Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/75

 fixed, it follows that the strata overlying the above-mentioned Platendolomit, and ranging from a depth of 1590 ft. 9 in. to 1698 ft. 10 in., belong to the lowest part of the Bunter Sandstone ; while those that immediately underlie it, at a depth of from 1740 to 2001 feet, must be referred to the upper region of the Zechstein.

The limestones which were so repeatedly raised during the boring caused the reference of the former series to the Zechstein ; but the author states, as the result of his examination, that they differ in all their relations from the deeper limestones occurring at 1698 feet and upwards, and, on the other hand, correspond in none of their characters with the Plattendolomit (the uppermost member of the Zechstein), and that they therefore belong to the Bunter Sandstone.

Limestones being particularly abundant in the lowest portion of the Bunter Sandstone in Thuringia and in the district of Magdeburg, and occurring even in two forms, viz. (1) as " Rogenstein," often very coarse-grained, and (2) as close or fine-grained so-called "Hornkalk," the author concludes, from the comparison of a very complete series of them, that the " Hornkalk " corresponds entirely in petrographical and chemical characters with the beds in question, — and also that beds of rock-salt, analogous to those of Stassfurt or Schonebeck*, cannot be reckoned upon in Franconia; for the strata in which they lie are but slightly developed on the southern margin of the Thuringer-Wald, and at the best contain very little saline matter.

Below the Plattendolomit of the Zechstein, from the depth of 1740 feet to 1884 feet follow saline clays of red, bluish, and brownish colour, which appear to be traversed by lines of anhydrite, or of white gypsum. Boiling water extracts from them a tolerably large quantity of alkaline chlorides (one specimen of the red saline clay yielded 3.21 per cent, of chloride of sodium with very little chloride of potash), and little of the sulphates ; they are evidently the principal source of the saline contents of the Kissingen wells.

The still deeper anhydrite, from 1884 to 2001 feet, is dirty bluish- grey, very hard, and here and there contains druses, in which crystals of the mineral appear to have been formed.

At a depth of 2001 feet the boring was discontinued, in consequence of the breaking and jamming-in of the chisel ; and the question therefore still remains, whether the anhydrite forms the base of the salt-bearing beds of the Zechstein in Franconia, or whether it is only an intercalated bed between an upper very poor deposit, which owes its importance entirely to the mineral waters which derive their salt from it, and a lower and richer rock-salt formation.

That this is possible appears, e. g., from the fact that in the Triassic deposits of Baden and Lothringen the salt-bearing portion contains several divisions of the pure rock-salt beds, which are

Zeitschr. d. deutschen geol. Gesellschaft, vol. xix. 1866, p. 373, which gives the most striking proof of the rock-salt in question belonging to this series of beds, as shown by many well-sections.
 * A very complete memoir on Schonebeck is that by C. v. Alberti in the