To be able to log a find of this EarthCache, you must visit Kepwick Quarry and answer some questions and then send your answers to me through the Messenger Centre or my Geocaching Profile. You do not have to wait for a reply from me before posting your log. I will contact you if there are any problems with your answers.
Please park at the suggested parking area (N 54° 19.004 W 001° 14.950) and walk down the road to Kepwick Quarry. There is no space to park at the quarry.
Limestone
Limestone is a sedimentary rock normally formed from the compressed remains of marine organisms in warm, shallow ocean environments. Over millions of years, layers of shells, coral, algae, and other calcium-rich debris settle on the seabed. This sediment is then compacted and hardened into solid rock through a process called lithification.
The formation of limestone, which is primarily composed of calcium carbonate (CaCO3), involves both biological and chemical processes.
Sedimentation and accumulation:
- Marine animals like corals and shellfish and microscopic organisms called foraminifera extract calcium carbonate from the ocean water to build their shells and skeletons.
- When these organisms die, their remains fall to the ocean floor, forming layers of calcium carbonate sediment. This is the main method of limestone formation.
Compaction and cementation:
- As more layers of sediment accumulate, the weight from above compacts the layers below.
- Water carrying dissolved calcium carbonate seeps through the sediment, and the mineral precipitates out, acting as a natural cement that binds the loose particles together into solid rock.
Chemical precipitation:
- In some cases, limestone can form directly from seawater. This occurs when conditions, such as decreased pressure or increased temperature, cause dissolved calcium carbonate to precipitate (to be deposited in a solid form) out of the water.
Fossils in Limestone
Fossils are commonly found in limestone because it is a type of sedimentary rock that often forms in marine environments, which are rich with living organisms that have hard parts. The conditions that form limestone are often ideal for the preservation of these organisms as fossils. Common fossils found in limestone include ammonites, belemnites, crinoids, bivalves, and gastropods.
Some limestone does not contain fossils due to:
- Inorganic formation processes, when water becomes oversaturated with calcium carbonate, the mineral can precipitate out of the solution to form limestone.
- Extreme environmental conditions, if the water becomes deficient in oxygen, most fossil-forming organisms cannot survive, leading to the deposition of limestone without fossils; or strong currents and turbulence can destroy delicate organic remains before they can be preserved; or some very shallow, near-surface marine areas can become supersaturated with calcium carbonate, leading to inorganic precipitation that outpaces biological accumulation.
- Post-depositional alteration of the rock, heat and pressure can cause the mineral structure of the rock and its fossils to rearrange into a new, interlocking crystalline structure, which can obliterate the original fossil shape.
Kepwick Quarry
The limestone at Kepwick Quarry in the Hambleton Hills of North Yorkshire was formed during the Jurassic period, approximately 142 to 205 million years ago. During the Jurassic period, the area that is now the North York Moors was covered by warm, shallow, sub-tropical seas. These seas were teeming with marine life, including invertebrates like corals, crinoids, and molluscs. The shells and hard parts of these creatures, along with other calcium carbonate sediments, accumulated on the seabed over millions of years. Layers of this sediment were gradually buried, compacted, and cemented together to form the rock known as ooidal limestone. The area was later uplifted by tectonic forces, and subsequent erosion exposed the Jurassic rocks, including the limestone quarried at Kepwick.
Kepwick quarry has probably existed for hundreds of years. The limestone around Kepwick was considered amongst the best in Yorkshire for agricultural use, pulverised to improve or ‘sweeten‘ acidic soils.
A step-change occurred in 1833 when Colonel Sir Joshua Crompton, the 19th-century owner of the Kepwick Estate, built a horse-drawn tramway, 3½ miles long, from the quarry to his kilns at Leake to manufacture quicklime, slaked lime, cement and mortar.
The tramway included a 1 in 5 self-acting incline, where a rake of loaded tubs was lowered by gravity down the slope, at the same time pulling up a rake of empty ones. A bridge was constructed to carry the incline over the Kepwick to Hawby road. This road, today partially tarmacked, still carries the delightful name of ‘Rag Robin Turn‘.
Questions - send your answers to me through the Messenger Centre or my Geocaching Profile
Examine the limestone in front of you. Can you see any fossils? Yes or no?
If you see any fossils - describe the fossils and how you think they were formed.
If you can't see any fossils - describe why you think there are no fossils in this limestone.
Please include a photo of you or your geocaching name with your log, to prove you visited the site.