Clwyd Limestone Group facts for kids

The Clwyd Limestone Group is a special set of rock layers found in north Wales. These rocks were formed a very long time ago, during a period called the Carboniferous (specifically, the Lower Carboniferous, also known as the Mississippian period). Think of it like a giant stack of pancakes, but made of rock! This group is part of an even bigger collection of rocks called the Carboniferous Limestone Supergroup.

What is the Clwyd Limestone Group?

The Clwyd Limestone Group is a type of stratigraphic unit. This is a fancy way of saying it's a defined sequence of rock layers. Geologists use these units to understand the Earth's history. These rocks are mostly made of limestone. Limestone often forms from the shells and skeletons of tiny sea creatures that lived in ancient oceans.

How Old Are These Rocks?

The rocks in the Clwyd Limestone Group formed between 359 and 323 million years ago. This time is known as the Lower Carboniferous period. During this period, much of Wales was covered by warm, shallow seas. This was a perfect environment for the creatures whose remains would eventually form limestone.

Where Can You Find the Clwyd Limestone Group?

You can find these rocks in several places across north Wales. Their biggest area is along the Clwydian Range. This is a chain of hills in northeast Wales. The rocks are visible just east of the highest parts of these hills. They stretch from a place called Llandegla all the way to Prestatyn on the coast.

Other Places to See These Rocks

The Clwyd Limestone Group also appears in other areas. You can see it curving along the western side of the Vale of Clwyd. It also pops up in famous spots like the Great Orme and Little Orme near Llandudno. These are well-known headlands that stick out into the sea.

You can also find these rocks on Anglesey, a large island off the coast of Wales. There are three main areas on Anglesey where they are found. A smaller section is located south of the Menai Strait, between Bangor and Y Felinheli. Further south, the rocks form an impressive cliff face at Creigiau Eglwyseg, north of Llangollen. They even extend near the border with England, at Llanymynech Hill.

What is the Clwyd Limestone Group Made Of?

While the main rock type is limestone, the Clwyd Limestone Group also contains other rocks. These include mudstone and sandstone. Geologists divide the Clwyd Limestone Group into smaller parts called "formations." Each formation is a distinct set of rock layers.

Different Rock Formations

In different areas, the Clwyd Limestone Group is made up of different formations. For example, on Anglesey, it includes the Loggerheads Limestone Formation and the Cefn Mawr Limestone Formation. At the Great Orme, you'll also find the Llanarmon Limestone Formation and the Red Wharf Limestone Formation. Some of these formations, like parts of the Llanarmon and Red Wharf Limestones, contain dolomitic rock, which is a type of limestone rich in magnesium.

In the Clwydian Range, the lowest part is the Foel Formation. Above it are the Llanarmon Limestone, Leete Limestone, Loggerheads Limestone, and Cefn Mawr Limestone formations. The very top layers are the limestones and sandstones of the Minera Formation. These different layers tell a story about how the environment changed over millions of years.