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Chalk is so common in Cretaceous marine beds that the Cretaceous Period was named for these deposits. The name Cretaceous was derived from Latin creta, meaning chalk. [10] Some deposits of chalk were formed after the Cretaceous. [11] The Chalk Group is a European stratigraphic unit deposited during the late Cretaceous Period.
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 weight of overlying sediments caused the deposits to become consolidated into chalk. [9] British chalk deposits are considered stratigraphically to belong in the Chalk Group. Evidence of erosion along the cliff top. Due to the Alpine orogeny, a major mountain building event during the Cenozoic, the sea-floor deposits were raised above sea ...
Chalk mining is the extraction of chalk from underground and above ground deposits by mining. [1] Mined chalk is used mostly to make cement and bricks . Chalk mining was widespread in Britain in the 19th century because of the large amount of construction underway (and the Industrial Revolution ). [ 2 ]
The residents then migrated away into smaller communities. However trade with the old cities did not flourish. The small surplus produced in these small communities did not allow development of trade, and the cities died out. [107] The Indo-Aryan peoples migrated into the Indus River Valley during this period and began the Vedic age of India. [108]
Limestone is very common in architecture, especially in Europe and North America. Many landmarks across the world, including the Great Pyramid and its associated complex in Giza, Egypt, were made of limestone. So many buildings in Kingston, Ontario, Canada were, and continue to be, constructed from it that it is nicknamed the 'Limestone City ...
The putative galloanseran bird Austinornis lentus has been found in the Austin Chalk. [2] [3] The general absence of dinosaurs is a reflection of the Austin limestone being marine in origin, primarily composed of microscopic shell fragments from floating sea organisms known as "coccolithophores" (the same organisms that contributed to the White Cliffs of Dover, on the south coast of England). [4]
Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, [1] [2] categorized as the variety of chert that occurs in chalk or marly limestone. Historically, flint was widely used to make stone tools and start fires. Flint occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones.