How does a global flood explain detailed geological layering?

One formation in New Jersey is six kilometers thick. If we grant 400 days for this to settle, and ignore possible compaction since the Flood, we still have 15 meters of sediment settling per day. And yet despite this, the chemical properties of the rock are neatly layered, with great changes (e.g.) in percent carbonate occurring within a few centimeters in the vertical direction. How does such a neat sorting process occur in the violent context of a universal flood dropping 15 meters of sediment per day? How can you explain a thin layer of high carbonate sediment being deposited over an area of ten thousand square kilometers for some thirty minutes, followed by thirty minutes of low carbonate deposition, etc.?