The movement of lithospheric plates and the incipient Alpine Orogeny resulted in repeated marine transgressions. Then, many basins were formed and filled with thick sediment accumulations, especially the so-called Bohemian Cretaceous Basin. Well sorted shallow-marine quartzose sandstones are sediments with the highest thickness in this basin. Their progressive weathering produced the famous rock cities. Finer sediments were deposited in deeper sea, giving origin to calcareous claystones, marlstones and spiculitic marlstones (so-called “opukas” or “gaizes”). Some beds contain abundant remains of marine fauna.