Welcome to Weymouth Harbour.
Weymouth Harbour Portland Roach, you are looking for the river quayside walls and the stone that makes a decorative feature of what could be just a quayside. This is not like other quaysides... lining either side of the river are Portland Roach stones.
This EarthCache will ask you about what you can see within the stone... FOSSILS!
Portland Roach
Portland Roach is a very recognisable rock due to its numerous fossils within. The rock is quarried just along the coast in Portland. Portland Roach is a limestone formed in the seas many millions of years ago in the Jurassic period. The rock is made up of ooliths which form from sand and within that are the shells and hard parts of millions of creatures. Bivalves and Turreted Gastropods (Portland screws) are common within the rock and you will see that the rock is full of imprints of many fossils .
Bivalves
Bivalves are shell animals than have two shells connecting by a hinge… common ones found in this rock are oysters and oyster fragments, and you will likely be able to find imprints of many varying sized and shaped bivalves.
Ooliths
Ooliths make up some of the material in between the fossils and imprints, they look like round sand grains but can grow and grow depending on the conditions they formed in. Ooliths are layered grains which form around a particle. These particles could be a tiny fragment of shell or a grain of quartz, or some other tiny particles. Most of ooliths in this rock are very small and would need a good set of eyes to see, maybe a magnifying glass would help?
You can complete this EC on either side of the river along the quayside
Questions
Look closely at the stone and describe what you can see. You may like to include measurements, shapes, textures and colours that you can see.
1. Please describe the rock and colouring of the rock, if you are close enough can you feel or see the texture of the ooliths? Can you measure any of the ooliths? What does it feel or look like? (This is the stone between the fossils)
2. Can you identify the Portland screws within the stone? Please can you describe their appearance, for example shape, texture, size and number of levels in the spirals. What is the most spirals you can find?
3. Please describe the amount of fossils, spacing of fossils, and describe an alternative fossil to the Portland screws.?
4. Optional photos or selfies of the quayside are welcome. But please not any close up shots of the rock which would reveal the answers.
Hope you enjoy this EarthCache.
