Sarsen Stones (lead authors JT and WGT) Updated Jan 2020
Sarsen stones are early Cenozoic (Paleocene) non-marine sandstones (quartzites and flint conglomerates) patchily distributed as outliers on the Chalk downlands of Wiltshire, Hampshire and Dorset. During the Paleocene-Eocene Thermal Maximum (PETM 55my) these were intensely silicified to become silcretes. They were used in the construction of Avebury and Stonehenge megalithic monuments in Wiltshire (and sometimes domestic buildings, kerb stones, etc.).
Dorset examples include: Nine Stones Circle, Kingston Russell Circle, Hampton Circle, Rempstone, Grey Mare and Her Colts and the Hell Stone. The silcretes are generally light grey and some are rich in flint pebbles* and thus conglomeratic.
Dorset examples include: Nine Stones Circle, Kingston Russell Circle, Hampton Circle, Rempstone, Grey Mare and Her Colts and the Hell Stone. The silcretes are generally light grey and some are rich in flint pebbles* and thus conglomeratic.
|
|
Winterbourne Abbas Nine Stones – Conglomeratic silcrete
As well as the grey sarsens of prehistory, there are also brown ferruginous sandstone masses (ferricrete), remaining on some high ground as outliers, probably also formed during the PETM and subsequently, but in areas with high concentrations of iron compounds.
Silcretes and ferricretes also formed in younger sands within the Palaeogene, if climate and soil conditions were appropriate. Such durable rocks were recycled by rivers during the periglacial conditions of the Recent Ice Ages and are thus known from Pleistocene terraces, modern beaches and offshore.
See also Heathstone
For more information: http://www.southampton.ac.uk/~imw/Sarsens-Erratics.htm
*NB: Flints are created rounded (after trace fossils) so rounded pebbles in a conglomerate does not indicate rounding by erosion in a high energy environment such as a beach. The flint conglomeratic sarsens are terrestrial deposits.
Silcretes and ferricretes also formed in younger sands within the Palaeogene, if climate and soil conditions were appropriate. Such durable rocks were recycled by rivers during the periglacial conditions of the Recent Ice Ages and are thus known from Pleistocene terraces, modern beaches and offshore.
See also Heathstone
For more information: http://www.southampton.ac.uk/~imw/Sarsens-Erratics.htm
*NB: Flints are created rounded (after trace fossils) so rounded pebbles in a conglomerate does not indicate rounding by erosion in a high energy environment such as a beach. The flint conglomeratic sarsens are terrestrial deposits.
