The Jurassic Series in England

See S. S. Buckman, "Certain Jurassic (Lias-Oolite) Strata of South Dorset, and their Correlation," Q.J.G.S., vol. lxvi. (Iwo), p. 52; and vol. lxxviii. (1922), p. 378; J. F. Jackson, "The Junction Bed of the Middle and Upper Lias on the Dorset Coast," Q.J.G.S., vol. lxxxii. (1926), P. 490. The Northampton Sand of Northamptonshire (1928) (collected papers reprinted) ; R. H. Rastall, "The Blea Wyke Beds and the Dogger in North-East Yorkshire," Q.J.G.S., vol. lxi. (1905), PP. 441-460.

Bajocian

(from Bayeux, Normandy), including at the base the Aalenian (from Aalen, Wurttemberg), and the Bajocian (sensu strictu) above. These two divisions are usually known as the Inferior Oolite, but are separated by a plane of major uncon formity. The Aalenian includes at the base the upper part both of the Bridport Sands of Dorset, and of the Northampton Sands, mentioned above. The greatest development of the Inferior Oolite occurs in the Cotswold Hills (25o ft.); these shallow-water, ma rine, highly fossiliferous limestones, however, thin out and dis appear both to the south in the Mendip region, and to the north on the eastern borders of Oxfordshire. South of the Mendips, in Somerset and Dorset, they reappear as 5 to 15 ft. of limestones; their richness in ammonites (fossils rare in the Cotswolds), and the absence of other fossils common in the Cotswolds, has been taken to indicate that Dorset (with Normandy) formed part of a separate basin of deposition. In Yorkshire, the Bajocian and Aalenian are represented by fissile sandy limestone flags, contain ing plants—the Lower Estuarine Series ; temporary transgressions of the sea are indicated by thin bands with marine fossils.

See S. S. Buckman, "The Bajocian of the Mid-Cotteswolds," Q.J.G.S., vol. li. (1895), p. 388, and "Deposits of Bajocian age in the Northern Cotteswolds," Q.J.G.S., vol. liii. (1897), p. 607 and vol. lvii. (19oi), p. 126.

Bathonian

(from Bath, Somerset) ; here taken to consist of a lower division or Vesulian (from Vesoul, Haute Saone, France), a middle division or Fullonian (from Fuller's Earth), and an upper division or Bradfordian (from Bradford-on-Avon, Wiltshire).

The Vesulian consists of fossiliferous, gritty ragstones, formerly grouped with the "Inferior Oolite" division; it rests with pro nounced unconformity on the denuded surface of the flexured Bajocian. The Fullonian contains the Fuller's Earth Clays and Rock of Dorset, and the highly fossiliferous white limestones of Somersetshire, Gloucestershire and Oxfordshire which might be termed the Great Oolite proper. At Stonesfield, north of Oxford, a local flaggy facies at the base of the Great Oolite is quarried for roofing slates—the Stonesfield Slates. The Bradfordian is sub

divided for the most part on lithological grounds (ammonites being absent) into Bradford Clay below and Forest Marble above. In Lincolnshire, the Bradfordian is represented by an argillaceous facies, the Great Oolite Clay.

In Yorkshire, the whole of the Bathonian passes into a poorly fossiliferous series of brackish and freshwater sandstones, the Upper Estuarine Series. The beginning of this change can already be seen in Lincolnshire, where an Estuarine Series separates Great Oolite (upper Fullonian) from the Lincolnshire Limestone.

The Cornbrash (from a "brash" or loose rubble which in Wiltshire forms a good soil for corn), the highest member of the old division of Lower Oolites, is usually grouped with the Bradfordian; the upper Cornbrash is however more properly classed with the Callovian.

See for Vesulian:—L. Richardson, "The Inferior Oolite and Contigu ous Deposits of the Bath-Doulting District," Q.1 .G .S., vol. lxiii. (1907), p. 383 ; and between Rissington and Burford, vol. lxiii. (1907), P. 437; and of the Doulting-Milborne Port District, vol. lxxi. (1915), P. 473 ; and of the Crewkerne District, vol. lxxiv. (1918), P. 145. Fullonian Bradfordian: M. Odling, "The Bathonian Rocks of the Oxford District," Q.J.G.S., vol. lxix. (1913), P. ; J. Pringle, "Geology of Oxford," Mem. Geol. Survey (1926), p. 13; J. A. Douglas, and W. J.

Arkell, "The Stratigraphical Distribution of the Cornbrash," Q.J.G.S., vol. lxxxiv. (1928), p. 172.

Oxfordian

(from Oxford) here including the Callovian at the base (from Callovium = Kellaways, near Chippenham, Wilt shire), and the Divesian (from Dives, Calvados, Normandy) in the middle. The best known feature of this formation is the Ox ford Clay, the outcrop of which stretches from Dorset to York shire, forming a belt of low-lying valleys, it is usually a dark clay, and the fossils are often preserved in pyrites. At the base in the Midlands and Wiltshire is a calcareous sandstone (Kellaways Rock), sometimes resting on Callovian clays (Kellaways Clay). The Kelloway Rock of Yorkshire, a highly fossiliferous sandstone, is equivalent not only to the Kellaways Rock and Clay of Wilt shire, but also to the whole of the Lower Oxford Clay. Towards the top of the series (Oxfordian sense strictu) a sandy facies ap pears at different horizons in different places (Lower Calcareous Grit) ; although it contains an essentially Oxfordian fauna, it is often grouped with the Corallian. In Yorkshire, a calcareous facies (Hambleton Oolite) appears at the top of the Oxfordian.