Geoscience Reference
In-Depth Information
Fig. 3.6
Weischselian erosion and accumulation redistribution load recalculated in meters of water
load using averaged rock density (
left
) and its total isostatic uplift-subsidence effect in meters
(
right
)
the ocean load. Figure
3.6 (right)
shows that the sediment loading of marine areas
can cause isostatic subsidence five times greater than the loading by glacial meltwa-
ter. The uplift associated with erosion is smaller (<10% of the glacial isostasy) for
the Baltic area, but for some areas of coastal Norway it could be a significant part
of the observed postglacial uplift.
3.5 Conclusions
Although it is possible that bedrock erosion was evenly distributed between all the
glacial cycles, most of the modification of the bedrock surface and shaping major
overdeepened troughs was probably accomplished by the first glaciations of the
Quaternary. Younger glaciations mainly removed sediments deposited by previous
glacial cycles, reducing the thickness of the Quaternary succession and locally incis-
ing the bedrock surface. The isostatic effect of the glacial erosion and sedimentation
significantly impact the total postglacial rebound. Subsidence in submarine areas
adjacent to the continental glaciers can be much larger than that induced by the
postglacial rise in sea level. Isostatic uplift caused by erosion is minor for the Baltic
area, but could be a significant part of the observed postglacial uplift in coastal areas
of Norway.
Acknowledgments
This study was funded by the Research Council of Norway and StatoilHydro,
as part of the project “Ice Ages - Subsidence, Uplift and Tilting of Traps - The Influence on
Petroleum Systems” (Petromaks 169291; “GlaciPet”). The authors wish to express their gratitude
for the support. We also want to thank William W. Hay for constructive comments on an earlier
version of this chapter. We are grateful to Patrick Madison and Golden Software team for the
development of Surfer, MapViewer and other products that were involved in investigations. Thanks
also to M. Amantova who digitized numerous data used in the research.
