Geological Survey of Denmark and Greenland Bulletin
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Nr. 4, Review of Survey activities 2003, pp. 21-24 |
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The search for new, deep-seated drinking water resources in
Denmark has increased significantly during the past five years
as a result of the discovery of excessive amounts of nitrate,
pesticides and other pollutants in shallow groundwater bore-
holes (e.g. Nygaard et al. 2004, this volume). To find and
map these aquifers, a multidisciplinary sequence stratigraphic
approach has successfully been applied to the Miocene
deposits of southern Jutland, where especially the Odderup
and Ribe Formations are known as a main aquifer for drink-
ing water from several test wells (Rasmussen et al. 2002).
Denmark has increased significantly during the past five years
as a result of the discovery of excessive amounts of nitrate,
pesticides and other pollutants in shallow groundwater bore-
holes (e.g. Nygaard et al. 2004, this volume). To find and
map these aquifers, a multidisciplinary sequence stratigraphic
approach has successfully been applied to the Miocene
deposits of southern Jutland, where especially the Odderup
and Ribe Formations are known as a main aquifer for drink-
ing water from several test wells (Rasmussen et al. 2002).
Recently, a more systematic study of the Miocene succes-
sion in central and western Jutland has been initiated by the
Geological Survey of Denmark and Greenland (GEUS)
under contract with local authorities. It includes detailed sed-
imentological descriptions of outcrops, sedimentological and
Geological Survey of Denmark and Greenland (GEUS)
under contract with local authorities. It includes detailed sed-
imentological descriptions of outcrops, sedimentological and
log-interpretations of new stratigraphic boreholes and inter-
pretation of new high-resolution seismic data (Fig. 1). A
number of outcrops and wells have been studied palynologi-
cally, resulting in a detailed dinoflagellate cyst stratigraphy
and in palynofacies interpretations. The results of these stud-
ies have been integrated in the regional geological and strati-
graphic model (Fig. 2). Two new aquifers have been dis-
covered: the Bastrup sand and the Billund sand. The Bastrup
sand has already been exploited as a main aquifer in central
and southern Jutland, and has been referred to either the Ribe
or Odderup Formations. However, new stratigraphic results
reveal that the Bastrup sand is a separate unit in the Miocene
succession. The Billund sand is a deep-seated aquifer located
more than 100 m and often more than 150 m deep, and is
therefore not penetrated by standard water supply wells which
rarely reach c. 100 m.
pretation of new high-resolution seismic data (Fig. 1). A
number of outcrops and wells have been studied palynologi-
cally, resulting in a detailed dinoflagellate cyst stratigraphy
and in palynofacies interpretations. The results of these stud-
ies have been integrated in the regional geological and strati-
graphic model (Fig. 2). Two new aquifers have been dis-
covered: the Bastrup sand and the Billund sand. The Bastrup
sand has already been exploited as a main aquifer in central
and southern Jutland, and has been referred to either the Ribe
or Odderup Formations. However, new stratigraphic results
reveal that the Bastrup sand is a separate unit in the Miocene
succession. The Billund sand is a deep-seated aquifer located
more than 100 m and often more than 150 m deep, and is
therefore not penetrated by standard water supply wells which
rarely reach c. 100 m.
The Billund sand was first revealed by multichannel seis-
mic data deriving from former oil-exploration carried out in
21
The Billund delta: a possible new giant aquifer in central
and western Jutland
and western Jutland
Erik S. Rasmussen, Karen Dybkjær and Stefan Piasecki
Fig. 1. Map of southern Jutland showing palaeoenvironments of the
Billund delta, the location of boreholes and the seismic section men-
tioned in the text.
Fig. 2. Lithostratigraphy of the Miocene succession in Jutland compiled
from Larsen & Dinesen (1959), Rasmussen (1995), Dybkjær & Rasmussen
(2000) and Rasmussen et al. (2002). BS, Billund sand; GS, Gram silt/sand;
HS, Hvidbjerg sand; VFS, Vejle Fjord Sand Member.
Geological Survey of Denmark and Greenland Bulletin 4, 2124 (2004) © GEUS, 2004
the Billund area (Fig. 3A). The resolution of these seismic
data is very poor, but one interpretation of the dipping reflec-
tors (clinoforms) seen in Fig. 3A was of a delta complex. This
agrees with outcrop studies along the fjords of eastern Jutland
which suggest that a spit complex was deposited in this area
during the Early Miocene. The Billund sand was tested by the
Vandel Mark well in 2001, which penetrated c. 40 m of sand
at a depth of 200 m. The presence of a regional major sand
body was later confirmed by new high-resolution seismic
data and by the Billund and Løvlund wells in 2002. The
Billund well penetrated 50 m of medium- to coarse-grained
sand, and chemical tests of the water quality were good.
However, a water supply well at Fjand in western Jutland has
had problems with so-called `brown water' water enriched
in organic matter (humus). Saline water may also be expected
close to older deep-seated faults.
data is very poor, but one interpretation of the dipping reflec-
tors (clinoforms) seen in Fig. 3A was of a delta complex. This
agrees with outcrop studies along the fjords of eastern Jutland
which suggest that a spit complex was deposited in this area
during the Early Miocene. The Billund sand was tested by the
Vandel Mark well in 2001, which penetrated c. 40 m of sand
at a depth of 200 m. The presence of a regional major sand
body was later confirmed by new high-resolution seismic
data and by the Billund and Løvlund wells in 2002. The
Billund well penetrated 50 m of medium- to coarse-grained
sand, and chemical tests of the water quality were good.
However, a water supply well at Fjand in western Jutland has
had problems with so-called `brown water' water enriched
in organic matter (humus). Saline water may also be expected
close to older deep-seated faults.
This paper summarises the results of a mapping pro-
gramme of the Billund sand initiated in the summer of 2003.
22
Fig. 3. Two seismic sections from the Billund area. A: the old multichan-
nel seismic line DCJ-05. B: the new shallow seismic line GI01 (courtesy
of COWI A/S). The red framed area in Fig. 3A corresponds to the sec-
tion shown in Fig. 3B. The clinoformal reflection pattern is indicated in
yellow.
Fig. 4. Correlation panel of four boreholes, with gamma-ray log signature, trending NS in the Billund area. The seismic section adjacent to the Store
Vorslunde well shows the correlation of a clinoformal reflection pattern with sand. Note that the Billund delta pinches out between the Vandel Mark
and the Almstok wells. Seismic data courtesy of COWI A/S.
The Billund delta
The Billund sand represents a major Early Miocene delta
prograding southwards from Norway into the Danish area.
The study of the Billund delta includes interpretation of seis-
mic data, lithological descriptions and interpretation of logs
from new boreholes, sedimentological descriptions and inter-
pretation of outcrops, dating and correlation of the succes-
sion by biostratigraphy (mainly dinoflagellates) and finally
interpretation of the depositional environment based on
palynofacies. Integration of these disciplines has resulted in a
robust geological model for the delta that provides a basis for
the prediction and location of good reservoir rocks suitable as
aquifers for drinking water.
prograding southwards from Norway into the Danish area.
The study of the Billund delta includes interpretation of seis-
mic data, lithological descriptions and interpretation of logs
from new boreholes, sedimentological descriptions and inter-
pretation of outcrops, dating and correlation of the succes-
sion by biostratigraphy (mainly dinoflagellates) and finally
interpretation of the depositional environment based on
palynofacies. Integration of these disciplines has resulted in a
robust geological model for the delta that provides a basis for
the prediction and location of good reservoir rocks suitable as
aquifers for drinking water.
Seismic mapping
In order to map the extent and thickness of the delta, seismic
data from both the North Sea and Jutland have been used.
Based upon the study of the seismic data an isochore map of
the delta has been constructed. The delta extends from 50 km
west of the present-day west coast of Jutland trending
NWSE across Jutland, from Ringkøbing in the west to
Billund in central Jutland. East of Billund the main delta
bends northwards, and the eastern limit follows a line from
the town of Give northwards. The estimated size of the delta
is in the order of 10 000 km
data from both the North Sea and Jutland have been used.
Based upon the study of the seismic data an isochore map of
the delta has been constructed. The delta extends from 50 km
west of the present-day west coast of Jutland trending
NWSE across Jutland, from Ringkøbing in the west to
Billund in central Jutland. East of Billund the main delta
bends northwards, and the eastern limit follows a line from
the town of Give northwards. The estimated size of the delta
is in the order of 10 000 km
2
whereas its thickness varies from
300 m in the North Sea to less than 100 m in central Jutland.
Associated spit complexes that outcrop in eastern Jutland are
rarely thicker than 30 m. In some areas the seismic data are
characterised by strongly southwards-dipping reflectors (cli-
noforms; Fig. 3B). Correlation of seismic data with borehole
information reveals that where the clinoforms are distinct,
Associated spit complexes that outcrop in eastern Jutland are
rarely thicker than 30 m. In some areas the seismic data are
characterised by strongly southwards-dipping reflectors (cli-
noforms; Fig. 3B). Correlation of seismic data with borehole
information reveals that where the clinoforms are distinct,
they represent massive sands (Fig. 4); north of Billund, the
massive sands may be up to 75 m thick. The Billund delta
complex is characterised by a pinchout distance of c. 2 km
which in recent delta systems is a characteristic feature of
wave-dominated deltas (cf. Løseth & Helland-Hansen 2001).
massive sands may be up to 75 m thick. The Billund delta
complex is characterised by a pinchout distance of c. 2 km
which in recent delta systems is a characteristic feature of
wave-dominated deltas (cf. Løseth & Helland-Hansen 2001).
Study of boreholes
A number of recent, deep boreholes have penetrated the
Billund delta (Fig. 4). These show that the delta comprises a
coarsening-upwards succession of medium- to coarse-grained
sand with gravel and thin clay layers locally present. A very
coarse-grained layer succeeded by a thinning-upwards suc-
cession in the Store Vorslunde borehole indicates that some
of the sand was deposited in channels. The thickness of the
delta sand varies from 40 m in Store Vorslunde to 50 m in the
Billund borehole. However, the Eg-3 well (Fig. 1), an old
deep exploration well, indicates that up to 100 m of sand may
be present.
Billund delta (Fig. 4). These show that the delta comprises a
coarsening-upwards succession of medium- to coarse-grained
sand with gravel and thin clay layers locally present. A very
coarse-grained layer succeeded by a thinning-upwards suc-
cession in the Store Vorslunde borehole indicates that some
of the sand was deposited in channels. The thickness of the
delta sand varies from 40 m in Store Vorslunde to 50 m in the
Billund borehole. However, the Eg-3 well (Fig. 1), an old
deep exploration well, indicates that up to 100 m of sand may
be present.
Study of outcrops
A spit system corresponding to the down-drift part of the
Billund delta outcrops along the fjords in eastern Jutland
(Fig. 5; Friis et al. 1998). These deposits are known as the
Vejle Fjord Formation (Fig. 2). During the last five years
these outcrops have been relatively well exposed, and new
sequence stratigraphic, biostratigraphic and sedimentological
studies have been carried out indicating that a major
NWSE-trending spit was located near the southern part of
Vejle Fjord. North of the spit, organic-rich, fine-grained sed-
iments were laid down in a lagoon. Sand-rich lagoonal sedi-
ments were deposited near inlets, e.g. at Dykær. South of the
Billund delta outcrops along the fjords in eastern Jutland
(Fig. 5; Friis et al. 1998). These deposits are known as the
Vejle Fjord Formation (Fig. 2). During the last five years
these outcrops have been relatively well exposed, and new
sequence stratigraphic, biostratigraphic and sedimentological
studies have been carried out indicating that a major
NWSE-trending spit was located near the southern part of
Vejle Fjord. North of the spit, organic-rich, fine-grained sed-
iments were laid down in a lagoon. Sand-rich lagoonal sedi-
ments were deposited near inlets, e.g. at Dykær. South of the
23
Fig. 5. Block diagram showing the deposi-
tional model of the Billund delta. In the
upper block diagram the seismic panel shows
a prograding delta and the pinchout between
the Billund and Almstok wells. The lower
diagram illustrates data from outcrops and
wells indicating the presence of a spit
complex. Note that the spit complex corre-
lates with the delta front at Store Vorslunde.
Seismic data courtesy of COWI A/S.
24
spit, ebb-dominated tidal deltas were deposited; examples of
these are exposed in a sandpit at Pjedsted (Fig. 6). At Lille-
bælt, upper and lower shoreface sediments were deposited,
and are excellently exposed in coastal cliffs at the old Lillebælt
bridge (Lillebæltsbro) on Funen and at Børup (Fig. 1). The sedi-
mentological study of the Vejle Fjord Formation indicates
that the sediments were laid down in a wave-dominated depo-
sitional environment with some tidal influence (Rasmussen
et al. 2002).
these are exposed in a sandpit at Pjedsted (Fig. 6). At Lille-
bælt, upper and lower shoreface sediments were deposited,
and are excellently exposed in coastal cliffs at the old Lillebælt
bridge (Lillebæltsbro) on Funen and at Børup (Fig. 1). The sedi-
mentological study of the Vejle Fjord Formation indicates
that the sediments were laid down in a wave-dominated depo-
sitional environment with some tidal influence (Rasmussen
et al. 2002).
Future perspectives
The Billund delta may be one of the most important future
aquifers for drinking water in western and central Jutland.
Furthermore, the excellent seismic data and the good
outcrops in eastern Jutland make it possible to use the
Billund delta as a good analogue for Jurassic reservoir rocks
in the Central and Viking Grabens of the North Sea.
aquifers for drinking water in western and central Jutland.
Furthermore, the excellent seismic data and the good
outcrops in eastern Jutland make it possible to use the
Billund delta as a good analogue for Jurassic reservoir rocks
in the Central and Viking Grabens of the North Sea.
References
Dybkjær, K. & Rasmussen, E.S. 2000: Palynological dating of the
OligoceneMiocene successions in the Lille Bælt area, Denmark.
Bulletin of the Geological Society of Denmark 47, 87103.
Bulletin of the Geological Society of Denmark 47, 87103.
Friis, H., Mikkelsen, J. & Sandersen, P. 1998: Depositional environment
of the Vejle Fjord Formation of the Upper Oligocene Lower Miocene
of Denmark: a back island/barrier-protected depositional complex.
Sedimentary Geology 17, 221244.
of Denmark: a back island/barrier-protected depositional complex.
Sedimentary Geology 17, 221244.
Larsen, G. & Dinesen, A. 1959: Vejle Fjord Formation ved Brejning: sed-
imenterne og foraminiferfaunaen (oligocænmiocæn). Danmarks
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van der Keur, P., Olesen, S.E., Rasmussen, J., Rosenberg, P. &
Vosgerau, H. 2004: Pesticide leaching in Danish groundwater: identi-
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fication of vulnerable areas. Geological Survey of Denmark and
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chemistry. Bulletin of the Geological Society of Denmark 42, 5767.
Rasmussen, E.S., Dybkjær, K. & Piasecki, S. 2002: Miocene depositional
systems of the eastern North Sea Basin, Denmark. Development of
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sedimentological and stratigraphical principles in modern sedimentol-
ogy. Danmarks og Grønlands Geologiske Undersøgelse Rapport
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Fig. 6. Tidal sandstone deposits from an ebb-dominated delta succession
associated with a spit complex, deposited down-drift from the main
Billund delta. Pjedsted sandpit, for location see Fig. 1. Width of track
approx. 50 cm.
Authors' address
Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: esr@geus.dk
Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: esr@geus.dk
