mirror of
https://expo.survex.com/repositories/expoweb/.git/
synced 2024-11-22 07:11:55 +00:00
111 lines
5.5 KiB
HTML
111 lines
5.5 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0//EN">
|
|
<html lang=en>
|
|
<head>
|
|
<title>
|
|
Geology outline
|
|
</title>
|
|
<link rel="stylesheet" type="text/css" href="css/main2.css" />
|
|
</head>
|
|
<body>
|
|
<h1>Outline Geology of the Loser Plateau</h1>
|
|
|
|
Much of the area of the Loser Augst-Eck plateau is rough limestone pavement
|
|
(<b>karren</b>), liberally covered with dense areas of dwarf pine, and
|
|
interspersed with small cliffs, open shafts and snow patches. To the new
|
|
visitor, it all looks alike, and even to the geologist, there are few
|
|
marker beds and no obvious structure. This tended to produce the attitude
|
|
that "its all limestone, with caves in", and little more effort was made.
|
|
|
|
<p>Articles speculating on the geology appeared from time to time in
|
|
<b>Cambridge Underground</b>, written by people with varying degrees
|
|
of expertise, and based on either limited literature searches or some
|
|
evidence gathered "on the ground" - including a perusal of various cave
|
|
surveys. Jared West's <a href="years/1987/geolog.htm">article</a> in C.U.
|
|
1988 pretty much summarises the literature. A geologic sketch map of the area
|
|
is based on "The Geology of the Eastern Alps", by Prof. E.R.Oxburgh (The
|
|
Geologists Association, London, 1968):
|
|
|
|
<p><img src="maps/jared.png" width=1258 height=632>
|
|
|
|
<p>From this it can be seen that our area is composed of the massively bedded
|
|
white Dachsteinkalk limestone of Triassic age. The summit of the Loser and
|
|
adjacent peaks is more recent Jurassic limestones. The oldest of these,
|
|
particularly obvious in the Bräuning Wall, are quite thinly bedded
|
|
Liassic marls. All these sediments have been pushed NNE in the
|
|
Totengebirgs-Decke, a massive thrust. This is bounded to the SW, roughly
|
|
along the line of the road from Altaussee to Blaa-Alm, by a thrust plane. SW
|
|
of this boundary, the surface is entirely composed of Jurassic sediments,
|
|
with little of speleological interest. To the SE, the Loser block is bounded
|
|
by a fault which runs along the NW shore of the Altausseer See. The
|
|
Trisselwand is composed of Jurassic limestone, younger than the Liassic
|
|
marls, and is also massively bedded and seems to contain at least some cave
|
|
development.
|
|
|
|
<p>Less obvious is the observation that in the Rettenbachtal to the west of
|
|
Loser, Jurassic rocks are again exposed, separated from the Dachsteinkalk
|
|
outcrop by a band of Liassic marls, which also extend NE up the valley of
|
|
Grüne Bichl. This is apparently the trace of a second thrust plane,
|
|
(higher than the one shown on the map above) where the Dachsteinkalk has
|
|
effectively slid north lubricated by a layer of salt (which itself is most
|
|
obvious in the local Salzbergwerk - salt mines). This suggests that the
|
|
situation is rather more complex than the single thrust depicted above,
|
|
but, if true, at least eliminates the idea that the Loser plateau is a
|
|
nappe, with these lower beds inverted, and a shattered core at half the
|
|
depth of the Dachsteinkalk which would prevent exploration to great depth.
|
|
This is supported by direct exploration of the Stellerweg streamway, which
|
|
has reached roughly lake level, which is quite near the level of the main
|
|
thrust plane.
|
|
|
|
<p>The Dachsteinkalk all looks very similar, and much of the rock underground
|
|
is concealed by mud or breakdown, so it has proved very difficult to make any
|
|
meaningful observations. It has become clear, however, that all or most of
|
|
the vertical development in the caves is fault- or joint-guided, on two
|
|
roughly perpendicular sub-vertical sets of faults/joints. That some of these
|
|
are indeed faults is shown by clear offset of beds in a few places where
|
|
prominent shelly beds act as markers. Some faults are also apparent running
|
|
for significant distances on the surface, sub-parallel with the massive
|
|
fault bounding the Loser block to the SE.
|
|
|
|
<p>The fossil phreatic passages seem to be much less dependent on joint
|
|
direction, and appear to follow certain beds of the Dachsteinkalk. The
|
|
clearest example is Yapate Inlet and Chicken Flied Nice, near Burble
|
|
crawl in <a href="smkridge/161/top.htm">Kaninchenhöhle</a>.
|
|
|
|
<p><img src="smkridge/161/fullsize/cfngeo.png" width=600 height=530>
|
|
|
|
<p>Here, the small inlet tube of Burble Crawl, and the original
|
|
main trunk tube of CFN are both formed in a massive creamy white
|
|
bed of limestone just above a 0.8m thick zone of thinly bedded
|
|
limestone. At Staircase 36, the beds can be seen to be offset at
|
|
a fault running roughly at right angles to the main passage, and
|
|
Yapate Inlet, south of the fault, is formed in exactly the same
|
|
bed, but a few metres lower in altitude. The much later vadose
|
|
downcutting has revealed the lower beds including the two shelly
|
|
beds containing many fossil bivalves. These fossils stand out
|
|
particularly well on the wall of Staircase 36 itself, where they
|
|
provided much-needed holds for the climb.
|
|
|
|
<p><i>to be continued</i>
|
|
|
|
<hr>
|
|
|
|
<!-- LINKS -->
|
|
<img alt=">" src="../icons/lists/0.png">
|
|
Back to <a href="../index.htm">CUCC Home page</a><br>
|
|
<img alt=">" src="../icons/lists/0.png">
|
|
Back to <a href="index.htm">Expedition Intro page</a><br>
|
|
<img alt=">" src="../icons/lists/0.png">
|
|
<b>Main Indices:</b><br>
|
|
<img alt="--->" src="../icons/lists/1.png">
|
|
<a href="infodx.htm"><b>Index</b> to Expo</a> information pages<br>
|
|
<img alt="--->" src="../icons/lists/1.png">
|
|
<a href="areas.htm">Description of CUCC's area</a> and split to subareas<br>
|
|
<img alt="--->" src="../icons/lists/1.png">
|
|
Full <a href="indxal.htm">Index to cave descriptions</a> in area 1623<br>
|
|
<img alt="--->" src="../icons/lists/1.png">
|
|
List of (links to) <a href="pubs.htm">published reports and logbooks</a>
|
|
|
|
</body>
|
|
</html>
|
|
html>
|