The upheaval of the Jura Mountains of France and Switzerland is a relatively recent (11 Mya) geological event, and karstic springs are a characteristic feature of this formation. As a matter of fact, all endemic species of aquatic insects (Ephemeroptera, Trichoptera, Plecoptera) from the Jura Mountains described so far are typical inhabitants of karstic springs. Dating the origin of karstic springs in the Jura Mountains therefore would contribute greatly to our understanding of the population history of aquatic insects in the Jura Mountains.
Dear Mr. Reding,
I think you better redirect your ideas towards the inorganic material deposited in caves and cavities of karstified limestone units such those of the Jura Mts.. The residual clay minerals (speleothems), particularly those accommodating K in their structure, e.g., micaceous phyllosilicates, and the APS minerals associated with them, in places, under low pH, such as alunite are prime objectives of these investigations. There is a nice example from the Carlsbad Caves (cited in DILL, H.G. (2001) The geology of aluminum phosphates and sulphates of the alunite supergoup: A review.- Earth Science Reviews, 53: 35-93). Rarely palygorskite has been used. In combination with fission-track methods of phosphates you might achieve good results (uplift and unroofing story). Some caves and cavities have fillings you can sloppily depict as an “exploded geological drugstore” with a wide variety of organic and inorganic material washed into the caves. In this case you are going to date the infilling stage of the “underground storage system „which is , of course, a bit younger than the onset of karstification.
I wish you much success
H.G.Dill
Hi,
Our dating of a Tortonian swamp deposit in central Jura (CR Acad Sci Paris, 314 ser. II : 359-364), now turned into lignite squeezed in a fault zone, evidences that freswater ecosystems existed in the Jura already by this date (ca. 11 My indeed). However older freshwater deposits are known, e.g. the Pontarlier Molasse, dated as late Burdigalian (ca 17-16 My). It unconfomably overlays a marine molasse, and thus could point out the beginning of Jura upheaval.
good luck for your research
Hi Marc,
there is also evidence of emerged platform in late Kimmeridgian (dinoaur tracks, paleosol, micro karst).
I would suggest dating speleothems from limestone caves from which springs emerge. The problem will be that you don't know the speleothem's depositional history - it could be recent or old. Appearance can be misleading because calcite deposition within a cave can vary with space and time. I would be leary of clay deposits unless they could be obtained from beneath, for example, a layer of flowstone that might preserve the the original depositional chemistry. I should think that a statistical approach both within individual caves and in different caves over the area would yield the best results. Just for your information speleothems, stalactites and stalagmites, for example, are commonly composed of calcite or aragonite, not "residual clay minerals".
The Karstification depends on the fracturing network, the intensity of rainfall and the nature of limestone.
The beginning of karstification is difficult to date. the filling of the cavities can be evacuated by the floods of water in the karstic system. The floods will reshape and / or transport the deposited sediments. Precision is compromised.
In addition, the oldest waters can be dated by isotopes methods for dating old groundwater (14C and 2H).
One can use U-Pb methods to date calcite and aragonite in speleothems and there may be other techniques as well. I don't think that dating groundwater in karstic systems is worthwhile because such water likely is a mix of modern and possibly ancient water. I think that there is a large body of literature available regarding the dating of carbonates in general and speleothems in particular.
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