Tracks and Trails on Whiteford Sands

Furrowed trails made by common winkles on wet beach sand

You don’t exactly have to keep your nose to the ground to see them but you do have to be a keen observer to notice all the different tracks and trails left on the soft wet sediments of the beach at low tide. Larger marks left by people and vehicles are the first ones you see. Bird footprints are every where. The birds are feeding on all sorts of invertebrate seashore creatures like worms, small crustacea and molluscs – all of which leave holes, burrows and furrows as they move in and out of the sand and across the surface. Some of the pictures shown here simply aim to give the general context for the area of Whiteford Sands that I was walking across. If you look closely the other images, you will see not only the ripples in the sand but also the intricate network of traces left by the virtually invisible organisms that inhabit this ecosystem. The larger furrows in photos 1, 12 and 13 are made by the common winkle (Littorina littorea Linnaeus). I cannot name each animal that is responsible for each of the other types of trace. However, I am sure that there will be some specialists out there who could, especially those researchers concerned with the interpretation of trace fossils (the ichnologists).

Click images to view full size.

View looking west towards the sea at Whiteford Sands

View looking north-east towards the dunes at Whiteford Point

Wet seashore sand with marine invertebrate and other tracks and traces

Wet seashore sand with marine invertebrate tracks and traces with bird footprints

View looking north-east over wet seashore sand ripples with marine invertebrate tracks and traces at Whiteford Sands

Wet seashore sand ripples with marine invertebrate tracks and traces

Wet seashore sand ripples with marine invertebrate tracks and traces

Wet seashore sand ripples with marine invertebrate tracks and traces

Wet seashore sand ripples with marine invertebrate tracks and traces

Wet seashore sand ripples with marine invertebrate tracks and traces

Furrowed trails made by common winkles on wet beach sand

Furrowed trails made by common winkles on wet beach sand

Clustered Periwinkles at Whiteford

Large groups of common winkles clustered around the base of large stones on the beach

At low tide many thousands of common winkles or periwinkles (Littorina littorea Linnaeus) seek shelter from dessication and predation by clustering together in the few hiding places available on the beach. At Whiteford Sands these niches include the overhung bases of larger stones, crevices in ancient timbers from the rapidly emerging submerged forest, and nooks and crannies in the recently exposed ancient peat. Alternating layers of peat and clay, overlain by rocks from glacial till, provide algae-covered surfaces on which gastropods can feed, and islands of low tide refuge in the vast expanses of sand on this sea shore.

Large groups of common winkles clustered around the base of large stones on the beach

Large groups of common winkles clustered around the base of large stones on the beach

Large groups of common winkles clustered around the base of large stones on the beach

Large groups of common winkles clustered around submerged forest wood on the beach

Large groups of common winkles clustered around submerged forest wood on the beach

Large groups of common winkles clustered around submerged forest wood on the beach

Large groups of common winkles clustered in exposed ancient peat beds on the beach

Large groups of common winkles clustered around submerged forest wood on the beach

Winter Walk at Whiteford Sands

Red fishing buoy flotsam

Crisp and cold, bright and sunny, just right for blowing away the cobwebs with a walk along the strand at Whiteford Sands. On this particular winter’s day the tide had brought ashore lots of flotsam – fishing nets, buoys, floats, and crates, shoes, hard hats, and miscellaneous plastic rubbish that rested on a driftline of sand, pebbles or shells. Here are some of the things that caught my eye as I strolled the high water mark from Cwm Ivy Tor to the spit beyond Whiteford Point on Boxing Day 2013. Click on any of the images in the gallery below to view in a larger format and slideshow.

Sand Dune Erosion at Whiteford

Sand dune erosion at Whiteford Sands on the north Gower coast in South Wales

Shorelines evolve. Changes happen – sometimes slowly and sometimes quickly. The winter of 2013 to 2014 brought severe storms and winds that impacted on all our British coastlines. Whiteford Sands on the north shore of the Gower Peninsula in South Wales was no exception. By May 2014 a dramatic change in the long line of dunes bordering the sands was clear to see. The dunes have been fixed for a long time with the outer slopes stabilised with marram grass, and a turf covering further inland. Small changes had been occurring steadily for many years with a gradual wearing away of the dunes.  High tides and extreme weather events had been nibbling at the seaward faces. The erosion process has not been continuous but interspersed with periods of accretion both by water-borne and wind-borne sand.

The sand was originally deposited by a melting ice sheet in Carmarthen Bay, including the Loughor estuary on which Whiteford Sands is situated, and at Pendine Sands and Rhossili Bay. The first direct evidence for glaciation on Wales dates to 480,000 years ago in the Anglian Stage of the Pleistocene in the Quaternary Period when ice sheets enveloped Wales and the adjacent sea. The last ice coverage in the region was the Late Devensian Era about 24,000 years ago. There seem to be only minimal additions to the sand deposits from local sources since then because the Carboniferous limestones of the area dissolve rather than disintegrate into particles or grains. The sand is a therefore a finite resource albeit one that is controversially exploited locally by dredgers on the Helwick Bank just off the tip of Gower.

The sand is basically mobile within the area on the shorter and longer timescales. A useful and interesting research report on this subject is that by V J May on Carmarthen Bay in the Geological Conservation Review in which the sediment transport around the region is discussed. Figure 11.12 presents a sketch map of the key geomorphological features and sediment transfers of Carmarthen Bay. Figure11.13 depicts variations in accretion and erosion since 1950 in Carmarthen Bay. Figure 1.17 illustrates geomorphological features of Rhossili bay and Whiteford Burrows. The report records how and in which directions the sand is being shifted by river/estuarine currents, onshore and longshore drift; and where attrition and accumulation of sand is most marked. It is an intriguing read and gives much to elucidate the field observations I have been making in the area over the last decade.

The Rise and Fall of Whiteford Sands

View looking towards the lighthouse at Whiteford on the Gower Peninsula showing rock strewn beach with patches of sand

The photographs in this post illustrate the way that vast quantities of wind- and wave-borne sand at Whiteford Sands on the Gower Peninsula move around the shore over time. I have taken one fixed object, a piece of ancient timber with an unmistakable shape that projects from the early to post Holocene deposits of peat and clay, and taken shots of it on every visit to the beach over the past ten years or so. The following images show how the sand level changes periodically to reveal or conceal the underlying layers with the surface scattering of rocks that were dumped by the melting ice during the last glacial event. Beaches like Whiteford are incredibly dynamic. Click on any image in the gallery below to view as a slideshow in chronological order.

 

Traces on the shore at Whiteford (1)

Sandgrain tubes of marine worms and sea shells

Fossils can include not only the actual preserved remnants of organisms from times long past (like shells and bones), and the replacements of such organisms (such as infilled moulds and casts), but also the evidence of their existence – for example their modified habitats, trails, burrows, tubes, marks and structures left by their feeding activities. Such evidence of long dead creatures is referred to as trace fossilisation; and the study of fossil traces is termed ichnology.

Part of the process of identifying the exact nature of trace fossils and reaching an understanding of their significance, involves making observations of the behaviour of related or similar present day organisms. This includes a study of their activities and the impact of them on their immediate environment in life. It also involves making records of the way in which the organisms change – what happens to them and their habitat after death (taphonomy).

Many of the trace fossils which I have discovered while walking along seashores and looking at cliffs, outcrops and boulders on beaches were made by various invertebrate seashore creatures in soft intertidal sediments that have later been buried, compressed, and hardened into rock. Recent marine worm tubes of various kinds are a fairly common occurrence on beaches and also as fossils in the sedimentary rocks of, for example, the Dorset coast in England. A short while ago I posted some photographs of fossil worm tubes that I found at Winspit.

For these reasons I was particularly interested to see the millions of sand grain tubes of marine polychaete worms on the low tide beach at Whiteford Sands on the north coast of the Gower Peninsula in South Wales. Many could be seen in situ, no doubt with worms in residence, projecting from the surface of the wet sand like some kind of stunted crop with seashells scattered among them. On the shallow bank created by a beach stream wending its way seawards, it was fascinating to see how far down into the sediments the tubes extended, a thick layer of unknown depth. It reminded me of a fantastic illustration in a book I recently acquired by Wilhelm Schäfer called Ecology and Palaeoecology of Marine Environments, originally published in Edinburgh by Oliver & Boyd in 1972. Copyright considerations mean the book is not old enough for me to reproduce the drawing here for you without written permission but Figure 190 on page 326 shows a cross-section through bedded sands and muds and shell deposits with many-branched and frequently extended dwelling tubes of Lanice conchilega cutting across the layers – just like the deposits on Whiteford Sands. Even though the book is old it is still widely available secondhand and is a wonderful repository of information.

Pebbles at Whiteford (4)

Pebbles, shells, and a feather on the beach near Whiteford Point

A sand bar spreads southeast from Whiteford Point in Gower, South Wales. At low tide in the Burry Estuary, it is part of a very extensive sandy area over which cockle and mussel fisherman can traverse in vehicles from places further along the north Gower coast. The sand depth is variable and mostly envelops a spit of pebbles. Sometimes the pebbles are entirely hidden. Sometimes they are partially exposed. Intermixed with the pebbles are seashells – cockles, mussels, whelks, and oysters are the most commonly occurring. There is a wide range of colours and textures in the pebbles and they are particularly interesting because of the range of rock types they represent.

As you take a 360 degree scan of the horizon from this isolated expanse of sand and pebbles, there is not a single rocky outcrop in sight. So where have these beach stones come from? The collection includes sedimentary rocks from the locally occurring Carboniferous limestone and Devonian sandstones, mudstones, and conglomerates – like the bedrock exposed at Rhossili and at Broughton Bay. It also includes samples from higher up in the Carboniferous strata such as the Millstone Grits, sandstones, and shales, and Coal Measure layers. These strata underlie the Burry Estuary into which this spit extends, east Gower, and the Swansea district and way beyond. There are many rock types with which I am not familiar but I notice that some are metamorphic and igneous in nature. So how have all these rocks ended up on this spit, far from their place of origin?

Part of the answer is undoubtedly the effect of sea drift, currents, and storms carrying weathered and broken stones along the shores of Carmarthen Bay and into the estuary or inlet – but a significant proportion of the stones are thought to have been brought to the area from considerable distances away by glaciation, and deposited by the melting of an ice sheet, possibly in the late Devensian era about 24,000 years ago. Most of these stones lie hidden in a mass beneath the Whiteford Dunes but some are exposed high on the shore at the foot of the dunes, and beneath the disused iron lighthouse on Whiteford Point. Over time the waves have dislodged the often frost-shattered stones from the surface of the deposit, and washed them further along the beach around the Point to form pebble spits and banks, in the process smoothing and rounding them into the pebbles visible today.

Click here for more posts about Whiteford Sands, Whiteford Point, and Whiteford Burrows.