Geoscience Reference
In-Depth Information
'Bath Stone' (Bathonian, Middle Jurassic) is a generic
term for the pale to dark yellowish-brown, oolitic
limestones quarried and mined around the city of Bath
(Somerset, England). Figure
52
shows 'Monks Park'
limestone (oosparite), a variety of 'Bath Stone' that consists
mainly of ooliths that are well cemented by sparite.
'Portland Stone' (Portlandian, Upper Jurassic) is perhaps
the best known and possibly the most widely used of
England's building stones. It is an even-grained, buff-
coloured, porous oolitic limestone (oolitic grainstone) that
weathers to a white colour on buildings. Three main beds
are still quarried, the 'Whitbed' (
53, 54
), 'Basebed', and the
51
52
51
'Clipsham Blue/Cream' limestone (Lincolnshire,
England) consisting of intraclasts (red, nonferroan
microcrystalline calcite) cemented by ferroan sparry
calcite (blue) with no macropores. The thin section
has been stained in accordance with Dickson's
method; PPT, ×150.
52
'Monks Park' limestone (Wiltshire, England)
consisting of ooliths (pink, nonferroan microcrystalline
calcite) cemented by ferroan sparry calcite (blue) with
no macropores. The thin section has been stained in
accordance with Dickson's method; PPT, ×35.
53
54
53
'Portland Whitbed' limestone (Dorset, England)
consisting chiefly of grain-supported ooliths (brown)
with traces of shell, and with a high proportion of
macropores (10%, yellow); XPT, ×35.
54
Close view of 'Portland Whitbed' limestone
showing differences in porosity. The brightest areas
are more porous; UV, ×150.
