Outside Thorndon Visitor Centre there is a geological specimen on display which is a foreigner to these parts. This fossilised tree stump of a large conifer was found in the nineteenth century by workers in a Dorset stone quarry around one hundred and fifty miles south west of Essex.
In the late Jurassic period Britain had a tropical climate and was inhabited by dinosaurs. The forests were dominated by conifers, ginkgos and cycads and that is when this stump would have been a living organism. After the tree’s death the wood of the stump gradually became fossilised and every cell of the wood has been converted to stone, a process known as petrification. The petrification process occurs when wood becomes buried in arid or stagnant sediment; the resulting lack of water or oxygen inhibits decomposition. Mineral-laden water flowing through the sediment deposits mineral in the wood cell-by-cell and, as the plant's lignin and cellulose decays, a perfect stone replica forms in its place. (from Wikipedia article on Petrification – accessed Mar 2015)
After spending millions of years trapped in the rock formation in Dorset where it was found, the fossilised stump was transported to London where it formed part of the geological collection of the Passmore Edwards Museum in East London for a century, before being donated to Thorndon Country Park by the Essex Field Club.
In order to log a find on this earthcache please send us an email via our profile with the answers to the questions below.
Please Note : Logs without a corresponding email or message will be deleted. We're sorry to have to introduce this rule but we have had a few unsubstantiated logs since publication. So far we have had to delete several unsubstantiated logs. We will send a chaser if we don’t receive a message or email but failure to reply will always result in the offending find log being deleted.
Questions to answer
1. Describe the texture and colour of the stump
2. Can you identify any sign of contamination by other minerals during petrification? If so, state what contaminant you suspect and why
3. What element must be absent in order for petrification to occur?
While not obligatory, a photo of you or your GPS near the stump would be appreciated.
Many thanks to Ros Smith and Ian Mercer of Essex Rock and Mineral Society for their assistance in developing this EarthCache, and many thanks to Essex Country Parks for giving permission to place this EarthCache
.