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The Chalk Group is now divided into a White Chalk Subgroup and a Grey Chalk Subgroup, both of which are further subdivided into formations.These modern divisions replace numerous earlier divisions, references to which occur widely on geological maps and in other geological literature.
The White Chalk Subgroup is locally divided into six formations, the uppermost of which is further subdivided into two members. Two distinct members are also identified within the lowermost formation. Ranging from Cenomanian to Campanian (c.84-72 Ma) in age, these strata are (uppermost/youngest at top): Culver Chalk Formation Spetisbury Chalk ...
Overlying the Selborne Group is the Chalk Group, a suite of limestones of Upper Cretaceous age which is formally divided into a lower/older Grey Chalk Subgroup (of Cenomanian age) and an upper/later White Chalk Subgroup (of Cenomanian to Campanian age). The Grey Chalk corresponds to the traditional Lower Chalk division and comprises 15-25m of ...
The Ulster White Limestone Group is a late Cretaceous lithostratigraphic group (a sequence of rock strata) in Northern Ireland. The name is derived from the characteristic chalk rock which occurs particularly along the Antrim coast.
Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the ...
Test shape is highly variable among different foraminifera; they may be single-chambered (unilocular) or multi-chambered (multilocular). In multilocular forms, new chambers are added as the organism grows. A wide variety of test morphologies is found in both unilocular and multilocular forms, including spiraled, serial, and milioline, among others.
An annotated picture of the Norwich Test Specimen, figured in Lankester (1914), Plate 3. [ 53 ] The discovery of chipped and flaked flints in the Norwich Crag and Red Crag basement beds in the late 19th and early 20th centuries was claimed as evidence for some of the earliest human settlement in Britain. [ 54 ]
The group is composed of, in ascending order, the Mooreville Chalk Formation, Demopolis Chalk Formation, Ripley Formation, and Prairie Bluff Chalk Formation. Dinosaur and mosasaur remains are among the fossils that have been recovered from the Selma Group.