Dorket Head Field Trip - Evening of 25/6/03

Ibstock Brick Company Quarry
Dorket Head
Mapperley
Nottinghamshire
Leader: Andy Howard. BGS

The purpose of this excursion was to examine those formations of the Mercia Mudstones exposed by the deep quarrying for clay at the Dorket Head Quarry on the Mapperley Plains plateau.

At the breezy end of what had mercifully been a dry and sunny day, 25 members assembled under the leadership of Andy Howard as guests of the Ibstock Brick Company.

Under the watchful eye of site security, Plant Manager Mike Chapman explained how this was the last of a number of quarries that had once ranged across the surrounding area. However, the difference here, from those that had existed in the Arnold, Carlton, Nottingham, Wilford and Mapperley areas, was the quarrying from above and not laterally, into the escarpment, in the manner that had made these reserves so attractive elsewhere.

Capable of producing millions of bricks a year, the actual plant was not part of the itinerary and, being situated several 100 yards away from the quarry beyond a crossroads leading to Calverton and back into Arnold, was concealed in a former quarry almost of its own making.

Considered a major site within a consortium of companies based in the Irish Republic, the site claimed to be the largest producer of facing bricks in the UK. Other statistics included the extraction of about 100,000 tons of clay per year and the backfilling of 150,000 tons of largely domestic waste and some incinerator ash in the same period.

The resulting land surface was then considerably higher than the original, but the prediction was that this would shrink back over time.

The quarry had also recently moved along the top of the plateau in an easterly direction and the reserves at this particular locality were expected to last another 18 years. Followed in turn by landfill whose methane production fired the kilns, the plant itself was expected to last a full 25 years, resulting in a shortfall in reserves for which the company would have to look elsewhere.

Explaining that as it was a working quarry everyone needed hard hats and stout footwear or Wellingtons, we were also informed that only weeks before vandals had attacked the site damaging windows, starting some vehicles and setting others on fire. Nevertheless, we felt our vehicles were quite safe and a Security Guard could be later seen examining the area (and us) with binoculars from a vantage point.

Descending to the quarry floor Mike and Andy explained we were actually just above the Radcliffe Formation, with the blocky mudstones of the Gunthorpe Formation and its various skerry bands surrounding us.

As the steeply sloping eastern face of the quarry suggested, this quarry also differed from others as the clays, and skerries, were extracted together by the, top to bottom, ‘planing’ action of the large machines the vandals had damaged. It was this method that provided the plant with the constant and consistent supply of reddish coloured material the plant needed for the making of an attractive good quality facing brick.

After hearing the formation had been originally mapped and named by (then) British Coal Geologist and a founder member and former President of the society Richard (Dick) Elliott (of which the Radcliffe Formation retained his original title) and how the site would then be prepared for landfill, the group were reminded of the lecture on Wagga Wagga before proceeding to split up and examine a number of locations.

Several examples of salt pseudomorphs were discovered (first location below) and, on some cross sections of silt or sandstones, fine and extremely delicate inter-bedded current markings, suggested to the group its deposition in an arid, sabka like environment with occasional, yet substantial, flash floods (second location below).

Observing the dip slope was about 1 degree to the east, the group also readily picked out and some photographed several infilled water channels containing finely layered coloured clays; and thinly bedded dolomitic fine sandstones and mudstones.

Finally making its way to the highest point of the eastern face where only the topmost Plains Skerry formation had been removed, the group could then understand how this resistant, if not unstable looking formation of mudstones had given rise to the plateau that was in fact the Mapperley Plains.

John Wolff