Geological Survey of Denmark and Greenland Bulletin 19 - 2009

Lithostratigraphy of the Cretaceous–Paleocene Nuussuaq Group, Nuussuaq Basin, West Greenland

Gregers Dam, Gunver Krarup Pedersen, Martin Sønderholm, Helle H. Midtgaard, Lotte Melchior Larsen, Henrik Nøhr-Hansen and Asger Ken Pedersen

The Nuussuaq Basin contains several kilometres of siliciclastic sediments overlain by a thick pile of volcanic rocks. The sediments, which are exposed on Disko, Nuussuaq, Upernivik Ø, Qeqertarsuaq and Svartenhuk Halvø in central West Greenland, have been studied since the early 19th Century. The focus has changed through time from early studies on the occurrence of coal, fossil plants and invertebrate fossils to modern sedimentological and stratigraphical studies to decipher basin evolution and to encourage exploration for hydrocarbons.

The Nuussuaq Basin is the only onshore analogue for the subsurface sedimentary basins offshore West Greenland that are known primarily from seismic data. It is consequently important that the Nuussuaq Basin outcrops are at a scale comparable to seismic sections and furthermore that the lithostratigraphic subdivision presented here emphasises unconformity-bounded formations that potentially may be traced regionally, also on offshore seismic data.

This bulletin presents the lithostratigraphy of the Cretaceous–Paleocene sedimentary succession of the Nuussuaq Basin. The Nuussuaq Group (new) overlies Precambrian basement rocks and is overlain by volcanic rocks of the West Greenland Basalt Group. The Nuussuaq Group comprises ten formations, five of which are erected herein whilst the remainder are redefined or revised in accordance with modern practice. Six of these formations are further divided into members (a total of eighteen, of which fifteen are new) and two beds are formally erected.

Abstract

The Nuussuaq Basin is the only exposed Cretaceous–Paleocene sedimentary basin in West Greenland and is one of a complex of linked rift basins stretching from the Labrador Sea to northern Baffin Bay. These basins developed along West Greenland as a result of the opening of the Labrador Sea in Late Mesozoic to Early Cenozoic times. The Nuussuaq Basin is exposed in West Greenland between 69°N and 72°N on Disko, Nuussuaq, Upernivik Ø, Qeqertarsuaq, Itsaku and Svartenhuk Halvø and has also been recorded in a number of shallow and deep wells in the region. The sediments are assigned to the more than 6 km thick Nuussuaq Group (new) which underlies the Palaeogene plateau basalts of the West Greenland Basalt Group. The sediment thickness is best estimated from seismic data; in the western part of the area, seismic and magnetic data suggest that the succession is at least 6 km and possibly as much as 10 km thick. The exposed Albian–Paleocene part of the succession testifies to two main episodes of regional rifting and basin development: an Early Cretaceous and a Late Cretaceous – Early Paleocene episode prior to the start of sea-floor spreading in mid-Paleocene time. This exposed section includes fan delta, fluviodeltaic, shelfal and deep marine deposits.

The Nuussuaq Group is divided into ten formations, most of which have previously been only briefly described, with the exception of their macrofossil content. In ascending stratigraphic order, the formations are: the Kome Formation, the Slibestensfjeldet Formation (new), the Upernivik Næs Formation, the Atane Formation (including four new members – the Skansen, Ravn Kløft, Kingittoq and Qilakitsoq Members – and one new bed, the Itivnera Bed), the Itilli Formation (new, including four new members, the Anariartorfik, Umiivik, Kussinerujuk and Aaffarsuaq Members), the Kangilia Formation (including the redefined Annertuneq Conglomerate Member and the new Oyster–Ammonite Conglomerate Bed), the Quikavsak Formation (including three new members: the Tupaasat, Nuuk Qiterleq and Paatuutkløften Members), the Agatdal Formation, the Eqalulik Formation (new, including the Abraham Member), and the Atanikerluk Formation (including five members: the Naujât, Akunneq (new), Pingu (new), Umiussat and Assoq (new) Members).

Authors’ addresses

​G.D.
DONG Energy
Agern Allé 24–26, DK-2970 Hørsholm, Denmark
Mail: greda@dongenergy.dk


G.K.P.
Department of Geography and Geology, University of Copenhagen
Øster Voldgade 10, DK-1350 Copenhagen K, Denmark
Mail: gunver@geol.ku.dk


M.S.
Geological Survey of Denmark and Greenland
Present address: DONG Energy
Agern Allé 24–26, DK-2970 Hørsholm, Denmark
Mail: mason@dongenergy.dk


H.H.M.
DONG Energy
Agern Allé 24–26, DK-2970 Hørsholm, Denmark
Mail: helmi@dongenergy.dk


L.M.L.
Geological Survey of Denmark and Greenland
Øster Voldgade 10, DK-1350 Copenhagen K, Denmark
Mail: lml@geus.dk


H.N.-H.
Geological Survey of Denmark and Greenland
Øster Voldgade 10, DK-1350 Copenhagen K, Denmark
Mail: hnh@geus.dk


A.K.P.
Geological Museum, University of Copenhagen
Øster Voldgade 5–7, DK-1350 Copenhagen K, Denmark
Mail: akp@snm.ku.dk