The cache co-ordinates take you to the site of an old quarry on Addingham Edge, which sits on the western edge of the Ilkley Moor massif. It is an area of small cliffs, and uneven ground. Be careful, watch your footing, and you need to be below the EarthCache to do both stages.
The rocks around you were deposited during the carboniferous period, a time when when the whole of what is now the North of England was covered by huge river deltas and lagoons. Sediments, mainly sands, silts and muds, were eroded from hills in an area that now includes Scandinavia and Greenland and were swept into vast river deltas and lagoons in a central basin in a position now occupied by the Pennines. The sediment settled to the bottom as the water slowed down in the deltas and lagoons. The nearest equivalent sediments of today are forming in huge river deltas such as the Mississippi delta. As time went on, sediment formed of sand, pebbles and rocks was laid down into layers known as sediment. This overtime formed a rock known as sandstone.
There are enough EarthCaches about sandstone, what we are here to see is right infront of your eyes. You are looking for a upstanding rock.
Looking at the rock you will see linear structures, in a miss match of patterns. This is known as a log jam. During the carboniferous period, the sediment which formed this rock was in a river channel, and during periods of flood, debris was washed downstream. Included in this debris , were logs and branches of trees further upstream. Eventually one branch or log would get caught, and then others would also be caught, eventually the channel becoming blocked by a jam of branches. It still happens today in river channels, such as in the River Aire and River Wharfe. Behind this log jam, sediments then built up. Now, there were a variety of plants during this period, and as we have today there were different species. Hence, why not all of the log jam looks the same.
What we have here is a fossil. Looking at the alignment of a log jam it can help give us an indication of the paleocurrent direction of the watercourse, in a log jam, the logs can be arranged perpendicular to the overall sediment transportation direction in the watercourse.
What is a fossil?
Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (Strata) is known as the fossil record.
This log jam is an example of Ichnofossils, which are also known as trace fossils, and are geological records of biological activity. Trace fossils may consist of impressions made on the substrate by an organism: for example footprints and feeding marks, and root cavities. The term in its broadest sense also includes the remains of other organic material produced by an organism — for example fossilized droppings or chemical markers — or sedimentological structures produced by biological means. Trace fossils contrast with body fossils, which are the fossilized remains of parts of organisms' bodies, usually altered by later chemical activity or mineralization.
This being an EarthCache, in order to log it, I ask that you answer some questions. Please send them 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. It is not meant to be difficult to do.
1. Please describe the appearance of the fossils. By this I ask, what do they look like, are they all the same, or are they different. What is the predominant feature of the fossils that stands out to you?
2. Are all the fossils alligned in the same direction?
3. How tall and wide is this rock?
4. Please measure the width of the widest fossil that you can find, how wide and long is it in cm?
5. How many individual fossils can you count on this feature?