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Dense Conglomerates and Proofs of Subsidence. Flora of the Lower Molasse. American Character of the Flora. Theory of a Miocene Atlantis. Lower Miocene of Belgium. Rupelian Clay of Hermsdorf near Berlin. Mayence Basin. Lower Miocene of Croatia. Oligocene Strata of Beyrich. Lower Miocene of Italy. Lower Miocene of England. Hempstead Beds. Bovey Tracey Lignites in Devonshire. Isle of Mull Leaf-Beds.
They have yielded more than 200 species of fossil plants, described by the late Professor Unger. The only abundant plant among the Radaboj fossils which is characteristic of the Upper Miocene period is the Populus mutabilis, whereas no less than fifty of the Radaboj species are common to the more ancient flora of the Lower Molasse of Switzerland.
There are, indeed, no less than 81 species of these Older Miocene plants which pass up into the flora of Oeningen. This fact is important as bearing on the propriety of classing the Lower Molasse of Switzerland as belonging to the Miocene rather than to the latter part of the Eocene period.
The first of them, that of Utznach, is a delta formed at the head of the ancient and once more extensive lake. The argillaceous and lignite-bearing strata, more than 100 feet in thickness, rest unconformably on highly inclined and sometimes vertical Miocene molasse.
I shall now proceed to treat of the third division, which is of Lower Miocene age. Nearly the whole of this Lower Molasse is fresh-water, yet some of the inferior beds contain a mixture of marine and fluviatile shells, the Cerithium margaritaceum, a well-known Lower Miocene fossil, being one of the marine species.
For ages, in spite of a gradual depression of the land and adjacent sea-bottom, the rivers continued to cover the sinking area with their deltas; until finally, the subsidence being in excess, the sea of the Middle Molasse gained upon the land, and marine beds were thrown down over the dense mass of fresh-water and brackish-water deposit, called the Lower Molasse, which had previously accumulated.
Among the ferns met with in profusion at Monod is the Lastraea stiriaca, Unger, which has a wide range in the Miocene period from strata of the age of Oeningen to the lowest part of the Swiss Molasse. Cinnamomum Rossmassleri, Heer. Daphnogene cinnamomifolia, Unger. Among the laurels several species of Cinnamomum are very conspicuous.
Proportion of recent Species of Shells. faluns more ancient than the Suffolk Crag. Upper Miocene of Bordeaux and the South of France. Upper Miocene of Oeningen, in Switzerland. Plants of the Upper Fresh-water Molasse. Fossil Fruit and Flowers as well as Leaves. Insects of the Upper Molasse. Middle or Marine Molasse of Switzerland. Upper Miocene Beds of the Bolderberg, in Belgium. Vienna Basin.
The very recent secondary rocks everywhere present analogous phenomena; the molasse of the Pays de Vaud contains a fetid shelly limestone, and the cerite limestone of the banks of the Seine is sometimes mixed with sandstone. The strata of calcareous breccia are composed of an infinite number of sea-shells, from four to six inches in diameter, and in part well preserved.
In part of the Swiss Molasse, which belongs exclusively to the Lower Miocene period, the number of plants has been estimated at more than 500 species, somewhat exceeding those which were before enumerated as occurring in the two upper divisions.
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