Grotte St. Barbe, Müllertal, Luxembourg - Cave Entrances (Natural) on Waymarking.com

Geological composition of the region

"Luxembourgish Switzerland" and in particular the Muellerthal, through which the small river Ernz Noir curls before joining with the Sauer river, has a very particular geological composition. The ground is composed from Luxemburgish sandstone with a thickness of up to 100 meters (1). The sandstone is composed from a layer of clay and limestone (2), which also covers the sandstone in locations that have not been eroded (3). The originally plain massive sandstone formation (4) was eroded to today´s level (5) and formed the current valley form of the Muellertal. Wide joints can be found on either side of the valley (6). Those have been formed by changes in pressure and constant erosion. As a result, giant sandstone blocks (7) have separated from the walls and travel slowly (over thousands of years) down the sides of the valley. The layer of clay and the groundwater between clay and sandstone support this movement (9). The groundwater cannot pass through the clay and accumulates on top of the clay layer. Many springs in the valley attest the existence of his water, which has also sedimented a large amount of calcareous sinter also called tufa (10) at the bottom of the valley. Large blocks of sandstone lean forward and form small canyons (13) or they neal against the brim and form grottos and caves (14). Medium-sized blocks (15) have rolled down into the river and formed a number of waterfalls throughout the valley. Erosion sediments, sand, and gravel accumulate on the plateau (16), on the base of the rocks (17), and on the slopes (18). In some places, overhangs form natural canopies (19) (cf. Heuerts, 1966).

The terminology "Luxembourgish sandstone" was introduced by the German geologist Johannes Steininger (1794-1874). He was teaching physics at a high school in the nearby town of Trier. The sandstone was formed in the Lias sea around 195MJ (early Jura) and is composed from a layer of marley and clay from the Keuper-Rhaetium (Trias) time. (cf. Massard, 2008)

Tufa is generally formed through spring water which is hypersaturated with carbonates. Calcium carbonate (CaCO3) is hardly soluble without CO2, in consequence the high CO2 concentration is mandatory to solve it in the water in the form of calcium bicarbonate (Ca(HCO3)2). Water in aquifers underground can be exposed to levels of CO2 much higher than atmospheric. When the environment the water runs through changes significantly (mainly changes in partial pressure), by emerging for instance from the tab, in time it comes into equilibrium with CO2 levels in the air by outgassing its excess CO2. A quick outgasing reaction will also take place when running through the turbulences of a waterfall. After releasing the CO2, the calcium carbonate then precipitates, sink to the ground and begin to recrystallize. Over time the layer is overgrown by vegetation and the cycle starts new. By repetition of this cycle, the number of layers increases and forms a massive rock. The high concentration of aragonite in the Muellerthal supports the crystallization into calcite. In some of the caves, large deposits of monohydrocalcite (another limestone precipitate) also called "moonmilk" can be found. This generaly clalcite, aragonite or hydromagnesite based cheese-like white substance has the unique quality not to harden and turn to stone due to enclosed water molecules.

The Grotte St. Barbe is a unique cave that is completely formed by boulder chokes (12). Usually, one would expect a typical sandstone cave which is small and dry, but St. Barbe is different. Two large, parallel joints form a cave system with a total length of 600 meters and a maximum depth of 40 meters. The entry passage is characterized by a small vertical crack, where a steel rope is fixed to ease the passage. Following this, visitors go encounter a number of small halls that are stacked and very representative for a cave of this type. In this area some "moonmilk" deposits can be found on the walls. Afterward the path continues until a chimney is reaches, which needs to be climbed (fixed ropes present). While water flow forms a monotone decline in usual caves, boulder choke caves are very chaotic and do not contain such a monotone decline. After arriving at the "cathedral", the visitor encounters first evidence of the clay layer, on which the sandstone resides. Later, when reaching the "pays de merveilles" area, the visitor encounters large sinter sediments and stalagmites. Such formations are completely uncharacteristic for sandstone caves. They prove the continuous presence of carbonated water.

The Muellertal caves are also the home of many cave organisms. A big part of them are so called trogloxene inhabitants, animals that only pass some time of the life in the subteranean world. These are mainly hibernating mamals with the need to get back to the surface to get food. Some animals living normally at the surface have developed the capacity to survive in the underground and pass the entire life in caves, they are called troglophile. Finally, the evolution has generated fully adapted animals that are specialized for the life in the caves. Those troglobites need extended underground ecosystems and are mainly absent from small cave systems like the Ste Barbe cave.

Type of Land: Local Park Managed By: there is no manager Contact Info: no phone as well Type of Cave: Crevice Cave Contains Stalactites: yes Contains Stalagmites: yes Contains Bats: yes Price of Admission: 0.00 (listed in local currency) Website: Not listed

Visit Instructions:
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Recent Visits/Logs:

Date Logged Log User Rating   11/17/2012 Lyngerup.dk visited it 08/25/2010 De FoLaBi's visited it

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