Rocks at Redend Point in Studland Bay – 4

Orange cliff rocks on the north side of Redend Point in Studland Bay, Dorset, England.

I revisited Redend Point at Studland in Dorset yesterday for the first time in several years. Here are some of the pictures I took. I was only able to look at the north side of the Point because of the state of the tide. The colours seem different from my last trip there. This could be to do with how much rain there has been but also possibly to do with the weathering affect on the iron. [The part of the Point with the wonderful pink and yellow stripes and patterns was further on – to the south of the Point which I could not reach].

More rocks have fallen from the ferruginous sandstone and from the overlying clays. This has brought down a large tree which now lies across the beach. In some areas the sea has undercut the sandstone to produce small caves. These have floors composed of a mixture very fine pale sand, rust-stained flints from the nearby chalk strata around the corner, and bright orange sandstone with pot-holes and eroded channels draining seawards. In this northern part of the Point the colours manifest by the Redend Sandstone seemed less varied than four years ago, and the carved graffiti was much greater than previously noted. Such a shame that almost every surface was disfigured.

Beach boulder and pebbles on the north side of Redend Point in Studland Bay, Dorset, England.

Flint pebbles and boulders on the north side of Redend Point at Studland Bay in Dorset, England.

Flint pebbles on the north side of Redend Point at Studland Bay in Dorset, England.

Beach boulder and pebbles on the north side of Redend Point in Studland Bay, Dorset, England.

Cliff rocks on the north side of Redend Point in Studland Bay, Dorset, England.

Beach boulder and pebbles on the north side of Redend Point in Studland Bay, Dorset, England.

Lower cliff rocks on the north side of Redend Point in Studland Bay, Dorset, England.

Lower cliff rocks on the north side of Redend Point in Studland Bay, Dorset, England.

Lower cliff rocks on the north side of Redend Point in Studland Bay, Dorset, England.

 Boulder and cliff on the north side of Redend Point in Studland Bay, Dorset, England.

Beach boulder on the north side of Redend Point in Studland Bay, Dorset, England.

Boulder and cliff on the north side of Redend Point in Studland Bay, Dorset, England.

Rocks at Redend Point in Studland Bay – 1

Rock texture, colour, and pattern in Redend Sandstone  at Studland Bay

Examples of rock texture, colour and pattern in Redend Sandstone (also known as Creekmoor Sand) which is a basal member of the Poole Formation (formerly referred to as the Bagshot Formation), of the Bracklesham Group. The pastel almost rainbow colours are caused by iron staining. Hollow pipes (as in the shot immediately below), which can be up to 15 cm diameter and sometimes extend as much as 4 m through the strata, are of unknown origin. The sandstones were laid down in the Eocene.

REFERENCE

Cope, J. C. W., 2012, Geology of the Dorset Coast, Geologists’ Association Guide No. 22, 191-194, ISBN 978-0900717-61-1.

Rock texture, colour, and pattern in Redend Sandstone at Studland Bay

Rock texture, colour, and pattern in Redend Sandstone at Studland Bay

Rock texture, colour, and pattern in Redend Sandstone at Studland Bay

Pebbles with Lichen at Chesil

Bright orange lichen encrusting a beach pebble in a sheltered zone

On the eastern flank of the great pebble bank of Chesil Beach in Dorset, on that part adjacent to the Fleet Lagoon where fishermen’s huts are strewn along the water’s edge, the pebbles were sufficiently undisturbed in the spring of 2011 for vegetation to get a grip. A few scattered plants had established themselves amongst the rounded stones; and many pebbles in the same area were coated with slow-growing black or bright orange lichens.

This type of colonisation of beach shingle is a fairly uncommon phenomenon because, in general, the constant movement and abrasion of the pebbles does not allow plants to establish a root system or lichens to encrust the surface of the pebbles themselves. However, in this particular location on the leeward sheltered side of the pebble bank, there had been a period of years of relative stability that enabled vegetation to start growing.

During the winter of 2013 to 2014 the Chesil Bank sustained enormous damage from the storms. The wave action resulted in massive movements of the pebbles. I haven’t revisited the site since the storms but I strongly suspect that the plants and lichens will have suffered and may no longer exist. I must go and check it out. Whatever the outcome of last winter’s weather and subsequent maintenance work on the pebble bank, the slow colonisation process will surely begin again but will take time to restore the habitat to its former situation.

Pebbles with patches of black lichen on the Chesil Bank in Dorset

Pebbles with patches of black lichen on the Chesil Bank in Dorset

Pebbles with patches of black lichen on the Chesil Bank in Dorset

Plant growing on pebbles at Chesil Beach

Plants and bright orange lichen growing on beach pebbles

Pebbles with patches of black lichen on the Chesil Bank in Dorset

Makeshift boardwalk up the Chesil Bank in Dorset

Beach Boulders at Eype 3

Another gallery of rock pictures from Eype beach. I hope the photographs in this and preceeding posts on the same subject will prove a useful resource for students of geology as well as those interested in the aesthetics of geology.

COPYRIGHT JESSICA WINDER 2014

All Rights Reserved

Eype Beach Stream 4

Beach Boulders at Eype 2

Sedimentary rock boulders on the seashore extending into the sea

Another gallery depicting the amazing rock boulders on the seashore at Eype in Dorset, England, and the contexts in which they are found on the beach.

The cliffs at Eype, and the boulders on the beach below them, are made of Middle Lias sedimentary rocks from the Jurassic Period. It is difficult to judge the scale of the cliffs from looking at the photographs, so you might like to know that the silty sand and hard sandstone bands of the Three Tiers layers at the base can reach a maximum of 9m thick (although much of that is buried in this location); the clays and sandstones of the Eype Clay Member above that are 60 metres deep; on top of that the soft sands of the Downcliff Sands Member are 30 metres deep; and above that the soft sandstones of the Thorncombe Sands Member are 21 metres thick. This makes for a sequence of rock strata measuring a potential 120 metres (390 feet) in height – the measurements are approximate as the depth of the layers varies a lot.

In their book Classic Landforms of the West Dorset Coast, Brunsden and Goudie state that

The coastal cliffs of West Dorset owe their shape to the relief and orientation of the coastline, the variable properties or lithology of the rocks, the geological structure, the history of relative land and sea movements, the sequences of environmental change, the difference in erosional energy of the sea between the more exposed and sheltered parts of Lyme Bay, and to the complex sub-aerial processes which currently act on the cliffs themselves.

At Eype, the boulders on the beach demonstrate not only the variable lithology of the rocks in the cliffs above but also their structure. The alternating bands of different rock composition and colour are evidence for the cyclical nature of changing environmental conditions throughout geological history, including changes in sea level relative to land; while their presence on the seashore illustrates the ongoing erosional processes affecting the coastline to this day.

COPYRIGHT JESSICA WINDER 2014

All Rights Reserved

Beach Boulders at Eype 1

Stratification in a beach boulder

As the soft rocks of the exposed Eype Clay Member mudstones in the cliffs at Eype are eroded, the harder sandstone and limestone rocks (that were laid down at a later date above them) are under-mined. The unsupported rocks then break under their own weight, slide down the cliff and eventually come to rest on the orange gravel and pebbles of the shore. At the western end of Dorset’s Eype beach, part of the Jurassic Coast World Heritage Site, the boulders extend continuously from the base of the cliff out into the sea. Elsewhere along the shore, the boulders are clustered at the cliff foot adjacent to the soft micaceous mudstone layer. Most of the images shown here were photographed in a stretch of shore just a couple of hundred metres long.

The boulders tend to be very large, some about two metres in height and width. Their shapes are endlessly variable and their colours are generally complementary shades of yellow and grey. They can be patterned by layers of contrasting width, colour, and composition; or by scattered fossils and iron nodules. This is the first of several posts showing the fascinating variety of composition and form of these boulders, and the contexts in which they can be found. The boulders in these photographs are the same ones from which I photographed the rock textures in an earlier post. Every boulder seems unique in its appearance.

COPYRIGHT JESSICA WINDER 2014

All Rights Reserved