Brassington Formation

Brassington Formation
Stratigraphic range: Mid-Late Miocene Serravallian-Tortonian
Type Geological formation
Unit of Great Britain Superficial Deposits Supergroup
Sub-units Kirkham Member, Bees Nest Member, Kenslow Member
Underlies Alluvium
Overlies Carboniferous Limestone (more specifically the Peak Limestone Group)
Area Staffordshire, Derbyshire
Thickness up to 70 metres (230 ft)
Lithology
Primary Sand
Other Clay, Silt, Gravel
Location
Region Europe
Country  UK
Extent 220 km2
Type section
Named for Brassington
Named by Boulter et al.
Location Bees' Nest Pit
Year defined 1971
Thickness at type section 43 metres (140 ft)

The Brassington Formation is a geological formation in the United Kingdom, and the country's most significant onshore Miocene deposit. it is preserved as around 60 inliers in karsts of Carboniferous limestone, specifically the Peak Limestone Group, in a triangular region on the borders of the Staffordshire and Derbyshire counties. The lithology largely consists of unconsolidated sand with clay and minor silt components. Pebble beds are also a significant component. It is divided up into three members, which are in ascending order the Kirkham Member, Bees Nest Member and the Kenslow Member. The Kenslow Member is dated to the Serravallian to Tortonian stages based on palynology.

Lithology

The main source rocks for the Brassington Formation are the Triassic sandstones of the Sherwood Sandstone Group.[1]

Kirkham Member

The Lithology of the Kirkham member consists of up to 40–50 m of cream or white coloured (originally red coloured) kaolinitic fluvial derived unfossiliferous sand, gravel and pebble beds, possibly with local cementation.

Bees Nest Member

The lithology of the Bees Nest Member consists of interbedded mottled sandy and silty clays of varying colours (green, grey, red and yellow brown), it is 6 m thick in the Bees Nest pit and up to 21 m in the Kenslow Pit. It represents a low energy aquatic or lacustarine depositional setting

Kenslow Member

The Lithology of the Kenslow Member consists of up to 6 m of massive lacustarine grey coloured clay, with the uppermost parts containing abundant wood fragments. It was deposited in a shallow lacustrine to swampy setting.

Paleoenvironmental Interpretation

The vegetation from the Kenslow member suggests a subtropical, seasonally wet climate, with an average temperature of 26-28°C for the warmest month, and 6-12°C for the coldest month. The palynomorph assembelage is dominated by pollen of the genera Picea, Pinus, Tsuga and Sciadopitys, the last of which today is confined to a single species in Japan. It was probably deposited close to sea level, but a significant distance from the sea. Fossil wood and pollen referable to the genus Cryptomeria has also been found.[2]

References

  1. ↑ Walsh, Peter T.; Banks, Vanessa J.; Jones, Peter F.; Pound, Matthew J.; Riding, James B. (2018-01-31). "A reassessment of the Brassington Formation (Miocene) of Derbyshire, UK and a review of related hypogene karst suffosion processes". Journal of the Geological Society. 175 (3): 443–463. doi:10.1144/jgs2017-029. ISSN 0016-7649.
  2. ↑ Pound, Matthew J.; Riding, James B. (2015-11-10). "Palaeoenvironment, palaeoclimate and age of the Brassington Formation (Miocene) of Derbyshire, UK". Journal of the Geological Society. 173 (2): 306–319. doi:10.1144/jgs2015-050. ISSN 0016-7649.
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