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107 lines
5.8 KiB
HTML
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<title>CUCC Austria Expeditions: Geological Outline</title>
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<h1>Outline Geology of the Loser Plateau</h1>
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<p>Much of the area of the Loser Augst-Eck plateau is rough limestone pavement
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(<b>karren</b>), liberally covered with dense areas of dwarf pine, and
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interspersed with small cliffs, open shafts and snow patches. To the new
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visitor, it all looks alike, and even to the geologist, there are few marker
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beds and no obvious structure. This tended to produce the attitude that "its
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all limestone, with caves in", and little more effort was made.</p>
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<p>Articles speculating on the geology appeared from time to time in
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<b>Cambridge Underground</b>, written by people with varying degrees
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of expertise, and based on either limited literature searches or some
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evidence gathered "on the ground" - including a perusal of various cave
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surveys. Jared West's <a href="years/1987/geolog.htm">article</a> in C.U.
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1988 pretty much summarises the literature. A geologic sketch map of the area
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is based on "The Geology of the Eastern Alps", by Prof. E.R.Oxburgh (The
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Geologists Association, London, 1968):</p>
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<div class="centre"><img src="maps/jared.png" width="1258" height="632"
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alt="Geological map" /></div>
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<p>From this it can be seen that our area is composed of the massively bedded
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white Dachsteinkalk limestone of Triassic age. The summit of the Loser and
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adjacent peaks is more recent Jurassic limestones. The oldest of these,
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particularly obvious in the Bräuning Wall, are quite thinly bedded Liassic
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marls. All these sediments have been pushed NNE in the Totengebirgs-Decke, a
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massive thrust. This is bounded to the SW, roughly along the line of the road
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from Altaussee to Blaa-Alm, by a thrust plane. SW of this boundary, the surface
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is entirely composed of Jurassic sediments, with little of speleological
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interest. To the SE, the Loser block is bounded by a fault which runs along the
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NW shore of the Altausseer See. The Trisselwand is composed of Jurassic
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limestone, younger than the Liassic marls, and is also massively bedded and
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seems to contain at least some cave development.</p>
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<p>Less obvious is the observation that in the Rettenbachtal to the west of
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Loser, Jurassic rocks are again exposed, separated from the Dachsteinkalk
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outcrop by a band of Liassic marls, which also extend NE up the valley of
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Grüne Bichl. This is apparently the trace of a second thrust plane,
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(higher than the one shown on the map above) where the Dachsteinkalk has
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effectively slid north lubricated by a layer of salt (which itself is most
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obvious in the local Salzbergwerk - salt mines). This suggests that the
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situation is rather more complex than the single thrust depicted above, but, if
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true, at least eliminates the idea that the Loser plateau is a nappe, with
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these lower beds inverted, and a shattered core at half the depth of the
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Dachsteinkalk which would prevent exploration to great depth. This is
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supported by direct exploration of the Stellerweg streamway, which has reached
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roughly lake level, which is quite near the level of the main thrust plane.</p>
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<p>The Dachsteinkalk all looks very similar, and much of the rock underground
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is concealed by mud or breakdown, so it has proved very difficult to make any
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meaningful observations. It has become clear, however, that all or most of the
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vertical development in the caves is fault- or joint-guided, on two roughly
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perpendicular sub-vertical sets of faults/joints. That some of these are indeed
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faults is shown by clear offset of beds in a few places where prominent shelly
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beds act as markers. Some faults are also apparent running for significant
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distances on the surface, sub-parallel with the massive fault bounding the
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Loser block to the SE.</p>
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<p>The fossil phreatic passages seem to be much less dependent on joint
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direction, and appear to follow certain beds of the Dachsteinkalk. The clearest
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example is Yapate Inlet and Chicken Flied Nice, near Burble crawl in <a
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href="1623/161/top.htm">Kaninchenhöhle</a>.</p>
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<div class="centre"><img src="1623/161/fullsize/cfngeo.png" width="600"
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height="530" alt="Cross-section sketch of Yapate and Burble Crawl" /></div>
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<p>Here, the small inlet tube of Burble Crawl, and the original main trunk tube
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of CFN are both formed in a massive creamy white bed of limestone just above a
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0.8m thick zone of thinly bedded limestone. At Staircase 36, the beds can be
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seen to be offset at a fault running roughly at right angles to the main
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passage, and Yapate Inlet, south of the fault, is formed in exactly the same
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bed, but a few metres lower in altitude. The much later vadose downcutting has
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revealed the lower beds including the two shelly beds containing many fossil
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bivalves. These fossils stand out particularly well on the wall of Staircase 36
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itself, where they provided much-needed holds for the climb.</p>
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<p><i>to be continued...</i></p>
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<hr />
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<ul id="links">
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<li>Back to <a href="../index.htm">CUCC Home page</a></li>
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<li>Back to <a href="index.htm">Expedition Intro page</a></li>
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<li><b>Main Indices:</b>
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<ul>
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<li><a href="infodx.htm"><b>Index</b> to Expo</a> information pages</li>
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<li><a href="areas.htm">Description of CUCC's area</a> and split to subareas</li>
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<li>Full <a href="indxal.htm">Index to cave descriptions</a> in area 1623</li>
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<li>List of (links to) <a href="pubs.htm">published reports and logbooks</a></li>
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</ul></li>
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<li><b>Pictures:</b>
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<ul>
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<li><a href="gall0.htm">Text only Index</a></li>
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<li><a href="gallery/0.htm">Index pages (with thumbnails)</a></li>
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</ul></li>
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<li>Table of <a href="folk/index.htm"><b>members</b> of CUCC expeditions</a> 1976-present</li>
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</ul>
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</body>
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</html>
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