Wilbury Hills to Shapenhoe Clappers Geography and Fauna

(via the Icknield Way)

Map of the area covered click to enlarge to whole screen, walks are shown on the Links below

Walks along the Icknield Way short routes interesecting the Icknield Way at or around:

I think that you can better understand and appeciate walking in an area if you have some understanding of the Geography/Geology, History and Mythology of the area

I hope to give you some insite into the area of the Chilterns between Hitchin and Shapenhoe Clappers

Geology

The geology of the area is mainly composed of chalk a deep-water sedimentary deposit, but in two area around Ickleford and Barton there are clay beds indicative of sedimentary deposits of shallower water areas compared to the chalk deposition, these clays are known as the Gault formations.

Chalk Formations

The Chilterns are chalk hills which forming around 145 million years ago (the Cretaceous period), in sub-tropical seas. Fast forward 70 million years to 65 million years ago, tectonic forces acted on these sedimentary rocks compressing and uplifted them to raise these undersea deposits to form the land surface, then allowing weathering and effects of erosion to form the landscape.

The Chalk is part of the Late Cretaceous limestone succession in southern and eastern England. It is a soft porous white limestone, deposited in a marine environment.

Chalk is a limestone that consists of coccolith biomicrite. A biomicrite is a limestone composed of fossil debris (“bio”) and calcium carbonate mud (“micrite”). Most of the fossil debris in chalk consists of the microscopic plates, which are called coccoliths, of microscopic green algae known as coccolithophores. In addition to the coccoliths, the fossil debris includes a variable, but minor, percentage of the fragments of foraminifera, ostracods and mollusks. The coccolithophores lived in the upper part of the water column. When they died, the microscopic calcium carbonate plates, which formed their shells settled downward through the ocean water and accumulated on the ocean bottom to form a thick layer of calcareous ooze, which eventually became the Chalk Group.

The Chalk Group usually shows few signs of bedding, other than lines of flint nodules which become common in the upper part. Nodules of the mineral pyrite also occur and are usually oxidized to brown iron oxide on exposed surfaces.

Flint is very common as bands parallel to the bedding or as nodules embedded in chalk. It is probably derived from sponge spicules or other siliceous organisms as water is expelled upwards during compaction. Flint is often deposited around larger fossils such as Echinoidea which may be silicified.

Gault Formation

The Gault Formation is a geological formation of stiff blue clay deposited in a calm, fairly deep-water marine environment during the Lower Cretaceous Period.

Tectonic forces

The tilting of the chalk during the tectonic episode has resulted in the area dominated by escarpments that are riddled with dry valleys and a gentle dip slope. the escarpment faces mainly to the north west with the dip slope gently sloping to mainly to the south east.

Quaternary

The next era that had a great effect on the area is the Quaternary period, and the Pleistocene epoch which started 2.6 million years ago, this time is also known as the ice age, which although very cold could also be times as warm or warmer than now.  Scientists think that the period that we are living in is a warm period between an ice age. The colder periods are known as ‘glacials’ and warm times as ‘interglacials’.  

The last glacial period ended only 12000 years ago.  This area of the UK was not covered by ice during the last glacial, it was though right at the edge of the glaciers and very, very cold.  This cold  area is known as tundra. Tundra means that the land was subject to being frozen and thawed frequently and this resulted in great changes to the landscape.

Dry Valleys

Chalk is a permeable rock that mean that water can flow freely through it and that the chalk can act as an aquifer so that it can as a store for water. But being permeable does cause a problem how can streams or rivers flow and create valleys when and water will just permeate the ground and not be able to flow across the landscape as a river or stream.  One exception to the valleys without streams is the valley near Barton. This stream starts at a spring at bottom of an escarpment and flows along the valley bottom, but this stream did not really have a great influence on the formation of the valley.

A distinctive geomorphic feature of the landscape of the Chilterns especially in this area are the dry valleys.  

Dry Valleys are valley that do not have streams in them and as most valleys are formed when streams or rivers flow through them cutting down into the rock, so how these valleys formed is still a matter of debate.  Some scientist thinking it is due to the land being frozen so that the rain cannot penetrate the soil and rock as the ground was frozen (permafrost) so the rock was impermeable allowing rivers to flow across the land and then cut into the sediments so form valleys.

Flora and Fauna SSSI interpretation

There are several Site of Special Scientific Interest, in this area three notable sites are Deacon Hill, Barton Springs and Knocking Hoe but there are several others, by visiting them the flora and fauna can be appreciated, perhaps using wikipedia is a good springboard to findout more.

The habitat in the area are varied but the main types are the steep well-grazed slopes there are also woodland on some slopes, and in the lower ground and on the higher ground to the south of the slopes and to the north lowland clay soils are dominated with agricultural crops including rape, broad beans and various grain crops dominated by wheat.

Characteristic plants of this area not including the agricultural land are chalk slope grasses and herbs. The grassland slopes have areas of scrubland with many small trees and bushes common species include hawthorn, buckthorn and wayfaring tree also found black bryony, old man’s beard and false-brome. Flora of interest also include pasqueflower (Pulsatilla vulgaris), field fleawort and a dwarf form of hairy violet.  The main grasses present are sheep’s fescue, false oat-grass and upright brome. Forbs found here include spring sedge, autumn gentian, yellow-wort, fragrant orchid, common spotted-orchid, common milkwort, common rock-rose, cowslip, eyebright, clustered bellflower, harebell, carline thistle, wild thyme, marjoram, moschatel and wild candytuft.

There are also at Knocking Hoe several nationally rare plants, including moon carrot, spotted catsear, field fleawort, burnt tip orchid and pasque flower. There are also a variety of wild flowers such as the autumn lady’s tresses.

There is also some scrubland, the main trees being hawthorn, which often invades chalk downland, a buckthorn and wayfaring tree, with black bryony and old man’s beard; false-brome usually dominates these areas. Adapted from Wikipedia.