Online Encyclopedia

GAULT

Online Encyclopedia
Originally appearing in Volume V11, Page 534 of the 1911 Encyclopedia Britannica.
Spread the word: del.icio.us del.icio.us it!

GAULT  , in

geology, one of the members of the
See also:
Lower Cretaceous
See also:
System . The name is still employed provincially in parts of England for a stiff blue clay of any kind; by the earlier writers it was sometimes spelt " Galt " or " Golt." The formation now known as Gault in England has been variously designated " Blue
See also:
Marie," " Brick Earth," " Golt Brick Earth " and " Oak-tree-
See also:
soil." In certain parts of the south of England the Gault appears as a well-marked deposit of clay, lying between two sandy formations; the one above came to be known as the " Upper
See also:
Greensand," the one below being the " Lower Greensand " (see GREENSAND) . Since the typical clayey Gault is continually taking on a sandy facies as it is traced both horizontally and vertically; and since the fossils of the Upper Greensand and Gault are inseparably related, it has been proposed by A . J . Jukes-Browne that these two series of beds should be regarded as the arenaceous and argillaceous phases of a single formation, to which he has given the name " Selbornian " (from the
See also:
village of Selborne where the beds are well
See also:
developed) . Lithologically, then, the Selbornian includes the blue and grey clays and marls of the Gault proper; the glauconitic sands of the Upper Greensand, and their
See also:
local
See also:
equivalent, the " maim," " maim rock " or " firestone," which in places passes into the micaceous
See also:
sandstone containing sponge spicules and globules of
See also:
silica, the counterpart of the rock called " gaize " on the same horizon in
See also:
northern France . In
See also:
Yorkshire,
See also:
Lincolnshire and parts of Norfolk the Selbornian is represented by the Red
See also:
Chalk . The maim is a ferruginous siliceous rock, the silica being mainly in the colloidal condition in the form of globules and sponge spicules; some
See also:
quartz grains,
See also:
mica and
See also:
glauconite are usually
See also:
present along with from 2 to 25% of calcareous
See also:
matter . Chert-bands and nodules are
See also:
common in the Upper Greensand of certain districts; and calcareous concretions, locally recognized as cowstones (Lyme Regis), doggers or buhrstones, are not infrequent . The
See also:
principal divisions of the Selbornian stage with their characteristic zonal fossils are as follows:
See also:
Warminster Beds Pecten as per and Cardiaster fossarius . Upper Gault
See also:
Devizes Beds or Merstham Beds with Schloenbachia rostratus . Hoplites lautus .

Lower Gault H. interruptus . Acanthoceras mammillatum . The Gault (with Upper Greensand) crops out all

round the
See also:
Wealden
See also:
area; it extends beneath the
See also:
London basin and reappears from beneath the northern scarp of the Chalk along the
See also:
foot of the Chiltern Hills to near
See also:
Tring . In the south of England the Gault clay is fairly constant in the lower
See also:
part, with the Greensand above; the clay, however, passes into sand as it is followed westward and, as already pointed out, the clay and sand appear to pass into a red chalk towards the north-east . The Gault overlaps the Lower Green-sand towards the east, where it rests upon the old Paleozoic axis; it also overlaps the same formation towards the west about
See also:
Frome, and thence passes unconformably across the
See also:
Portlandian beds, Kimeridge Clay, Corallian beds and Oxford Clay; in south Dorsetshire it rests upon the Wealden Series . The Gault (with Upper Greensand) passes on to the
See also:
Jurassic and Rhaetic rocks near Axmouth, and oversteps-farther westward, in the Haldon Hills, on to the
See also:
Permian . A large outlier occurs on the Blackdown Hills of Devonshire . Good localities for fossils are Folkestone—where many of the shells are preserved with their
See also:
original pearly nacre,—Burnham, Merstham, Isle of Wight, the Blackdown and Haldon 'Hills, Warminster, Hunstanton and Speeton, Black Venn near Lyme Regis, and Devizes (malmstone and gaize) . The beds are well developed in the vale of Wardour, and in the Isle of Wight; the Gault forms the so-called " blue slipper " at
See also:
Ventnor which has been the cause of the landslip or undercliff . The Gault of north France is very similar to that in the south of England, but the French
See also:
term Albien includes only a portion of the Selbornian formation . The Gault of north-west Germany embraces beds that would be classed as Albien and Aptien by French authors; it comprises the " Flammenmergel "—a pale siliceous marl shot with flame-shaped darker patches—a clay with Belemnites minimus, and the Gargasmergel " (Aptian) . In the Diester and Teutoberger Wald, and in the region of
See also:
Halberstadt, the clays,and marls are replaced by sandstones, the so-called Gault-Quader .

See also:
Continental writers usually place the Gault or Albian at the
See also:
summit of the Lower Cretaceous; while with
See also:
English geologists the practice is to commence the Upper Cretaceous with this formation . In addition to the fossils already noticed, the following may be mentioned: Acanthoceras Desmoceras Beaudanti, Hoplites splendens, Hamites, Scaphites, Turrilites, Aporrhais retusa, Trigonia aliforme, also
See also:
Ichthyosaurus and Ornithocheirus (Pterodactyl) . From the clays,. bricks and tiles are made at Burham, Barnwell, Dunton Green, Arlesey,
See also:
Hitchin, &c . The cherts in the Greensand portion are used for road metal, and in the Blackdown Hills, for
See also:
scythe stones; hearthstone is obtained about Merstham; phosphatic nodules occur at several horizons . See CRETACEOUS SYSTEM; ALBIAN; APTIAN; also A . J . Jukes-Browne, " The Gault and Upper Greensand of England," vol. i., Cretaceous Rocks of Britain; Mem . Geol . Survey, 1900 .

End of Article: GAULT
[back]
GILBERT WILLIAM GAUL (1855— )
[next]
GAUNTLET (a diminutive of the Fr. gant, glove)

Additional information and Comments

There are no comments yet for this article.
» Add information or comments to this article.
Please link directly to this article:
Highlight the code below, right click and select "copy." Paste it into a website, email, or other HTML document.