Red Crag Formation facts for kids

Quick facts for kids Red Crag Formation Stratigraphic range: Late Pliocene - Early Pleistocene ~3.3–2.5Ma PreЄ Є O S D C P T J K Pg N ↓
Red Crag at Bawdsey Cliff in Suffolk
Type	Geological formation
Unit of	Crag Group
Sub-units	Sizewell Member
Underlies	Norwich Crag Formation
Overlies	Coralline Crag Formation
Thickness	up to 20 metres (70 ft), locally up to 45 m, offshore up to 70 m
Lithology
Primary	Sand
Location
Region	Europe
Country	England

The Red Crag Formation is a special layer of rock and sand found in England. You can see it in places like south-eastern Suffolk and north-eastern Essex. It gets its name because it's often reddish from iron and "crag" is an old word from that area for shells.

This formation is part of a bigger group called the Crag Group. These layers were formed a very long time ago when Britain was connected to Europe. The area where the Red Crag formed was a bay with strong ocean tides. The size of this bay changed over time due to rising and falling sea levels. These changes were caused by natural cycles in Earth's orbit, called Milankovitch cycles.

What is the Red Crag Formation?

The Red Crag Formation is mostly made of coarse, sandy material mixed with lots of shells. These materials were laid down by huge underwater sand waves. These waves moved slowly towards the southwest, parallel to the ancient coastline.

Where Can You See It?

The best place to see the Red Crag is at Bawdsey Cliff. This area is so important that it's called a Site of Special Scientific Interest (SSSI). Here, you can see about 2 kilometres (1.2 mi) of the Crag exposed along the coast.

What Fossils Can You Find?

Many fossils are found in the Red Crag. The most common ones are bivalves (like clams) and gastropods (like snails). These shells often look worn because they were tumbled around by the strong ocean currents.

Excitingly, parts of megalodon teeth have been found in the Red Crag along the coast near Walton-on-the-Naze! Megalodon was a giant, extinct shark.

Red Crag cliffs at Bawdsey, Suffolk.

Different Parts of the Red Crag

Deep underground in eastern Suffolk, the Red Crag Formation has a specific part called the Sizewell Member. This part is made of coarse, shelly sand with thin layers of clay and silt. Scientists believe it formed in deeper parts of the ancient sea, where very large sand waves moved across the seabed.

There's another layer called the Thorpeness Member. It was once thought to be part of the Red Crag, but now many scientists think it belongs to the Norwich Crag Formation, which is a different, younger rock layer.

How Old is the Red Crag?

Scientists believe the Red Crag started forming in the late Pliocene epoch and might have continued into the early Pleistocene epoch. These are huge spans of time in Earth's history!

The British Geological Survey suggests the Red Crag formed between about 3.3 and 2.5 million years ago (mya). The Red Crag found at Walton-on-the-Naze is thought to be the oldest part. It might have formed very quickly, perhaps in just a few decades, between 2.9 and 2.6 mya.

This specific time period is so important that it has its own name in the UK: the Waltonian stage. It's often compared to the Reuverian Stage in the Netherlands. It can be tricky for scientists to figure out the exact start and end dates for the Red Crag. This is because there aren't many fossils or other clues that can pinpoint the age precisely. Also, it can be hard to tell the Red Crag apart from the Norwich Crag Formation, which lies on top of it.

Images for kids

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  Geological map of the Crag Deposits.

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  Fossils from the Red Crag.

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  Shark tooth fossil from the Red Crag at Felixstowe in Suffolk.