SPURS OF ROC KA VISITOR’S GUIDE TO THE GEOLOGYOF THE EASTERN SPERRINS

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The Sperrin Area of Outstanding Natural Beauty (AONB) is one of Ireland’s largest upland areas. The name is thought to derive from ‘na speiríni’ meaning Spurs of Rock. It is these rocks that give the mountains their special character and form the foundation of the landscape we see today.

Situated in the eastern part of the Sperrin Area of Outstanding

Natural Beauty (AONB), the Sperrins Gateway region has a

remarkable diversity of rock types within a relatively small area.

This field guide has been developed to allow you to explore this

special landscape.

Mullaghmore

Spurs of RockThe rocks and landscapes of the Sperrins Gateway area tell us a story that begins 650 million years ago and continues to the present. The landscape that we see today is only a small moment of geological time and the area has witnessed many changes in its long and interesting history.

An ancient ocean

The oldest rocks in the Sperrins Gateway area are called schist and date back to between 650 and 580 million years ago. They would have originally been laid down as sand, silt and mud at the bottom of an ancient ocean called the Iapetus Ocean.

Mountain building

The Iapetus Ocean would have been 1000s of kilometres wide separating the two halves of Ireland on either side. Plate tectonic movement caused these two halves to slowly come together and eventually collide. This collision caused the Earth’s crust to crumple forming a huge mountain chain that at its peak would have been higher than the Himalayas. This force also generated huge amounts of heat and pressure, changing the original rocks into schist.

At the edge of the Iapetus Ocean was a chain of submarine volcanoes that would have erupted on the sea floor. The resulting lava formed in the shape of pillows as it cooled rapidly on contact with the cold seawater. Remnants of these volcanoes are preserved in the Sperrins Gateway region.

Tropical seas

During the Carboniferous period, approximately 350 million years ago, the Sperrins Gateway region lay on or very close to the equator and was covered by a shallow tropical sea. Many animals lived in the sea such as corals, brachiopods (sea shells) and crinoids (sea lilies), the remains of which, together with the lime-rich mud of the sea floor, are now found as limestone.

Hot deserts

Over the next 100 million years, the Sperrins Gateway region moved northwards and by 250 million years ago (Triassic period) it was at the same latitude as the Sahara Desert today. The resulting red sandstones are a clue to this environment, and although no fossils have been found in this area, it is likely that large reptiles, the precursors to the dinosaurs would have roamed the landscape.

EARTH CRUST

WATER

PILLOW LAVA

MAGMA

VENT

CO2 CO2

CO2

CO2 CO2

CO2CO2

LIMESTONE

CO2

CO2

Crystal clear seas

Around 80 million years ago, during the Cretaceous period, global sea levels rose and almost all continents were covered with water. The warm climate and shallow sea led to the production of white limestone (or chalk), formed as a result of countless skeletons of microscopic sea creatures accumulating on the sea floor.

Landscapes of fire

As plate tectonic activity continued, around 60 million years ago, the North Atlantic Ocean started to open, as the continents that we now know as North America and Eurasia began to rip apart. This led to major volcanic activity and molten rock spewing out across much of the landscape forming the basalt plateau that covers much of north-east Northern Ireland. These are the youngest rocks in the Sperrins Gateway region.

The big freeze

During the last 2 million years the Earth has become much cooler and on several occasions the ice at the poles has grown to cover huge areas of the planet. Each of these occasions is known as a glaciation and the most recent one only ended 15,000 years ago. In the Sperrins Gateway region, the ice was over one kilometer thick, and the movement and melting of the ice sheets has sculpted the landscape into the shapes that we see today.

The human era

Around 9,000 years ago, the first humans arrived in the Sperrins Gateway region and since then have continued to alter the landscape. Whether this is through agriculture, quarrying, road building or any other means of development, humans are arguably the single greatest force for change that the planet has ever seen.

Geological history

The rocks of the Sperrins Gateway area represent seven of the 12 geological time periods and contain some of the oldest rocks in Northern Ireland. The geological history is wonderfully diverse and has resulted in the unique patchwork of landscape that you see today.

Where do rocks come from?

All rocks can be classified as belonging to one of three different rock groups.

Igneous rocks form as molten rock (or magma) cools and solidifies.

Sedimentary rocks form as sediments such as sand, silt and mud harden to form solid rock, or from chemical precipitates (such as limestone).

Metamorphic rocks form when either sedimentary or igneous rocks change form as a result of intense heat and / or pressure. They do not melt but simply change form.

Basalt

An igneous rock formed by cooling lava, erupted on to the surface of the earth. It cooled rapidly forming a fine-grained crystalline rock which is dark grey or black in colour. The crystals are too small to be seen by the naked eye.

A type of igneous rock that forms within the Earth. It forms as magma, slowly cools and solidifies allowing for crystals to grow large enough to be seen with the naked eye. It has interlocking crystals that are often white, grey and pink in colour but this can vary.

A medium to dark grey sedimentary rock that contains abundant fossils of corals, brachiopods (sea shells) and crinoids (sea lilies). It formed as the accumulation of lime-rich mud and the remains of sea creatures on a sea floor.

A bright white sedimentary rock that contains fossils of belemnites (squid-like creatures) and sea urchins. It is primarily made up of the remains of microscopic algae known as coccoliths that would have accumulated on a sea floor.

A type of sedimentary rock that is made up of sand. It can be deposited in a number of environments but in this case it would have been in an arid environment.

A type of metamorphic rock that has a distinctive layering, known as foliation. This occurs as a result of grains being drawn out under intense pressure to form sheet-like flakes. It displays a characteristic sheen known as schistosity.

Limestone (Cretaceous) containing belemnite fossil

Limestone (Carboniferous)Granite Sandstone Schist

Co. Londonderry

Co. Antrim

Co. Tyrone

Co. Fermanagh

Co. Armagh

Co. Down

0 20km

Schist

Clay

Limestone and sandstone

Sandstone

Basalt, gabbro and granite

Granite

Sandstone and limestone

Basalt

Sandstone and slate

Newry

Belfast

Londonderry

Omagh

Enniskillen Armagh

LoughNeagh

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Moneymore

Draperstown

The Solid Geology of Northern Ireland

Reading the landscape

The best way to discover the geology and landscape of the Sperrins Gateway region is to get out and see them for yourself. We have suggested a number of places to see the best examples of some of the features described. At some of these sites there is more information provided.

Geology sites The incredible views over the Moyola Valley and Mullaghmore tell the story of ancient oceans, continental collisions and the destructive power of glaciers.

Geological feature:Evidence of ice

Grid Ref C728 011

Location:Mullaghmore, Moydamlaght-Birren Road

Glacial scratches (striations) on the side of MullaghmoreHanging Valley of Parkaveadan Burn and U-shaped Moyola valley are all remnants of the last glaciation.

Facilities:Public road with occasional spot (mountain tracks) where it is suitable to park temporarily.

1. Eagle’s Rock Craig na shoke 2. Striations

Geological feature: Landscapes of Fire

Grid Ref C747 002

Location: Eagle’s Rock Craig na shoke

Terrain:Remnant of a basalt escarpment highlighting the volcanic activity that took place here about 60 million years ago. Cliff face, steep and uneven.

Facilities:Car parking at entrance to Moydamlaght Forest. Waymarked trail to Eagle’s Rock.

3. Schist overlain by glacial sand and boulder clay

Geological feature: Mountain Building

Grid Ref H725 996

Location: McDaid’s Pit, Feeny Road

Terrain/features:Schist, sand and gravel deposits

Facilities:None. Temporary car parking at unofficial viewpoint information panel on site. Good place for long range view of Mullaghmore, Eagle’s Rock and Moyola valley.

These sites tell us the story of melting glaciers at the end of the last glaciation.

4. Creagh sand & gravel area 5. Teal Lough 6. Glacial erratic

Geological feature: Evidence of ice: moraines

Grid Ref H759 899

Location:Creagh sand and gravel

Terrain/features: Left behind as sand and gravel when the glaciers melted, moraines are found in many parts of the Sperrins. They are quarried at various locations in the region and still supply the building and road construction industry.

Facilities: Quarry activity can be seen and heard from Lough Fea. No access to operational quarries. Car parking and visitor facilities including a walking trail around the lough, angling (permit required) public toilets, play park, picnic tables and interpretive signage.

Geological feature:Evidence of ice

Grid Ref H741 887

Location: Lough Fea, Teal, Mill and Cow Loughs

Terrain/feature:Kettle Lakes were formed as blocks of ice broke off the melting glacier and then were surrounded by sand and gravel. As the ice melted a hole was left behind and filled to form a lake.

Facilities: Informal lay-by car park and geology information panel.

Geological feature: Glacial erratic

Grid Ref H726 957 and H743 884

Locations:Tullybrick Road and Crockbrack

Terrain/feature: Erratics: The name Tullybrick means ‘speckled field’ and is a description of the many large boulders strewn across the landscape. These are glacial erratics, boulders carried along by glaciers and then dropped as the ice melted. Crockbrack translates from Irish Cnoc Breac, as speckled hill, on which you can see a number of these large boulders.

Facilities:Outstanding views of landscape from public road/East Sperrins Scenic Driving route. Sixtowns heritage trail covers the Tullybrick townland and a waymarked walking trail, the Crockbrack Way starts in Moneyneena village.

7. Spelhaogh gap

Geological feature: Evidence of ice

Grid Ref H713 987

Location: Craigagh Hill

Terrain/features:The gap here was cut in a very short period by melt water that drained shrinking ice sheets towards the end of the last glaciation. Melt water damned behind ice blocking the valleys and overflowed at low points in flanking ridges eroding characteristic deep gorges.

Facilities:None, open mountain terrain very steep, uneven ground boggy in places. Challenging hillwalk not currently waymarked, Spelhoagh ridgeway includes the peaks of Oughtmore and Mullaghaneany.

The intricacies and interplay of the living landscape can be seen from the summit of Slieve Gallion.

Ladder Farms 8. Views from Slieve Gallion 9. Slieve Gallion Pillow Lavas 10. Quarry/Basalt overlaying limestoneand a basalt dyke

Geological feature: Agriculture

Locations:Various, including hills of Slievemoyle and Coolnasillagh above the Fivemilestraight Road between Moneyneena and Tobermore.

Terrain/features: Ladder farms or long marches are a common characteristic feature throughout the Sperrin region. The small fields stretch uphill in a row from the farmhouse and farm buildings giving the appearance of a ladder. This field system ensured each farmer had a share of the good land in the valley with the quality of land decreasing upslope, where there was access to turf for fuel and finally common grazing.

Facilities: Long range views from various locations throughout the region.

Geological feature: Human Era

Grid Ref H813 894

Location: Slieve Gallion summit

Terrain/feature:Views of the living landscape, rolling hills, raised bogs of Curran and Ballynahone.

Facilities: Public road to near summit, optional leg of scenic route. Communications mast near summit. Waymarked walking trail from Iniscarn Forest car park to summit.

Geological feature: Mountain building

Grid Ref H821 882

Locations:Slieve Gallion view point, Drummuck, Tullynagee Road

Terrain/feature:Granite, schist bedrock. Schist is punctuated by volcanic intrusions of dolerite and basalt pillow lava. Formed as hot molten rock which erupts on the sea floor, pillow lavas are so-called as the outer layer of lava cools on contact it the water to form a skin that then fills up with lava from behind to create a pillow shape.

Facilities:Car park, picnic site and view point. Geology information panel.

Geological feature: Crystal clear seas Grid Ref H865 874

Location:Carmean Quarry

Terrain/feature:Limestone quarry: characteristic white limestone overlying black basalt. Operational limestone quarry. In front of the quarry are the now obsolete limekilns that were in use until the 1970s.

Facilities:No access (operational quarry). Long range views (especially of the lime kilns from the Moneymore Road (East Sperrins Scenic Drive).

Situated amidst the drumlin belt at the foot of Slieve Gallion, the low agriculturally rich lands around Desertmartin were formed by the movement of glaciers.

The Cullion Road runs along a ridge of the historical landscapes of Slieve Gallion providing amazing views to the north and south. This is also the Ballinderry and Moyola watershed. The streams of Slieve Gallion either flow south to the Ballinderry River or north to the Moyola River, so as you travel along the road you’ll cross the watershed between the two.

Drumlins 12. Cullion Road

11. Drumbally Hill ASSI

13. Ballybriest

Geological feature: Evidence of ice and human era

Location:Around Slieve Gallion

Terrain/features: The small rounded hills are predominantly drumlins, formed as loose material beneath the glacier which was sculpted into shape as it crept across the landscape. The highest drumlins were used as protective sites to build raths and hill forts such as the one known at Drumbally Hill Fort. It is a bivallate rath with extensive views in all directions. The site survives quite well except for the outer ditch. Flint arrows have been found nearby.

Facilities: Private. Long range view from Moneymore Road.

Drumbally Hill has been designated as an Area of Special Scientific Interest (ASSI) because of its Earth Science interest.

Geological feature: Human Era, Tropical seas

Grid Ref H844 934

Location: Drumbally Hill, near Desertmartin

Terrain/features:Originally the rock formed as a lime mud on the floor of a shallow, tropical sea. The exposure contains some fossil shell fish. The exposure is what is left of a large quarry that once existed at the site. The limestone quarried here was of Carboniferous age (350 million years old) and is much older than that found at Moneymore (80 million years old). The quarry was said to produce excellent quality lime and provided limestone to farmers and landowners over a wide area.

Facilities: Private no access.

Geological feature: Evidence of ice and human era

Grid Ref H773 881

Location:Crockandun Hills, Cullion Road

Terrain/features: Glacial deposit, sand and gravel, kettle loughs and quarry industries.

Facilities: Unofficial view point at entrance to quarry.Geology information panel.

Geological Archaeology

Grid Ref H761 884

Location:Ballybriest court tomb

Terrain/features: Neolithic man cleared the land of thick dense forest so that they could farm the fertile glacial till of the upper valleys. They built tombs for their dead on prominent sites such as Ballybriest often constructed with glacial erratic found nearby. Archaeology, glacial deposits.

Facilities: Layby parking at site and interpretation signage.

People and the landscape

Ballybriest Court Tomb The Sperrins Quarry Moneymore

Archaeology Man has greatly altered the landscape. The Sperrins is an area rich in archaeological sites. The first peoples were hunter gatherers and left little evidence on the landscape; however, during the Neolithic period (4000-2000BC) people began to clear the dense forests to make way for farming. These people were also monument builders and left their mark on the landscape.

Large stone tombs, cairns on hilltops, stone circles, pillars and alignments are typically found across the Sperrins. Rocks were taken from the immediate area in monument building but the complexity of some sites indicates an understanding of the different properties and colours of rock.

The use of different rock types to create a desired effect can be seen at various sites and it is likely that some of the rock used were sought out and brought some distance to the site.

Agriculture The underlying geology of an area influences the soil, which ultimately determines which habitats and what agriculture can develop.

Most of the slopes of the Sperrins are draped in blanket bog, composed of the remains of the vegetation that accumulated after Neolithic farmers began clearing wood to make way for farming.

The nature of this landscape, encompassing moorland and bog means that livestock farming is important. Arable crop production was restricted to the fertile valleys and lowland. Potatoes and oats were the main crops.

Aggregates industry Rock is one of the most important natural resources known to man. It is very important to the UK economy. It is used in construction of buildings and roads.

The large deposits of sand and gravel and deposits of limestone are exploited by the quarry industry in the Sperrin region. These aggregate materials, building stones and minerals are extracted from the landscape and transported around the country to supply the construction industry.

Quarrying can have a huge impact on the landscape as the material is removed it changes the shape of the landscape.

Built heritage For centuries local stone has provided a source of high quality, versatile and durable building material. The most important civic, ecclesiastical and industrial buildings in many communities are made of stone, as are many houses, bridges, boundary walls and monuments. The rich and varied rock in the Sperrins is reflected in the diversity of stone-built heritage. As a result, stone-built structures play a hugely important role in defining the distinctive character and ‘sense of place’ that distinguishes different places.

Whilst much of the underlying rock is hidden beneath a layer of peat across the Sperrins, the geology evident in places such as Draperstown and Moneymore where the local rock types are represented in the buildings in each location.

Biodiversity and the landscape

Bog pool The Moyola River Mullaghmore Crockbrack

The soil is determined by the underlying geology, and soils are the foundation of the food chain, supporting the plants that shape the rich variety of habitats and wildlife that are intrinsic to the landscape character of the Sperrins Gateway.

The diverse habitats include: • blanket bog and moorland • ancient native woodland• conifer forests• boundary features such as hedges, banks and ditches• loughs and pools• grassland • arable and cultivated land.

Rivers such as the Moyola, fed from mountain streams, are home to salmon, trout, populations of otter, bats and the kingfisher.

Understanding the links between the geology, biodiversity and landscape uses will help to sustain and protect the landscape character.

Place names and the landscape Place names often describe the landscape or features seen within it. Looking at the meaning of place names we get a glimpse into what these places meant to people in the distant past and how people and landscape are connected.

Some examples of places names based on geology:

Brackagh speckled or broken landCarmean smooth hill or rockCahore townland of the circular fortCloughfin land covered in white stones (quartz) Carnanbane little white cairn in reference to white stone Crockbrack speckled hillDrum/Drom hill or ridgeDrumard high ridgeDrumcrow hard ridgeDrummeen little ridge or drumlinMullagh summitTullybrick speckled hill

Habitats & Wildlife

Picture credits:

L. Gibson, Raymond P. Brady, Gareth Wray, Calvin Harlow, GSNI

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© Crown copyright and database right 2009. Permit No. 90194

Desertmartin

Tullybrick

Moneyneena

Cullion Road

Slieve Gallion

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1 Eagle’s Rock2 Birren Road3 McDaid’s Pit4 Creagh5 Teal Lough6 Crockbrack7 Craigagh Hill8 Slieve Gallion9 Slieve Gallion View Point

10 Carmean Quarry11 Drumbally Hill12 Cullion Road 13 Ballybriest

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