A Limestone Landscape

About 330 million years ago, warm seas deposited marine sediments in layers, or strata. These became compressed to form the limestone rock that is the basis of the distinctive AONB landscape.

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Limestone Pavement at Gait Barrows NNR

The limestone was eroded by ice during the Ice Age, with lumps being plucked off the bedrock and moved sometimes great distances to form the limestone erractics. Other boulders and debris were transported to the area by ice flowing down from the Lake District fells.  The Limestone was then exposed to weathering and being dissolved by meltwater and rainwater over millennia.

In post-glacial times, vast stretches of outwash plains were the source of wind-blown soils, which were deposited in hollows in the limestone and other shallower soils formed from the weathering of the rock. 

Peat mosses formed over low-lying ground where shallow lakes and mires developed. This variation in soils caused a complex mosaic of habitats to develop, which now support a huge diversity of plants and animals. People have shaped the landscape, for example through farming, industry and developing settlements and transport links and continue to do so. This complex interaction of natural and man made processes has produced the nationally protected landscape we live in, visit, work in and enjoy today.  

The AONB Partnership aims to take action and influence decisions so that our outstanding landscape can be conserved and enhanced for future generations.

The AONB landscape is characterised by a range of limestone hills and crags with intervening low-lying mosses and the expanse of Morecambe Bay dominating the western edges. There are many semi-natural ancient woodlands, wildflower-rich limestone grasslands, extensive limestone pavements, deep peat mosses, coastal salt marshes and estuarine mudflats. Features such as limekilns, drystone walls, hedgerows and pathways are distinctive features that reflect man's use of the land over time.
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Diverse habitats

The huge variety of habitats and the plant communities they support, that developed on the land following the last Ice Age, is a result of the variation in soil types found in the AONB.

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Gryke detail on a limestone pavement

This variety of soils is an important feature of the area, with both acid and alkaline soils being present in close association.

Acidic loess soils accumulated in some of the dips between limestone outcrops. These soils were wind-blown or aeolian deposits, forming in hollows and depressions in the limestone. The grains of soil are small in size, composed of quartz and clay minerals and were probably derived from the extensive sandur (glacial outwash plains) that developed at the end of the ice age in Morecambe Bay, before sea levels rose to their present levels.

In other places alkaline Rendzina soils formed from the weathering of the limestone, forming thin beds over the limestone bedrock.

Peat mosses also formed in the area following glacial retreat, where waterlogged raised mires developed over significant areas of low-lying ground. ( During the retreat of the glaciers there would have been significantly more water in and on the landscape than currently, with large meandering rivers, outwash plains, even morraine and perhaps ice dammed lakes and flooded valleys.)

 

 

 

Scenery and Landscape

The scenery of the Arnside and Silverdale Area of Outstanding Natural Beauty is the result of how people have shaped the natural features of the land.

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View south from Arnside Knott

The area has developed a complex mosaic of landscape types that reflect the area’s rich cultural and historical heritage.

Looking more closely at the Carboniferous Limestone Geology shows a more varied character than is at first apparent. The Limestone is subdivided into three characteristic types, the Urswick Limestone, the Park Limestone and the Dalton Beds.

The three blocks exhibit different lithologies and appearances: the Dalton Beds are interbedded limestones, sandstones and mudrocks, the Park Limestone is thinly bedded and fragmentary when weathered and the Urswick is relatively massive, being thickly bedded.

Additionally there are recurrent beds of mudstones and shales. The most extensive is the Woodbine shale that outcrops in a number of locations around the AONB and is close to the boundary between the Upper and Lower Urswick limestones.

These differing lithologies and the structural movements within them have ensured the development of a wide variety of landforms and contributed to the formation of many different karst landscape features. The bedrock is covered by a wide variety of soils, ranging from acid to alkaline, allowing the landscape to evolve as a complex mosaic influenced by a great diversity of habitat types and land uses.

The scenic qualities of the landscape are created by the interactions of geology, landform, vegetation, climate and cultural/social features such as land use, settlement and enclosure.

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Panoramic view of the Arnside Viaduct at high tide

 
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