Arkell.1956.Jurassic..

FRANZ JOSEPH LAND 501
FRANZ JOSEPH LAND
The archipelago of Franz Joseph Land contains the most northerly
known Jurassic in the world, on latitude 8o° N. The outcrops are mainly
on the south-westerly Northbrook Island and Hooker Island, but also
on some of the adjoining islets. The most complete and best-known
sections are at and near Cape Flora on Northbrook Island (Nansen,
1899; Pompeckj, 1899; Koettlitz, 1898; Newton & Teall, 1897). Here
Jurassic shales with layers of nodules and sandstone, with up to 14 m.
of carbonaceous and pebbly sands at the base, rise from sea level to a height
of about 175 m. They are overlain by 25 m. of Cretaceous basalts containing
and overlain by plant-bearing sandstones (whence Cape Flora
takes its name). At the top is a capping of permanent ice.
The lowest 3 m. of the shale series is a marl containing pelecypods
(Meleagrinella, etc.) and brachiopods (Discina, Lingula) believed to indicate
a Lower Bajocian date (Pompeckj, 1899). Above this is a considerable
gap without fossils. The first ammonite fauna spans a large thickness
of beds and represents two Lower Callovian zones with Arctocephalites
koettlitzi (Pompeckj, 1899, pi. ii, fig. 12), A. arcticus, A. ellipticus Spath
(1932, pi. xiii, fig. 6), A. pilaeformis Spath (Newton, 1897, pi. xl, fig. 2) and
Cadoceras frearsi (d'Orb.) (ib. p. 131) (Macrocephalus and Koenigi Zones).
(For further figures of this fauna see Whitfield, 1906.) After another gap
follow beds with Cadoceras tschefkini (d'Orb.) and Pseudocadoceras nanseni
(Pompeckj) (pi. ii, figs. 1-6, and fig. 16, p. 87). Pseudocadoceras is another
genus represented in the Hackness Rock, but it abounds also in the earlier
Kellaways Rock of South Cave (both in Yorkshire) and it is also abundant
in Alaska. Finally, at the top, is a poorly-preserved faunule of Quenstedtoceras
(Pompeckj, pi. ii, fig. 9), one of which was found embedded in the
base of the basalt (Koettlitz, 1898, p. 638).
Arcticoceras, Pseudocadoceras and Quenstedtoceras are also recorded from
Hooker Island (Samoilovich & Bodylevsky, 1933; Oghnev, 1933).
The plant-bearing beds are believed to be Hauterivian-Barremian
(Wealden); on some of the islands Berriasian ammonites are recorded
below (Spizarskij, 1937).
SPITSBERGEN AND KING CHARLES ISLANDS
Spitsbergen and its associated islands stand on the north-west edge of
the Barents shelf. To the west and north the sea floor sinks rapidly. The
shallow seas that now divide the islands of the Spitsbergen and Franz
Joseph groups and separate them from the mainland may be regarded as
a temporary transgression over the margins of the mobile shelf.
Conditions were essentially similar in the Jurassic. A narrow island
probably broke the water close to the edge of the shelf immediately to the
west of Spitsbergen, supplying some sediment; but in general deep water
lay to the west as it does to-day, connecting the polar ocean with Britain.
The first Jurassic transgression occurred in the Toarcian, bringing a
typical English and NW. German ammonite fauna over Spitsbergen only.
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