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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 screen, screen pipe is slotted well casing that is positioned within the producing horizon to prevent the inflow of detrital particles into a well while allowing the inflow of water. see also well screen.?

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

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KarstBase a bibliography database in karst and cave science.

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Geodinamica Acta, 1997, Vol 10, p. 12-29
Ground-water silicifications in the calcareous facies of the Tertiary piedmont deposits of the Atlas Mountain (Hamada du Guir, Morocco)
Abstract:
The Tertiary piedmont deposits (Hamada Formations), on the southern edge of the Haut-Atlas mountains, form extensive tablelands in the Boudenib area. They consist of two main sedimentary sequences, the Hamada de Boudenib and the Hamada du Guir, of Eocene and Miocene age. Both sequences show elastic facies at their base (conglomerates, calcareous sandstones, silty clays) and end with thick lacustrine limestones and pedogenic calcretes are characterised by rather confined facies, palygorskite-rich, with some gypsum in the second sequence. The recent evolution of the region is marked by the dissection of the tableland that is lined with high cliffs. The water flaw is mainly through wide karst features as there is no major river on the tableland. Silicifications which affect the different facies, form pods of various shape and size, and show an erratic spatial distribution. In the calcareous sandstones, there are irregularly shaped tubules of about 5 cm in diameter, more planar bodies from 5 to 50 cm thick, which frequently display voids lined with translucent silica concretions. The conglomerates display relatively few silicifications, the more characteristic ones consist of a silica cortex on some Limestone pebble and silica plates fitting closely the base of the pebbles. The lacustrine limestones and the calcretes from the upper part of the formation show frequently well developed silicifications. These show very variable shapes; horizontally stretching layers, interconnected or isolated amoeba-like bodies, thin slabs, karst micro-breccia, with frequent concretionnary structures, and quartz crystallisations. Limestone nodules remain often included in these silicifications. The more argillaceous facies display either small tubules or thin plates formed of translucent concretionnary silica. As a rule, the importance of the voids and related structures (concretions, drusy crystals) has to be noticed in all these silicifications, sometimes they are also linked with fractures or karst pipes. Petrography of the silica minerals, their relation with the primary structures. their distribution and their succession, give invaluable information on the silicification processes. Microcrystalline and fibrous quartz are the most common silica minerals, including minor amounts of opal and euhedral quartz. But micrographic arrangements show clearly that primary opal deposits have been more extensive and have recrystallized into chalcedony, microcrystalline quartz, or even ''flame-like'' quartz. Silica deposits in voids make up an important part of the silica pods. The tubules and thin plates of translucent silica of the argillaceous facies are formed of laminar chalcedony deposited around voids. Silica deposits in voids are also particularly obvious in the sandstones. The pores between the quartz grains are then cemented by fibrous quartz and little opal. Some samples show very large cemented voids that cannot be related to the primary porosity of the sandstone. These large voids correspond to the dissolution of the primary calcareous cement, which even led to the collapse of the sandstone fabric. In the limestones, there are silicified micro-karst breccia with a very high primary porosity cemented by quartz crystals, and even in the large microcrystalline quartz zones there are numerous void fillings, the primary porosity often exceeding 50%. There is obviously the alternation of silica deposits and calcite dissolution. Beside the void filling, silicifications comprise also matrix epigenesis, that is replacement of the carbonate by silica with preservation of most of the limestone structures, without development of voids. Nevertheless, the epigenesis of the limestone matrix is restricted to the vicinity of the voids. The silicifications relate to diagenetic processes. The main part of the silica is formed of void deposits and matrix replacement (epigenesis) on the edge of the voids. These void deposits give evidence of the feeding solutions. The regularity of the deposits all around the voids point out to a hydrologic regime characterised by a ground-water our now. Silica originates most probably from alteration of the magnesian clay minerals along the ground-water path. Regarding the low solubility of silica in surficial waters, high flows are needed in order to renew continuously the silica precipitated from solution. This points to a relatively humid climate at time of silicification, and to relief and incised landscapes to bring about these high flows


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