Walking on Fossils
What are fossils?
Fossils are the fossilized remains of animals or plants from earlier lithic ages that were covered by material while alive or shortly after their death. An important prerequisite for the preservation of these parts is that no oxygen can reach the organic substance, which would otherwise lead to decomposition. This criterion can be met by a high sedimentation rate, i.e. by rapid embedding or by an oxygen-poor environment. If this is the case, decay occurs first, and later the structures of the living being are transformed by chemical processes or gradually replaced by them.
For this reason, well-preserved fossils are found in places with rapid sedimentation, such as swamps, the sea, lakes, moors or shallow seas. Scientists assume that around a billion animal and plant species emerged 542 million years ago, some even 1.6 billion years ago. However, less than 1 percent of this biodiversity has been preserved only as fossils, as much of it has been destroyed by erosion over time.
Fossilized Coral
Fossilized coral was formed when parts of the ancient coral were gradually replaced by natural minerals such as calcite and silica. The corals grew in the oceans for nearly 500 million years during the Ordovician period. Many thrived in warm, shallow waters.
Over time, they became buried under sediment as the land surface moved and the ocean rose and fell. Temperature and pressure from compaction caused the deposits to slowly turn into stone, a process called petrification. Fossilized coral is a medium-sized coral known for its honeycomb appearance.
Individual coral organisms known as polyps secrete a calcareous substance that forms a coral skeleton. When the skeletons joined together, they formed large coral reefs made up of millions of individual organisms. Over time, parts of the reefs fossilized. The correct name for fossil coral is "agate coral" or "agate fossil coral." Fossil coral is formed by the process of replacing calcium carbonate (coral) with silica.
Silica ranges from slightly amorphous opal to dense forms of chalcedony. Depending on the exact mineral concentration, fossil coral specimens may have slightly different densities. Although the pattern and body color of fossil coral is quite distinct, it can be confused with other types of agate, such as moss agate or dendritic agate.
Fossilized Oyster (Gryphaeidae)
Gryphaeidae is an extinct genus of mussels that was related to oysters. Their fossil shells are found mainly in the Jurassic layers (from around 200 million years ago to 135 million years ago). Their shells are characterized by a very strongly curved left flap, which is closed by the flat right flap like a lid. The mussel shells are very thick-walled. Gryphaea is a dysodont mussel, meaning it has no teeth on its lock. Relatives of the genus Gryphaea from the Gryphaeidae family are still widespread in the oceans today.
To log the cache, answer the following questions. You can find lots of fossilized corals and oyster on the paved ground on the footpath between Farrants Way and Market Square:
1: Feel the polyps (arms) with your fingers - do they protrude slightly or are they pointing inwards? Why do you think this is the case?
2: Look closely at the fossilized corals - how big are each polyp (arm)?
3: Look closely at the fossilized oysters - what size, shape and colors can you see?
4: In what geological age and how many years ago did the fossilized corals and oysters form?
Groundspeak has changed the Earthcache rules since June 2019, the cache owner can request a photo of you or a personal item on site!
You don't have to wait for permission to log - if the answers are wrong I will contact you - without answers your log will be deleted.