The Ripple Beds
In front of you is a high rock face that is covered with beautiful large and small ripples.
The trench below the viewing platform and outside the safety fence is accessible for fossil collecting from the fallen scree material.
Close view of ripples
The thin beds of rock that are covered in ripples here belong to the upper part of the Nodular Member. They clearly indicate a shallow sea with wave action reaching down to the seabed and the direction of ripples is consistent from one layer to the next suggesting that the wind and ocean currents were from the same direction for a long time period. The larger size of the ripples in the higher beds suggests that the strength of the waves was higher when these rippled beds were formed.
Closer inspection shows that these ripples are symmetrical which suggests that they were formed in tidal conditions in shallow water.
As you look across these beds to the left the ripples disappear and the surfaces of these layers becomes disturbed and churned-up. This is believed to be caused by a colony of burrowing creatures that lived in this part of the seafloor which turned the seabed over in search of food leaving it in a chaotic state as we see it today. Geologists call such disturbance of rock layers by animals ‘bioturbation’.
If you look further to the left you can see the fossil reef mound and it is clear that these flat uplifted beds of rock in front of you do not contain reef mounds so they represent the open seabed in between the patch reefs..
It is worth spending a little time having a look to see what fossils you can find in the scree in the trench below and thinking about how these types of fossils compare to those found at the reef mound in that last locality. Do Task 10 before taking the route back past the reef mounds to site 11.
Task Site 10 Questions
What are the features that you can see on this rock face?
a) Dinosaur footprints
c) Geological faults
d) Coral reefs
An area high on the rock face to the left does not have ripples on its surface, why is this?
a) Volcanic activity disturbed the sea bed
b) Animals have burrowed into it and churned it over
c) Earthquakes mixed it up
d) A storm has stirred it up
Why is there a long thin trench below the rock layers with the ripples?
a) It’s a huge geological fault
b) Where limestone has been quarried away
c) A river flowed here
d) Ice age glaciers carved it out