Arkell.1956.Jurassic..

EAST OF THE PARIS BASIN 63
Zone, including a great range of Parkinsonia, Procerites, Zigzagiceras,
Morphoceras, Ebrayiceras, Oxycerites, etc. (Revised list in Mouterde,
1953, p. 170.) Above this bed follow limestones and pale marls, undated.
An anomaly requiring investigation is the alleged occurrence in the
Zigzag Zone of St Benin d'Azy of the type and sole known European
specimen of Micromphalites busqueti (de Grossouvre, 1919, p. 359, pi. xiv,
2), which seems identical with forms common in Arabia in the early-
Upper Bathonian.
At St Gaultier, Indre, there occurs at the local base of the Bathonian
a celebrated marly bed with freshwater gastropods, Viviparus aurelianus
and Valvata benoisti (Cossmann, 1899). The bed is only 0-5 to 1-5 m.
thick, and is overlain by 10 m. of Bathonian limestones, with Rhynchonella
elegantula in the upper part. It is usually considered Upper Bathonian
('Bradfordien'), but since it rests directly on Upper Bajocian limestone
with Parkinsonia it may well be older, more nearly the age of the similar
Viviparus and Valvata bed in Oxfordshire (p. 30).
BAJOCIAN (up to 220 m.)
The Bajocian has now been elucidated in great detail in many works
too numerous to quote, and its complicated variations of facies (oolites,
coral reefs, ironshot oolite, crinoidal limestone—'calcaire a entroques'—,
marls, oyster lumachelles, etc.) are now so thoroughly sorted out that
it is possible to compress the results into a single table (p. 64). This
is based on works which cite adequate faunas of ammonites for each
zone—especially the detailed monographs on the northern area by Bonte
(1941) and Maubeuge (1951a), on the southern by Mouterde (1953),
for the central region papers by Thiery (1922, 1922a) and Maubeuge
(1943, 1945, 1945a, 1947, 1947a, 19486, 19496, 1951a, 19526) and for the
Rhine valley Guillaume (1927), Gillet (1928) and Theobald & Maubeuge
(1949). For the Lower Bajocian older works with many figures of
ammonites by Benecke (1905) and Branco (1879) cannot be dispensed
with; more modern figures are given by Schneider (1927), Gerard &
Bichelonne (1934), Gerard (1937) and Gillet (1937).
The monograph by Mouterde (1953) is an immense mine of information
on faunal associations and successions, to which no brief commentary
could do justice. Anyone working on Liassic and Bajocian stratigraphy
will have to study it. Mouterde establishes that in the region west of
the massif of Morvan the ironshot oolite facies and crinoidal limestone
facies are interchangeable in all the zones of the Lower and Middle
Bajocian, and that the ironshot oolite facies locally continues through
the Upper Bajocian, and even into the Lower Bathonian, migrating
persistently eastwards, in the direction of the ancient massif, as if following
a retreating shoreline (p. 429). In central Lorraine it has been established
that species of Teloceras pass up into the Subfurcatum Zone, as in the
Jura, Germany and Poland (Maubeuge, 1952c), while the upper part
of the Parkinsoni Zone contains a stout-whorled Parkinsonia like that
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