This EarthCache in Edinburgh, looks at some of the oldest rocks in Scotland. Not the oldest, but still an.old age pensioner. The below photographs show where the EarthCache is, and what to look at.
🪨 The geology.
These rocks are 490 millions of years old, and originally come from the Southern Uplands. When they were originally deposited, the South of Scotland was very different from today.
They were originally laid down in a deep ocean, during the Ordovician and Silurian periods. The ocean, known as the Lapteus Ocean, was situated south of the equator, between two continents known as Avalonia and Laurentia. Sediment from these continents was washed down into the Lapteus Ocean, where it settled as sandstone and Siltstone. Lighter sediment was carried further out to sea and deposited as mudstone on the deep ocean floor. Movement of continental plates caused earthquakes, and this caused the heavier sediment of sandstones and mudstonss to be carried at high speed by the water into the deeper ocean, in the process scouring out the deeper ocean floor. This scouring action, basically gauged out the floor in places, leaving holes, in a process known as turbidity. Over time these were filled with further sediment, during the Ordovician and Silurian periods.
🪨 We are here to look at evidence of the turbidity.
The evidence of the turbidity action, can still be seen today in the form of flute casts, and that is what we are here to look at. As the sediment moved at speed across the ocean floor, it gauged out depressions, a bit like you leave your footprint in the sand . Over time, these depressions filled with sediment, and as you see here there is evidence of this. The long axis of the flute cast , gives an indication of the direction of the flow, with the rounded bulbous end indicating what direction the turbidity flow came from. It is a bit like a footprint, but caused by the movement of sediment.
This being an EarthCache, in order to log it, I ask that you complete the above tasks. Please send the answers to me, and do not include them in your log. You can send them to me by using the message facility or email, both of which can be found by looking at my profile.
1. Please look at the flute casts and tell me which direction the turbidity flow came from?
2. Please describe what you see and feel here, in terms of shapes and colour of rock.
3. Please explain turbidity, with relation to these flute casts.
4. Please have your photograph taken, or that of your device. Please have the photograph taken.infront of the oldest rocks (you will need to look at the display to work out where you need to be).