Bierton Clay Pit SSSI
reference: SP 839
of site: 0.07 ha;
location and parking:
2 km NE of Aylesbury, off the A418. The site can be viewed from the footpath
which runs along the southern end of the complex of small ponds. Actual access
is from the eastern end where a main entrance will be found and parking is best
Disused clay pit, now flooded.
The succession spans the Kimmeridgian-Tithonian (Portlandian) boundary and
includes an exposure of the basal Upper Lydite Bed of the Portland Sand. (Lydite
is a distinctive shiny, black, cherty rock). This is a correlatable Bed across
the area, but there are very few exposures and these are only temporary. The bed
is a transgressive horizon, that is, it shows evidence for a rise in sea level
after a period of non-deposition and erosion. This event left a pebble bed over
a substantial gap in time (an unconformity). This site is therefore useful for
and potential educational use
(geology, ecology, archaeology, industrial archaeology):
No geological exposure is currently available, but could be potential future
exposures if ponds are drained are new drainage channels or ditches are dug.
Ecological interest only.
The pit is flooded, no conservation is appropriate for geological interest from
to site (present and future): None at present.
(basic risk assessment): The pit is flooded and care should be taken if walking around the
perimeter of the water.
P. F. 1963. The beds between the Kimmeridge and the Gault Clays in the Thame-Aylesbury
area. Proc. Geol. Assoc. 74, 393-418.
R. 1967. The position of the Middle Volgian in the English Jurassic. Proc.Geol.
Assoc. 78, 128-133.
A. M. 1934. A field meeting at Aylesbury. Proc. Geol. Assoc. 45,
A. M. and Wilson, V. 1949. Field meeting in the north
E. 1925. The petrology of the Upper Kimmeridge Clay and Portland Sand in Dorset,
Wiltshire Oxfordshire and Buckinghamshire. Proc. Geol. Assoc. 36,
M. J. 1974. The stratigraphy and palaeoecology of the Hartwell Clay (
P. C. and Ford, T. D. (eds.) 1968. The geology of the East
Midlands, Leicester University Press, 400 pp.
Note if new sections are dug for drainage, etc. Otherwise not suitable for group