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<title>1987: Cambridge Underground report</title>
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<center><font size=-1>Cambridge Underground 1988 pp 8-13</font>
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<h2>The Geology of the CUCC Expedition area,<br>
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Totengebirgs, Austria</h2>
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<p><b>Jared West</b></center>
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<p><u>Abstract</u>: The CUCC expedition area in Austria is situated in the
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Northern Calcareous Alps, the northern part of the Eastern Alps. The
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sedimentology and structural geology of the Northern Calcareous Alps is
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described.
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<h3>Structure and Genesis of the Eastern Alps</h3>
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<p>The caving area is situated in the Eastern Alps. The northern part of this
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range is known as the Northern Calcareous Alps (Nordkalkalpen). This is a
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band of MEsozoic limestones about 50km wide which stretches from Voral in the
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east to Vienna in the west. To the south is the axial zone of the Eastern
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Alps, and to the north is the Tertiary Molasse (Fig. 1). The Eastern Alps are
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considered to be made up of piles of horizontal sheets which may extend
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laterally for hundreds of kilometres, but which may be only a few kilometres
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thick. Three, possibly four, structural levels can be recognised. The
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basement rocks (gneiss) are overlain by Palæozoic and then Mesozoic
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sediments. Repetition of the sequence of Mesozoic sediments is the result of
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overthrusting of the sheets during the Tertiary. The strike of the rocks
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tends to be east-west as they are arched about an axis in this direction.
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Generally, the dip direction in the Northern Calcareous Alps is northward,
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because they are to the north of the axis.
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<p>The thrusting and arching is related to a shortening of the crust in a
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north-south direction, which occurred during the Alpine mountain building
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period. The Alps were formed when the African tectonic plate ploughed into
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the Eurasian plate from the south. The Indian plate similarly ploughed into
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Tibet, creating the Himalayas. These processes of collision are still in
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progress; the Alps are still rising at about the same rate as they are being
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eroded. If uplift were to cease, and erosion continue at the present rate,
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the Alps would be denuded after just three million years. This is very little
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on the geological time scale.
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<h3>Summary of the Geological History of the Calcareous Alps</h3>
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<p>Due to subsidence in the basement in the Permian, an east-west zone of
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sedimentation was established. In some areas, evaporitic rocks (gypsum and
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salt) were laid down. These are characteristic of shallow seas in a hot
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climate. The facies belts were established in the Triassic, these being
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controlled largely by how fast the basement was subsiding. Where the rate of
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subsidence was fast, it outpaced deposition and the sea bottom subsided below
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the photic zone, resulting in deep water sediments rather than reefs. It can
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be concluded that subsidence was more rapid in the south of the depositional
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area during the Triassic. In the Jurassic, the pattern of subsidence changed,
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affecting the facies belts. There may have been local areas of elevation. In
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some areas deposition continued into the Cretaceous. During Late Cretaceous
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time, parts of the Calcareous Alpine facies became detached and slid over
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others. The main northwards movement leaving the Calcareous Alps in their
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present position occurred during the Eocene.
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<h3>The Northern Calcareous Alps: Sedimentary Rock Types</h3>
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<p>The oldest rocks seen in the area are of Triassic age, and were produced
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in a submarine reef environment. The existence of three distinct reef-related
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depositional environments (facies) can be inferred from the rocks (Fig. 2)
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<ol>
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<li>Haupt Dolomit facies. This rock type was laid down behind the main reef,
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in the quiet back reef lagoon. Cycles of deposition are apparent as are
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periods of aerial exposure. The facies is mostly characteristic of the
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northern part of the Kalkalpen. It interfingers to the south with the
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Dachstein Limestone (Dachsteinkalk) unit. The maximum thickness of the Haupt
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Dolomit is 2000m.
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<li>Dachstein Limestone facies (Dachsteinkalk). This is the cave-bearing
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formation and two lithologies are present. The first is a thinly bedded
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limestone of shallow water origin, again behind the main reef. The thinly
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bedded nature of the rock causes caverns to collapse before reaching any
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appreciable size. The second lithology is massively bedded limestone
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containing abundant fossils, and is extensively cavernous. It formed the main
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body of the reef. The maximum thickness, and hence cave depth potential, is
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1800m and the unit occurs mostly in the middle region of the Kalkalpen.
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<li>Halstatt facies. This consists of red and black shales and pale deep
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water limestones, perhaps laid down further from the land than the other two
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types. It occurs to the south of, and interfingers with, the Dachstein
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Limestone facies.
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</ol>
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<p>The younger Jurassic rocks correspond only slightly to the underlying
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Triassic in terms of depositional environment. In the North there are marls
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and cherty limestones, whereas in the South, reef limestone are more
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important. Units of coarse clastics (sandstones and breccias) occur.
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<h3>Structure of the Northern Calcareous Alps</h3>
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<p>Generally, the region is not intensely folded, being more characterised by
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broad open flexures with tight folding being confined to fault zones. The
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Triassic rocks have the form of almost horizontal thrust sheets. There is
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little disturbance along the thrust planes and these may be difficult to
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recognise. The sheets are broken into blocks by steeply dipping faults. Many
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of the 'hading rifts' in the caves have formed along such faults. Complex
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deviations from this structure occur where salt and anhydrite from the
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underlying Permian evaporite beds have penetrated the overlying Triassic
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strata in the form of Diapirs, as it has in the 'salt mountain' near
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Halstatt. It is thus generally agreed now that the rocks of the Northern
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Calcareous Alps are not in their original depositional location but have been
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brought in from the south by thrust faulting. This has been deduced from
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borehole information as well as from the outcrop pattern, though how far to
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the south the rocks were formed is not clear, nor is it agreed whether
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thrusting occurred mainly along one plane or equally along several.
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<h3>Guide to the CUCC area: the Totengebirgs and the Loser Plateau</h3>
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<p>A map of the area is given (<a href="../../maps/jwfig3.htm">Fig. 3</a>).
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The Halstatt facies crops out in a fault bounded basin. In places it is
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overlain by the Zlambach beds and Lias marls. To the north are the
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Totengebirgs and to the south the Dachstein, where the massive coralliferous
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Dachstein limestone crops out. The Loser Plateau is in the upper right of the
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map: the plateau is believed to be an Upper Miocene erosion surface. walking
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from the car park at the Loser mountain restaurant along the Stogerweg
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footpath to the east, a remarkable wall of rock is seen to stnad high above
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the plateau. This is composed of Jurassic clastic rocks, with some Zlambach
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beds (uppermost Triassic) at their base. They are more resistant to
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weathering than the limestone. The limestone in the area immediately around
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the Loser carpark is the thinly bedded type, which is poorly cavernous. To
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find any decent sized caves one has to walk some 3km to the east where the
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massively bedded type is found. Unfortunately these types are not
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differentiated on the map. The depth potential of the area is limited to
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slightly more than a kilometre by the water table rather than the base of the
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Dachstein limestone, this being at the level of the surface of the adjacent
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lake Altausseer See.
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<p>Acknowledgements: I am indebted to Hans Schönlaub of the Geologische
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Bundesanstalt, Wien for his help in sending literature, and to Professor
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Oxburgh of the Department of Earth Sciences, Cambridge, for allowing the
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reproduction of his diagrams.
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<p>Bibliography:
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<p>OXBURGH, E.R. (1968), The Geology of the Eastern Alps, The Geologists Association, London.
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<p>PLOCHINGER, B. (1984), Nordkalkalpen, Monograph of the Austrian Geological Survey, Wien.
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<p>TOLLMAN, A. (1985), Die Nordlichen Kalkalpen.
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<hr />
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<!-- LINKS -->
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<ul>
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<li>Cambridge Underground 1988,
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<a href="../../../jnl/1988/index.htm">Table of Contents</a></li>
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<li>1987 Expedition info:
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<ul>
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<li><a href="log.htm">Logbook</a></li>
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<li>Cambridge Underground Expo Report:
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<ul>
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<li><a href="report.htm">Expedition description</a></li>
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<li><a href="158gd.htm">Donner-und-Blitzen Höhle</a>, Mike Richardson</li>
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<li><a href="ent113.htm">Entrance 113</a>, Mike Richardson<br>
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<!-- </ul></li>
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<li><a href="bcracc.htm">BCRA Caves & Caving Report</a><br> -->
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</ul></li>
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<li><a href="../../pubs.htm#pubs1987">Index</a> to all publications</li>
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<li><a href="../../index.htm">Back to Expeditions intro page</a></li>
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<li><a href="../../../index.htm">CUCC Home Page</a></li>
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</ul>
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