Old Red Sandstone

Old Red Sandstone, often called ORS, is a special group of rocks found near the North Atlantic Ocean. These rocks are from a very old time called the Devonian period. You can find them in eastern Great Britain, Ireland, Norway, and along the east coast of North America. They also stretch up into Greenland and Svalbard.

These rocks were once part of a huge, ancient land called Euramerica. In Britain, scientists call this group of rocks a "supergroup" because it is very important for studying old fossils. The word "Old" helps to tell it apart from another group of rocks called the New Red Sandstone, which is younger and found in many parts of Britain.

Sedimentology

The Old Red Sandstone is a group of sedimentary rocks formed in different places during the late Silurian, through the Devonian and into the early Carboniferous periods. These rocks are mostly made from pieces of land and conglomerates. They also include materials from dunes, lakes, rivers, and coastal areas.

The red color of these rocks comes from iron oxide. They also include conglomerates, mudstones, siltstones, and thin limestones. These rocks are linked to the erosion of the Caledonian Mountains, formed when the ancient continents of Avalonia, Baltica, and Laurentia came together.

Many fossils, such as early fishes, arthropods, and plants, are found in these rocks. Some layers have fossils, while most of the rock does not. Similar-aged rocks in South West England come from the sea and are not part of the Old Red Sandstone.

Stratigraphy

The Old Red Sandstone is made mostly of rocks from land. Because of this, it does not usually contain fossils from the sea. This makes it hard to match different places where these rocks are found. Scientists gave special names to the different layers of rocks in each area. These names are still used sometimes, but now more people use international names.

The Old Red Sandstone is found in many different areas called basins. One big basin is in North East Scotland and nearby seas. It covers places like the Moray Firth, Caithness, Orkney, and Shetland. Another area with these rocks is around Oban and the Isle of Kerrera on the west coast of Scotland.

There are also many places in the Midland Valley of Scotland where these rocks are found, along with some volcanic rocks. In the Scottish borders, there are outcrops from East Lothian to Berwickshire. The Anglo-Welsh Basin stretches across South Wales, from Pembrokeshire through places like Carmarthenshire, Powys, and Monmouthshire, and into parts of England like Herefordshire, Worcestershire, and Gloucestershire.

History of study

In 1787, a scientist named James Hutton found something interesting near Jedburgh. He saw layers of old rock on top of even older rock at Inchbonny. Later, he and a friend, John Playfair, went to the coast near Berwickshire and found more examples near Cockburnspath. They even took a boat trip with another scientist, Sir James Hall, and saw a clear example at Siccar Point.

During the early 1800s, scientists studied these rocks. One of them, Adam Sedgwick, learned that these rocks belonged to a time we now call the Devonian. The name "Old Red Sandstone" was first used in 1821 by a Scottish scientist named Robert Jameson to describe these red rocks. People once thought these rocks were similar to rocks in Germany, but we now know they formed around the same time in different places.

Use as a building stone

The Old Red Sandstone has been used a lot for building in many places. You can see it in buildings near Stirling, Stonehaven, Perth, and Tayside. People in Caithness in Scotland also used this stone a lot. It was also used in places like Herefordshire, Monmouthshire, and old Brecknockshire in Wales.

Notable buildings

Canada

• New York Life Insurance Building, Montreal

England

• Goodrich Castle, Herefordshire
• Ross-on-Wye market hall, Herefordshire
• Shrewsbury Castle, Shropshire
• Hereford Cathedral, Herefordshire
• St. Mary Magdalene church, Taunton, Somerset

Scotland

• Arbroath Abbey, Angus
• Balvaird Castle, Perthshire
• Muchalls Castle, Aberdeenshire
• St Magnus Cathedral, Orkney
• Stonehaven Tolbooth, Aberdeenshire

Wales

• Raglan Castle, Monmouthshire
• Tintern Abbey, Monmouthshire
• Brecon Cathedral, Powys