BAJOCIAN

This article appears in Volume V03, Page 226 of the Encyclopedia Britannica.

Encyclopedia Britannica - Main :: BAI-BAR

BAJOCIAN , in geology, the name proposed in 1849 by d'Orbigny for the rocks of Middle Jurassic age which are well developed in the neighborourhood of Bayeux,

Calvados

CALVADOS

. The Bajocian stage is practically equivalent to the Inferior Oolite of ,British geologists. It corresponds fairly closely with the Lower and Middle Brown Jura of Quenstedt, and with the Dogger of Oppel. By means of the fossil ammonites the Bajocia strata have been subdivided into the following zones, in descending order:
Zone of Parkinsonia Parkinsoni and Cosnaoceras garantianum
Coeloceras subcoronatum (Humphriesianum)
Sonninia Romani
Stephaeoceras Sowerbyi
Harpoceras concavum
Murchisonae Substage Aalenien
opalinum of Mayer-Eymar.
It should be remarked that some European geologists prefer
to include the Parkinsonia zone in tile base of the overlying Bathonian (q.v.).
The Bajocian rocks of Europe are mostly limestones of various kinds, very frequently oolitic. At Bayeux, the type

district

DISTRICT

, they are ferruginous oolites; in the Jura and

Lorraine

LORRAINE

a coral limestone overlies a crinoidal variety; calcareous sandy and many beds occur in Maine and Anjou; in Poitou the limestone is dolomitic and bears nodules of chert. Rocks of the same age, as recognized by their fossil contents, have a wide range; they are found in north Africa, Goa,

Somaliland

SOMALILAND

, German

East

EAST
EAST, ALFRED (1849- )

Africa, and north-west Madagascar; through southern Europe they may be followed into Turkestan, and-the Kota-Maleri beds of the Upper Gondwana

series

SERIES (a Latin word from serere, to join)

of India may possibly belong to this stage. In

South

SOUTH
SOUTH, ROBERT (1634–1716)

America they appear in Bolivia, Chile and Argentina; in North America, in British Columbia, Dakota,

Mexico

Oregon

OREGON

and California. The Bajocian sea also included parts of New

South

SOUTH
SOUTH, ROBERT (1634–1716)

Wales, New Zealand (Flag Hills beds ?), Borneo and Japan, and it extended into the polar region of eastern Greenland and Franz Josef Land.
In addition to the ammonites already mentioned, the large belemnites (Megateuthis giganteus) and terebratulas (T. perovalis) are worthy of notice; crinoids and corals were abundant, and so also were certain forms of Trigonia (T. costata), Pleurotomaria and Cidaris.
See JuRAssic; also A. de Lapparent, Traite de geologie, vol. ii. (5th ed., 1906); and H. B. Woodward, " The Jurassic Rocks of Britain," vol. iv., 1894 (Mem. Geol. Survey) ; both works contain references to

original

ORIGINAL

papers. (J. A. H.)

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