68 
NEWER PLIOCENE PERIOD. 
[Ch. VI. 
These marls are sometimes gypseous, and belong to a great 
argillaceous formation which stretches over a considerable part 
of Sicily, and contains sulphur and salt in great abundance. 
The strata of this group have been in some places contorted in 
the most extraordinary manner, their convolutions often resem- 
bling those seen in the most disturbed districts of primary clay 
slate. 
But we wish, at present, to direct the reader's exclusive at- 
tention to strata decidedly referrible to the "newer Pliocene 
era, and we have yet to mention the igneous rocks associated 
with the sedimentary formations already alluded to. 
Volcanic Rocks of the Val di Noto. — The volcanic rocks 
occasionally associated with the limestones, sands, and marls 
already described, constitute a very prominent feature through- 
out the Val di Noto. Great confusion might have been ex- 
pected to prevail, where lava and ejected sand and scoriae are 
intermixed with the marine strata, and, accordingly, we find it 
often impossible to recognize the exact part of the series to 
which the beds thus interfered with belong. 
Sometimes there are proofs of the posterior origin of the lava, 
and sometimes of the newer date of the stratified rock, for we 
find dikes of lava intersecting both the marl and limestone, 
while, in other places, calcareous beds repose upon lava, and 
are unaltered at the point of contact. Thus the shelly lime- 
stone of Capo Santa Croce rests in horizontal strata upon a mass 
of lava, which had evidently been long exposed to the action 
of the waves, so that the surface has been worn perfectly 
smooth. The limestone is unchanged at its junction with the 
igneous rock, and incloses within it pebbles of the lava*. 
The volcanic formations of the Val di Noto usually consist 
of the most ordinary variety of basalt with or without olivine. 
The rock is sometimes compact, often very vesicular. The 
some which he obtained from the same localities, but I have met with no zoolo- 
gists who could name the species. 
* This locality is described by Professor Hoffmann, Archiv fur Mineralogie, &c. 
Berlin, 1831. 
