Dorket Head Field Trip - Evening of 25/6/03
Ibstock Brick Company Quarry
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