New Red Sandstone
Red, desert-derived sandstones deposited from the late Permian into the early Triassic (late Paleozoic–early Mesozoic). Common in Britain, notable for iron-rich red colour, desert deposits, and use as building stone.
Overview
The New Red Sandstone is a suite of continental sandstones and associated sediments laid down in arid environments during the transition from the late Permian into the early Triassic. These rocks are particularly well known from Britain but have equivalents worldwide. They form conspicuous red cliffs, plateaux and lowland plains where they are exposed, and they represent a time when large parts of what is now Europe lay under desert and continental basins rather than shallow seas.
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Composition and appearance
Most New Red Sandstone consists of medium- to coarse-grained sandstones with a distinctive red, pink or orange hue. The red colour is produced by iron oxides (principally hematite) coating the sand grains. Associated lithologies may include conglomerates, siltstones, mudstones and evaporites (salts and gypsum) in basins that experienced periodic salting and drying. Bedding commonly shows cross-bedding and ripple structures indicative of wind-blown dunes and ephemeral river channels.
Age, deposition and environments
These rocks were deposited in continental settings during the late Permian into the early Triassic, broadly spanning the late Paleozoic to early Mesozoic eras (roughly several hundred million years ago). Typical depositional environments include desert dune fields (ergs), playa lakes (ephemeral salty lakes), alluvial fans and braided river systems. In such settings sediment was derived from weathering of older uplands, transported by wind and short-lived streams, and accumulated in interior basins under largely arid climatic conditions.
Distribution and notable exposures
In Britain, New Red Sandstone occurs in several basins and plains and can be seen as red scarps and lowland deposits. It commonly underlies later marine Jurassic strata, such as the Lias, marking a change from continental to marine conditions in the rock record. Elsewhere, similar 'red bed' sequences of Permian–Triassic age are widespread across Pangaea-derived regions and are an important marker of arid continental environments of that interval.
Fossils, economic uses and significance
Because they formed mainly in deserts and ephemeral rivers, New Red Sandstone sequences generally contain fewer marine fossils than adjacent marine units. They may, however, contain plant fragments, freshwater bivalves in isolated lakes, and especially trace fossils such as reptile and amphibian footprints preserved in muddy surfaces. Economically, these sandstones have long been quarried as durable building stone, flagstones and rubble for walls, and they influence soil and landscape development where they are widespread.
Distinction from the Old Red Sandstone and other facts
The New Red Sandstone is distinguished from the Old Red Sandstone by age, colour intensity and stratigraphic position. The Old Red Sandstone is largely Devonian in age and typically less vividly red. The New Red Sandstone often rests unconformably on older rocks and is itself sometimes capped by later marine deposits. Its iron-rich coloration and sedimentary structures make it a classical example of continental "red beds" in geology texts.
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AlegsaOnline.com New Red Sandstone Leandro Alegsa
URL: https://en.alegsaonline.com/art/69594