Arkell.1956.Jurassic..

THE CAUCASUS 3 6
3
dated to the Sauzei and Humphriesianum Zones. (See also Kakhadze,
I
943-)
On the north slopes of the western Caucasus, in Kuban, the Bajocian
is represented in a great series of sandy clay-shales at least 500 m. thick
and expanding westwards. At the base occur Ludwigia murchisonae
(Sow.) and many other ammonites; a long way higher occurs Oppelia
subradiata (Sow.) with many Phylloceratids and Lytoceratids and Lissoceras
aff. oolithicum (d'Orb.); then come 30 m. of clayey sandstones with
Strenoceras subfurcatum; and finally clays with Parkinsoniae. In some
places, however, the whole Lower and Middle Bajocian, up to the Subfurcatum
Zone, are represented by coal-bearing sandstones like those of
the Lias, and the Subfurcatum Zone may be as much as 100 m. thick.
The Upper Bajocian hereabouts yields interesting assemblages of Strenoceras,
Garantiana and Parkinsonia, including new forms (Zatvornitzki,
1914, with 2 pis. of ammonites). The heavily-auriculate dwarf Cleistosphinctes
asinus (Zat.) (pi. xvii, fig. 20) is a close relative of C. cleistus
(Buckman) (1920, Type Am., pi. CLXI) from the Subfurcatum Zone of
Dorset. In the north-eastern Little Caucasus the Bajocian is said to
be up to 5000 m. thick, with important volcanic rocks
(Leontyev, 1950).
throughout
TOARCIAN AND LOWER BAJOCIAN
In the eastern Caucasus the Toarcian and Lower Bajocian are developed
as immense thicknesses of shales, sandy shales and sandstones, altogether
8500 m. thick. The succession according to Golubyatnikov (1940) is as
follows:—
Alternating sandstones and shales, with Ludwigia murchisonae, Graphoceras
concavum, Leioceras acutum, up to 2000 m.
Alternating shales and sandstones with Leioceras opalinum, Pseudolioceras
beyrichi (Schloenbach), Dumortieria moorei (Lycett), D. levesquei
(d'Orb.), etc., 2400 m.
Shales with conspicuous sandstones: Grammoceras thouarsense (d'Orb.),
G. fallaciosum Bayle, etc., 1000-1200 m.
Shales alternating with sandy shales and sandstones: Peronoceras subarmatum
auct. (P. verticosum Young & Bird sp.?), 1000 m.
Shales with several patches of thick sandstones: Hildoceras cf. gyrale
Buckman, Harpoceras cf. exaratum (Young & Bird), 2100 m.
Renz (1904) also described the black shales of Daghestan as continuing
down through the Upper Lias, with Posidonia bronni and Harpoceras
serpentinum (Rein). Limestones and marls of Toarcian age have been
recorded from various other parts of the Caucasus.
MIDDLE AND LOWER LIAS
The lowest Jurassic beds all over the Caucasus consist of dark plantbearing
shales and sandstones with seams of coal, a facies similar to the
Gresten Beds of Austria, and attaining great thicknesses. Occasionally
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