Textures and patterns in chalk cliffs at Studland Bay – showing white strata and darker flint nodule layers; different degrees of weathering, fracturing and smoothing of the rock surfaces; subtle inherent variations in colouring; greyscale shading brought about by dirt and biological encrustations; and more dramatic green algal coatings on the wave-washed cliff base.
The upper part of the sandy beach at South Beach, Studland in Dorset is littered with pebbles and stones of many colours and interesting patterns and textures. They are mostly flint and ironstone that has weathered out of the chalk that forms impressive cliffs from here to Old Harry Rocks and the Foreland or Handfast Point in the distance.
Click on any image to enlarge and view in a gallery.
Barton, CM, Woods, MA, Bristow, CR, Newell, AJ, Weathead, RK, Evans, DJ, Kirby, GA, Warrington, G, Riding, JB, Freshney, EC, Highley, DE, Lott, GK, Forster, A, and Gibson, A. 2011. Geology of south Dorset and south-east Devon and its World Heritage Coast. Special Memoir of the British Geological Survey. Sheets 328, 341/342, 342/343, and parts of 326/340, 327, 329 and 339 (England and Wales), 9–100.
Cope, JCW, 2012 Geology of the Dorset Coast, Geologists’ Association Guide No. 22, Guide Series Editor SB Marriott, The Geologists’ Association, 191-194.
Swanage Solid and Drift Geology (map), British Geological Survey (Natural Environment Research Council) 1:50,000 Series, England and wales Sheets 342 (East) and part of 343
Playing with sand on an industrial scale at Weymouth Beach in Dorset this week, earth moving machinery has been restoring the shore to pristine condition by redistributing imported sand – ensuring plenty for sun-bathing and sand castle-making before the better weather and the influx of visitors arrive in this new season.
Here are some more pictures of the boulders at the eastern end of Charmouth Beach in Dorset, England, all exhibiting natural fracture patterns in sedimentary rock belonging to the Jurassic Charmouth Mudstone Formation. I’m not sure which particular layer they come from but it could be the Black Ven Marl Member. Perhaps someone can help me out with the identification? These images show the boulders at the foot of the cliff adjacent to the landslip or mud slide. In contrast to the dark boulders at the water’s edge shown in the previous post, these are dry and therefore lighter in colour.
I wonder if these boulders could have been the inspiration for an artwork in the sculpture park in Tout Quarry on the Isle of Portland featured in an earlier post.
The shoreline at Charmouth looked particularly dramatic on this April visit as storm clouds periodically burst and blue skies were only intermittent. Charmouth Beach lies on the World Heritage Jurassic Coast in Dorset, England. The rocks are mainly Jurassic Period Charmouth Mudstone Formation. The character of the cliffs changes as you walk from west to east because the sedimentary rock layers gently slope and disappear beneath the beach surface level while new rock strata are freshly revealed at eye level. The predominance of softer rocks has led to a great deal of cliff slippage, and this means that the chronological sequence of the layers is frequently obscured by fallen debris; it makes it difficult to distinguish which rocks are which. The numerous rockfalls regularly contribute to the boulders on the beach and in this post I feature some boulders that exhibit some interesting fracture patterns. Of course these are not the only rock type on the beach, and I will post some more photographs of other patterns and textures in boulders and in the cliff face on the eastern half of Charmouth Beach in due course.
The alternating dark and light rock layers of the Belemnite Marls (belonging to the Lower Lias division of the Jurassic Period) at Seatown in Dorset, England, are riddled with small trace fossil burrows. These are mostly tunnels that were dug into the soft seabed sediments by marine organisms such as marine worms and crabs before the sediments became lithified or converted to hard stone. The patterns of these trace or ichno fossils in the cliffs show a wide range of sizes in the burrows with cross-section and longitudinal section views. Some of the tunnels are branched, some are u-shaped, and many are irregular. The shape and size of the burrows, and the particular location of the stratum in which they appear, provide clues to the identity of the creatures responsible. The burrows include Rhizocorallium, Thalassinoides, and Chondrites (Woods 2011). Most of the burrows shown in the photographs here are easy to see because of their contrasting colour – they have been excavated in layers of the darker sediment and have at a later stage been in-filled with the lighter coloured sediments from the layer above. The opposite can also happen, with burrows in lighter sediment being infilled with darker material from above, as seen in a couple of the pictures. Not all the trace fossils are burrows. Some traces appear to be a breaking up of the semi-solidified surface deposits with inter-mixing of sediment from the deposit above.
Woods, M. A. (compiler) (2011) Geology of south Dorset and south-east Devon and its World Heritage Coast: Special Memoir for 1:50,000 geological sheets 328 Dorchester, 341/342 West Fleet and Weymouth, and 342/343 Swanage, and parts of sheets 326/340 Sidmouth, 327 Bridport, 329 Bournemouth and 339 Newton Abbot. British Geological Survey, Keyworth, Nottingham. ISBN 978-085272654-9, pp 28-33.