Holwell Quarries is a 1.3 hectare

Hectare

The hectare is a metric unit of area defined as 10,000 square metres , and primarily used in the measurement of land. In 1795, when the metric system was introduced, the are was defined as being 100 square metres and the hectare was thus 100 ares or 1/100 km2...

 geological Site of Special Scientific Interest at Holwell near Nunney

Nunney

Nunney is a village and civil parish near Frome in the Mendip local government district within the English county of Somerset. The parish includes the hamlet of Holwell.The name of the village comes from Old English and means Nunna's island....

 on the Mendip Hills

Mendip Hills

The Mendip Hills is a range of limestone hills to the south of Bristol and Bath in Somerset, England. Running east to west between Weston-super-Mare and Frome, the hills overlook the Somerset Levels to the south and the Avon Valley to the north...

 in Somerset

Somerset

The ceremonial and non-metropolitan county of Somerset in South West England borders Bristol and Gloucestershire to the north, Wiltshire to the east, Dorset to the south-east, and Devon to the south-west. It is partly bounded to the north and west by the Bristol Channel and the estuary of the...

, notified in 1952.

Holwell Quarries represent an internationally important geological locality. A comprehensive assemblage of Triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

 (including Rhaetic), Lower Jurassic and Middle Jurassic

Middle Jurassic

The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger....

 fissure fillings are well displayed. The Rhaetic fissure fillings have yielded the richest assemblage of vertebrate faunas known from the British Triassic. Fissure deposits have also yielded 8 or 9 genera of Reptiles: a Crocodilian, a Placodont

Placodont

Placodonts were a group of marine reptiles that lived during the Triassic period, becoming extinct at the end of the period. It is believed that they were part of Sauropterygia, the group that includes Plesiosaurs...

 (the first record in Britain of this sub-order), and the dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s Thecodontosaurus

Thecodontosaurus

Thecodontosaurus is a genus of herbivorous basal sauropodomorph dinosaur which lived during the late Triassic period ....

 and Palaeosaurus

Palaeosaurus

Several very different genera of prehistoric animals have been named Palaeosaurus or Paleosaurus since the 1830s. Further confusing the matter, all of the species are poorly known or poorly preserved and both spellings have been used interchangeably, even by the same authors.The repeated recurrence...

. The Lower Jurassic fissure fillings yield ammonites and brachiopods which are important in dating these deposits.

Sources

• English Nature citation sheet for the site (accessed 10 August 2006)

External links

• English Nature website (SSSI information)