Appendix CRF - Part 3 - Northamptonshire County Council

Radiological Assessment 0820-2
Version 2
ENRMF was originally a clay pit, which exploited the refractory clays at the base of
the Upper Estuarine Series. The base of the pit is therefore effectively the top of the
Lincolnshire Limestone, necessitating the need for an artificial geological barrier over
most of the site, as described above.
Group Formation Thickness Lithology Notes
Great Oolite Group
Inferior Oolite Group
Lias
Group
Glacial Till
(Pleistocene)
Great Oolite Limestone
(formerly Blisworth
limestone)
Upper Estuarine Series
Upper and Lower
Lincolnshire Limestone
0 – 7m Yellow-brown clay with
chalk and limestone
fragments
0 – 1.9 m Yellow micritic limestone
9 – 12 m Grey-brown firm silty
mudstone
15 – 20 m Oolitic, pisolitic and
massive limestones
interbedded with sandy
limestones
Grantham Formation 0 – 2m Fine sands, sills, silty
clays and mudstones.
Northampton Sand ~2m Sands and sandstones
with siderite nodules,
some subordinate
limestones and silts.
Upper Lias >2m Grey mudstones and clays
with subordinate thin
limestone bands
Patchy distribution; not
present in the south east
comer of the site
Locally fissured. Has
been excavated to win
clay from the base of the
unit.
The only formation
remaining beneath the
excavation. Fractured,
with some small voids
and fissures.
Noted in most boreholes
drilled at King’s Cliffe.
Sometimes present at the
base of the Lower
Lincolnshire Limestone.
Table 2.2 Outline geological succession in the region of the ENRMF landfill site.
Drilling near the site confirmed the presence of the Blisworth Limestone (Great Oolite
Limestone) to the east of the site. The underlying Upper Estuarine Series
(corresponding to the material exploited at the clay pit) ranges in thickness from 4.2
m to 12.9 m, with a typical thickness of 11.5m.
The Upper Estuarine Series is mainly argillaceous which has been divided into two
parts. The lower part is the Lower Freshwater Sequence which appears to be devoid
of marine fossils and is composed of dark or brown grey mudstones and seatearths
with abundant rootlets and listric surfaces. Bioturbated laminae, load casts and sand
filled cracks are common sedimentary features. This lower sequence is around 5 m
thick. The upper division of the Series is composed of a cyclical sequence of marine
and brackish/freshwater sediments. The marine beds are composed of shelly
Galson Sciences Limited 7 14 July 2009
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