The causes of the occurrence of abundant chalk in the Cretaceous time.
Answer to Problem 1RQ
The chalk was abundant during the Cretaceous period due to the presence of coccolithophores in the warm sea.
Explanation of Solution
Coccolithophores were a single-celled organism that had tiny shield-like plates. These plates armour the coccolithophores while accumulating inside the grains of limestone. The occurrence of coccolithophores in the fine grain of limestones are known as chalk. During the late Cretaceous period, the low ratio of magnesium-calcium(Mg2+/Ca2+) resulted in the precipitation of calcite. The precipitation of calcite also favored the accumulation of coccolithophores.
In the southeastern coast of England, the famous chalk deposits are present. These deposits are called as “the chalk”. Another common region of chalk deposits includes Gulf Coast in United States, Kanas, Africa, Denmark, and Australia.
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