Helping San Diego, California and beyond since 1997.
Do you need
volunteer, community service, work, military or court hours?
|
|
Helping San Diego, California and beyond since 1997.
|
|
Click here and add this page to your favorites!
|
Encyclopedia Britannica - Main :: GAG-GEO |
|
|
GAULT , in geology, one of the members of the Lower Cretaceous 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 Marie," " Brick Earth," " Golt Brick Earth " and " Oak-tree-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 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 village
The principal divisions of the Selbornian stage with their characteristic zonal fossils are as follows: Warminster Beds Pecten as per and Cardiaster fossarius. Upper Gault 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 Wealden area; it extends beneath the London basin and reappears from beneath the northern scarp of the Chalk along the foot of the Chiltern Hills to near Tring. In the south of England the Gault clay is fairly constant in the lower 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
Frome
Series . The Gault (with Upper Greensand) passes on to the Jurassic and Rhaetic rocks near Axmouth, and oversteps-farther westward, in the Haldon Hills, on to the Permian. A large outlier occurs on the Blackdown Hills of Devonshire. Good localities for fossils are Folkestonewhere many of the shells are preserved with their original
The Gault of north France is very similar to that in the south of England, but the French 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 patchesa clay with Belemnites minimus, and the Gargasmergel " (Aptian). In the Diester and Teutoberger Wald, and in the region of Halberstadt, the clays,and marls are replaced by sandstones, the so-called Gault-Quader. Continental writers usually place the Gault or Albian at the summit of the Lower Cretaceous; while with 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 Ichthyosaurus and Ornithocheirus (Pterodactyl). From the clays,. bricks and tiles are made at Burham, Barnwell, Dunton Green, Arlesey, Hitchin, &c. The cherts in the Greensand portion are used for road metal, and in the Blackdown Hills, for scythe
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 If you wish, you can link directly to this article.
<a href="http://jcsm.org/StudyCenter/Encyclopedia/GAG_GEO/GAULT.html"> GAULT </a> |
|
|
(Previous) GAUL, GILBERT WILLIAM (1855 ) |
(Next) GAUNTLET (a diminutive of the Fr. gant, glove) |
|
Sponsored Advertisements