2001-08-15 19:29:27 +01:00
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Geology outline
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<h1>Outline Geology of the Loser Plateau</h1>
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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
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marker beds and no obvious structure. This tended to produce the attitude
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that "its all limestone, with caves in", and little more effort was made.
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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):
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2001-08-16 13:43:09 +01:00
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<p><img src="maps/jared.png" width=1258 height=632>
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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
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Liassic marls. All these sediments have been pushed NNE in the
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Totengebirgs-Decke, a massive thrust. This is bounded to the SW, roughly
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along the line of the road from Altaussee to Blaa-Alm, by a thrust plane. SW
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of this boundary, the surface is entirely composed of Jurassic sediments,
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with little of speleological interest. To the SE, the Loser block is bounded
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by a fault which runs along the NW shore of the Altausseer See. The
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Trisselwand is composed of Jurassic limestone, younger than the Liassic
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marls, and is also massively bedded and seems to contain at least some cave
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development.
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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,
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but, if true, at least eliminates the idea that the Loser plateau is a
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nappe, with these lower beds inverted, and a shattered core at half the
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depth of the Dachsteinkalk which would prevent exploration to great depth.
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This is supported by direct exploration of the Stellerweg streamway, which
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has reached roughly lake level, which is quite near the level of the main
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thrust plane.
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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
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the vertical development in the caves is fault- or joint-guided, on two
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roughly perpendicular sub-vertical sets of faults/joints. That some of these
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are indeed faults is shown by clear offset of beds in a few places where
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prominent shelly beds act as markers. Some faults are also apparent running
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for significant distances on the surface, sub-parallel with the massive
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fault bounding the Loser block to the SE.
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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
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clearest example is Yapate Inlet and Chicken Flied Nice, near Burble
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crawl in <a href="smkridge/161/top.htm">Kaninchenhöhle</a>.
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2001-08-16 13:43:09 +01:00
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<p><img src="smkridge/161/fullsize/cfngeo.png" width=600 height=530>
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<p>Here, the small inlet tube of Burble Crawl, and the original
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main trunk tube of CFN are both formed in a massive creamy white
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bed of limestone just above a 0.8m thick zone of thinly bedded
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limestone. At Staircase 36, the beds can be seen to be offset at
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a fault running roughly at right angles to the main passage, and
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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
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downcutting has revealed the lower beds including the two shelly
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beds containing many fossil bivalves. These fossils stand out
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particularly well on the wall of Staircase 36 itself, where they
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provided much-needed holds for the climb.
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<p><i>to be continued</i>
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<hr>
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<!-- LINKS -->
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<img alt=">" src="../icons/lists/0.png">
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Back to <a href="../index.htm">CUCC Home page</a><br>
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<img alt=">" src="../icons/lists/0.png">
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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.png">
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<b>Main Indices:</b><br>
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<img alt="--->" src="../icons/lists/1.png">
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<a href="infodx.htm"><b>Index</b> to Expo</a> information pages<br>
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<img alt="--->" src="../icons/lists/1.png">
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<a href="areas.htm">Description of CUCC's area</a> and split to subareas<br>
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<img alt="--->" src="../icons/lists/1.png">
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Full <a href="indxal.htm">Index to cave descriptions</a> in area 1623<br>
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<img alt="--->" src="../icons/lists/1.png">
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List of (links to) <a href="pubs.htm">published reports and logbooks</a>
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</body>
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</html>
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