Introduction

Blue Anchor is perhaps the most unusual, alien environment we've ever encountered. The geology of the area includes two completely different rock types. At the far eastern end (beyond the view visible above) the rock is of early Jurassic origin, whereas the western end of the beach (as pictured) is the older Triassic, comprising the fossil bearing Rhaetian and the non-fossiliferous red Keuper Marl.

The geology of Blue Anchor

An illustration of the geological formations present at Blue Anchor - Note the Jurassic representation is
provided to demonstrate the approximate position of where the Lower Lias begins.

The point at which the two formations meet is known as the Blue Anchor Fault. The fault is a normal fault - generated by extensional forces within the Earth's crust, causing the overhanging side of the fault (known as the hanging wall) to drop down. The result is relatively young rocks in the hanging wall resting against older rocks in the opposing footwall side of the fault. In this case, the Penarth Group in the hanging wall has slide down the fault plane into contact with the older Mercia Mudstone. This activity took place during the Late Jurassic, some 50 million years after the rocks were deposited, and was probably a response to the same extensional regime which caused the opening of the Atlantic Ocean between the UK and America. This opening took place at the end of the Triassic, causing the sea to flood in from the south. The corresponding change from Triassic desert salt-pan conditions to Jurassic shallow tropical marine conditions is recorded in the rock succession at Blue Anchor.

Blue Anchor fault - Late-Triassic / Early Jurassic (Left) meets Red Triassic Keuper Marl (right).

Where to look for fossils?

You'll need to travel beyond the red Keuper Marl in order to reach the fossil bearing Triassic bone beds and Jurassic limestone beyond. Along the way you'll pass the most remarkable geology along the beach and at the peninsular. At this point the Triassic rock is interlaced with bands of salmon-pink Gypsum crystals (a mineral form of Calcium Sulphate). These crystals appearance within the rock is striking, and make this area feel like a Martian landscape.

Left: Examining the scale of a large cliff collapse. Right: Gypsum crystals within a foreshore boulder.

Gypsum crystals from the backshore.

The abundance of these crystals means collecting fragments from the beach (backshore) is easy; however, so unique is this area, that visitors are discouraged from hammering into the boulders on the foreshore. In a single trip it would be easy to gather hundreds of crystals from the beach alone. For more information about the features and processes controlling coastal fossil collecting locations click here.

As with all coastal locations, a fossil hunting trip is best timed to coincide with a falling or low-tide. For a relatively low one-off cost we recommend the use of Neptune Tides software, which provides future tidal information around the UK. To download a free trial click here. Alternatively a free short range forecast covering the next 7 days is available on the BBC website click here.

What fossils might you find?

Fossils are most abundant within the Westbury Formation, located towards the top of the cliffs at the peninsular pictured above. The specimen below was collected from the backshore and clearly shows a near complete Plesiosaur humerous (see following diagram).

Plesiosaur humerous from the Westbury Formation, found on the backshore.

Plesiosaur skeleton diagram, indicating the position of the humerous.

As you move further east along the coast, fragments of the Lower Lias rocks can be found on the foreshore and backshore, these yield the best finds, in particular the ammonite Psiloceras planorbis, which retain their mother-of-pearl-like shell.

Left: Carefully exposing fragile ammonites within the Jurassic shale. Right: Complete but fragile ammonite Psiloceras planorbis.

Left: Small ammonite (Psiloceras planorbis). Right: Large ammonite within the Jurassic limestone.

Left: Hundreds of cavities caused by small bivalve shells. Right: Large bivalve shells within the Jurassic limestone.

Tools & equipment

Left: Splitting shales using a heavy duty hammer and chisel. Right: A small brush is useful for removing any loose rock fragments or dust.

It's a good idea to spend some time considering the tools and equipment you're likely to require while fossil hunting at Blue Anchor. Preparation in advance will help ensure your visit is productive and safe. Below are some of the items you should consider carrying with you. You can purchase a selection of geological tools and equipment online from UKGE.

Hammer: A strong hammer will be required to split prospective rocks. The hammer should be as heavy as can be easily managed without causing strain to the user. For individuals with less physical strength and children (in particular) we recommend a head weight no more than 500g.

Chisel: A chisel is required in conjunction with a hammer for removing fossils from the rock. In most instances a large chisel should be used for completing the bulk of the work, while a smaller, more precise chisel should be used for finer work. A chisel founded from cold steel is recommended as this metal is especially engineered for hard materials.

Safety glasses: While hammering rocks there's a risk of injury from rock splinters unless the necessary eye protection is worn. Safety glasses ensure any splinters are deflected away from the eyes. Eye protection should also be worn by spectators as splinters can travel several metres from their origin.

Strong bag: When considering the type of bag to use it's worth setting aside one that will only be used for fossil hunting, rocks are usually dusty or muddy and will make a mess of anything they come in contact with. The bag will also need to carry a range of accessories which need to be easily accessible. Among the features recommended include: brightly coloured, a strong holder construction, back support, strong straps, plenty of easily accessible pockets and a rain cover.

Walking boots: A good pair of walking boots will protect you from ankle sprains, provide more grip on slippery surfaces and keep you dry in wet conditions. During your fossil hunt you're likely to encounter a variety of terrains so footwear needs to be designed for a range of conditions.

For more information and examples of tools and equipments recommended for fossil hunting click here or shop online at UKGE.

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.

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