User:Huligan0/Purbeck Monocline
The Purbeck Monocline is a geological fold. The term 'fold' is used in geology when one or more originally flat sedimentary strata surfaces are bent or curved as a result of plastic (ie. permanent) deformation. A monocline is a step-like fold, in which one limb is roughly horizontal. The Purbeck Monocline occured during the late Oligocene and early Miocene epochs, about 30 million years ago. It is the northernmost 'ripple' of the the Alpine Orogency.
The effect of the Purbeck Monocline resulted in the large ridge of near vertical Cretaceous chalk which now forms the Purbeck Hills. This chalk band runs from Swyre Head via Flower's Barrow to Old Harry Rocks and then under the sea to The Needles and forms the central spine of the Isle of Wight.[1]
The Purbeck Hills separate the small broad peninsula, the Isle of Purbeck, from the rest of England. The structural geology of the isle of Purbeck is basically that all the rock beds dip down towards the north. The affect of this geology is that the resistant beds, the Chalk and Limestone, form two ridges and the Wealden between them is eroded to form a valley.
Some visible features along the monocline include the disharmonic folds and faults, known as the Lulworth Crumple, at Stair Hole,[2] Lulworth Cove, Arish Mell and at Peveril Point further east. These features also include the polygonal thrust ridges developed in the harder rock bands at Kimmeridge Bay and related to the growth of the monocline is the fault at Ballard Down.
References
[edit]- ^ Underhill, John R.; Paterson, Susan. (November 1998). "Seismic evidence for the development of key structures along the Purbeck-isle of wight disturbance". Journal of the Geological Society. Retrieved 2010-11-16.
{{cite web}}: CS1 maint: date and year (link) - ^ West, Ian (2010). "Geology of Stair Hole". School of Ocean and Earth Science, Southampton University. Retrieved 2010-11-16.