Ammonites
Ammonites were ocean-living, prehistoric animals similar to today’s Nautilus. They became extinct some 66 million years ago, along with the dinosaurs, but a large number are preserved as fossils in stratified rock and are of great interest and value to geologists. They varied enormously in size, from a few centimeters to as large as two meters in diameter.
The reasons for this are:
1. they are distributed widely throughout the world
2. they are present in large numbers, because they had a hard shell which was ideal for fossilization
3. they had relatively brief longevity because of their high rate of evolution
This information is used by geologists for correlating the age of different geological sites by comparing ammonite species found there and the stratification they lie in. These sites could be local to, or on the other side of the world from, each other.
This use of ammonite fossils in stratigraphy (the branch of geology that studies rock layers, or strata, and layering, or stratification) was first introduced by Friedrich Quenstedt and Albert Oppel, in the 19th century, and is very accurate in dating geological sites.
Fossil Formation
The process by which the ammonites in the wall were fossilised is illustrated below.
QUESTIONS
1. At the coordinates, find the largest exposed piece of ammonite and measure it (it's about 1.5 metres up). Can you estimate its diameter?
2. Look closely at what would have been the central part of the ammonite (the smaller section to the right). Can you say how many ridges are present?
3. A metre or so to the left of this ammonite, is a smaller fragment. Can you describe the shape, colour and texture of the flint structure that it is resting on?
4. In which two geological periods did ammonites live?
5. The walls are constructed predominantly of flint rubble (with some Roman brick). Do the ammonites appear to be of the same flint, or some other sedimentary rock-type?
6. Flint is a hard form of which mineral?
To claim this EarthCache, please email me, via the link above, with the answers.
Sources: UK Fossils, British Geological Survey, Discovering Fossils, Fossil Facts and Finds, Wikipeda
St. Martin's Church
St Martin's Church is a redundant Anglican church in the town of Colchester, Essex, England. It is recorded in the National Heritage List for England as a designated Grade II listed building, and is under the care of the Churches Conservation Trust. The church stands in the centre of the town, near the town hall.
The nave and the tower of the church date from the 12th century. The aisles, the transepts, and the chancel were added in the 14th century. The tower was damaged in 1648 during the Civil War, and has never been repaired. Following this damage, the church fell into disrepair, and in 1748 the historian Philip Morant wrote that it was in a ruinous condition and that no services were being held in it. A considerable restoration took place during the late 19th century, during which the architect Giles Gilbert Scott revealed the wagon roof in the chancel. An ambitious plan of restoration was later prepared by Rev Ernest Geldart, but it was never realised. The church then became neglected again, and in 1953 it was declared redundant.
The church was used by a theatre group between 1957 and 1987, but by the latter date it had become structurally unsafe. It then continued to deteriorate until it was vested in the Churches Conservation Trust in 1996. By this time some emergency repairs had been carried out, which were financed by English Heritage. The Trust then continued to repair the building, planning this in two phases. In the first phase, the church was made dry and stable. The second phase involved cleaning the interior of the church, including the wall paintings, limewashing the remainder of the walls that had been painted black by the theatre company, refurbishing the vestry, and providing wheelchair access. This work was supported by a grant from the Heritage Lottery Fund and was completed in 2003. The work was granted a Colchester Civic Trust award later in that year. The church remains consecrated.
The truncated tower and the nave are Norman in style. Many Roman stones have been incorporated into the walls of the tower and the nave. Internally, at the apex of the arch of the chancel roof is the carving of a green man. Two glazed plaques of encaustic tiles, surviving from Geldart's aborted restoration, are in the aisles. The interior of the church is unfurnished, and it is now used as an art centre.
Source: Wikipeda
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For full information on how you can expand the Church Micro series by sadexploration please read the Place your own Church Micro page before you contact him at churchmicro.co.uk
See also the Church Micro Statistics and Home pages for further information about the series.
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