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Updated: June 3, 2025


Among the fresh-water strata of this age near the base of the Pyrenees are marls, limestones and sands, in which the eminent comparative anatomist, M. Lartet, has obtained a great number of fossil mammalia common to the faluns of the Loire and the Upper Miocene beds of Switzerland, such as Dinotherium giganteum and Mastodon angustidens; also the bones of quadrumana, or of the ape and monkey tribe, which were discovered in 1837, the first of that order of quadrupeds detected in Europe.

To enlarge on the numerous subdivisions of the Parisian strata would lead me beyond my present limits; I shall therefore give some examples only of the most important formations. Beneath the Gres de Fontainebleau, belonging to the Lower Miocene period, as before stated, we find, in the neighbourhood of Paris, a series of white and green marls, with subordinate beds of gypsum.

The best lime marls provide excellent material for the correction of soil acidity, the actual value per ton being practically the same as that of the finest pulverized limestone. Some dealers in marl make extravagant claims for their goods, but any farmer may easily put these claims to the test and learn that he should not expect more than a fairly good carbonate of lime can do.

At the head of this valley is Split-Mountain Canyon, 8 miles long, with ragged, craggy walls 2700 feet high. It contains a number of medium rapids. Island Park separates it from Whirlpool Canyon. It is a charming little valley, full of islands, a mere expansion of the walls, 9 miles long, 9 miles of rainbow, for the surrounding rocks and marls are of every hue.

Some are jasper, and look like masses of red sealing-wax; others are agate, or opalescent chalcedony, beautifully lined and variegated; many retain the graining, layers, knots, and other details of their woody structure. In places where the marls had been washed away gently, the emigrants found trunks complete, from root to summit, fifty feet in length and three in diameter.

In Tuscany, as at Radicofani, Viterbo, and Aquapendente, and in the Campagna di Roma, submarine volcanic tuffs are interstratified with the Older Pliocene strata of the Sub-apennine hills in such a manner as to leave no doubt that they were the products of eruptions which occurred when the shelly marls and sands of the Sub-appenine hills were in the course of deposition.

Low mesas, dry, treeless, stretch back from the brink of the canyon, often showing smooth surfaces of naked, solid rock. In some places the country rock is composed of marls, and here the surface is a bed of loose, disintegrated material through which one walks as in a bed of ashes. Often these marls are richly colored and variegated.

Formations of quartzose porphyry, pyroxenic porphyry and trachyte, of grauwacke, muschelkalk and quadersandstein, which are frequent towards the west, have not yet been seen in Venezuela; but it may be also observed that in the system of secondary rocks of the old continent muschelkalk and quadersandstein are not always clearly developed, and are often, by the frequency of their marls, confounded with the lower layers of Jura limestone.

The Swiss Lower Miocene may best be studied on the northern borders of the Lake of Geneva, between Lausanne and Vevay, where the contiguous villages of Monod and Rivaz are situated. The strata there, which I have myself examined, consist of alternations of conglomerate, sandstone, and finely laminated marls with fossil plants.

Limestone contains the calcium and magnesium that must be the chief source of supply of American soils, though marls, ashes, etc., have their place. The burning of the stone has been the leading means of bringing it to a condition of availability to the soil, excepting, of course, the vast work of disintegration carried on through all the ages by nature.

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