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BGS Technical Report WA/97/03 15 December 1997
3. UPPER CARBONIFEROUS
Carboniferous rocks underlie the Trias over the entire area but have only been proved in one
borehole.
3.1 Millstone Grit Group
The Pastures Hospital Borehole SK 23 SE/19 [2968 33 171 with a surface elevation of about 91
m (see Section 8, Boreholes) proved 17.45 m of strata interpreted as part of the Millstone Grit
Group. The drillers log dating from 1899-1901, recorded interbedded ‘red granite’, ‘blue shale’
and ‘grey rock’ underlying ‘red sandstones’ and ‘marls’ (=Sherwood Sandstone Group) below
a depth of 157.28 m or about 66 m below OD. The descriptions are equivocal but the probable
interpretation is that they represent red and grey, coarse-grained, arkosic sandstones interbedded
with dark bluish grey, shaly mudstones.
4. TRIASSIC
4.1 Sherwood Sandstone Group
Strata belonging to this group (Warrington et al., 1980) have only been proved in the Pastures
Hospital Borehole SK 23 SE/19 [2968 33 171, between depths of 141.73 m and 157.28 m. The
sequence rests on supposed Millstone Grit Group (see previous section).
4.1.1 Bromsgrove Sandstone Formation
This unit, named by Warrington et al. (1980), was formerly referred to as ‘Lower Keuper
Sandstone’ (e.g. Fox-Strangways, 1905). It is considered to be mainly of Anisian age (G W
Warrington, oral communication 1997). Elsewhere it is usually characterised by thick-bedded,
fine- to medium-grained, pebble-Pee, fluviatile sandstones and subordinate interbedded
mudstones and siltstones. In the present area, the only information comes from the Pastures
Hospital Borehole. The lower part of the 15.55 m-thick Triassic sequence assigned to this
formation is predominantly composed of ‘red sandstone’ with some ‘grey rock’ (siltstone?) and
about 21% ‘marl’.
4.2 Mereia Mudstone Group
The mudstone-dominated, readily degradable strata of this group (Warrington et al., 1980) form
rockhead over the entire Etwall area. In the south much of the ground is covered by superficial
deposits and there are only a few surfwe sections. There is little landform feature control on the
form of the geology. Information on the disposition of the strata at surface mostly comes fkom
borehole data and temporary excavations associated with major construction projects such as the
Derby Southern Bypass. These and stratigraphical information proved elsewhere in the
Loughborough district allow the following stratigraphy to be delineated.
4