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| Titel |
Three-dimensional basin analysis of the Heidelberg Basin, Upper Rhine Graben |
| VerfasserIn |
Gerald Gabriel, David Tanner, Nicole Martini, Hermann Buness, Charlotte M. Krawczyk |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250046497
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| Zusammenfassung |
| The Heidelberg Basin (HB) is a part of the Upper Rhine Graben that has undergone very
strong subsidence throughout its existence. We present the first results of three-dimensional
structural modelling of the basin, based on interpretation of reflection seismics, and
decompaction based on our own porosity data measured from core material. Firstly, we
mapped six horizons from all available industrial (ca. 100 km) and our own reflection
seismic sections (ca. 15 km), which lie within a 8 km radius around the Heidelberg
Uni-Nord 1/2 boreholes. We interpret these horizons as Base Quaternary, Internal and
Base Pliocene, Base Upper Miocene, Internal and Base Mid Miocene Hydrobien
beds.
This data was used to construct a three-dimensional geometrical model of the Heidelberg
Basin using GoCAD. The model shows that the HB has a N–S and E–W areal extent of
only 10 Ã 6 km, directly abutting the eastern boundary fault of the Upper Rhine
Graben. The strongest syn-sedimentary tectonic subsidence occurred during the Upper
Miocene, Upper Pliocene, and Quaternary. Furthermore, the sedimentary depocentre
shifted 2 km northwards over time to the present location, directly below the city of
Heidelberg.
Using 300 core samples, we determined the porosity of the Quaternary sediments from
their dry, saturated and submerged masses. We constructed an exponential porosity/depth
relationship for these rocks, which was then attributed to the model. We determined that
Quaternary sediments have porosities of over 60% at the surface, but towards the
base of the Quaternary, porosity is less than 35%. This strong decrease means, for
instance, that 740 m of sediments were compacted to produce the present ca. 500 m
thickness of Quaternary strata. This data were then used to decompact and backstrip the
whole 3D model using the software 3Dmove. The results show that the basin was
under continuous subsidence, with a slightly less subsidence rate during the Upper
Miocene, but with higher rates in the Pliocene to present-day, thus the basin subsidence
in general is accelerating. At the depocentre of the basin, the slowest rate rate of
subsidence was 0.1 mm a-1, while during the Quaternary this increased to 0.2 mm a-1.
In comparison, values for the Rhine Graben outside of the HB are ca. 30–50%
less. |
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