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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.
Chalk streams are rivers that rise from springs in landscapes with chalk bedrock. Since chalk is permeable, water percolates easily through the ground to the water table and chalk streams therefore receive little surface runoff. As a result, the water in the streams contains little organic matter and sediment and is generally very clear. [c]
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 ...
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 ...
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'.
Most of the area takes the form of an elevated, gently rolling plateau, cut by numerous deep, steep-sided, flat-bottomed valleys of glacial origin. The chalk formation of the hills provides exceptionally good drainage, with the result that most of these valleys are dry; indeed, surface water is quite scarce throughout the Wolds.
Niobrara Chalk was weathered and opalized in the Valentine phase of the Ogallala Formation. The Niobrara Formation / ˌ n aɪ. ə ˈ b r ær ə /, also called the Niobrara Chalk, is a geologic formation in North America that was deposited between 87 and 82 million years ago during the Coniacian, Santonian, and Campanian stages of the Late ...
An evaporite (/ ɪ ˈ v æ p ə ˌ r aɪ t /) is a water-soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. [1] There are two types of evaporite deposits: marine, which can also be described as ocean deposits, and non-marine, which are found in standing bodies of ...