New Red Sandstone
From Wikipedia, the free encyclopedia
The New Red Sandstone is a chiefly British geological term for the beds of red sandstone laid throughout the Permian (280 million years ago) to the beginning of the Triassic (240 million years ago) that underlie the Jurassic Lias; the term distinguishes it from the Devonian Old Red Sandstone.
Its upper layers consist of mudstones, but most of the formation consists of reddish sandstones, interbedded with evaporite minerals like salt and gypsum; these indicate deposition in a hot, arid environment.
[edit] Central UK Locations
The New Red Sandstone covers much of central England, where it generally forms a low-lying plain. Thick layers (up to 1100m thick) are present in the faulted Cheshire and north Shropshire basin, which features escarpments forming small prominent hills. The sandstone also underlies parts of Lancashire and Cumbria, and east of the Pennines it extends through Nottinghamshire and central Yorkshire. Smaller outcrops occur in other parts of Britain such as the Red Cliffs of Dawlish and East Devon.
[edit] Lithology
In terms of its lithology, the New Red Sandstone (often shortened in literature to NRS) comprises true sandstones, mudrocks and evaporite strata. The sandstone member is monomineralic, consisting only of quartz grains (negligible amounts of other minerals may be present), and they are cemented together with the ferric iron oxide haematite (Fe2O3). The presence of this particular iron oxide is evidence for a terrestrial environment of deposition such as a desert, and gives the rocks the red color which they are named after. The common effect of rusting produces exactly the same deposit, but as a result of a different process. The sandstone member lacks fossils (as do most terrestrial rocks). The grains in the member have a high degree of sphericity, are very well sorted and typically have a small size range (0.5mm to 2mm).
The NRS is a texturally mature rock, and is a common building stone in the Cheshire area due to its abundance and mechanical strength [1] & [2].
[edit] References
- Palmer, Douglas. Earth Time: Exploring the Deep Past from Victorian England to the Grand Canyon. Chichester: John Wiley & Sons, Ltd, 2005. ISBN 0-470-02221-3 pp. 137-8, 159.
- Durrance, E & Laming, D.J.C. The Geology of Devon University of Exeter Press 1982 ISBN 0-85989-247-6.
