So your stand is that they layered themselves year after year, in one place, for how long, with no changes in the environment to disrupt the pile?
And why in just this one area?
It seems your question has been answered long ago.
With such a slow rate of accumulation, how did such monumental chalk beds form on an earth, which is, according to the Bible, a little over 6000 years old? For the chalk formations to have reached the thickness they are today in a few thousand years, the production of microorganisms would have had to greatly increase sometime in the past. In fact, under the right conditions, rapid production and accumulation of these microorganisms on the ocean floor is possible. These conditions include turbulent waters, high winds, decaying fish, and increased temperature and nutrients from volcanic waters and other sources.
With catastrophic volcanic activity warming the oceans and releasing large amounts of CO2, and with the torrential rains and the churning and mixing of fresh and salt waters, the Flood of Noah’s day produced the right conditions for a “blooming” production of microorganisms and the chalk’s rapid accumulation. The three major sections of the White Cliffs of Dover give evidence of three major “blooms” in chalk formation, which would have taken place during the year-long Flood.
The purity of the chalk itself also points to rapid accumulation. One cannot imagine a scenario where deposits over millions of years could maintain such purity without accumulating some contaminating sediments from other events.
Additional evidence for a global Flood in the White Cliffs of Dover includes the layering of the chalk in alternating thin, hard layers and thick, soft layers. In these hard layers, called hardgrounds, we find fossils of mollusk shells and other sea creatures, some as large as 3 feet (1 m) across (ammonites), which could not have been buried alive slowly! The same chalk formation in the Netherlands has yielded a very large Mosasaurus skull. Since sea life was not part of Noah’s cargo on the Ark, they had to endure the ravages of the Flood. Marine life would have been swept into the rapidly forming chalk and other sedimentary layers and quickly buried by successive deposits. That is why we find
fossils of sea creatures in even the highest chalk layers, now far above the ocean.
Source.