Mr. Pengelly has confirmed Sir H. De la Beche's opinion
that much of the upper portion of this old lacustrine formation has been removed
by denudation. (Philosophical Transactions 1863. Paper by W. Pengelly F.R.S. and
Dr. Oswald Heer.)
At the surface is a dense covering of clay and gravel with angular stones
probably of the Post-pliocene period, for in the clay are three species of
willow and the dwarf birch, Betula nana, indicating a climate colder than that
of Devonshire at the present day.
Below this are Lower Miocene strata about 300 feet in thickness, in the upper
part of which are twenty-six beds of lignite, clay, and sand, and at their base
a ferruginous quartzose sand, varying in thickness from two to twenty-seven
feet. Below this sand are forty-five beds of alternating lignite and clay. No
shells or bones of mammalia, and no insect, with the exception of one fragment
of a beetle (Buprestis); in a word, no organic remains, except plants, have as
yet been found. These plants occur in fourteen of the beds-- namely, in two of
the clays, and the rest in the lignites.
Pages:
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473