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Nottingham castle sandstoneMost of the city of Nottingham lies on a thick layer of
pebbly sandstone, the Nottingham castle sandstone. This rock layer extends well beyond Nottingham where it is
called the Sherwood sandstone. It was laid down in Triassic times,
about 250 million years ago, by a large river delta intermittently flooding a
sandy desert plain. The climate was hot and mostly dry.
Sand dunes formed and shifted and occasional heavy rains brought down
larger stones from nearby mountains.
This explains the cross-bedding of the sandstone layers and
the mixture of relatively fine-grained sandstone with pebbles. Animals left
occasional tracks in the sand but no fossils formed. Some geological maps call the layer the “pebble beds” or the Bunter pebble beds. It is slightly younger than the Buddleigh Salterton pebble beds from which the stones of Chesil beach arise. The rock is very soft which makes it good for carving out caves, but not much use for building. Instead, it is used in crushed form as sand or aggregates. It is also porous and millions of years of rainwater slowly soaking into it has formed a huge fresh water reservoir - a valuable resource today. The most famous outcrop occurs beneath Nottingham castle itself
At Brewhouse Yard
and behind the Olde Trip to Jerusalem Inn
EastwardsIt also outcrops further east, beyond the Broadmarsh Centre, along Cliff Road.
And behind the petrol station at the junction of Canal Street and London Road
The layer continues east until it dips under the first layer of mudstone, the Sneinton Formation at, you guessed it, Sneinton. I am not aware of any more exposures in this direction. 24 Dec 2005 update. Whoops! I've just discovered two exposures further east. Both are on Sneinton Hermitage near the junction with Manvers street. The cliff has been almost completely encased in brick but the exposures are clearly Nottingham Castle sandstone.
WestwardsTo the west, along Castle Boulevard, a series of further exposures lie behind a row of modern flats.
Caves and dovecotes have been carved. Here are some close up views
The final exposures going west on Castle Boulevard are behind the MFI car park.
Westward of this the ridge of sandstone has been eroded by the river Leen, albeit a sad little culvert these days. Here it is passing to the east of the Queens Medical Centre.
Continuing west there is an exposure on the northern bank of the lake in the Nottingham university grounds.
All these exposures are probably more or less natural. As the river Trent cut through the soft sandstone at the end of the last ice age it formed a wide flood plain. Castle Rock and the low cliffs along Castle Boulevard formed the northern border of that original flood pain. Until man covered it in tarmac, The Meadows were just that - marshy meadows criss-crossed by the constantly moving channels of the rivers Trent and Leen. Over most of the rest of Nottingham, the Castle sandstone is invisible under your feet, but the odd exposure occurs. There is one on Hucknall road next to Nottingham Prison, just south of the junction with Valley Road.
Some close ups.
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