Limestone Geology

A Story of the Carboniferous Age

The Peak District, Derbyshire, is at the southern end of the Pennine backbone of hills which runs up through northern England. The Peak District is made up of a limestone upland plateau dissected by river valleys known as the White Peak and is surrounded to the west, north and east by high moorland outcrops of sandstone and shale known as the Dark Peak.

The core of the Peak District is mostly formed from pale grey, thickly-bedded limestones from the Carboniferous age deposited between 350 and 325 million years ago. The limestones form a sequence of strata up to two kilometres thick, although only the uppermost 600m are exposed at the surface.

The White Peak is also made up of limestone, with distinctive pale grey/white outcrops. Deep, narrow, tree-lined valleys and dales form a drainage network on the limestone plateau. There are also outcrops of volcanic rocks and deposits of dolomite and mineralised rocks.

The limestones were overlain by a succession of upper carboniferous sandstones and shales deposited by a giant river delta system between 325 and 315 million years ago. Today, the sandstone and shale sequence of the Millstone Grit has been eroded back to form a series of escarpments and moorlands which surround the limestone outcrop.

Limestone Geology at the Brassington Moor Quarry

The Brassington Moor Quarry exploits strata that form part of the Bee Low Limestone Group from the Carboniferous age which are around 330 million years old. The Bee Low Limestone Group forms one of Europe's purest deposits of natural calcium carbonate.

The rocks were originally deposited in a warm shallow sea, surrounded by much deeper water - very similar to the present-day Caribbean. At this time, the United Kingdom would have been located somewhere near the Equator in tropical latitudes. To the north of the quarry location, as far as Buxton and Castleton and eastwards into Lincolnshire, there would have been shallow lagoons, only a few metres deep. The area was far from land and therefore no river-borne sediments were present to disturb the slow accumulation of shell and coral debris. Over time, this was transformed into pure calcium carbonate.