Sand Patterns near Picquerel Point 2

Some more images showing the subtle colour transitions and delicate branching patterns that characterise the low relief natural sculptures in the fine clean sand on the shore near Picquerel Point at Grand Havre in the Channel Island of Guernsey. The dendritic patterns have been created by sea water draining down the beach as the tide recedes; and this has led to a sorting out of particles by size, weight, and colour. The darker sediments that outline and emphasise the design may be organic remnants or different darker minerals. These patterns are the best of their type that I have seen – perhaps due to the very fine sand. The patterns are so delicate they could almost be drawings.

Click on any image to view in larger format in a gallery.

Rocks at Trabeg on the Dingle Peninsula

Close-up of the Devonian conglomerate at Trabeg on the Dingle Peninsula

The sand looks black from a distance as you descend to the shore at Trá Chathail near An Trá Bheag (Short Strand) – otherwise known as Trabeg. The path cuts down deep through the stratified red rocks to get to the beach which is strewn with pebbles, mostly shades of red, maroon, green, grey, and white.

Trabeg is on the south coast of the Dingle Peninsula in Ireland, and is the “type section” of the Trabeg Conglomerate Formation which is exposed in the cliffs on the beach. This is place where that particular rock type was first described. The rock layers constitute part of the Dingle Group and were formed in the Devonian period between 345 and 395 million years ago. The conglomerates are composed of fairly well rounded pebbles of red sandstones and mudstones, with white vein quartz and chert. A few pebbles of volcanic rock and of grey limestone are also present.

The way in which the conglomerate rock has formed from the mass movement and subsequent accumulation of debris from terrestrial locations during, for example, river flood events, means that the pebbles are derived from a wide area covering many different geological types. The pebble beds or conglomerates are inter-bedded with layers of red sandstones and mudstones, the finer sediments of which were deposited normally by rivers during non-storm/flood times. The alternating layers are now tilted from the original horizontal orientation in which they were first deposited, and are clear to see dipping south at about 70 degrees.

As the cliffs at Trá Chathail are worn away by the action of waves and weathering, the pebbles contained in the conglomerate matrix are freed up and remain the shore below – an instant pebble beach. Added to these are pieces of other rock or matrix that became rounded into pebbles after they arrived on the beach. Some pebbles and rocks may have been transported by wave action from further along the coast were the geology is quite different: from the Eask Formation, West Cork Sandstone, Bulls Head Formation, and the earlier Silurian rocks of the Dunquin Group.

REFERENCE

Horne, Ralph R. (1976) Geological Guide to the Dingle Peninsula, Geological Survey of Ireland Guide Series No. 1, reprinted 1999.

A Walk to Morning Star Cove

Conifers stunted by harsh weather along the Louisbourg Lighthouse Trail

Ancient Acadian Forest cloaks the slopes right down to the shore along the trail from Louisbourg Lighthouse to Big Lorraine on Cape Breton Island. This unique forest is one of six identified for protection by the World Wildlife Fund because, here, the northern boreal forest blends with the southern hardwood forest to create a diverse habitat supporting a wide range of plant and animal life. The forest is mostly home to balsam fir with some black spruce and tamarack. Many of the trees are stunted and twisted from exposure to severe weather conditions, salt spray and poor soil in this coastal stretch. The bare sun-bleached branches on stands of dead trees are frequently covered with thick layers of pale branching lichens.

Amongst the trees are wetland areas of bog with shallow pools of open water which transition to fen with thick mats of sphagnum mosses, ground juniper, cotton grass, crowberry, and carnivorous pitcher plants. Despite the beautiful blue skies it was a particularly late and cold spring at the time of my visit (2 June 2016) and flowers were scarce but rare alpine species are known to occur in this location.

The forest, bogs, and fens sit on top of very old rocks responsible for the spectacular scenery along the coast beside the trail. All are derived from extensive volcanic activity in Precambrian (Neoproterozoic) times and belong to the Main-à-Dieu sequence. They include layered volcanic ash in the form of tuff, and varying kinds of conglomerates and breccias from pyroclastic flows down the sides of an arcing series of volcanoes where two land masses collided.

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

Thawing Hoar Frost on Beech Saplings

Icy rain and glistening dew drops from melting hoar frost on beech saplings

Freezing fog has lately covered all the vegetation in my village with a transparent icy coat bearing fringes of needle-like crystals. As the sun comes out to burn off the mist, the rising temperature begins to melt this hoar frost. As I walked along beside tall beech trees on one such frosty morning, an unexpected heavy rain of icy water began to fall from the thawing ice in the highest boughs, cascading down through the understorey of saplings where drops accumulated on the twigs and leaves, shining like diamonds in the low-slanting winter sun. Difficult to capture with the camera the brilliance of the eye-dazzling effect of reflections from the melt water rain and droplets.

Beach Stones at Corney Brook

There were no other visitors on the dull day that we turned off the Cabot Trail to look at the Corney Brook shore in the western Cape Breton Highlands. There was very low cloud cover, and it began to rain after a while, but there were treasures to be found – at least if you are like me and are fascinated by beach stones. Three main rock types are found at Corney Brook. The oldest are Neoproterozoic-Ordovician granitic pluton rocks of the Bras D’Or Terrane. Ordovician-Silurian metasedimentary rocks of the Aspy Terrane are slightly younger. And red sandstones and conglomerates belonging to the Horton Group come from the Devonian to Carboniferous Period.

The stones on the beach include all three types and probably a lot more due to the glaciation of the area. I wish I could identify and tell you the exact composition of each photographed pebble, stone or boulder – but that is tough for an amateur to determine. There is a great variety of colour, pattern, and texture to the stones which look dull when dry but amazing when wet. They include igneous and metamorphosed rocks like granite, gneiss, schist as well as sedimentary rocks like sandstone. It is possible to see just how difficult it is to not only understand the texts but also to convert into straight forward language for the non-specialist reader from the following detailed description that I discovered about the Corney Brook schist by Jamieson et al. (1987).

Comey Brook schist (unit 3d)
Medium- to high-grade pelitic and semi-pelitic schists, with minor marble and psammite, occurring on the Cheticamp River, Corney Brook, the northeastern end of Jumping Brook, and the central highlands near Calumruadh and Coinneach brooks, are referred to here as the Corney Brook schist. This unit is equivalent to the “medium grade belt” of Craw (1984). Pelitic and semi-pelitic members of the unit characteristically contain coarse staurolite, biotite, and garnet porphyroblasts, with kyanite at the highest grade, in a phyllitic to schistose matrix. Medium- to high-grade marbles, quartzites, albite schists and hornblendite recognized in the Corney Brook area (Plint et al., 1986) have not yet been identified south of the Cheticamp River. Centimetre- to metre-scale compositional layering, folded by tight to isoclinal folds, is interpreted as transposed bedding. Based on bulk compositions and rare relict primary textures, the Corney Brook schist is interpreted to have formed as a suite of clastic sediments interlayerd with felsic tuffs and minor basic flows – that is, it appears to represent the higher grade equivalents of units 3a-3c.

The softer sandstone cliffs are being eroded back by the sea. This has implications for the ground higher up and the roadway further back from the shore. For this reason a sea defence structure has been emplaced to protect the base of the cliffs. This is a gabion made of wire cages full of large beach stones and boulders that are stacked up into a wall, positioned at the most vulnerable part of the shore.

Sand Patterns near Picquerel Point

Natural abstract art showing dendritic drainage patterns in sand on the beach

Natural abstract art showing dendritic drainage patterns in sand on the beachSubtle colour transitions and delicate branching patterns characterise the low relief natural sculptures in the fine clean sand shown in this photograph. It was one of many taken on the shore near Picquerel Point at Grand Havre in the Channel island of Guernsey. The dendritic patterns have been created by sea water draining down the beach as the tide recedes; and this has led to a sorting out of particles by size, weight, and colour. The darker sediments that outline and emphasise the design may be organic remnants or different darker minerals. These patterns are the best of their type that I have seen – perhaps due to the very fine sand. They look like pencil sketches. I am definitely going to frame some of the images.