The Upper North
Sea Group (NU) unconformably overlies the Middle North Sea Group (NM) and
records deposition from Neogene to Present. The NU consists of post-Oligocene
shallow-marine sediments including clay, fine-to-coarse
grained sand, local gravel, peat, and brown coal seams (Van
Adrichem Boogaert, and Kouwe, 1993). The NU includes coarser sediments with more complex
geometries compared to the underlying NM (Tetyukhina et al., 2010). The target
interval of this study comprises three formations: (1) Breda Formation, (2)
Kieseloolite Formation, and (3) Oosterhout Formation.
The Breda Formation consists of
Miocene to earliest Pliocene age sediments deposited in a marginal marine environment.
The formation comprises foreset and
bottom-set beds deposited in delta-front setting (Doppert et al., 1975). Lithologies
include glauconitic sand, sandy clay, and
clay. A glauconite-rich layer occurs commonly at the base, which is interpreted as a
regional unconformity (Doppert et al., 1975).
Formation comprises Late Miocene, early Pliocene, and late Pliocene age
sediments deposited in a river floodplain and coastal lowland (Van Adrichem Boogaert, and Kouwe, 1993). The formation
consists of a wide variety of fluvial and lacustrine origin lithologies. The
lower half of the formation is composed of coarse-grained clastics (sand and gravel), while the upper
part consists of clay and sand (Van Adrichem
Boogaert, and Kouwe, 1993). The lower portion of the Kieseloolite Formation merges into marine
beds of the Breda Formation, and the upper portion merges into the Oosterhout Formation.
Formation contains Pliocene to earliest Pleistocene sediments deposited in a
shallow marine environment and in a
delta-front setting. Lithologies include sand, sandy clay, and greenish clay. The Oosterhout Formation overlies the Breda Formation and intertongues with and is overlain by the
deposits of Kieseloolite Formation, recording
progradation (Doppert et al., 1975).