- The document discusses revisions made by the Geological Survey of Denmark and Greenland (DGU) to the lithostratigraphic nomenclature of Tertiary strata in the Danish sector of the North Sea. - Traditionally, offshore and onshore lithostratigraphic nomenclature were kept separate, but the DGU revision established a single nomenclature based on existing Norwegian and UK schemes. - Some previously informal offshore unit names that correlated to onshore Danish units were formally designated as members of new formations according to the DGU scheme.

1. Stephen Crittenden – Consultant Petroleum Geologist
Date: April 2017 (originally compiled as a note in March 2008)
I am as of March 25th
2017 officially retired with a pension. (But…..I am still available for consultancy
work.)
I am sorting through my papers, notes and writings of the last 40 years and where possible I am
redacting and rewriting some articles, presentations etc and placing them in the public domain for
use by any geoscientist who cares to read them.
This article on the Lower Tertiary of the southern North Sea complements my previous post on slide
share:
https://www.slideshare.net/StephenCrittenden/north-sea-marl-vle-maureen-nomenclature-
linkedin-version
Tertiary Reference Lithostratigraphy
References:
1.Lithostratigraphy of the Paleogene-Lower Neogene succession of the Danish North Sea. Geological
Survey of Denmark and Greenland Bulletin 12, 2007.
2. King, C. 1983: Cainozoic micropalaeontological biostratigraphy of the North Sea. Institute of
Geological Sciences Report 82/7, 40pp.
3. Crittenden, S. 1986: Planktonic foraminifera and the biostratigraphy of the early Tertiary strata of
the North Sea Basin; A brief discussion. Newsletters on Stratigraphy, 15/3, 163-171.
Observation
The lithostratigraphy of the Tertiary strata developed above the Early Palaeocene (Danian) chalk of
the Ekofisk Formation and below the Mid Miocene to Recent Nordland Group in the Danish offshore
sector of the North Sea has been revised by the DGU (Reference 1). A detailed lithostratigraphical
nomenclature has been erected and defined. The nomenclature is pragmatic and is based upon
existing and established formal lithostratigraphical schemes used in the Norwegian and British (UK)
sectors of the North Sea (Figure 1). The Rogaland Group has been divided into four formations, and
six members and reference sections (figured well intervals) for each unit have been established by
DGU for the Danish sector of the North Sea. Descriptions of the lithology, biostratigraphy, age and
palaeoenvironmental setting are provided. No attempt was made by DGU to establish a sequence
stratigraphy model, as the main aim was to provide a robust and formalized lithostratigraphical
framework.
Comments
Traditionally, offshore lithostratigraphical unit nomenclature has been kept separate from onshore
nomenclature, despite the demonstrated identical nature of some mappable units in some instances
and the view of geologists regarding the onshore as the key to the offshore. The lithostratigraphical

2. nomenclature used for reporting within the Danish sector has been informal and based upon the
onshore Danish lithostratigraphy (Reference 2). For example, by comparison with the onshore
stratigraphy, a basal unit of the Hordaland Group within the Horda Formation has been referred to
the Røsnaes Clay Formation. This interval of reddish-brown to brick red claystones is very distinctive,
is characterized by a characteristic red stained planktonic foraminiferal fauna and is recognized in
the Norwegian, Danish, UK and Dutch sectors of the North Sea Central Graben (Reference 2 & 3). It is
an established “flooding event” in sequence stratigraphy terminology. In oil company reports, other
onshore lithostratigraphical unit nomenclatures have been used informally for a basal unit of the
Sele Formation, i.e the Østerrende Clay (placed by DGU in the Lista Formation), and for subdivisions
of the Lista Formation i.e the Holmehus Formation and the Æbelø Formation. This approach has
been adopted by commercial laboratories in their reporting of biostratigraphical analyses of wells
drilled in the Danish, Dutch, Norwegian and UK sectors of the North Sea offshore. However, it is best
to use published formalized nomenclature established for the offshore whenever possible, as this
ensures a common understanding between geoscientists both in industry and academia and
provides a sound foundation upon which to build and develop stratigraphical ideas (Figure 1).
Accordingly, it is suggested that the lithostratigraphical nomenclature used in the Danish Offshore by
commercial companies should be that formalized by the Geological Survey of Denmark and
Greenland, accepting that it is often the industry that has been the initial driving force behind the
framework and nomenclature. However, operationally (and in modelling) there may be practical
difficulties in companies implementing any change from the terminology used by them at present,
but at least they should all be aware of the DGU lithostratigraphical scheme.
Summary
Østerrende Clay becomes the Bue Member of the Lista Formation.
Holmehus Formation becomes the Ve Member of the Lista Formation.
Æbelø Formation becomes the Vile Member of the Lista Formation.
North Sea Marl becomes the Våle Formation.
The key identification points for these lithostratigraphical units remain the same as those seen in
numerous other reports produced by commercial operators and consultancy groups active in the
Danish Offshore.