Upper Quaternary marine Skagerrak (NE North Sea) deposits: Stratigraphy and depositional environment. A contribution to OSKAP (Oslofjord-Skagerrak Project) of the Department of Geology, University of Oslo
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Over the years Norsk Geologisk Tidsskrift has covered many diverse aspects of geosciences mostly related to problems from the area of
Scandinavia. From time to time individual issues of our journal have been devoted to one topic focusing on some special problem or area.
This issue of NGT contains a series of papers describing a 10m piston core of Upper Quaternary sediments from the Skagerrak. The authors were brought together by the Oslofjord-Skagerrak Project in a joint effort to study this unique record of the younger geological history of a key area of southern Scandinavia.
It is not easy to make a synthesis of all the different studies undertaken, so that the total picture becomes more than the simple sum of the individual contributions. It is, however, hoped that the results obtained may serve as a standard compilation for later studies of similar sediments.
A number of different methods and parameters have been used to date this core and to characterize some major changes of its depositional environment; all measurements and descriptions have been based on the same core, often also the same samples. It should henceforth be possible to correlate the individual measurements and to gain a comprehensive and well-documented understanding of the history of the core's depositional environment.
The Scandinavian land regions surrounding the Skagerrak have for many decades been areas of intensive studies relating to problems of their Quaternary history. The evolution of the depositional
environments of the marine areas adjacent to these land regions has, however, for a long time been poorly understood, mainly because
it has been very difficult to date this history properly and in sufficient detail. The core presented in this issue is one of very few cores from
the marine area adjacent to Denmark and Norway which have been dated successfully and which have been correlated in great detail to the late Quaternary chronostratigraphy. 
The Skagerrak is part of a seaway connecting the Baltic and North Seas. By unravelling and dating the late Quaternary history of its depositional environment it has also been possible to resolve certain aspects of the evolution of the adjacent epicontinental and deep-sea areas. Therefore, this core not only documents a history of local importance, but it also opens a perspective for reading and understanding signs which document the geological history of distant
areas. Our work on the core also made it possible to date the two youngest acoustostratigraphic sediment units of the Skagerrak.
The sediments encountered in the core contained large amounts of components derived from the Scandinavian land areas. Certain properties of the core and their stratigraphic changes could therefore be used to make statements about the late Quaternary history of the land surfaces in southern Norway and northern Denmark.
The papers about this sediment core should therefore open up a number of perspectives for further detailed studies of the history of the Skagerrak, which some 10,000 years ago was only a fjord opening into a polar ocean, but which since then has developed in to part of a wide sea region with very typical geological and oceanographic
characteristics and which today is of great influence on the North and Baltic Sea depositional environments. These sea regions are today heavily used by man, and investigations into their young geological history are also important for an evaluation of the stability of this environment. The studies of this sediment core offer some insight into such questions and it therefore seemed appropriate to have them published jointly in one issue of Norsk Geologisk Tidsskrift.

Bjørg Stabell, Jörn Thiede
Gunnar Juve, Knut Björlykke