Geodiversity
Oxfordshire Rock Types: Sharp's Hill
Sharp`s Hill Formation
Some Key Words
calcareous
Containing calcium carbonate
seatearth
A seatearth is a bed which typically shows considerable evidence of having been altered by plant activity and soil forming processes and are either in whole or part buried soils.
paralic
Interfingered marine and continental sediments.
proximal
The opposite of proximal is distal and these terms are also used in geology. If you're talking about the proximal sedimentary rock beds, you mean the ones closest to where the sediment came from. Proximal is related to proximity, which means "nearness," and approximate, which means close to the original.
terrigenous
made of sedimentsl eroded from the land and deposited in a marine environment.
Parent group:
Great Oolite
Age:
Jurassic/Bathonian
(166.1–168.3 Ma)
Description:
A varied sequence of greenish grey, silty, moderately shelly and calcareous mudstones, pale greenish grey shelly marls and fine-grained shelly limestones with marine and freshwater faunas. Rootlets are common, and some mudstones display seatearth textures and more variegated colours, also indicating shallow, proximal conditions. Subordinate siltstone and sandstone beds are present near the base of the formation.
Environment of deposition:
Fluctuating very shallow marine/paralic/emergent environment. A steady input of fine terrigenous material is apparent.
Boundaries:
Vertically, the Sharp's Hill Formation has a lower non-sequential boundary with the Chipping Norton Limestone Formation or the Horsehey Sand Formation. At its upper boundary it is conformably overlain by ooidal and shelly-detrital limestones of theTaynton Limestone Formation. Laterally, the Sharp's Hill Formation passes in the south-west into the Fuller's Earth Formation.
Spatial ditribution:
North Oxfordshire north-east of Milton-under-Wychwood and Minster Lovell.
Type section:
Sharp's Hill Quarry, Sibford Ferris (SP 338 359).
Reference section:
Horsehay Quarry, Duns Tew. (SP 456 273). At the reference section 4.6 metres of the fomation (clay, calcareous clay and fine-grained limestone facies) grounded on the Chipping Norton Limestone, is exposed.
Landform contribution:
together with the Horsehay sands (if present) it generally forms hollows between the more resistant, competent units of the Chipping Norton Limestone (below) Formation and the Taynton Limestone Formation (above).