An overview of the lithostratigraphical framework for the Quaternary deposits on the United Kingdom continental shelf

This stratigraphical framework report presents a
lithostratigraphical scheme for the Quaternary succession
on the United Kingdom continental shelf (UKCS). The
emphasis has been placed on the delineation and definition
of a series of lithostratigraphical groups that provide
the basis for first-order correlation between Quaternary
deposits, both offshore and onshore. The proposed scheme
is based on information derived from the extensive marine
dataset acquired by the British Geological Survey (BGS)
since the late 1960s, and published as a series of offshore
maps and regional reports.
The first part of the report (Chapter 1) introduces the
project and in particular focuses upon the fundamental
differences between onshore and offshore stratigraphical
approaches. Resolving this problem is fundamental to
creating a unified stratigraphical scheme that is applicable
to both domains. The timescale that we use defines the base
of the Quaternary System/Period and the Pleistocene Series/
Epoch at 2.58 Ma, as formally ratified by the International
Union of Geological Sciences (IUGS) (Gibbard et al.,
2010).
This is followed in Chapter 2 by a brief description
of the methodology that underpins the existing offshore
stratigraphy. Although this scheme has been constructed
largely on the basis of seismic stratigraphy, information on
the nature and age of the stratigraphical units is provided
by a wealth of borehole and short core data. Consequently,
the offshore scheme is best described as a hybrid of seismic,
litho- and biostratigraphy.
Chapter 3 outlines the principles behind the new
proposed lithostratigraphical scheme. Although the scheme
is not wholly lithostratigraphical in nature, the hierarchy
of lithostratigraphical nomenclature is adopted as the most
practical terminology for describing a succession that is
mappable at several levels, is divided by distinctive regional
bounding surfaces, and displays significant lithological
variation. By adopting a lithostratigraphical nomenclature
we retain consistency with a recently published BGS
onshore lithostratigraphical framework, thereby promoting
an integrated land–sea approach to Quaternary correlation.
A brief description of the new lithostratigraphical scheme
is presented in Chapter 4, with emphasis at the group level.
We define twelve groups from the Atlantic margin, North
Sea and Celtic Sea–Irish Sea region that represent regional
subdivision into predominantly non-glacial Lower–Middle
Pleistocene, and glacially-dominated Middle Pleistocene–
Holocene units. The proposed defining formations from
each group are presented in a series of accompanying
tables. Some of the larger estuaries (e.g. Moray Firth) and
the English Channel–South-west Approaches region remain
undivided at the present time.
A comparison of the UKCS lithostratigraphical scheme
with those in adjacent international sectors is presented in
Chapter 5, with specific focus on the Dutch and Norwegian
sectors. A major concern across the international boundaries
is that the lithostratigraphical hierarchy of equivalent units
varies between countries.
Chapter 6 presents some recommendations for further
work in order that the stratigraphical scheme be fully utilised
by the scientific community and industry. This includes: 1)
complete revision, update and population of the offshore
entries in the BGS Stratigraphical Lexicon of Named Rock
Units; 2) the production of a full framework report that
details all aspects of the offshore Quaternary succession
(groups, formations, members, etc); 3) a review of areas
where the Quaternary stratigraphy is ambiguous or poorly
defined; 4) the development of a single onshore–offshore
classification scheme that can be captured seamlessly
within the BGS Geological Spatial Database (GSD); and
5) the development of a unified North-west European
Quaternary stratigraphical scheme. It is concluded that
tasks 1 and 4 are essential corporate issues that underpin the
entire BGS superficial deposits framework.