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81.1427: UBSS Intro to Austrian Karst
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<font size=-1>Proceedings of the University of Bristol Spelaæological Society, 1981, <b>16</b>(1) pp5-10</font>
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<h2>An Introduction to Austrian Karst</h2>
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<h4>by S.R.Perry</h4>
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<h3>Abstract</h3>
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<p><font size=-1>The plateaux of the Northern Limestone Alps underwent uplift
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between Miocene and Pliocene times due to pressure from the Central Alps. The
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run-off from the Central Alps took a linear northerly direction to the
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Northern Foreshore. Subsequent dissection separated the plateaux physically
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and local radial drainage patterns developed. The surface features of the
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plateaux are dependant on glaciation, solution and weathering. The plateaux
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show good conditions for cave formation. This has occurred in two major
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phases, late Tertiary northerly phreatic tunnels and post glacial radial
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vadose development.</font>
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<h3>Introduction</h3>
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<p>This paper gives an introduction to the karst of Austria, as reviewed by
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Bauer and Zötl. (1972). It provides a background to the interest the
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University of Bristol Spelaeological Society is now showing in the Loser
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plateau area of the Totes Gebirge.
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<p>Karstifiable rock makes up about one sixth of Austria. Four fifths of the
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karst area lies in an east-west band of limestone, the Northern Limestone
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Alps, which lies to the north of the Central Alps. The hardrock Central Alps
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are separated from the Limestone Alps by the longitudinal rivers: the Inn,
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the Salzach and the Enns. The Northern Limestone Alps include the High Alps
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(summits greater than 2000m) and to their north the pre-Alps (summits less
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than 1500m) (Fig. 1)
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<p><img alt="Fig. 1 - 15k gif" width=780 height=450 src="81f1.gif">
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<p>The dominant rocks of the High Alps are the Triassic Limestones
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Wettersteinkalk and Dachsteinkalk. Both are fine-grained, light coloured,
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bedded strata up to 1500m thick. The pre-Alps contain many less permeable
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rocks including dolomites and shales. They have suffered greater surface
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erosion and show rounded hill forms, corroded flat in the Tertiary period
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(Tertiary denudational plains). The classic features of the High Alps are
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impressive steep sided, interdigitating plateaux and the corresponding
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narrow valleys.
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<h3>The Development of the Limestone Alps</h3>
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<p>The Triassic limestones were subjected to tectonic pressure from the
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Central Alps and suffered extensive nappe-type folding in the early Tertiary,
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with overthrusts reaching up to fifty kilometres in a northerly direction.
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The nappes were corroded by the run-off from the Central Alps and widespread
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denudational plains were formed. During early Miocene these plains were
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covered by a several hundred metre thick hardrock gravel blanket
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(Augensteine) washed from the Central Alps. The Augensteine can still be
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found, especially in the east of the range and where they have been deposited
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within caves and fissures by water action (Fig. 2).
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<p><img alt="Fig. 2 - 17k gif" width=720 height=450 src="81f2.gif">
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<p>During early Miocene, only a few hills would have shown above the
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Augensteine, but with the uplift of the Alps from then to Pliocene times the
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gravel cover was eroded away and widely extending plateaux were exposed. The
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plateaux survive as the High Alps, where they are of extensive limestone
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sequences (Wettersteinkalk and Dachsteinkalk) with low dip. These factors
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have reduced surface erosion by the development of extensive subterranean
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drainages. Such areas are termed 'Raxlandshaft' (Raxlandscape).
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<p>The Raxlandshaft was dissected by younger tectonic block movements to form
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the interdigitating plateaux. The subsequent down-cutting of valleys
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interrupted the previous generally northwards drainage from the Central Alps,
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which had formed the Tertiary denudational plains and the extensive
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horizontal phreatic cave systems of Austria, The Limestone Alps were isolated
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physically from the Central Alps by the Inn, the Salzach and the Enns, which
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diverted the run-off from the Central Alps to the Danube. This valley
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formation reached its present extent (and formed a hydrological barrier) by
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the beginning of the Quaternary period. Subsequent drainage was local to each
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plateau, with a radial distribution rather than a dominantly northern
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direction. The final major event was the Quaternary glaciation.
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<p>The limestone plateaux are most prominent in the isolated massifs of the
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Steinernes Meer, Tennengebirge, Dachstein, Totes Gebirge and east as far as
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the Vienna Basin. To the west a mountain chain form, the Northern Tyrolean
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Alps, formed of steeply dipping Wettersteinkalk and of less spelaeological
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interest, is continuous with the high alpine dolomite ranges.
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<h3>Surface Features of the Plateaux</h3>
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<p>Large karst features such as dolines predate Quaternary glaciation. The
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glaciers themselves enlarged surface rifts to gouge out straight narrow
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ravines several metres deep and up to one hundred metres or more long. These
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'Gassenlandschaft' are characteristic of the glaciated plateau and indicate
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the network of main faults and joints. Step-like scarps separated by flat
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beddings, 'Plattenlandschaft', are found in areas of distinctly bedded
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low-dip limestone, again due to glacial scouring. As the glaciers receded
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(the Dachstein still has a glacier which was once 400m thick) the released
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water aided the formation of numerous surface-open shafts, usually blocked
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with surface moraine or glacial scree.
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<p>Since the glaciation, small features, 'lapies', have developed: fine
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sharply fluted 'Trittkarren' formed above the tree line (about 1600m) and
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rounded bollard-like 'Rinnenkarren' up to one metre deep formed below the
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tree line, under soil cover. There is a band of overlap due to the timber
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line having fallen three to four hundred metres since the thermal maximum. On
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the bare plateau, where hte temperature is low (increasing the carbon dioxide
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solubility) and precipitation is high, post-glacial erosion is estimated at
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15-20cm of limestone. Lower down the vegetation reduces the available water
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(transpiration) but the acid soil increases the corrosive power of the
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slightly warmer water. Trittkarren are centimetres deep, Rinnekarren up to
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one metre deep. Above about 2200m, frost weathering is sufficient to prevent
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lapies formation.
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<h3>Hydrology</h3>
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<p>The development of an underground drainage system depends on the amount
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and structure of the bedrock, the surface morphology, the amount and quality
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of the water having access to the surface, the position of the base level of
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drainage (potential energy gradient) and the time available.
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<p>The tendency to cave formation rather than surface run-off is greatest if
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the surface is nearly horizontal. High precipitation and carbon dioxide
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content help. Surface features, such as lapies and Gassenlandschaft, direct
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water to the bedrock and subterranean drainage will then take advantage of
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and enlarge the internal weaknesses, with flow directed by the local base
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level. All the necessary factors, including depth of limestone are found
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<i>par excellence</i> in the high plateaux around the Dachstein, though
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changes in the parameters since Tertiary times have dictated several phases
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of cave development.
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<p>A limestone mass can be divided according to the drainage conditions in
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various regions. Highest is a zone of vadose development, where passages are
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essentially air-filled and gravity drives flow and passage formation
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vertically down planes of weakness, usually joints and faults. At some depth
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a level of permanent flooding is reached, where flow is dictated by
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hydrostatic pressure and may travel in many directions to reach base level.
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This phreatic zone is limited by the extent of the karstifiable rock. The
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upper portions of this karst water body will experience the most rapid motion
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and turnover, and will be the zone of greatest passage formation. This region
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overlaps with the vadose region in a zone where water level and flow type
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varies closely with the precipitation. A 9.7 km tunnel through the Schneealp
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has allowed direct observation of these zones in a Wettersteinkalk plateau to
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the east of the range.
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<h3>The Caves</h3>
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<p>The earliest phase of development is evidenced by Liassic deposits within
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the Tertiary limestone. These pockets are not relevant to the present caves,
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which divide into phreatic tunnels and precipitous vadose systems. The
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phreatic tunnels run in a northerly direction, formed by late Tertiary
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run-off from the Central Alps, before the latter were separated by their
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longitudinal valley systems. This drainage ran through the Limestone Alps to
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the base level of the northern foreshore and was associated with the
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drainage which formed the denudational plains. At this time, several large
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'poljes' are thought to have sat perhaps 1000m above the presnt plateau.
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<p>The phreatic tunnels of the major known caves lie between 1300 and 1800m
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above sea level. The systems often have several stories denoting successive
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uplifting of the Alps during their formation, the phreatic tunnels being
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formed in the upper, rapidly moving layer of the karst water body. The
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Dachstein Mammut Cave is a classic example with 16.5 km of passage lying at
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altitudes between 1250 and 1500m. The Eisriesenwelt Cave of the Tennegebirge
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has 42km of passage between 1600 and 1800m.
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<p>Late vertical developments, either connected with the horizontal passages,
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as in the 432m shaft of the Geldloch, or in separate shaft caves, such as
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the Gruberhornhöhle (854m total depth), were formed in the isolated
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vadose zones of the Quaternary plateaux. Much of the water supply was
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glacial and post-glacial meltwater (ie. local) and radial drainage patterns
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were formed with overlapping water systems running centrifugally within the
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plateau. Vertical connections in the Dachstein Mammut Cave betray their
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links with the glacier bed above by the moraine deposited at their junctions
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with the phreatic tunnels.
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<p>Spore tests reflect both types of cave form. Radial patterns were found
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for drainage from the centre of the Totes Gebirge. In contrast, drainage from
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the southern edge of the Totes Gebirge (Tauplitz fault zone) passed 30km
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north through the entire massif.
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<h4>Reference</h4>
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<p>Bauer, F and Zötl, J, 1972<br>
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In <i>Karst. Important Karst Regions of the Northern Hemisphere</i>,
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Ed. Herak, M. and Stringfield, V.T.
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<h4>Additional Reading</h4>
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<p>Jennings, J.N., 1971<br>
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<i>Karst.</i> M.I.T.Press
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<hr>
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<!-- LINKS -->
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<img alt=">" src="../../../icons/lists/0.gif">
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<a href="811309.htm">A Description of Some Caves</a>
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in the Totes Gebirge (same UBSS Proc.)<br>
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<img alt=">" src="../../../icons/lists/0.gif">
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<a href="../../areas.htm">1623 Area overview</a><br>
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<img alt=">" src="../../../icons/lists/0.gif">
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Back to <a href="../../index.htm">Expedition Intro page</a><br>
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<img alt=">" src="../../../icons/lists/0.gif">
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<a href="../../../index.htm">Back to CUCC Home page</a><br>
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<img alt=">" src="../../../icons/lists/0.gif">
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<a href="../index.htm">Other groups</a> who have worked in the area
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