Introduction

Marloes Sands is a geologically wondrous location, encompassing towering cliffs, a beautiful expanse of sand and clean sea water throughout the year. Although finding fossils can prove more difficult than at other locations, the geological features alone will impress most visitors. Unless you're actively studying the subject, or an experienced palaeontologist, this locality is not recommended for collecting fossils.

The surrounding area is managed by the National Trust, who provide information about the geology and wildlife from a small office within the cliff-top car park; the staff are always happy to direct visitors to the beach. A small parking charge is payable at the National Trust office upon arrival.

Left: National Trust car park and information office. Right: Public footpath leading to the beach - 700m.

Access to the beach is made along a gravel surfaced footpath, located 100m back along the road, north of the car park. The walk takes about 10 minutes and leads to the foreshore. Once you reach the beach a small wooden bridge crosses a small stream, beyond which a short walk leads to the vantage point that the following two photos were taken from.

Left: View over the southern end of the bay. Right: View over the northern end of the bay.

The geology of Marloes Sands

Marloes Sands comprises four main geological groups - Skomer Volcanic, Coralliferous, Gray Sandstone and Old Red Sandstone (fig.1 below). From the beach access point, heading south (left when facing out to sea), visitors will pass through each group in turn, until you reach the end of the bay (Old Red Sandstone).

Figure 1: Detailed stratigraphy of Marloes Sands - adapted from Walmsley and Bassett, 1976.

Fossils are less common in all but the Coralliferous Group (see stratigraphy above), which reveals a wealth of marine organisms from the Silurian period (circa 428 million years ago). The photo below Left: shows and accumulation of loose rocks from the Coralliferous Group, from which the specimens featured on this page were largely found.

Left: Vertical strata belonging to the Coralliferous Group. Right: Skomer Volcanic Group, containing lagoonal ripple marks.

Visitors can also find evidence of ripples within the older Skomer Volcanic Group, which are thought to have been formed in a shallow lagoon, 439 million years ago; the photos below show some of the large symmetrical examples found at the cliff base.

Left: Roy props up a large section of rock featuring ripple marks. Right: Some of the ripple marks are evident of large slabs.

At the southern end of the bay you reach the 'Old Red Sandstone' which was formed from sediments weathered out of a mountain chain, extending from what is now Scandinavia through Scotland to the Catskill Mountains of America. Although fossils weren't discovered here during our recent visit the Old Red Sandstone holds the evidence of an extraordinary period of the planet's history, when the vertebrates developed, flourished in the seas and rivers, and emerged on to the land, where the first vascular plants took root and the first arthropods crawled, breathed air and took wing.

Where to look for fossils?

Fossils are not abundant at Marloes Sands and visitors will need to search hard to find productive spots. The best places to search are the scree accumulations at the base of the cliff, although these themselves are limited to just a small number. In September 2007 there were two relatively productive areas, both situated towards the southern end of the bay; however, despite the illusion of rapid erosion this particular cliff collapse originally occurred over twenty years earlier. For more information about the features and processes controlling coastal fossil collecting locations click here.

What fossils might you find?

Once a productive spot is found it's possible to collect a range of marine based fossils, in particular Trilobites and Cephalopods, although these are among the less common specimens. The most common fossils are corals, brachiopods and bivalves, many of which have been crushed through time.

Left: A small trilobite tail. Right: A close-up on the trilobite.

Left: Two gastropods (Loxonema) in amongst a number of brachiopod impressions. Right: Isolated fragment of coral (favosites?)

Left: An impression of a brachiopod shell (Rhynchonellid).  Right: A small brachiopod (Lingula).

Left: A small section of a cephalopod clearly showing the horizontal segmentation of the body.  Right: A second cephalopod.

Left: A small inner side of a brachiopod shell (Leptostrophia). Right: A small coral.

Corals are also common within selected horizons, some of which feature delicate feather-like structures, as shown below. The presence of corals within this relatively brief window of time, reveals a period of shallow marine conditions, as the corals themselves required plenty of sunlight to survive.

Left: A narrow, feather-like coral. Right: A close-up of the coral.

Other interesting finds include isolated pebbles within the shales, known commonly as erratics; the photos below show two examples. Note, the example of the left shelters two small brachiopods along its lower edge, these were either washed into position after death, or more likely attached themselves to the pebble prior to burial. Erratics with smoothed edges (as shown) indicate they've been exposed to extensive rolling within a river/stream or on a beach foreshore, prior to deposition - this evidence reveals these shallow waters were also close to land.

Left: An isolated beach pebble and who brachiopods. Right: A second beach pebble containing multiple cracks caused by exposure to pressure through time.

Protecting your finds

It's important to spend some time considering the best way to protect your finds onsite, in transit, on display and in storage. Prior to your visit, consider the equipment and accessories you're likely to need, as these will differ depending on the type of rock, terrain and prevailing weather conditions.

Left: Fossil wrapped in foam, ready for transport. Right: A small compartment box containing cotton wool is ideal for separating delicate specimens.

When you discover a fossil, examine the surrounding matrix (rock) and consider how best to remove the specimen without breaking it; patience and consideration are key. The aim of extraction is to remove the specimen with some of the matrix attached, as this will provide added protection during transit and future handling; sometimes breaks are unavoidable, but with care you should be able to extract most specimens intact. In the event of breakage, carefully gather all the pieces together, as in most cases repairs can be made at a later time...continued.

A great family day out...

Left: Participants on various Discovering Fossils and Junior Geo fossil hunting events. Right: Families handle some real fossils at the event base.

Join us on an organised fossil hunt! Discovering Fossils and JuniorGeo have joined forces to provide a series of exciting prehistoric experiences for families and individuals of all ages and levels of knowledge. Our events include an introduction to the geology and fossils, followed by a group fossil hunt where everyone has an opportunity to find and collect a variety of fossils. To find out more CLICK HERE.

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