TY - JOUR
T1 - Deep saltwater in Chalk of North-West Europe: origin, interface characteristics and development over geological time
AU - Bonnesen, Ellen P.
AU - Larsen, Flemming
AU - Sonnenborg, Torben O.
AU - Klitten, Kurt
AU - Stemmerik, Lars
N1 - Funding Information:
Drilling of the Stevns 1 and Stevns 2 boreholes was carried out by the Cretaceous Research Centre and financially supported by the Danish Natural Science Research Council (FNU). The water δO measurements were kindly supplied by Niels Bohr Institute, Copenhagen University. Per Jensen from (GEUS) is thanked for help with the borehole investigations, and Torben Bidstrup (GEUS) for the discussion of the seismic data from Zealand. We want also to thank John Boserup (GEUS) for help with cutting the chalk cores into manageable sizes for porewater extraction and technicians at the Department of Environmental Engineering, DTU for assisting in setup of the diffusion experiment and analytical analysis. We acknowledge the financial support of Copenhagen Energy and the Danish counties of Copenhagen, Frederiksborg and Roskilde to the project “The saltwater interface in carbonate aquifers in Northeast Zealand” during which the Karlslunde boring and porewater analyses were made. Furthermore, we want to thank Kristoffer Amlani Ulbak, a former Masters student at the Department of Environmental Engineering, DTU, for help with the porewater extraction and chloride analysis of the Karlslunde core. Two anonymous reviewers, the Associate Editor and the Managing Editor are thanked for their constructive reviews, which improved the manuscript significantly. 18
PY - 2009
Y1 - 2009
N2 - High-concentration saltwaters occur in many places in the regional Chalk aquifers of North-West Europe; to investigate deep occurrences, profiles of interstitial porewater chemistry have been studied from three 250-450m deep cores drilled in the eastern parts of Zealand, Denmark. At the studied location, saline water in the Chalk resides at depths from 40 to 80m and salinity increases with depth. Concentrations of chloride up to ca. 30,000ppm have been observed at depths of 400m. Measured vertical hydraulic heads in open boreholes suggest that advective groundwater flow is now restricted in deeper parts of the Chalk formation and diffusive transport is thus the predominant transport mechanism. Laboratory-measured porosity and effective diffusion coefficients were used as input to a numerical 1D diffusion model of the interface between freshwater in an upper, fractured aquifer and modified connate formation water below. The model satisfactorily simulated the observed chloride and δ
18O profiles. The diffusive refreshening of the Chalk formation has been going on for about 0.9 million years. The connate water in the Chalk of parts of the sedimentary basin seems to have been modified by transport of saltwater from underlying Mesozoic and Paleozoic sediments during compaction, which presumably ceased around 4 million years ago.
AB - High-concentration saltwaters occur in many places in the regional Chalk aquifers of North-West Europe; to investigate deep occurrences, profiles of interstitial porewater chemistry have been studied from three 250-450m deep cores drilled in the eastern parts of Zealand, Denmark. At the studied location, saline water in the Chalk resides at depths from 40 to 80m and salinity increases with depth. Concentrations of chloride up to ca. 30,000ppm have been observed at depths of 400m. Measured vertical hydraulic heads in open boreholes suggest that advective groundwater flow is now restricted in deeper parts of the Chalk formation and diffusive transport is thus the predominant transport mechanism. Laboratory-measured porosity and effective diffusion coefficients were used as input to a numerical 1D diffusion model of the interface between freshwater in an upper, fractured aquifer and modified connate formation water below. The model satisfactorily simulated the observed chloride and δ
18O profiles. The diffusive refreshening of the Chalk formation has been going on for about 0.9 million years. The connate water in the Chalk of parts of the sedimentary basin seems to have been modified by transport of saltwater from underlying Mesozoic and Paleozoic sediments during compaction, which presumably ceased around 4 million years ago.
KW - Chalk
KW - Denmark
KW - Diffusion
KW - Porewater chemistry
KW - Saltwater/freshwater relations
UR - http://www.scopus.com/inward/record.url?scp=70350426393&partnerID=8YFLogxK
U2 - 10.1007/s10040-009-0456-9
DO - 10.1007/s10040-009-0456-9
M3 - Article
SN - 1431-2174
VL - 17
JO - Hydrogeology Journal
JF - Hydrogeology Journal
IS - 7
M1 - 1643
ER -
