From be799ef494c56352f285036eefc8fbad5941e93b Mon Sep 17 00:00:00 2001 From: olaf Date: Fri, 14 Sep 2012 22:52:19 +0100 Subject: [PATCH] added a new geological outline --- geolog.htm | 204 ++++++++++++++++++++++++++++++---------------------- geolog2.htm | 106 +++++++++++++++++++++++++++ 2 files changed, 226 insertions(+), 84 deletions(-) create mode 100755 geolog2.htm diff --git a/geolog.htm b/geolog.htm index cda68c844..fd90588e9 100644 --- a/geolog.htm +++ b/geolog.htm @@ -6,101 +6,137 @@ -

Outline Geology of the Loser Plateau

+

Loser Plateau: Geology and Speleogenesis

+

+As it's quite hard to find information about the geological history of the +Schwarzmooskogel in English, I started investigating. Not that I'd know much +about geology, but as a German native speaker I had a large selection of +literature available. Particularly helpful was the article +"Joachim Kuhlemann et al. . "Eine Zeitreise in den zentralen Nördlichen +Kalkalpen: von Tropischen Küstenebenen zu Eishöhlen. In Karst und Höhle 2002/2003, Der Schwarzmooskogel, p. 137-153. VdHK e.V. München. +ISSN 0342-2062", but all the other articles in that journal issue are highly +recommended as well. At the time of writing, there are furthermore two short +articles on the appearance and sedimentation of the limestone +here and +here. +

-

Much of the area of the Loser Augst-Eck plateau is rough limestone pavement -(karren), 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.

+

Formation of the Limestone

+

+There appears to have been a shallow sea in the area during the Permian +(299-251 Mya), which occasionally dried out. This is where the salt of the +nearby salt mines formed, interspersed with some sandstone sediments. Most of +the limestone then formed in the middle to late Triassic (250-200 Mya), when +the shallow sea got a bit deeper, but was still well within reach of sunlight. +This provided perfect conditions for algae and corals, which eventually turned +into limestone. The base rock was sinking at the time, but the enormous +production of sediments counterbalanced this downwards movement. These layers +of sediments are nowadays called Dachstein-limestone ("Dachsteinkalk"). +

-

Articles speculating on the geology appeared from time to time in -Cambridge Underground, 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 article 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):

+

+At the end of the Triassic and during the Jurassic (199-145 Mya), the sink +rate increased and the production of sediments could not keep up any more. +At the resulting deeper levels of the sea, dolomites and other limestones +started to form. In our area, the Loser-group and Bräuningzinken are +examples of these Jurassic limestones and dolomites. Due to various other +minerals mixed into the rock, it is not as well suited for cave formation as +the Dachsteinkalk, although major caves are still found (e.g. at Almberg). +

-
+

+Towards the end of the middle Jurassic, a new oceanic ridge started to form +between the Eurasian plate in the north and the Apulian and Adriatic plates in +the south. Due to the force this new Penninian ocean ridge exerted onto the +continental plates, the various layers of limestone and dolomite were pushed on +top of each other in so called thrust faults from the southeast to the +northwest. Some parts of the newly formed oceanic crust were uplifted as well, +and at the same time rocks were eroded and started back-filling the ocean. This +ocean lasted up to the middle Cretaceous (145-65 Mya), when the ocean started +to close again due to a change in tectonics. The subduction of the short lived +oceanic crust continued a few more million years and the ocean has completely +disappeared nowadays. In the process rocks were also eroded from the bottom of +the continental crust by friction of the subducted oceanic crust. Generally +the area around the Totes Gebirge also sunk a bit during the late Cretaceous +and early Paleogene (65.5-23 Mya). +

-

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.

+

First Caves and Mountains

+

+During the Eocene (55.8-33.9 Mya) the alpidian collision started to cause the +uplift of the Alps. However, in the beginning this mostly caused an uplift in +the western part of the Alps, and the eastern part including the Totes Gebirge +was still relatively low, even partially flooded by seawater. As a result, a +first karstification started in the area, which created what is called the +cave ruin level ("Ruinenhöhlenniveau"). This level is nowadays about 1800m +and higher above sea level and the stone bridge (Traungoldhöhle) is probably +a prime example of this cave level. +

-

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.

+

+However, the new mountain ridge to the southwest of the Totes Gebirge was +exposed to erosion and lots of sediments started to back-fill and cover the +cave ruin level in the Oligocene (33.9-23 Mya). The new sediments are called +Augenstein-Formation, and the rubble consisted of all kinds of odd materials +like quartz, gneiss, slate, some ore, sandstones and others. The sediments are +getting finer in the north and fine sands at the northern edge of Totes Gebirge +indicate that a coastline was present at the time, whereas coarser pebbles +and stones are found further south. The exact mineral composition of the +Augenstein-sediments found at various places even allows to reconstruct the +river network of the time, which was mostly oriented south to north. +Furthermore the absence of gneiss and slate in the Augenstein-sediments of the +Totes Gebirge indicate that these rocks, which nowadays form the Tauern +mountains south of our area, were mostly covered by limestone and other +sediments at the time. These sedimentary rocks are nowadays only present around +some peaks of the Tauern mountain range. Some rock metamorphosis has taken +place in the Augenstein-sediments and indicate a thickness of at least 1300m up +to maybe beyond 2000m, with a maximum of thickness around the Dachstein area. +

-

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.

+

+In the early Miocene (23-5.3 Mya) the eastern Alps were laterally stretched in +the east-west direction by more than 50%. This event also caused a collapse of +the mountains further south-west, a new layout of the river network along the +newly formed fault lines, and in the cause of both a complete stop of the +sedimentation of Augenstein-layers. Most of these sediments had been eroded +again by about 10 Mya. Karstification of the cave ruin level and below could +start again. +

-

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 Kaninchenhöhle.

+

More Caves

+

+During the last 10 Mya, the Totes Gebirge was raised by about 2000m, which is +equivalent to about 2mm per year. This uplift is generally considered to have +happened in distinct phases instead of a continuous process, as there appear +to be distinct levels of caves all around. The "level of big caves" +("Riesenhöhlenniveau") with extensive horizontal passages is nowadays at +around 1550m-1640m above sea level. It was formed in the late Miocene, about +10 Mya. +

-
Cross-section sketch of Yapate and Burble Crawl
+

+Due to the absence of plants and due to glaciation and hence absence of flowing +water, there was hardly any new cave formation in the Pleistocene (2.5 Mya - +10 Kya). However, most recently the level of spring caves +("Quellhöhlenniveau") has formed and is still actively forming at +altitudes equivalent to the present valley bottoms. As the distance of this +spring cave level to the older levels varies between 700m and 1000m in various +parts of the Alps (Tennengebirge, Steinernes Meer, Totes Gebirge), it is +believed that these different places have also been lifted by different rates +in the Pliocene era (5.3-2.5 Mya). +

-

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.

+

+It is obvious that the above geological history of the Totes Gebirge is mostly +an interpretation of the sparse evidence that is nowadays found at Dachstein, +Schönberg, Schwarzmooskogel, Woising, Tauplitz and the other areas. +New finds and new caves might necessitate a complete or at least a partial +rewrite. +

-

to be continued...

+

Olaf Kähler, September 2012

- + diff --git a/geolog2.htm b/geolog2.htm new file mode 100755 index 000000000..cda68c844 --- /dev/null +++ b/geolog2.htm @@ -0,0 +1,106 @@ + + + + +CUCC Austria Expeditions: Geological Outline + + + +

Outline Geology of the Loser Plateau

+ +

Much of the area of the Loser Augst-Eck plateau is rough limestone pavement +(karren), 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.

+ +

Articles speculating on the geology appeared from time to time in +Cambridge Underground, 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 article 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):

+ +
+ +

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.

+ +

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.

+ +

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.

+ +

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 Kaninchenhöhle.

+ +
Cross-section sketch of Yapate and Burble Crawl
+ +

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.

+ +

to be continued...

+
+ + + +