These hills are steeped in geological history, with the geology being from the carboniferous period. The bedrocks around here are mainly sandstones. There are plenty of other EarthCaches about to learn about sandstone, what I have brought you here to see are some calamite fossils and pith casts.
This is a two stage EarthCache, with tasks to do at each. It is quite near the Hawksworth Road, so please be careful, and whilst the cache is suitable for children, please keep a close eye on them near the road.
At Stage One.
Look at the large rock and you will see some lines and markings, these are fossils, namely fossil relics of the calamite tree. Calamites were a genus of extinct tree-like horsetails to which the modern horsetails are closely related. These plants were medium-sized trees, growing to heights of more than 30 meters (100 feet). The trunks of Calamites had a distinctive segmented, bamboo like appearance and vertical ribbing. The branches, leaves and cones were all borne in whorls. The leaves were needle-shaped, with up to 25 per whorl.
Task One : Near the top corner of the rock is a calamite fossil. Please examine it, how long is it, how wide is it, and how many lines are there?
To get to Stage Two, follow the line of the bottom of the rocky outcrop. You should come to a location where there is a small rock cave in the sandstone.
Time to look up. You are looking for a wide mark at the top of the outcrop, which is slightly darker than the rest of the rock. This is a pith cast.
The stems of modern horsetails are typically hollow or contain numerous elongated air-filled sacs. Calamites were similar in that its trunk and stems were hollow, like wooden tubes. When these trunks buckled and broke, they could fill with sediment. This is the reason pith casts of the inside of calamite stems are so common as fossils. Pith casts are also known as steinkern. As a Calamite tree matured the center of the stem (pith) became hollow, developing into a tube-shaped air cavity. The pith cast preserves an impression of the pith cavities outside surface, which represents the inside vascular and cortex tissue. It must be remembered that a fossil was probably surrounded with 4-5 times its width in (unpreserved) vascular tissue, so the organisms were much wider than the internal casts preserved.
Calamite fossil, the lines crossing the calamite are known as node lines.
Task Two.
Look at the pith cast.
How wide would you estimate it is? Using this measurement, please calculate the width of the original calaminte plant.
Looking at the node lines, are they equally spaced out?
This is an earthcache. In order to log it, I ask that you answer the questions in Task One and Task Two. Please send them to me, and do not include them in your log. You can send them to me by using the message facility or email, both of which can be found by looking at my profile.