Dunham classification
A cement marl bowl is an irregular depression as a result of different Verwitterungsrestistenz of Massenkalken and stored, bankigen marl limestones. The Massenkalke were from algae - sponge reefs in the White Jurassic ( 160-150 million years ago ( Ma) ) deposited. Your erosion relics that cement marl bowls, still form morphologically distinctive landforms on the Swabian Alb.
Demarcation
Cement marl bowls are to be distinguished from karst wells of the Swabian Alb, which can appear morphologically similar, but rather smaller, and as a phenomenon of advanced karstification extremely much younger (maximum Pleistocene age, ie younger than 2.6 million years).
Genesis
In the upper section of the White Jura, mainly from the footwall Bankkalk formation (formerly Jurassic sita ki 2 or 5), the formation of reefs was done almost on the entire Albplateau. In the former, shallow, tropical marine facies developed mainly conical Riffkomplexe and between irregular hollow shapes with mostly flat ground. The morphology of the Swabian Alb is still determined in the northern part ( Kuppenalb ) through this Massenkalk - rocks. In the molds encamped in the course of further geological gray zementmergelige sediments, but in bankigen layers. The marly sediments were softer and were more compacted than the harder reef limestones. The " power of the cement marl formation was measured in the center of some cement marl bowls up to 170 meters. "
For the territory of Alb and the eastern Middle Alb, from the western Nordlinger Ries edge up to and including the Münsinger cement marl bowl, the recent formations of the footwall Bankkalke and cement marl into a single formation, the " Mergelstetten formation " are summarized. In the remaining area of the Swabian Alb, the formation names used since then still be used.
Removal by tectonic influences
Since the Albplateau by uplift and tilting ( from northwest to southeast and layer traps to S ) in the higher ranges was subject to more ablation, weathering and other erosion processes that Alboberfläche is increasingly given to younger stratigraphic ranges in the direction of the layer falling to S up to. On the Kuppenalb and the witnesses mountains of the Middle Alb ( Kornbühl, Monkberg, Köbele and Aufberg ) exposed the Massenkalkriffe, already plotted on the Schichtflächenalb. The younger layer formations ( hanging wall Bankkalk formation, cement marl formation, lying Bankkalk Formation) are therefore north of the cliff line hardly exist. This is often the cement marl bowls removed morphologically on.
Erosion through time
In the middle part of the Flächenalb, as well as almost all of the Alb and cement marl bowls are still numerous. They are partly north and partly south of the Miocene cliff line " - that is partially still on the Kuppenalb. In places they are covered by above them preserved hanging-wall Bankkalke ( protected).
In the present morphology of the Albplateaus but the cement marl are completely in almost all cement marl bowls or " more or less" resolved. If the ( cement ) marl layers are not removed completely, the water-bearing properties of marl have a beneficial significance for the otherwise water-poor agriculture in the Alb.
Occurrence
The reef limestones from the time of the Upper Jurassic of the Swabian Jura are also those from Switzerland, France, Spain, Poland and Romania similar. Despite the widespread it is but so far not been able to find recent sponge beds that would be comparable with the fossils from the Jurassic period.
As marl clay mixtures with Kalkan parts of 85 % to 10 % are found in all karst areas around the world. Massenkalkgebilde are on the northern Swabian Alb as Kuppenalb Although prevalent. Cement marl bowls cleared- as relics marl benches between Massenkalken come, however, available only in the southern areas of the Franconian and mostly on the southern Swabian Alb. Particularly large and still are determining the geomorphology cement marl bowls on the Swabian Alb.
Several bowls are between Heidenheim and Sontheim, north and south of the cliff line, while both sides of the Brenztals. North of the cliff line are the bowls of Boehmenkirch - Söhnstetten ( sheet 7325 ), Härtsfeld (W Neresheim ) and the Hörvelsinger bowl ( also Langenau ).
The rare because hardly been emptied, large marl Stetter bowl ( type locality Mergelstetten ), reaches a vertical thickness of 120m. At its eastern edge - on the east side of the Brenz - is a recognized as Geotop quarry, the lower bearing marl, Zwischenkalke and Upper marl bearing unlocks.
The Lauchert still flows today directly through the two bowls of Gammertingen and Jungnau. The bowl of Gammertingen with a diameter of about 2 km is largely eliminated, but marked in the Geological Map, Sheet 7721 Gammertingen, in outline. In the southwest of Gammertingen the cement marl is still pending. Here we also found it again and again in excavations of houses and in the nick of railway line Gammertingen - Neufra at the station " Gammertingen - Europastr. " It is also still open. In the marly sediments were found for dating important silicified fossils, especially sea urchin spines and sponge spicules, but no index fossils.
The bowl to the nature reserve Blue, ( north of the road Nollhof Winter Lingen ) extends on both sides of the western fault zone of Lauchertgrabens.
Also on the Kuppenalb at Münsingen and Gächingen (St. Johann ) ( Geological Map, Sheet 7522 Urach ) are two large bowls. The Münsinger bowl extends over 12km2. It is surrounded by a ring of towering limestone mountains mass and only partially resolved.
A beautiful, well visible from Knopfmacherfelsen, example is the reamed bowl at Castle Bronnen in the Upper Danube between Fridingen and Beuron. Immediately on the steep side of the valley has cut the funnel-shaped bowl spät-miozäne/pliozäne the strong erosion of the Danube. The two Massenkalk rock on the high edge of the valley - the remains of sponge reefs - formed from the relief of the former Jurassic sea floor.