Reconstructing post-Jurassic overburden in central Europe: new insights from mudstone compaction and thermal history analyses of the Franconian Alb, SE Germany
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Published:2022-06-21
Issue:6
Volume:13
Page:1003-1026
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ISSN:1869-9529
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Container-title:Solid Earth
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language:en
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Short-container-title:Solid Earth
Author:
Freitag Simon, Drews MichaelORCID, Bauer Wolfgang, Duschl FlorianORCID, Misch David, Stollhofen Harald
Abstract
Abstract. The Franconian Alb of SE Germany is characterized by large-scale exposures
of Jurassic shallow marine limestones and dolostones, which are frequently
considered to be outcrop analogues for deep geothermal reservoir rocks in the
North Alpine Foreland Basin farther south. However, the burial history of
the Franconian Alb Jurassic strata is not well known as they were affected
by emersion, leading to extensive erosion and karstification with only
remnants of the original Cretaceous and Cenozoic cover rocks preserved. To
estimate the original thicknesses of the post-Jurassic overburden we
investigated the petrophysical properties and the thermal history of Lower
and Middle Jurassic mudstones to constrain their burial history in the
Franconian Alb area. We measured mudstone porosities, densities, and
maturities of organic material and collected interval velocities from
seismic refraction and logging data in shallow mudstone-rich strata.
Mudstone porosities and P-wave velocities vertical to bedding were then
related to a normal compaction trend that was calibrated on stratigraphic
equivalent units in the North Alpine Foreland Basin. Our results suggest
maximum burial depths of 900–1700 m, 300–1100 m of which is attributed
to Cretaceous and younger sedimentary rocks overlying the Franconian Alb
Jurassic units. Compared to previous considerations this implies a more
widespread distribution and increased thicknesses of up to ∼900 m for Cretaceous and up to ∼200 m for Cenozoic units in
SE Germany. Maximum overburden is critical to understand mechanical and
diagenetical compaction of the dolostones and limestones of the Upper
Jurassic of the Franconian Alb. The results of this study therefore help
to better correlate the deep geothermal reservoir properties of the Upper
Jurassic from outcrop to reservoir conditions below the North Alpine
Foreland Basin. Here, the Upper Jurassic geothermal reservoir can be found
at depths of up to 5000 m.
Funder
Bayerisches Staatsministerium für Wissenschaft, Forschung und Kunst
Publisher
Copernicus GmbH
Subject
Paleontology,Stratigraphy,Earth-Surface Processes,Geochemistry and Petrology,Geology,Geophysics,Soil Science
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