There are two excellent books available from the British Geological Survey Team in Edinburgh that highlight the geology of Dumfries and Galloway with information on excurtions where you will see really good exposures. Telephone 0131 667 1000 and ask for the Book Shop.
Earth Heritage is GREAT and free so contact email@example.com. If you become a member of GeoD you can receive the UK Geoconservation Newsletter free from firstname.lastname@example.org Other excellent magazines are; Down to Earth email@example.com ;Geoscientist www.geolsoc.org.uk If you have young budding geology enthusiasts in your family then Rockwatch www.rockwatch is for them!
Time-Travel the Shinnel Glen with Diana Turner
4,600 million years ago our world was formed.
Over the next 3,000 million years volcanic eruptions, land movement and mountain building continually changed the face of the globe. Massive islands with mighty oceans between, broke away from a single landmass at the South Pole and moved north.
From this time, Scotland and Northern Ireland were attached to North America and Canada and on the opposite shores of the Iapetus Ocean, Southern Ireland and England were attached to Europe and Asia. 500 million years ago the Iapetus Ocean began to close.
400 million years ago England and Southern Ireland collided with Scotland and Northern Ireland throwing up mountains as high as the Alps.
It wasn’t until about 250 million years ago that Britain began to separate from the American continent and 23million years ago when it finally came to where we are now.
Evidence in rocks today records climatic changes and geological processes as the continents moved from the South Pole to The North Pole. Ancient mountains, volcanoes, deep oceans, deserts, cold and temperate seas, tropical swamps, rivers, warm seas and oceans full of plant and animal life, have all contributed to what we know today as Dumfries and Galloway.
The Shinnel Valley is a wonderful part of this landscape and has been influenced by the Rock Formations and Fault Lines of the underlying rocks plus 16 Ice Ages during the past 1.8 million years.
Shinnel Water rises in the north west of Tynron in the Fingland Burn, below Colt Hill where it meanders over sandstones, containing grains of volcanic rock, and siltstone of the 2 kilometers thick Portpatrick Formation.
Patches of Moffat Shale Formation exposed around Shinnelhead are full of Graptolite and Radiolaria fossils. Volcanic dykes [tunnels] of microdioritic rock cut through some other patches but exposures are difficult to find. At Sharp Craig the Shinnel passes through the Fardingmulloch Fault into the Shinnel Formation sandstone and siltstone, with boulder conglomerate exposed around Appin and Everside.
Further towards Cormilligan, there are signsof the last Ice Age where melting Glaciers have dumped their loads of rock debris producing large mounds [now grass-covered] called Drumlins.
Mount Hooly Bridge sees the passage of the Shinnel Water under its arch and through the Glenfumart Fault into the Glenlee Formation sandstones abundant with tiny quartz grains and another mineral called pyroxene. These are inter-bedded with very thin layers of Graptolite-bearing siltstones around the Clodderoch Burn.
Around Tynron there is much to see. The Crags of Killiewarren, Auchengibbert, Craigturra and Tynron Doon all belong to the Glenlea Formation. However in Tynron Village you walk along the Orlock Bridge Fault when crossing over the Tynron Bridge, onto the “crazy” rocks of the Gala 2 Formation within the Moniaive Shear Zone. This zone is an area of Gala 2 rock, about 10k wide, that has been stretched and deformed by the strain posed upon it during the mountain building of previous times. The minerals and sand grains in these rocks have been elongated and the rock itself has been folded into crazy shapes eroded into the vertical bedding seen in the Shinnel River.
Most of the solid rocks within the triangle of roads between Tynron village, Clonehead and Shinnel Mill are covered in the “left-overs” of the last Ice Age about 15,000 years ago; numerous drumlins [hillocks of glacial rock debris] and kettle-holes of Court Hill below[dry hollows where a glacier has melted. Airds Loch, a kettlehole which still has water in it; Clonrae Varve [a lake formed by melted ice] andAird Linn Gorge where the Shinnel Water passes on its way to another varve at Shinnel Bridge; Erratics are everywhere [large rounded boulders carried far from their original formation and deposited on land when the glacier ice melts]. The biggest and best are seen at Clonrae and these are of conglomerate possibly carried down from Appin.
However Ford Hill Crags pop their head above ground boasting volcanic sheets and dykes of pink quartz crystals.
Before the debris between Lanhall and Low Lan built up during the last Ice Age, the Shinnel Water flowed passed Clonehead into the Cairn Water, instead of finishing its travels at its junction with the Scar Water at Penpont, but that’s a different story!