Arkell.1956.Jurassic..

476 BALTIC REGION AND POLAND
basin is bounded by the abrupt front of the Carpathian ranges south of
Cracow.
The principal outcrop forms the Jasna Gora cuesta running from
Cracow north-westwards past Czestochowa (Czenstochau) to Wielun and
beyond, with the last outcrops at Kalisz. The Jurassic limestone escarpment
faces south-west towards the Oder valley and the Sudetes massif,
against which and its easterly extension at depth the formations were no
doubt deposited. This is shown, despite the erosion of the Oder, by the
fact that in the cuesta the Bajocian, Bathonian and Callovian stages when
traced southwards in turn pass laterally from clays and marls into sands
and sandstones with conglomerates and successively wedge out, until a
condensed Lamberti Zone comes to rest on the Palaeozoics in places near
Cracow. The cuesta is dissected by the River Warthe, in the steep valleys
of which occur the classic exposures.
On the opposite side of the basin there are extensive outcrops on the
SW. flank of the Lysa Gora hills. Here the lowest Jurassic stage
present at the surface is the Callovian (Swidzinski, 1931). Beyond the
Lysa Gora and the upper Vistula the Jurassic extends, mainly buried
beneath Cretaceous and later rocks, approximately to the heavy broken
line shown in fig. 74 (after Sujkowski, 1946). It feathers out underground
against Devonian and Carboniferous rocks, which in the south surround
a levelled Archaean massif under the Podolian platform. Some attempt
to reconstruct the successive overlaps along this buried line, between
the Pripet and the Niemen, has been made by Halicki (1935) from the
distribution of erratics in the drift.
In the deep valley of the River Dneister, at Nizniov, at the point where
the Jurassic wedges out against the Podolian platform on the east and the
Carpathian front on the south, is a remarkable deposit, the Nizniov
Limestone, about 20 m. thick, sandwiched between Devonian below and
Cenomanian above. The only cephalopod known is a Nautilid of
Tithonian or Berriasian type, but on the strength of an extensive fauna
of gastropods and pelecypods the limestone is dated to the Upper
Kimeridgian or the Portlandian-Purbeckian or both (Alth, 1882).
The main outcrops of the Jasna Gora cuesta and around Cracow and
SW. of the Lysa Gora are formed by an immense development of
Upper Oxfordian and Lower Kimeridgian limestones, together about
700 m. thick. The facies, both lithological and palaeontological, is the
same as in the Swabian Alb. The chief landscape-former is some 400 m.
of limestone, almost devoid of ammonites but zoned by brachiopods
(Wisniewska, 1932; Rozycki, 1948). The upper half is largely coralline
and belongs to the Tenuilobatus Zone. The lower half, belonging to the
Bimammatum Zone, is on the horizon of the Swabian-Franconian Werkkalk
but resembles the later (Kimeridgian) Schwammkalk, Felsenkalk,
and Plattenkalk. Huge lenticular masses of unbedded Felsenkalk, composed
largely of sponge remains, have resisted compaction and weathering
more successfully than the surrounding flaggy limestones (Plattenkalk)
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