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| Titel |
Constraints for estimating the future burial depth of host rocks for geological waste disposal: a case study from the Boom Clay, Campine area, Northern Belgium |
| VerfasserIn |
K. Beerten, M. De Craen, S. Brassinnes |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250066925
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| Zusammenfassung |
| An important requirement for geological formations hosting a repository for radioactive
waste is sufficient depth to ensure isolation of the waste for a very long time period, up to 1
Ma and beyond. Over such long timescales, the repository depth and the thickness of
the overburden may vary significantly due to various geodynamic processes. In
Belgium, the Boom Clay in the Campine area (NE-Belgium) is considered as reference
host formation for the geological disposal of radioactive waste. First results are
presented that illustrate the possible impact of future climate change (based on several
scenarios studied in the BIOCLIM project (BIOCLIM, 2001)) and tectonic movements
in the Campine area on the thickness of the sediment mass overlying the Boom
Clay.
At present, the subcrop area of Boom Clay in the Campine area is relatively flat (between
~ 0 m a.s.l. near the river Scheldt estuary in the west and ~ 60 m a.s.l. on the Campine
Plateau in the east) and is occupied by several sub-basins that belong to the rivers Meuse and
Scheldt. Future development of the area will heavily depend on the behaviour of
these rivers and tributaries throughout the considered timeframe, in response to
climatic changes and tectonic movements. The area is characterised by a long burial
history, with some minor isolated uplift and erosional events during the last 30
Ma.
In a global warming scenario during a long interglacial (> 50 ka AP), and/or in the case
of subsidence, (relative) sea-level may rise such that various parts of the Boom Clay area will
be occupied by the marine realm. This is likely to be a minimal erosion scenario because the
baseline for landscape evolution will rise in the upstream parts while estuarine and
marine deposition may increase the thickness of the overburden in the downstream
parts.
In the case of a continuation of Pleistocene glacial cycles, i.e. the alternation between
warm interglacials and cold glacials, the area will be exposed to erosion and denudation as
occurred before. From a detailed analysis of the geological record described in the literature it
is determined that during a future glaciation with significant sea-level fall, the river Scheldt
basin will become a tributary of the major river system occupying the North Sea valley. This
situation already existed ~ 400 ka BP ago, and was probably responsible for the formation of
the Flemish Valley. Today, this valley system is completely filled with sediment, but may be
reactivated during next glaciations. Together with extreme uplift rates taken from
the Maastricht area, south of the Boom Clay subcrop zone, the total amount of
erosion may add up to 100-150 m after 1 Ma, which is regarded as a conservative
value.
We conclude that constraints for future burial depths and erosion rates in the Campine
area should consider the combined effect of both climate change and internal geodynamics
(uplift/subsidence). Such effects can easily be deduced from geological archives in the region,
that take into account specific and local circumstances.
References
BIOCLIM (2001). http://www.andra.fr/bioclim/documentation.htm |
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