Due to humanities need for irrigation and other uses for water we have dried up many naturally occurring bodies of water. What do we find when we dry up these lakes? Massive flat plains produce by modern sedimentation that sit on top of the existing geologic column. Lake Umari in the Middle East is just one example of many:
As you can see, the lake produced a flat plain for miles and miles, and the evaporation of the water produced a salt crust. This is what you are going to find under thousands of lakes across the world, and under our oceans right now. This is the type of sedimentation that is happening right now.