Onshore
As part of our onshore investigation we went to Renney Rocks in Heybrook Bay. The aim of the day was to learn more about the rock formations seen in Plymouth in order to gain a greater understanding of the local rock forms and help us to analyse the side scan data we collected (see Geophysics page).
Method
Our Group was presented with a local map of the area. On this map there were high and low water lines and some of the more significant rock structures. Using this we were able to work out our location on the map and with the help of a compass clinometer, devices capable of measuring the bearing of the rock as well as the pitch of the rock faces, it was easy to gain our bearings.
Using the compass, we analysed the slash and the strike of borders between rock types and marked these onto our maps. This was done several times in various places to learn the topography of the area.
We also examined an exposed bank with several layers of sediment within it. By looking at the spacing, size, roundness and spherocity of the rocks we determined that the exposed geological layers consisted of:
- Shingle
- A slurry of rocks generated by the melting permafrost at the end of the last ice age.
- Mud and clay
- River worn pebbles
Introduction
Results
It was clear to see that there were many faults present, including the formation of a fold. Looking at this fold we attempting to mark the point in which the angle completely redistributed and what angle this had subsided towards. After looking at this we moved across the gap between the fault to try and work out what displacement could be seen. Due to this being such a prolific structure it was fairly easy to find. For example, a right latitude dextral fault was present, identified by little to no change in the angle of the rock faces. Lower down on the beach a second channel in the rock has appeared, which was identified as a congruent left fault. A rock cleavage was also present and had broken apart into several pieces as a result of tectonic action.