Arkell.1956.Jurassic..

LOWER BATHONIAN (up to c. 60 m.)
NORMANDY AND SARTHE 49
As in England, the stratigraphy of all but the basal beds of the Lower
Bathonian is uncertain owing to scarcity of ammonites. Guillaume
(1927) established the following succession on and near the coast at
Port-en-Bessin:
Calcaires de Maisy (8-10 m.) (perhaps Middle Bathonian)
Calcaires de Cricqueville (10-15 m
-)
Calcaires de Vierville (4-5-12 m.) with Posidonia alpina
Marnes de Port-en-Bessin (c. 40 m.) with Posidonia alpina.
Inland the marls (Lower Fuller's Earth pro parte) are believed to pass
laterally into the Calcaire de Caen (30-55 m.), famous building-stone
of the Normans; but the Calcaire de Caen may be in part also equivalent
to the Calcaires de Vierville & Cricqueville (Parent, 1945), sometimes
united as the Oolithe Miliaire but not corresponding to that group around
Caen, where the true Oolithe Miliaire is Middle and early-Upper
Bathonian. Ammonite records are insufficient for a decisive answer
(discussed Wetzel, 1924, pp. 217-8). Eudes-Deslongchamps (1864,
pp. 121-8) recorded ammonites nearly a metre in diameter which seemed
to him to be giant Am. parkinsoni; this and the vertebrates recall the
Hook Norton Limestone and indicate the Zigzag Zone.
The ammonites of this zone abound in three thin beds of limestone,
altogether 40-50 centimetres thick, which crop out on the shore east of
Port-en-Bessin (Guillaume, 19276):
Bed C: abundant Oppelia (Oxycerites) fallax (Gueranger), O. limosa
(Buck.), O. nivernensis de Gross., with Morphoceras, Ebrayiceras, Zigzagiceras,
Oecotraustes, etc.
Bed B : same fauna but Zigzagiceras and Morphoceras more abundant,
Oppeliids less common.
Bed A: still has O. fallax and other Oppeliids, Morphoceras and Ebrayiceras,
but also abundant Parkinsonia convergens (Buckman), P. pachypleura
Buck., and P. ?postera (Seebach), with large Procerites cf. schloenbachi de
Gross. (I was able to confirm and correct some of these identifications,
especially the Parkinsonidae, when the late Louis Guillaume showed me
his collection in Paris in 1951).
UPPER BAJOCIAN (up to 15 m.)
In the cliffs of Bessin the Zigzag Zone rests on a thick white compact
limestone with abundant sponge-remains ('Oolithe Blanche', but it is
not a true oolite), from which rare Parkinsoniae and Oppeliids have been
obtained but not determined. This corresponds to the 'schloenbachi
beds' and sponge limestone in the same position in Dorset, at the top of
the Parkinsoni Zone.
Under the white sponge limestone about Bayeux is the Ironshot Oolite,
famous as the source of so many perfect ammonites in the quarry at
Sully, about 3 miles NW. of Bayeux. It is only up to 2 m. thick, but
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