7 (contains 6 papers)
In collaboration with the Midtsønderjyllands Museum at Gram,
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1) Rasmussen E.S., 2005, The geology of the upper
Middle - Upper Miocene Gram Formation in the Danish area.
14 textpages, 10 textfigures
Summary: Sediments of the upper Middle - Upper Miocene Gram Formation
are distributed in central, west and south Jylland, Denmark. The Gram
Formation is subdivided into three units: bottom to top the
glaucony-rich, lowermost part, the Gram Clay, and the Gram sand. The
sediments of the Gram Formation were deposited in an open marine
depositional environment. The sediments of the Gram Formation
were deposited in an open-marine environment. The glaucony-rich part
was laid down under maximum transgression of the sea during the late
Middle Miocene, when the north-eastern boundary of the North Sea was
possibly located near the Sorgenfrei-Tornquist Zone in northern Jylland
and Skåne. Water depths were up to 100 m in the area covered by
the present-day west Jylland, but exceeded 500 m in the central part of
the North Sea. In the Upper Miocene, outbuilding of clastic sedimentary
wedges from the Fennoscandian Shield occurred from both the north and
east. This resulted in a high sedimentation rate during the deposition
of the Gram Clay. Locally, especially around salt structures, deeper,
partly anoxic, restricted depositional environments prevailed.
Expansion of these anoxic environments may have resulted in extreme
environmental conditions and resulted in mass mortality shown by
well-defined concretion horizons containing impressions of crabs.
The uppermost part of the Gram Clay, with fine-grained storm-sand
layers, and the Gram sand indicate periodical proximity of the
shoreline. Possibly as a result of increased subsidence of the North
Sea Basin in the Upper Miocene, up to 400 m of mainly shelfal deposits
were laid down in most parts of the eastern North Sea Basin.
2) Beyer C., 2005, A magnetic analysis of the Late
Miocene Gram Formation, Denmark.
10 textpages, 8 textfigures
Summary: Based on the assumption that the geomagnetic secular variation
in the Late Miocene posessed characteristics similar to the Quaternary
secular variation, the accumulation rates of the Miocene Gram Formation
was estimated by a magnetic analysis of a 16m vertical profile. The
magnetic susceptibility, intensity and direction were measured and
interpreted with respect to grain size, magnetic polarity and variation
of the rate of accummulation.
The analyses showed a general increase of accummulation rate upwards in
the profile from approximately 0.03mm/y to 0.40mm/y. The sedimentation
was extremely slow and possibly discontinuous in the lowermost part of
the sequence, part of which is interpreted as a condensed section. The
rest of the sampled profile showed more rapid and relatively continuous
sedimentation during a time of normal polarity.
A reverse polarity zone of 1.6m thickness was revealed in the interval
1.2 - 2.8m. The duration of this polarity zone is estimated to less
than 70.000 years which leaves only three possibilities for correlation
to the GPTS for the Tortonian stage, approximately 7.1 m.y., 7.4 m.y.
or 9.9 m.y.
The results indicate that the lowermost 3m were deposited during
approximately 100.000 years and the 8m above this interval were
deposited during approximately 20.000 years. The lowermost 8 m of the
formation was not accessible in the clay pit but is known from nearby
wells. This part of the sequence contains glauconite sand at the base
and was thus deposited considerably slower than the studied sequence.
3) Piasecki S., 2005, Dinoflagellate cysts of the
Middle – Upper Miocene Gram Formation, Denmark.
17 textpages, 4 textfigures, 3 plates
Summary: The dinoflagellate cysts of the Gram Formation provide the
biostratigraphic framework for the determination of the age of the
formation and reflect environmental and palaeoclimatic conditions
during deposition. The age of the Gram Formation is Late Serravallian
and Tortonian (late Middle Miocene to early Upper Miocene) estimated on
the basis of dinoflagellate cyst biostratigraphy; the basal
glaucony-rich interval is referred to late Serravallian, and the
overlying clays, silts and fine-grained sands are assigned to the
Tortonian. These age assignments are not consistent with the ages based
on molluscs and the foraminifers; for example, dinoflagellate cysts
indicate no Messinian strata in the Gram Formation whereas the
foraminifer stratigraphy does. Such stratigraphic contradictions are
discussed. Significant variations in the diversity and abundance of the
dinoflagellate cyst assemblages are interpreted to reflect relative
sea-level variations; maximum flooding is inferred in the basal Gram
Formation followed by steady shoreline progradation such that the
uppermost levels at the Gram locality represents a coast-near setting.
In localities further to the west and south, more marine floras occur
in the uppermost part of the formation. The dinoflagellate cyst
assemblage reflects the cooling climate during deposition of the Gram
Formation. Genera and species persistently present from the Palaeogene
disappear up through the succession, probably reflecting the
deteriorating climate. Species with tropical – subtropical
affinity occur in the underlying Hodde Formation but disappear in the
Gram Formation. However, the response of Neogene dinoflagellate
cyst assemblages to climatic and environmental parameters are not well
elucidated, and detailed interpretations of the Gram flora are
4) Hansen J. & Hansen T., 2005, A Late Miocene
brissid echinoid from Denmark.
5 textpages, 2 textfigures, 1 plate
Summary: Numerous specimens of the irregular echinoid Brissopsis
lyrifera have been collected from the Gram Formation (Upper Miocene) at
Gram clay pit, Denmark, and these are the oldest known records of the
species. Although poorly preserved, the tests closely resemble the
extant Danish form of B. lyrifera. This indicates the species has shown
evolutionary stasis over the last eight million years.
5) Fraaije R., Hansen J. & Hansen T., 2005,
Late Miocene decapod faunas from Gram, Denmark.
11 textpages, 4 textfigures, 1 plate.
Summary: Six species of decapod crustacean (two macrurans, one
anomuran, three brachyurans) are recognised from upper Miocene
strata exposed at the Gram clay-pit, south-west Jutland, Denmark. Three
new species, Retropluma borealis, Chaceon miocenicus, and Nephrops
kvistgaardae, are erected; the genera Tasadia and Munida are recorded
from the Danish Miocene for the first time.
6) Schnetler K.I., 2005, The Mollusca from the
stratotype of the Gram Formation (Late Miocene, Denmark).
128 textpages, 6 textfigures, 11 plates.
Summary: The mollusc fauna of the Gramian stratotype, the clay-pit of
the former Gram Brickworks, was studied. The material from the Gramian
part of the borehole Gram 1 (D.G.U. 141.277; 5.30 – 16.50 m) is
also included. The study gives a summary of our present knowledge of
the fauna. A total of 128 species of mollusca is recorded, of which 36
are new for the Gram locality. Five new species and one new subspecies
are established, viz. Mesopelex anderseni n. sp., Galeodea bicatenata
marqueti n. subsp., Nassarius (Tritonella) ronaldjansseni n. sp.,
Teretia guersi n. sp., Daphnella abrahamssoni n. sp. and Turbonilla
(Strioturbonilla) rothi n. sp. The new name Skenea ariejansseni nom.
nov. is introduced for Skenea minuta A.W. Janssen, 1967 (non Jeffreys,
1883). A lectotype for Pleurotomoides luisae (Von Koenen, 1872) is
designated. Remarks on taxonomy and palaeogeography are given. The
Nassariidae will be revised in a separate paper (Gürs &
Schnetler, in prep.).
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