Extraordinary preservation |
scale in cms
The photograph shows the top surface of a very thin limestone bed found in the mudstones and shales in the upper part of this outcrop.
This limestone bed contains the complete or nearly complete skeletons of many types of delicate sea creatures. Notice the tiny arms of the crinoid (or "sea lily" - a relative of starfish and sea urchins). Examination of living crinoids show that these tiny arms decay and fall apart soon after death (in a few hours). These crinoids must have been knocked over and buried alive or very soon after they died, because all the loosely stacked pieces of their arms are still together.
Rapid burial by mud (or "smothering") happens in the deeper parts of modern coastal areas and in modern seas, during and just after hurricanes and other strong storms. Perhaps this one bed was laid down in a single ancient hurricane! There are other ways fossils like this can be preserved. Can you think of another way?