Arkell.1956.Jurassic..

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UPPER BAJOCIAN (up to 28 m.)
WESTERN GERMANY
Where most fully developed in the central Swabian Alb, in the Kirchheim-Urach
district, the thickness is swollen much above the normal by
the incoming of 20 m. of clay in the Subfurcatum Zone and by 6-7 m. of
clay at top of the Parkinsoni Zone (the upper part of this perhaps transitional
to the Zigzag Zone) (Stahlecker, 1926, pp. 201-5). In Franconia
the usual thickness is seldom more than two or three metres. The
synonymy of the numerous species of Parkinsonia, Garantiana and
Strenoceras is so involved that no attempt to list the successive faunas
will be made. (For notes on the types of the basic species see Arkell,
1951, p. 9, notes 3-5). The stratigraphy is fully treated, with numerous
figures of the Parkinsoniae, by Schmidtill & Krumbeck (1931); see also
Wetzel (1924, pp. 179-201). The succession where most fully developed,
in the Swabian Alb, is as follows (Stahlecker, 1926, pp. 201-5).
Parkinsoni Zone
Upper parkinsoni beds, clays . . . . . . 67 m.
Parkinsoni Oolite . . . . . . . . 00-0 7 m.
Garantiana Zone
'Parkinsoni' nodules, with Garantiana
Subfurcatum Zone
Upper Subfurcatum beds or 'Hamitentone', clays . . 20 m.
Subfurcatenoolith, sometimes clay (with Strenoceras spp.,
Garantiana baculata, Spiroceras bifurcati, Teloceras spp.) 0-5-2 m.
In Franconia, condensation produces a mixture of part of the Garantiana
and Parkinsoni Zones, which Schmidtill & Krumbeck separate as middle
parkinsoni beds. This appears to be the main level of the true P. parkinsoni,
which may overlap with Garantiana spp., just as various Garantianae
overlap with Strenoceras spp. At Gruibingen Teloceras of several species
(but not T. blagdeni) have been obtained from the Subfurcatum Zone
(Maubeuge, 1952).
MIDDLE BAJOCIAN (up to c. 40 m.)
Zone of Stephanoceras humphriesianum. Coronaten-Schichten. The
subzone of Teloceras blagdeni at top is well differentiated (Blagdeni
Schichten). In the Humphriesianum Subzone three levels are recognized
in favourable places, characterized by different combinations of species
of Stephanoceras, Skirroceras, Stemmatoceras and Normannites. The
numerous well-preserved Stephanoceratids have been revised and figured
by Weisert (1932) and Schmidtill & Krumbeck (1938). Stephanoceras cf.
humphriesianum (Sow.) occurs in the middle level, in which Cadomites
cf. daubenyi and C. cf. stegeus (Buck.) are also recorded. Normannites
and its subgenera go all through, starting with N. braikenridgei (Sow.)
in the lower level. In basal clays with Megateuthis giganteus various
Stephanoceratids occur with Chondroceras cf. grandiforme Buckman,
and elsewhere Dorsetensia liostraca Buck., D. regrediens Haug (Stahlecker,
1926, p. 196, 1934, p. 95; Frank, 1942, pp. 21-29) and D. complanata
Buck. (Maubeuge, 1950, p. 43). Some other mollusca are figured by
Kuhn (1938).
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