NEWER PLIOCENE STRATA OF THE UPPER VAL D'ARNO.
When we ascend the Arno for about ten miles above Florence, we arrive at a deep
narrow valley called the Upper Val d'Arno, which appears once to have been a
lake, at a time when the valley below Florence was an arm of the sea. The
horizontal lacustrine strata of this upper basin are twelve miles long and two
broad. The depression which they fill has been excavated out of Eocene and
Cretaceous rocks, which form everywhere the sides of the valley in highly
inclined stratification. The thickness of the more modern and unconformable beds
is about 750 feet, of which the upper 200 feet consist of Newer Pliocene strata,
while the lower are Older Pliocene. The newer series are made up of sands and a
conglomerate called "sansino." Among the imbedded fossil mammalia are Mastodon
arvernensis, Elephas meridionalis, Rhinoceros etruscus, Hippopotamus major, and
remains of the genera bear, hyaena, and felis, nearly all of which occur in the
Cromer forest-bed (see Chapter 13).
In the same upper strata are found, according to M. Gaudin, the leaves and cones
of Glyptostrobus europaeus, a plant closely allied to G.
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