by tilt) above the present mean sea level; 3/ two exposed marine platforms respectively at +29m and +7m above the present mean sea level. The ages of the former makatean shores are inferred by using: (1) the Pacific glacio-eustatic sea-level curve for the last 140,000 yr BP, (2) the Pacific oxygen isotope curve for the last 900,000 yr BP, and (3) a constant uplift rate during the Pleistocene. In this way, according to their age and elevation, the sea-level indicators at about +1m, +7m and +27m (+29m) above the present mean sea level can be respectively related to the Holocene transgression (Flandrian) dated between 6,000 and 1,500 yr BP, to the last Pleistocene interglacial period (Sangamon) dated between about 130,000 and 110,000 yr BP, and to a Middle Pleistocene interglacial period (Yarmouth) dated between about 315,000 and 485,000 yr BP. If we assume that a sea level similar to the present occurred during the Yarmouth inter-glacial period, the uplift rate is valued at 0.085 mm/yr to 0.056 mm/yr. Thus the sea-level associated with the marine notch at about +56m (+47m) may be about 650,000 yr to 1 M.y. old and can be associated with another Pleistocene interglacial period (Aftonian). Consequently, as indicated by the former shores, the sea level fluctuations can be related to the major glacio-eustatic quaternary events. This climatic and eustatic setting is used to explain the karst observed on the Makatea island. Carbonate dissolution and essentially vertical karst genesis were the result of the superposition of several cycles. Each cycle was initially composed of a solution of the carbonates during an interglacial period, followed by a drainage of the saturated solutions during the marine regression associated with the consecutive glacial period. Nevertheless, this scheme is not enough to explain the specific morphology of the makatean karstic cavities and we suggest using insular phosphatisation to explain this karst genesis. It is generally accepted that phosphate rock deposits on coral reef islands are the result of chemical reaction between seabird guano and reef limestone. Furthermore, petrographic and stable isotope studies suggest several generations of phosphorite formation and reworking episodes in the history of these deposits. The primary deposition of phosphates must have begun during a glacial period. This deposition was followed by some redistribution of phosphorites during the interglacial period and by additional precipitation of apatite from meteoric waters. This assumed process of phosphogenesis is consistent with both the field observations and the geodynamic evolution of Makatea. Thus, the particular morphology of the makatean karst can be the result of the dissolution of the carbonates caused by phosphoric acid etching. This acid is derived from the evolution of the phosphorites during the pleistocene interglacial periods.

Evolution des karsts Ocaniens (Karsts, bauxite et phosphates), 1992, Bourrouilhlejan, Fr.
EVOLUTION OF THE PACIFIC OCEAN KARSTS - Karst phenomena constitute one of the main characteristics of the "high carbonate islands" of the Pacific Ocean. They are the key to the under-standing of the geological evolution, the stratigraphy, from Lower Miocene to Pleistocene and mid-Holocene, the diagenesis, mainly dolomitization and the current economic interest based on bauxite and phosphate. The eustatic variations have been numerous over the past 25 million years and can be added or substracted from the emersion and submersion movements of the plate supporting these carbonate platforms. Each island therefore has its own complex geological background with dolomitization, calcrete, bauxitic soils, fossil marine notches and karst surface either submerged or filled with phosphate, which can be mined for profit. Thanks to a thorough study of these platforms, it has been possible to establish an evolution of karst genesis in accordance with the evolution of the Pacific lithosphere and also to draw up a new model of phosphate genesis linked to phosphato-bauxitic soils and meromictic anoxic lakes.

MURUROA ATOLL (FRENCH-POLYNESIA) .1. STRUCTURE AND GEOLOGICAL EVOLUTION, 1992, Buigues D, Gachon A, Guille G,
From a geographical point of view, the atoll of Mururoa belongs to the Tuamotu archipelago. In its largest dimension Mururoa (28 x 10 km) is oriented N080-degrees-E, a direction which is different from that of the other atolls of the Tuamotu, generally oriented parallel to the Pacific plate motion, N130-degrees-E. The atoll of Mururoa is built on a submarine plateau of 130 km long and 30 km wide. The western side of this plateau is 90 km long and N080-degrees-E oriented, the eastern one 40 km long and N095-degrees-E oriented. Three deep main structures of the atoll are revealed by strong aeromagnetic anomalies elongated and oriented once more N080-degrees-E. They represent ancient riftzones, similar to the present time Hawaiian ones. The most important of them, situated at southern end of the atoll, is the prolongation of the eastern plateau. The principal petrographic facies have been defined from the numerous drill holes bored in the upper 1,100 m. From the base to the top are represented volcanic deposits, a volcano-sedimentary serie of both carbonate and volcanic origin and finally reefal carbonates (limestones and dolomites). The volcanic facies represent successively submarine, transitional and aerial volcanic activity. They are commonly affected by early stage of hydrothermalism, due to lava-sea-water chemical interaction, and are frequently supported by differentiated dykes, occasionally interrupted by reefal limestones. The main geometrical distribution of the facies through the atoll and the radiochronology lead to the following model of formation : during early stages of the atoll building two main separate edifices emerged before joining and forming a single volcano. This double structure was similar to the present time morphology of Tahiti. The volcanic activity ceased 10.6 Ma ago, an age which perfectly suits a hot spot origin, at present located to the south-east of Pitcairn island

GENERAL CENOZOIC EVOLUTION OF THE MALDIVES CARBONATE SYSTEM (EQUATORIAL INDIAN-OCEAN), 1992, Aubert O, Droxler Aw,
Analyses and interpretation of an industrial multi-channel seismic grid, a 2.3 km-deep industrial well (NMA-1) and two ODP (Sites 715 and 716), have generated new insights into the evolution of the Maldives carbonate system, Equatorial Indian Ocean. The present physiography of the Maldives Archipelago, a double chain of atolls delineating an internal basin, corresponds only to the latest phase of a long and dynamic evolution, far more complex than the simple vertical build-up of reef caps on top of thermally subsiding volcanic edifices. Through the Cenozoic evolution of the Maldives carbonate system, distinct phases of vertical growth (aggradation), exposure, regional or local drowning, and recovery of the shallow banks by lateral growth (progradation) have been recognized. The volcanic basement underlying the Maldives Archipelago is interpreted to be part of a volcanic ridge generated by the northern drift of the Indian plate on top of the hotspot of the island of Reunion. The volcanic basement recovered at well NMA-1 and ODP Site 715 has been radiometrically dated as 57.2 1.8 Ma (late Paleocene) by 40Ar-39Ar. Seismic and magnetic data indicate that this volcanic basement has been affected by a series of NNE-SSW trending subvertical faults, possibly associated with an early Eocene strike-slip motion along an old transform zone. The structural topography of the volcanic basement apprears to have dictated the initial geometry of the Eocene and early Oligocene Maldives carbonate system. Biostratigraphic analyses of samples, recovered by drilling in Site 715 and exploration well NMA-1, show that the Maldives shallow carbonate system was initiated during the early Eocene on top of what were originally subaerial volcanic edifices. The Eocene shallow carbonate sequence, directly overlying the volcanic basement at NMA-1, is dolomitized and remains neritic in nature, suggesting low subsidence rates until the early Oligocene. During this first phase of the Maldives carbonate system evolution, shallow carbonate facies aggraded on top of basement highs and thick deep-water periplatform sediments were deposited in some central seaways, precursors of the current wider internal basins. In the middle Oligocene, a plate reorganization of the equatorial Indian Ocean resulted in the segmentation of the hotspot trace and the spreading of the Maldives away from the transform zone. This plate reorganization resulted in increasing subsidence rates at NMA-1, interpreted to be associated with thermal cooling of the volcanic basement underlying the Maldives carbonate system. This middle Oligocene event also coincides with a regional irregular topographic surface, considered to represent a karst surface produced by a major low-stand. Deep-water carbonate facies, as seen in cuttings from NMA-1, overlie the shallow-water facies beneath the karst surface which can, therefore, be interpreted as a drowning unconformity. In the late Oligocene, following this regional deepening event, one single central basin developed, wider than its Eocene counterparts, and the current intraplatform basin was established. Since the early to middle Miocene, the shallow carbonate facies underwent a stage of local recovery by progradation of neritic environments towards the central basin. The simultaneous onset in the early middle Miocene of the monsoonal wind regime may explain the development of bidirectional slope progradations in the Maldives. During the late Miocene and the early Pliocene, several carbonate banks were locally drowned, whereas others (i.e. Male atoll) display well-developed lateral growth through margin progradations during the same interval. Differential carbonate productivity among the atolls could explain these diverse bank responses. High-frequency glacialeustatic sea-level fluctuations in the late Pliocene and Pleistocene resulted in periodic intervals of bank exposure and flooding, and developed the present-day physiography of atolls, with numerous faros along their rims and within their lagoons

VOID-FILLING DEPOSITS IN KARST TERRAINS OF ISOLATED OCEANIC ISLANDS - A CASE-STUDY FROM TERTIARY CARBONATES OF THE CAYMAN-ISLANDS, 1992, Jones B. ,
Caves, fossil mouldic cavities, sinkholes and solution-widened joints are common in the Cayman and Pedro Castle members of the Bluff Formation (Oligocene Miocene) on Grand Cayman and Cayman Brac because they have been subjected to repeated periods of karst development over the last 30 million years. Many voids contain a diverse array of sediments and/or precipitates derived from marine or terrestrial environs, mineral aerosols, and groundwater. Exogenic sediment was transported to the cavities by oceanic storm waves, transgressive seas, runoff following tropical rain storms and/or in groundwater. At least three periods of deposition were responsible for the occlusion of voids in the Cayman and Pedro Castle members. Voids in the Cayman Member were initially filled or partly filled during the Late Oligocene and Early Miocene. This was terminated with the deposition of the Pedro Castle Member in the Middle Miocene. Subsequent exposure led to further karst development and void-filling sedimentation in both the Cayman and Pedro Castle members. Speleothems are notably absent. The void-filling deposits formed during these two periods, which were predominantly marine in origin, were pervasively dolomitized along with the host rock 2 5 million years ago. The third period of void-filling deposition. after dolomitization of the Bluff Formation, produced limestone, various types of breccia, terra rossa, speleothemic calcite and terrestrial oncoids. Most of these deposits formed since the Sangamon highstand 125 000 years ago. Voids in the present day karst are commonly filled or partly filled with unconsolidated sediments. Study of the Bluff Formation of Grand Cayman and Cayman Brac shows that karst terrains on isolated oceanic islands are characterized by complex successions of void-filling deposits that include speleothems and a variety of sediment types. The heterogenetic nature of these void-filling deposits is related to changes in sea level and climatic conditions through time

MATHEMATICAL-MODELING OF CATCHMENT MORPHOLOGY IN THE KARST OF GUIZHOU, CHINA, 1992, Ming T. ,
This paper establishes statistical relationships describing the morphology of three contrasting drainage areas in the karst plateau of Guizhou. A landscape model proposed takes as its basis a two-tiered morphology: an upper tier of peaks and cols which maintains a dynamic equilibrium; and a lower tier defined by depression or valley bases which can evolve differentially in time and space. Thus equilibrium and evolutionary processes coexist in this type of karst landscape within the same timespan. The evlution of subcatchments is shown to be not necessarily the same as that of the total catchment because of tectonic factors

The astronomical theory of climate and the age of the Brunhes-Matuyama magnetic reversal, 1994, Bassinot Fc, Labeyrie Ld, Vincent E, Quidelleur X, Shackleton Nj, Lancelot Y,
Below oxygen isotope stage 16, the orbitally derived time-scale developed by Shackleton et al. [1] from ODP site 677 in the equatorial Pacific differs significantly from previous ones [e.g., 2-5], yielding estimated ages for the last Earth magnetic reversals that are 5-7% older than the K/Ar values [6-8] but are in good agreement with recent Ar/Ar dating [9-11]. These results suggest that in the lower Brunhes and upper Matuyama chronozones most deep-sea climatic records retrieved so far apparently missed or misinterpreted several oscillations predicted by the astronomical theory of climate. To test this hypothesis, we studied a high-resolution oxygen isotope record from giant piston core MD900963 (Maldives area, tropical Indian Ocean) in which precession-related oscillations in [delta]18O are particularly well expressed, owing to the superimposition of a local salinity signal on the global ice volume signal [12]. Three additional precession-related cycles are observed in oxygen isotope stages 17 and 18 of core MD900963, compared to the composite curves [4,13], and stage 21 clearly presents three precession oscillations, as predicted by Shackleton et al. [1]. The precession peaks found in the [delta]18O record from core MD900963 are in excellent agreement with climatic oscillations predicted by the astronomical theory of climate. Our [delta]18O record therefore permits the development of an accurate astronomical time-scale. Based on our age model, the Brunhes-Matuyama reversal is dated at 775 10 ka, in good agreement with the age estimate of 780 ka obtained by Shackleton et al. [1] and recent radiochronological Ar/Ar datings on lavas [9-11]. We developed a new low-latitude, Upper Pleistocene [delta]18O reference record by stacking and tuning the [delta]18O records from core MD900963 and site 677 to orbital forcing functions

MESSINIAN (LATE MIOCENE) KARST ON GRAND-CAYMAN, BRITISH-WEST-INDIES - AN EXAMPLE OF AN EROSIONAL SEQUENCE BOUNDARY, 1994, Jones B. , Hunter I. G. ,
The Cayman Unconformity, which separates the Pedro Castle Formation (Pliocene) from the underlying Cayman Formation (Miocene), is a sequence boundary that developed during the Messinian, when sea level was at a lowstand due to glaciation in the Southern Hemisphere. By the end of the Messinian, Grand Cayman was an atoll-like island that had an elevated peripheral rim that was up to 41 m above the central depression. The Cayman Formation contains paleocaves and paleosinkholes that were linked to the Cayman Unconformity. The topography on the Cayman Unconformity is attributed to erosional processes, because (1) there is no evidence of carbonates that formed by constructional processes (i.e., reefs, dunes) in the elevated peripheral rim, and (2) there is ample evidence of dissolutional features in the Cayman Formation. The topography developed on the interior of Grand Cayman during the Messinian was uneven. A deep, basin-like depression, with its base as much as 50 m below the peripheral rim, formed on the western part of the island. By comparison, the floor of the depression on the eastern part of the island was 20-30 m higher. The difference in the topography, which is a reflection of the amount of bedrock dissolution, suggests that the effective rainfall was highest over the western part of the island. The relief on the Cayman Unconformity and associated structures shows that base level during the Messinian karst development was at least 41 m below present-day sea level. This is also provides an estimate of the Messinian lowstand position because the base level in oceanic karst settings is usually controlled by sea level

DEBATE ABOUT IRONSTONE - HAS SOLUTE SUPPLY BEEN SURFICIAL WEATHERING, HYDROTHERMAL CONVECTION, OR EXHALATION OF DEEP FLUIDS, 1994, Kimberley M. M. ,
Ironstone is any chemical sedimentary rock with > 15% Fe. An iron formation is a stratigraphic unit which is composed largely of ironstone. The solutes which have precipitated to become ironstone have dissolved from the Earth's surface, from the upper crust, e.g. the basaltic layer of oceanic crust, or from deeper within the Earth. Genetic modellers generally choose between surficial weathering, e.g. soil formation, and hydrothermal fluids which have convected through the upper kilometre of oceanic crust. Most genetic modellers attribute cherty laminated iron formations to hydrothermal convection and noncherty oolitic iron formations to surficial weathering. However, both types of iron formations are attributable to the exhalation of fluids from a source region too deep for convection of seawater. Evidence for a deep source of ferriferous fluids comes from a comparison of ancient ironstone with modern ferriferous sediment in coastal Venezuela. A deep-source origin for ironstone has wide-ranging implications for the origins of other chemical sedimentary ores, e.g. phosphorite, manganostone, bedded magnesite, sedimentary uranium ore, various karst-filling ores, and even petroleum. Preliminary study of a modern oolitic iron deposit described herein suggests that the source of iron and silica to iron formations may have been even deeper than envisioned within most hydrothermal convection models

BLUE HOLES - DEFINITION AND GENESIS, 1995, Mylroie J. E. , Carew J. L. , Moore A. I. ,
Blue holes are karst features that were initially described from Bahamian islands and banks, which have been documented for over 100 years. They are water-fined vertical openings in the carbonate rock that exhibit complex morphologies, ecologies, and water chemistries. Their deep blue color, for which they are named, is the result of their great depth, and they may lead to cave systems below sea level Blue holes are polygenetic in origin, having formed: by drowning of dissolutional sinkholes and shafts developed in the vadose zone; by phreatic dissolution along an ascending halocline; by progradational collapse upward from deep dissolution voids produced in the phreatic zone; or by fracture of the bank: margin. Blue holes are the cumulative result of carbonate deposition and dissolution cycles which have been controlled by Quaternary glacioeustatic fluctuations of sea-level. Blue holes have been widely studied during the past 30 years, and they have provided information regarding karst processes, global climate change, marine ecology, and carbonate geochemistry. The literature contains a wealth of references regarding blue holes that are at times misleading, and often confusing. To standardize use of the term blue hob, and to familiarize the scientific community with their nature, we herein define them as follows: ''Blue holes are subsurface voids that are developed in carbonate banks and islands; are open to the earth's surface; contain tidally-influenced waters of fresh, marine, or mixed chemistry; extend below sea level for a majority of their depth; and may provide access to submerged cave passages.'' Blue holes are found in two settings: ocean holes open directly into the present marine environment and usually contain marine water with tidal now; inland blue holes are isolated by present topography from surface marine conditions, and open directly onto the land surface or into an isolated pond or lake, and contain tidally-influenced water of a variety of chemistries from fresh to marine

Early Accounts of Caves in Mauritius, 1995, Middleton, Greg

A survey is attempted of published accounts of lava caves on the Indian Ocean island of Mauritius up to the early 20th century. A number of writers mentioned caves as part of the natural curiosities of the island, though there was a high level of information recycling. The earliest written cave account dates from 1769; the cave it relates to is also the most written-about and, on current knowledge, is the oldest on the island. On neighbouring Rodrigues the earliest record is thought to date from 1789.


Petroleum geology of the Black Sea, 1996, Robinson A. G. , Rudat J. H. , Banks C. J. , Wiles R. L. F. ,
The Black Sea comprises two extensional basins formed in a back-arc setting above the northward subducting Tethys Ocean, close to the southern margin of Eurasia. The two basins coalesced late in their post-rift phases in the Pliocene, forming the present single depocentre. The Western Black Sea was initiated in the Aptian, when a part of the Moesian Platform (now the Western Pontides of Turkey) began to rift and move away to the south-east. The Eastern Black Sea probably formed by separation of the Mid-Black Sea High from the Shatsky Ridge during the Palaeocene to Eocene. Subsequent to rifting, the basins were the sites of mainly deep water deposition; only during the Late Miocene was there a major sea-level fall, leading to the development of a relatively shallow lake. Most of the margins of the Black Sea have been extensively modified by Late Eocene to recent compression associated with closure of the Tethys Ocean. Gas chromatography--mass spectrometry and carbon isotope analysis of petroleum and rock extracts suggest that most petroleum occurrences around the Black Sea can be explained by generation from an oil-prone source rock of most probably Late Eocene age (although a wider age range is possible in the basin centres). Burial history modelling and source kitchen mapping indicate that this unit is currently generating both oil and gas in the post-rift basin. A Palaeozoic source rock may have generated gas condensate in the Gulf of Odessa. In Bulgarian waters, the main plays are associated with the development of an Eocene foreland basin (Kamchia Trough) and in extensional structures related to Western Black Sea rifting. The latter continue into the Romanian shelf where there is also potential in rollover anticlines due to gravity sliding of Neogene sediments. In the Gulf of Odessa gas condensate has been discovered in several compressional anticlines and there is potential in older extensional structures. Small gas and oil discoveries around the Sea of Azov point to further potential offshore around the Central Azov High. In offshore Russia and Georgia there are large culminations on the Shatsky Ridge, but these are mainly in deep water and may have poor reservoirs. There are small compressional structures off the northern Turkish coast related to the Pontide deformation; these may include Eocene turbidite reservoirs. The extensional fault blocks of the Andrusov Ridge (Mid-Black Sea High) are seen as having the best potential for large hydrocarbon volumes, but in 2200 m of water

Chapter 11 Southern Svalbard:Bjornoya and submarine geology, 1997, Harland W. Brian, Geddes Isobel, Doubleday Paul A. ,
The area south of Spitsbergen (about 76{degrees}31'N) to latitude 74{degrees}N, and between longitudes 10{degrees}E and 35{degrees}E, by which Svalbard was first defined, contains the small island of Bjornoya (Bear Island, Baren Insel) and the rest is sea (Fig. 11.1). The 500 m isobath conveniently separates the edge of the Barents shelf from the Norwegian Sea Basin which runs south from Spitsbergen between 14{degrees} and 16{degrees}30'E. To the east, the large shallow area, Spitsbergenbanken, less than 100 m deep, supports Bjornoya at its southwestern end, extends northeast to Hopen and joins Edge{degrees}ya. It is separated from Spitsbergen to the north by the Storfjordyrenna and to the east by Hopendjupet. These submarine valleys appear to drain westwards into the ocean deep with deltaic fronts convex westward. This chapter focuses first on Bjornoya which though small is a key outcrop in the Barents Sea and distinct in many respects from Spitsbergen being about 250 km distant. The chapter then surveys a little of what is known of the surrounding sub-sea area. Bjornoya (20 km N-S and 15 km E-W), as the southern outpost of Svalbard, has long been a key to Svalbard geology since it is generally free all year from tight sea ice. But though its location is convenient, its cliffs generally bar access. Indeed there are very few places where landing by other than inflatable dinghy are feasible. After the island had been claimed by a Norwegian syndicate in 1915 mining of Tournaisian coal began in 1916 and exported over 116000 ... This 250-word extract was created in the absence of an abstract

Groundwater circulation and geochemistry of a karstified bank-marginal fracture system, South Andros Island, Bahamas, 1997, Whitaker Fiona F. , Smart Peter L. ,
On the east coast of South Andros Island, Bahamas, a major bank-marginal fracture system characterised by vertically extensive cavern systems (blue holes) is developed sub-parallel to the steep-sided deep-water re-entrant of the Tongue of the Ocean. In addition to providing a discharge route for meteoric, mixed and geochemically evolved saline groundwaters, a strong local circulation occurs along the fracture system. This generates enhanced vertical mixing within voids of the fracture system, evidenced by the increasing mixing zone thickness, and the thinning and increasing salinity of brackish lens waters from north to south along the fracture system. Furthermore, tidally driven pumping of groundwaters occurs between the fracture and adjacent carbonate aquifer affecting a zone up to 200 m either side of the fracture.The resultant mixing of groundwaters of contrasting salinity and within and along the fracture system and with the surrounding aquifer waters, together with bacterial oxidation of organic matter, generates significant potential for locally enhanced diagenesis. Undersaturation with respect to calcite within the fresh (or brackish)-salt water mixing zone is observed in the fracture system and predicted in the adjacent aquifer, while mixing between the brackish fracture lens and surrounding high fresh waters causes dissolution of aragonite but not calcite. The latter gives rise to considerable secondary porosity development, because active tidal pumping ensures continued renewal of dissolutional potential. This is evidenced by calcium and strontium enrichment in the brackish lens which indicates porosity generation by aragonite dissolution at a maximum rate of 0.35% ka-1, up to twice the average estimated for the fresh water lens. In contrast saline groundwaters are depleted in calcium relative to open ocean waters suggesting the formation of calcite cements.The development of a major laterally continuous cavernous fracture zone along the margin of the carbonate platform permits enhanced groundwater flow and mixing which may result in generation of a diagenetic `halo' at a scale larger than that generally recognised around syn-sedimentary fractures in fossil carbonates. This may be characterised by increased secondary porosity where a relative fall in sea-level results in exposure and formation of a meteoric groundwater system, or cementation by `marine' calcite both below this meteoric system, and where the bank surface is flooded by seawater

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