Linford Quarry is a regionally important geological site. There is a good, if limited outcrop of the local Blisworth Limestone. The site is easily accessible on foot or by bicycle. Limestone is a very interesting rock. It is almost always formed in a marine environment. Limestone is composed, mostly of the mineral calcite. Calcite is derived principally from the remains of organisms whose remains accumulate on the sea bed. Over time these accumulations compress to form rock. Some limestones are nearly 100% calcite, but most have some other deposits among them, like mud or sand. Because limestone is mainly a marine deposit it quite often contains fossils. By analysing these fossils, geologists can identify the type of environment in which this deposit was formed. Blisworth limestone takes it name from Blisworth in Northamptonshire. It was first identified and studied while the Blisworth tunnel was being constructed, in the early 19th century, for the Grand Union canal. Blisworth Limestone is part of the "Great Oolite Group". Blisworth limestone was created in a hot, shallow sea during the Jurassic era, 200 to 145 million years ago. Water partially evaporated leading the calcium carbonate to precipitate out on to small nuclei, The gentle motion of the tides gradually rolled these nuclei around until they formed spheres, that resemble eggs, hence the name oolite, from the Greek for egg. This particular exposure is characterised by alternating layers of rock and clay This represents a fluctuating change in the depth of the sea at this time. Clay is characteristic of deeper ocean deposits.
The published co-ordinates take you to one of the stone circles. If you look closely you will notice that some of the stones exhibit fossils. Mostly brachiopods, oysters and other bi-valves. As mentioned these fossils reflect the environment in which the limestone was formed. In this case a warm, shallow sea, rich in nutrients.
To claim this EarthCache you have to answer the following questions:-
1. What is the chemical formula for calcite?
2. How many stones make up the circle you are in?
3. For this question you need to move. Find the remains of the nearby quarry. How high would you estimate the "flaggy" rock face to be?
Send me a message (not email) to my profile.
Many thanks to The Milton Keynes Parks Trust for permission to place this cache.