Mud cracks and rain prints
Muddy sediment deposited in shallow water is often exposed long enough during low tides or dry seasons to dry and crack. Under the right conditions, further deposition of sediment fills in and preserves the cracks. When exposed by erosion, fossilized mud cracks may look like a honeycomb of ridges. The impressions of raindrops that pitted soft sediment may also be preserved. The shape of the rain-print rim may indicate which direction the rain was falling.
Kansas Rocks and Minerals, Kansas Geological Survey Educational Series 2.