Castle Martin and surrounds - a geological excursion.

 More from Tom's recent field trip....

Castle Martin
Top: The Green Bridge carboniferous limestone arch formed by erosion due to 3 distinct layers of limestone.
Bottom left: another archway formed in the limestone near to The Cauldron.
Bottom right: Elegug Stacks

Left top: Quay Cove trace fossils of soft-bodied worms in Carboniferous Limestone
Left bottom: Quay Cove tension gashes due to deformation.
Right: West Angle Bay parasitic folds.

Skrinkle Haven - Church Doors Cove.
Top left: fossils (mainly crinoids). The fossils at this locality are mainly broken into fragments, which is interpreted as the fossils having been transported to the site during storms, hence creating storm beds.
Bottom left: an example of storm bedding- the abrupt change between mudstone and limestone can be seen to the left of each paler limestone bed. To the right there is graded bedding as the limestone and mudstone merge together. This shows the storm sediments abruptly forming and then settling towards the end when the storm eventually diminishes. This sedimentary feature can be then used to determine 'way up' and which rocks are younger and hence laid last.
 Right: A cross section through the bedding and wave ripples. The ripples seen are symmetrical and hence are due to wave action instead of river flow that creates asymmetrical ripples. This is another feature that helps determine 'way up'.