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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 perched ground water is ground water separated from an underlying body of ground water by an unsaturated zone [6]. see also ground water, perched.?

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

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Your search for maldives (Keyword) returned 3 results for the whole karstbase:
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

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

Giant pockmarks in a carbonate platform (Maldives, Indian Ocean), 2011, Betzler C. , Lindhorst S. , Hubscher C. , Ludmann T. , Furstenau J. , Reijmer J.

Circular structures and depressions in carbonate platforms are known to represent karst chimneys or sinkholes which form as a response to rock solution. This formation mechanism is plausible for shallow-water carbonates which lie in the reach of meteoric diagenesis or fresh-water lenses. Circular structures which occur in deeper waters, however, need an alternative interpretation. Such an example of sea-floor depressions in more than 300. m deep waters occurs in the Inner Sea of the Maldives carbonate platform in the Indian Ocean. The structures were mapped with multibeam and Parasound, multi-channel seismics were used to link the depressions with structures at depth. The circular depressions have diameters of up to 3000. m and depths of up to 180. m. The craters are interpreted as pockmarks formed through the venting of gas and fluids. Gas and fluid lenses below the pockmarks are reflected by bright spots in the seismic sections as well as a reduction of the instantaneous frequency. These areas at depth are linked to chimneys connected to faults and drowned Oligocene carbonate banks. A model is presented that relates the different forms and sizes of the structures to distinct development stages of sea floor deformation to one process. Early stages of gas and fluid migration into the shallow part of the sedimentary succession induce formation of dome-shaped bodies. Initial gas and fluid escape to the sea floor is reflected by the formation of sand volcanoes and aligned small pockmarks. Active pockmarks are the deepest, and have the shape of truncated cones in cross section. Mature pockmarks are characterized by erosion of the flanks of the structure by bottom currents. Late stage pockmarks are bowl-shaped in cross section, and are to different degrees filled by drift sediments. Packages of strata revealing high reflection amplitudes and high interval velocities interpreted as microbially-mediated carbonate precipitates underlie some of the pockmarks. The pockmarks in the Maldives show that circular structures other than solution-related features can be abundant in carbonate platform deposits and that such structures may be more abundant in the geological record of carbonate platforms as previously thought. Pockmarks in the Maldives indicate that the archipelago is an example of a hydrocarbon system which consists of an isolated oceanic carbonate platform overlying a volcanic basement and lacustrine source rocks.

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