In most places the Cretaceous rocks are, during the Pleistocene, covered with loess. Studying them is only possible in quarries and other man made enclosures. Typelocation Maastrichtian Something about flint. A lot of the Cretaceous formations in southern Limburg contain flint. During the last 200 years a number of theories about the origin of flint have been brought forward, but none of them have been generally accepted.
Some people even suggest flint can originate in a number of different ways.
Also unsolved is the question about the moment flint formed. Even the question were the SiO2 came from is still a matter of debate. One of the latest theories suggest an important role played by fresh water. Normally there is a delicate balance in sea water between the minerals dissolved in it. This caused a supersaturation with silicic acid and this cristallized into flint were circumstances were favourable like round the remains of organisms.