Muchimuk cave system

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The Muchimuk cave system is a more than 20 km long system of caves in the Churì-Tepui in southeastern Venezuela . The first access was discovered in 2002 during a flight of the Aprada-Tepuis by Charles Brewer-Carías in the mountainous region of Chimantá and explored by several expeditions from 2004 onwards. Initially viewed as individual caves, it became clear in the course of the research campaigns that at least some of the individual caves are connected to one another and form a large cave system.

location

The Churí-Tepui is part of the Chimantá massif ( Macizo del Chimantá ) in the Canaima National Park in southern Venezuela and is located northeast of the Amurí and Akopán tepuis at the southeast end of the massif. The massif consists of several individual tepuis , the number of which is given as ten or eleven, including Chimantá, Amurí, Akopán, Tirepón, Eruoda and Murei. The highest point of the massif with 2698 m is on the Eruoda-Tepui.

The approximately 170 km² large surface of the Churì-Tepuis is criss-crossed by a regular system of intersecting crevasses and divided in the northwest by steep breaks running from south-southwest to north-northeast.

Geological background

The tepuis are remnants of what is known as the Auyan Tepui leveling area, the formation of which may have already started in the chalk . The surface of the Chimatà-Tepuis consists of pebbly sandstones of the Matauí formation, the uppermost formation of the Precambrian Roraima group . The Roraima Group is a group of Paläoproterozoikums that throughout the Guiana Shield is widespread. It mainly consists of hard, quartzitic sandstones. The sandstones are gently folded, there are various fracture systems that the weathering can attack. The layer sequence is intruded by Precambrian diabase - sills and - Dykes .

History of exploration

In 2002 Charles Brewer-Carías discovered a river on a flight to the Aprada-Tepui , which flowed out of the rock face of the Churì-Tepui. Apparently it was a large opening because it was visible from the plane. After this discovery, Brewer-Carías undertook repeated flights in early 2002 to investigate a possible access to the cave. As with almost all tepuis, a helicopter approach turned out to be the easiest way to get to the cave entrance.

The first exploration took place on March 28, 2004 by a group of twelve scientists and nature experts. After the dangerous helicopter approach to the entrance of the cave, they penetrated about two kilometers into the cave before a cave lake - later named Lago Chayo - forced them to turn back.

A group of seven researchers went on a second expedition between May 28 and June 2, 2004. This time, qualified speleologists took part in the venture to measure the cave and take photos. From a base camp at the entrance to the cave, they set off to several cave passages and set up a temporary camp in a 90 by 150 meter hall, which they named Planetario ( planetarium ). The researchers named the cave after its discoverer Cueva Charles Brewer , it has the largest cavities of all known caves formed in sandstones or quartzites . The large cave has a raging cave river, waterfalls and large halls up to 60 m wide and an average height of 15 to 20 meters.

A research expedition took place every year from 2005 to 2007, and new caves were discovered that are part of an entire cave system. The knowledge of the cave system was constantly expanded in this way. In 2009 two expeditions were carried out: in January twelve speleologists visited the Churí-Tepui, and in May a group of nine speleologists, three scientists, a journalist from GEO magazine , six photographers and a six-person film team, several pilots and eight residents of the nearby one Yunek Indian village. The expedition led to the discovery of 16 more caves, provisionally named Las Cuevas del Queso ( The Cheese Caves ). According to the results of this exploration, the caves Cueva Colibri , Cueva Muchimuk , Cueva Charles Brewer , Cueva del Diablo and Cueva Zuna, previously mapped as individual caves , are connected in a cave system known to date over 17.8 km, which is the one with a length of 16.14 km longest quartzite cave to date, the Cueva Ojos de Cristal in Roraima-Tepui , clearly surpassed.

The cave system

In mid-2009, the following individual caves ( Spanish Cuevas ) were known (approximately from south to north):

  • Cueva Juliana , length 1 km
  • Cueva Zuna , length 2.5 km
  • Cueva del Diablo , length 2.3 km
  • Cueva Charles Brewer , length 5.7 km
  • Cueva Tetris (also Big Hole ), length 150 m
  • Puente de Diana
  • Cueva Croatia
  • Cueva del Bautismo del Fuego (also Cueva Fuego)
  • Cueva Cañon Verde
  • Cueva Muchimuk , length 3.2 km
  • Systema de La Araña 2.8 km
  • Sima Noroeste
  • Cueva Eládio 1.2 km
  • Cueva Colibri , length 3.6 km

Formation of the quartzite caves

Karst formation is very common in areas where the subsoil consists of limestone or other easily soluble rocks . The formation of karst forms in silicate rocks such as sandstone and quartzite ( pseudokarst ) is rare compared to this, and little is known about the prerequisites and the course of the processes. Such caves have already been described from other areas, not only made of sandstones, but also of granites . Their emergence is mainly attributed to malfunctions and breaks , but in some cases to solution processes.

An attempt to explain the formation of the Churì-Tepuis caves on the basis of solution processes was proposed in 1990 by H. Briceño, C. Schubert and J. Paolini. A striking feature of the plateau surfaces are ombrotrophic peat bogs . Their formation in the area of ​​the Tepuis probably began as early as the early Holocene . Rainwater and river water as well as the water running off the peat bogs have a pH value in the range between 3.5 and 4.7, so they are all in the acidic range. The river and seepage water act on the sandstones by dissolving the silicate binder and releasing the grains of sand. In the opinion of the research group, this process, which lasts for a long time (possibly up to 70 million years), is the most important reason for the development of a karst-like topography of the plateaus and the surrounding Gran Sabana . The triggering of the cave formation through such dissolution processes would have the consequence that the surface shape of the tepuis and the caves would have to be classified in the series of “real” karst forms and not belong to the pseudokarst.

The cave exploration team around Brewer-Carías made further investigations while exploring the cave system. They examined the structure of the sandstone layers of the Churì-Tepuis and became aware of the fact that in the hard, very resistant and fine-grained sandstone layers there are repeatedly soft layers in which the sandstone is hardly solidified or even only loose sand is present. In these loose layers there are pillar-shaped columns made of very hard sandstone at almost regular intervals, which start from the overlying hard layer and through the soft layers create a connection to the underlying hard layer. The authors interpreted this situation as meaning that, during diagenesis , silicon-rich solutions in the fine sandstones migrating downward through the sandstones ensured a firm bond of the grains originally deposited as loose sand. In coarser layers, the permeability was significantly higher, and the solutions sank like fingers, so that the pillars formed, but the rest of the sand remained unconsolidated. Much later, when the sandstones of the Roraima group were again near the surface of the earth, water seeping in through cracks cleared the soft layers so that only the pillars remained and prevented the hard layers from collapsing. The progressive collapse of caves lying one above the other could then have led to the formation of the large caves of the Muchimuk cave system and those of other tepuis.

Other theories about the formation of caves in sandstone see a combination of solution and subsequent removal of the resulting loose sand masses as the cause.

The opal speleothems of the cave system

The caves have a whole series of speleothemes which, in contrast to the widespread calcite speleothems such as stalactites and sintered curtains, are made of opal . More than a dozen forms have been described from Charles Brewer Cave, including the following types:

  • Muñecos (pupae), mushroom-shaped, with a white style and dark brown cap, up to ten centimeters in height, stalagmite- like
  • Corales negros (black corals), coral-like shape, branched, black
  • Guácimos , irregularly branched forms
  • Mushroom-shaped, ball-like clusters of speleothems on cave ceilings that look like a Bovist colony
  • Riñon (kidneys), kidney-shaped speleothems
  • Sponge-like shapes
  • Telerañas (cobweb stalactites ), stalactite-like shapes formed around cobwebs

The occurrence of these formations is explained by the evaporation of cave water with the accumulation of dissolved silicon dioxide and the precipitation of finely atomized water on walls and ceilings outside the influence of flowing water. The numerous cobwebs that occur in the caves play a special role here; they are constantly wetted by fine dewdrops and, due to the precipitation of the opal on the filaments, provide a starting point for structures that resemble normal stalactites, but are not created by dripping water.

Bacteria also play a major role in the formation of the speleothemes. In the caves of the Sarisariñama Tepuis there are bacteria such as Arthrobacter , Corynebacterium , Bacillus , Pseudomonas and Azotobacter . In the speleothems of the Muchimuk cave system, structures have been demonstrated that could be traced back to sulfur bacteria such as Beggiatoa , cyanobacteria such as representatives of the Oscillatoriales and Chroococcales or Nostoc . Specific studies for biological activity have not been carried out, but the presence of bacteria such as in the Sarisariñama caves is believed. The bacteria are encrusted by opal and thus contribute to the growth of the structures. The encrusted bacteria form a mass of peloids , which has a porous rock structure. The porosity of the rock allows water to rise through the speleothems and promotes evaporation and thus the precipitation of opal on their surface.

literature

  • Marek Audy: Křemencový kras venezuelské Guayany . In: Vesmír . tape 82 , no. 133, 5 . Prague 2003, p. 256-265 .
  • Marek Audy: Brány do Ztraceného světa, Unikátní objevy na stolových horách VenezuelyJota . Brno 2008.
  • Marek Audy, Branislav Šmída: Jeskyně Charles Brewer. Mamutí jeskyně v kvarcitech Guayanské vysočiny . In: Vesmír . tape 84 , no. 135 . Prague 2005, p. 20-29 .
  • Branislav Šmída, Marek Audy, Hernán Biord, Federico Mayoral: Cueva Charles Brewer (Chimantá), Cueva Ojos de Cristal (Roraima): the greatest quartzite caves of the world (table-mountains, Venezuela) . In: Spravodaj Slovenskej speleologickej spoločnosti (Bulletin of the Slovak Speleological Society) . Liptovský Mikuláš 2005, p. 3–10 ( speleo.no ( memento of October 31, 2014 in the Internet Archive ) [DOC; 972 kB ]).
  • Branislav Šmída, Charles Brewer-Carías, Marek Audy, Federico Mayoral, Roman Aubrecht, Tomáš Lánczos, Ján Schlögl: Exploration summary about the quartzite caves discovered in the years 2004–2007 in the Chimantá Massive, Venezuela (people, discoveries, localities, literature ) . In: Spravodaj Slovenskej speleologickej spoločnosti (Bulletin of the Slovak Speleological Society) . tape 39 , no. 1 . Liptovský Mikuláš, S. 90-102 .
  • Branislav Šmída, Charles Brewer – Carías, Marek Audy, Federico Mayoral, Lukáš Vlček, Roman Aubrecht, Tomáš Lánczos, Ján Schlögl: The longest quartzite caves in the world: Cueva Ojos de Cristal (16.1 km) and Cueva Charles Brewer (4 , 8 km) and other giant caves on Venezuela table-mountains tepuy Roraima and Chimantá discovered by our 7 expeditions in 2002–2007. IVth European Speleological Congress, August 23-30, 2008, Vercors, France . In: Spelunca Mémoires . tape 33 , 2008, p. 239–243 ( fns.uniba.sk ( memento from August 7, 2016 in the web archive archive.today ) [PDF; 2,3 MB ]).
  • Lukáš Vlček, Branislav Šmída, Roman Aubrecht, Charles Brewer-Carías, Federico Mayoral, Tomáš Lánczos, Ján Schlögl, Tomáš Derka: Scientific expedition Chimantá - Roraima 2009 (Venezuela) . In: Gabrovšek F. & Mihevc A. (Eds.): 17th International Karstological School “Classical Karst”, Cave Climate, June 15–20, 2009, Postojna, Slovenia, Proceedings compact disc . 2009 ( fns.uniba.sk ( memento of July 18, 2011 in the Internet Archive ) [PDF; 1.1 MB ]).
  • Lukáš Vlček, Branislav Šmída, Roman Aubrecht, Charles Brewer-Carías, Federico Mayoral, Tomáš Lánczos, Ján Schlögl, Tomáš Derka: The new results from international speleological expedition Tepuy 2009 to Chimantá and Roraima table mountains (Guyana Highlands, Venezuela) . In: aragonite . tape 14 , no. 1 . Liptovský Mikuláš 2009, p. 57–62 (Slovak, fns.uniba.sk ( memento from March 1, 2012 in the Internet Archive ) [PDF; 684 kB ] with an English summary).

Web links

Individual evidence

  1. ^ Map of Canaima. (No longer available online.) Archived from the original on March 13, 2010 ; Retrieved January 7, 2010 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.thelostworld.org
  2. ↑ a b Branislav Šmída, Marek Audy, Federico Mayoral: Cueva Charles Brewer - Largest quartzite cave in the world. (No longer available online.) Archived from the original on January 8, 2006 ; Retrieved January 7, 2010 .
  3. ^ A b H. Briceño, C. Schubert and J.Paolini: Table-mountain geology and surficial geochemistry: Chimantá Massif, Venezuelan Guayana shield . In: Journal of South American Earth Sciences . tape 3 , no. 4 , 1990, pp. 179-194 .
  4. ↑ Chimantà. Retrieved January 7, 2010 .
  5. ↑ Churi-tepuí, Venezuela. Retrieved January 7, 2010 .
  6. ^ System Muchimuk map. (PDF) Retrieved on January 7, 2010 (aerial photo with map of the cave system).
  7. ^ 1. Expedition from Explorers. Retrieved February 18, 2010 (The twelve first explorers of Charles Brewer Cave 2004).
  8. ↑ Branislav Šmída, Charles Brewer-Carías, Federico Mayoral, Lukáš Vlček, Roman Aubrecht, Tomáš Lánczos: The TEPUY 2007 speleoexpedition (Chimantá and Roraima table mountains, Venezuela). Speleoforum - speleological meeting in the Moravian Karst, March 18th – 20th, 2008 . In: Speleoforum . No. 27 , 2008, p. 49–57 (Slovak, fns.uniba.sk ( memento from January 23, 2015 in the Internet Archive ) [PDF; 5.6 MB ] with an English summary). The TEPUY 2007 speleoexpedition (Chimantá and Roraima table mountains, Venezuela). Speleoforum - speleological meeting in the Moravian Karst, March 18. – 20., 2008 ( Memento of the original from January 23, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.fns.uniba.sk
  9. ↑ Branislav Smida: Official report about the Chimanta Tepuy 2009 expedition. Retrieved January 7, 2010 (results of the expedition in January 2009).
  10. ↑ a b Expedición MUCHIMUK 2009 al Chimanta. Retrieved January 7, 2010 .
  11. ^ Muchimuk 2009. Retrieved January 7, 2010 .
  12. ↑ Lukáš Vlček, Branislav Šmída, Charles Brewer-Carías, Marek Audy, Federico Mayoral, Roman Aubrecht, Tomáš Lánczos: Exploration history and opinions about the quartzite karst, speleological exploration of La Gran Sabana table mountains (Estado Bolívar, Venezuela) by the scientific Chimantá-Roraima expedition 2007 . In: Aragonite (Liptovský Mikuláš) . tape 13 , no. 2 , 2008, p. 34–46 (Slovak, fns.uniba.sk ( memento from August 7, 2016 in the web archive archive.today ) [PDF; 5.2 MB ] with an English summary). Exploration history and opinions about the quartzite karst, speleological exploration of La Gran Sabana table mountains (Estado Bolívar, Venezuela) by the scientific expedition Chimantá-Roraima 2007 ( Memento of the original from August 7, 2016 in the web archive archive.today ) Info: The archive link was used automatically and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / geopaleo.fns.uniba.sk
  13. ↑ Roman Aubrecht, Tomáš Lanczos, Branislav Šmída, Charles Brewer-Carias, Federico Mayoral, Ján Schlögl, Ľubomír Kováčik, Miloš Gregor: Venezuelan sandstone caves: a new view on Their genesis, hydrogeology and speleothems . In: Geologia Croatica . tape 61 , no. 2-3 . Zagreb 2008, p. 345–362 ( fns.uniba.sk ( memento from August 7, 2016 in the web archive archive.today ) [PDF; 7.0 MB ]).
  14. ^ Robert AL Wray: Quartzite dissolution: karst or pseudokarst? In: Cave and Karst Science . tape 24 , no. 2 , 1997, p. 81–86 (English, speleogenesis.info [PDF; 87 kB ] New publication at Speleogenesis and Evolution of Karst Aquifers ).
  15. ↑ Roman Aubrecht, Charles Brewer-Carias, Branislav Šmída, Marek Audy, Ľubomír Kováčik: Anatomy of biologically mediated opal speleothems in the world's large largest sandstone cave Cueva Charles Brewer, Chimantá Plateau, Venezuela . In: Sedimentary Geology . tape 203 , no. 3-4 . Amsterdam 2008, p. 181–195 ( fns.uniba.sk ( memento from August 7, 2016 in the web archive archive.today ) [PDF; 6.4 MB ]).
  16. ↑ Roman Aubrecht, Charles Brewer-Carias, Ľubomír Kováčik, Branislav Šmída, Lukáš Vlček, Tomáš lanczos: Microbial origin of opal speleothems in Venezuelan quartzite caves (Roraima group, Guyana highlands) . In: NZ Hajna, A. Mihevc (Ed.): 16th International Karstological School “Classical Karst”, Karst Sediments, Postojna, Proceedings . 2008 ( researchgate.net [PDF; 420 kB ]).

Coordinates: 5 ° 16 ′  N , 62 ° 2 ′  W