Flints & Ironstones at South Beach Studland

Beach stones derived from the chalk cliffs at South Beach, Studland, Dorset, England.

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.

REFERENCES

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

Rocks with Copper at Bunmahon

Colour and texture in quartz with copper minerals

Beautiful green-blue stained rocks are frequently found in stone walls at Bunmahon in southern Ireland. The small  village was at one time home to a successful copper mining industry. The copper is thought to have formed 354 million years ago at the beginning of the Carboniferous Period but possibly even earlier. The village is now the centre of the Copper Coast GeoPark and has a lovely roadside rock garden illustrating the geological history of the area. The copper mineral chalcopyrite (copper-iron sulphide) occurs as veins in white crystalline quartz and alters to copper carbonate forms such as green malachite and blue azurite.  Weathered stones show these colourful blue-green variants of the mineral, with the rusty patches representing the iron component. Stones of this composition are found in walls all around the area.

Rock Texture & Pattern at Main a Dieu

The wooden boardwalk from the Coastal Discovery Centre at Main á Dieu on the southeast coast of Cape Breton Island, in Nova Scotia, Canada, leads to a look-out platform that is built on top of a rocky outcrop. The rock is a basalt volcanic lava flow dating from the Neoproterozoic Period around 560 million years ago. The basalt is characterised by many interesting natural fracture patterns; veins and weathered surfaces of contrasting colours; and different textures depending on exposure to aerial or aquatic erosional elements.

[We stayed at the most excellent Louisbourg Harbour Inn while we explored this part of Cape Breton Island.]

REFERENCES

Atlantic Geoscience Society (2001) The Last Billion Years – A Geological History of the Maritime Provinces of Canada, Atlantic Geoscience Society Special Publication No. 15, Nimbus Publishing, ISBN 1-55109-351-0.

Barr, S.M. (1993) Geochemistry and tectonic setting of late Precambrian volcanic and plutonic rocks in southeastern Cape Breton Island, Nova Scotia. Can. J. Earth Sci. 30, pp. 1147-1154.

Donohoe, H. V. Jnr, White, C. E., Raeside, R. P. and Fisher, B. E, (2005) Geological Highway Map of Nova Scotia, Third Edition. Atlantic Geoscience Society Special Publication #1.

Hickman Hild, M. and Barr, S. M. (2015) Geology of Nova Scotia, A Field Guide, Touring through time at 48 scenic sites, Boulder Publications, Portugal Cove-St. Philip’s, Newfoundland and Labrador. ISBN 978-1-927099-43-8, pp. 66-69.

Keppie, J.D., Dostal, J. and Murphy, J.B. (1979) Petrology of the late Precambrian Fourchu Group in the Louisbourg Area, Cape Breton Island. Paper 79-1, Nova Scotia Department of Mines and Energy.

Fault Zone Rocks at Clarke Head Part 3

Broken rocks on the beach at Clarke Head, Nova Scotia, Canada.

More pictures of the beach at Clarke Head showing the multiplicity of rock colours, patterns, and textures of the boulders, broken rocks, and small shards derived from the jagged cliffs of the fault zone. Looking at these photographs now, I am transported right back to the great time I had exploring this location – one of many that I visited on my rock hounding tour of Nova Scotia earlier this year.

 

Rock Textures at Cap Rouge

Canada’s Atlantic Maritime Provinces have a fascinating geological history. Nova Scotia has an exquisite array of rock types and formations. The difficulty is gaining access to them without going off-road and hiking into the wilderness. Fortunately, along the Cabot Trail in the Cape Breton Highlands National Park there are many signed trail heads and information areas that bring an understanding of the wonderful surrounding landscape to the less adventurous or less able visitor. One of these roadside areas at Cap Rouge explains how the view shows the three basic types of rock (igneous, sedimentary, and metamorphic) in the one vista – provided it is not completely obscured by heavy rain and dense cloud cover as it was on the day I visited.

The wall bearing the information boards is, however, constructed from intensely metamorphosed rock from the adjacent highlands of French Mountain; and large boulders bordering the parking area (unfortunately unlabelled) provide further examples of the metasedimentary rocks from the Ordovician to Silurian rocks of the Aspy Terrane, and the Neo-Proterozoic to Ordovician grantitic pluton rocks of the Bras D’Or Terrane of the surrounding region . [A terrane “is a fault-bounded fragment of continental crust broken from one tectonic plate and later joined to another during continental collision, recognized as such by its distinctive rock units and separate sedimentary, igneous and metamorphic history as compared to adjacent parts of an orogen” (Hickman Hild and Barr , 2015). An orogen is the result of mountain building processes as preserved in the rock record].

REFERENCES

Hickman Hild, M. and Barr, S. M. (2015) Geology of Nova Scotia, A Field Guide, Touring through time at 48 scenic sites, Boulder Publications, Portugal Coce-St. Philip’s, Newfoundland and Labrador. ISBN 978-1-927099-43-8.

Donohoe, H. V. Jnr, White, C. E., Raeside, R. P. and Fisher, B. E, (2005) Geological Highway Map of Nova Scotia, Third Edition. Atlantic Geoscience Society Special Publication #1.

Calcite Veins in Threecliff Rocks – Part 1

View of Threecliff Bay on the Gower Peninsula

Threecliff Bay on the south coast of the Gower peninsula in South Wales is one of the most beautiful and interesting locations. The scenery is spectacular and the three rocky peaks that give the bay its name are clear to see. The Pennard Pill river follows great meandering loops as it approaches the sea and it flows down a valley created by weaknesses along a tear fault that skewed the alignment of the rock strata. The rocks on the east side of the valley do not line up with those on the west side. The strata in the east have been moved northwards.

The pictures in this post were taken where those displaced rocks outcrop in cliffs on the east side of the bay. They are composed of Carboniferous Limestone. I think they are from the Black Rock Limestone Subgroup – the only available geology map has out of date nomenclature for the various rocks types and calls this section of strata Penmaen Burrows Limestone (d1b). What fascinated me was the wonderful red tinge in the rocks due to the iron content and the intricate natural patterns of discontinuous white veins of calcite. I wonder if these veins are something to do with the pressures and heat resulting from the northwest to southeast tear fault that defines the valley. It looks as if a first set of cracks was infilled with calcite before a second set, cross-wise to the first, was formed in a subsequent event that generated yet more pressure and heat.

Rocks at Redend Point in Studland Bay – 3

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay

Several years ago I first posted some of these photographs of Studland Bay rocks but I think it is still worth posting some more now, as it is not every one who will have had the time and patience to burrow through the archives of rock postings on this web log. I never cease to be amazed by the stripe patterns, and the red, yellow, and purple colours of the Redend Sandstone (Creekmoor Sand) at Studland Bay. They are incredible.

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay

Rocks at Redend Point in Studland Bay – 2

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay

Pink and yellow patterned sandstone with Liesegang rings resulting from the dispersion of iron minerals dissolved in river water percolating through the rock. Photographed at Studland Bay in Dorset, England, in outcrops of Eocene-dated Redend Sandstone (Creekmoor Sand) of the Poole Formation in the Bracklesham Group. These soft sandstones in the low cliffs at the south end of the bay seem to be an irresistible  “canvas” for graffiti artists.

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay

Rock colour, pattern, and texture in Creekmoor Sand (Redend Sandstone) at Studland Bay