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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 and water mixture, also called Kreidemilch or Kreidetrübe, was passed through separation tanks where the finer impurities, the Grand, settled out. The chalk suspension freed from the grand then collected in the settling basin, where the still- suspended particles settled out and accumulated into a layer about 30 cm thick.
The Cretaceous is justly famous for its chalk; indeed, more chalk formed in the Cretaceous than in any other period in the Phanerozoic. [27] Mid-ocean ridge activity—or rather, the circulation of seawater through the enlarged ridges—enriched the oceans in calcium ; this made the oceans more saturated, as well as increased the ...
Dutch White – a pigment, formed from one part of white lead to three of barium sulfate. BaSO 4; Flowers of antimony – antimony trioxide, formed by roasting stibnite at high temperature and condensing the white fumes that form. Sb 2 O 3; Fool's gold – a mineral, iron disulfide or pyrite; can form oil of vitriol on contact with water and air.
For most of its length the tunnel bores through a chalk marl stratum (layer) The lower stratigraphic units of the chalk cliffs of Dover consist of a sequence of glauconitic marls followed by rhythmically banded limestone and marl layers. [8] Such alternating cycles of chalk and marl are common in Cretaceous beds of northwestern Europe. [9]
Gypsum is moderately water-soluble (~2.0–2.5 g/L at 25 °C) [13] and, in contrast to most other salts, it exhibits retrograde solubility, becoming less soluble at higher temperatures. When gypsum is heated in air it loses water and converts first to calcium sulfate hemihydrate ( bassanite , often simply called "plaster") and, if heated ...
The Chalk Group (often just called the Chalk) is the lithostratigraphic unit (a certain number of rock strata) which contains the Upper Cretaceous limestone succession in southern and eastern England. The same or similar rock sequences occur across the wider northwest European chalk 'province'.
The products of chalk weathering are dissolved in rainwater and are transported in stream flow. Chalk streams transport little suspended material (unlike most rivers), but are considered "mineral-rich" due to the dissolved calcium and carbonate ions. The surface water of chalk streams is commonly described as "gin clear".