Arkell.1956.Jurassic..

470 BALTIC REGION AND POLAND
England. (They should for the most part be assigned to the genus
Involuticeras: see p. 115).
The lowest Kimeridgian bed at Zarnglaff unfortunately yields no
ammonites. It is a 2-3 m. marl band full of gastropods and many other
fossils, including the large 'Pterocera' oceani of the French Lower Kimeridgian.
Elsewhere in the Baltic region, however, characteristic ammonites
of the English basal Kimeridgian zones (Cymodoce & Baylei) occur at
widely separated places. At Memel in Lithuania Amoeboceras cricki
(Salfeld) was found in a micaceous sandstone underlying drift (Frebold,
1926), and in Denmark a large Rasenia cf. cymodoce (d'Orb.), with smooth
outer whorl, was found in an erratic (Skeat & Madsen, 1898, pi. vii,
misidentified).
UPPER OXFORDIAN (Bimammatum Zone)
The top bed of the Oxfordian, under the 'Pterocera' marl, consists of
2-5-3-5 m
- °f limestone yielding Ringsteadia pseudocordata Dohm non
Blake & Hudleston, R. frequens Salfeld, R. aff. marstonensis Salfeld, R.
(Balticeras) pommerania Dohm, R. (B.) ramlowi Dohm, and large evolute
Perisphinctids with coarse-ribbed outer whorls: Pomerania robusta
(Dohm), P. schmidti (Dohm), P. latecosta (Dohm) and P. dohmi Arkell
(see Arkell, Mon. Am. Engl. Corallian Beds, p. lxiv). The inner whorls
of Pomerania being unknown, it seems advisable to keep them separate
from Decipia, but in any case the genus is very close to Decipia and has
nothing in common with Pictonia. (Cf. P. westburyensis Arkell, loc. cit.,
Monogr., p. 368-9, fig. 131). This is the true Pseudocordata Zone of
England. Underneath come another 4 m. of limestones yielding Ringsteadia
(Vineta) jaekeli (Dohm), which is closely allied to R. (V.) evoluta
Salfeld, also from the English Pseudocordata Zone. At the base of this
zone in the Zarnglaff quarry there is a conglomeratic bed.
The lowest 5-4 m. of varied beds at Zarnglaff contain Amoeboceras
alternans auct. which, to judge by the figure in Schmidt, 1905 (pi. x,
fig. 8), is one of the Amoeboceras of the drift in East Anglia (recte A.
ovale (Quenst.—Salfeld)), here, at Zarnglaff, placed in situ beneath the
Pseudocordata Zone, as inferred for England in the absence of sections.
This condensed ammonite succession in the two quarries at Zarnglaff
and Schwanteshagen is so important for European correlation that it is
summarized in the following table. The revised identifications are based
largely on my own examination of the ammonites in 1935 in the University
of Greifswald, through the kindness of Dr Konrad Richter. (See Richter,
1931, p. 24, pi. ii, for general photo of the collection.)
UPPER OXFORDIAN (Transversarium Zone)
Lower beds down to Callovian at Heilsberg, south of Konigsberg,
and to Lower Bathonian at Hohensalza near Posen, have been proved in
borings (Brinkmann, 1927, pp. 71, 74, with refs.). For exposed profiles of
the rest of the Oxfordian and the Callovian, however, the scene shifts to
http://jurassic.ru/