Geology of Northern Switzerland€¦ · Nagra (Geologist / Project Manager Field Investigation)...

Herfried Madritsch Nagra (Geologist / Project Manager Field Investigation)

Geology of Northern Switzerland

Overview & some key questions regarding the region’s seismic exploration

Annual Convention 2015 Baden 20th June 2015

Background

DMT Petrologic: G. Rybarczyk, F. Rost

geosfer ag (St. Gallen): H. Naef, P. Hammer, T. Ibele

Geologisches Institut Universität Bern: H.R. Bläsi, A. Matter, A. Pfiffner

Départment des Geosciences Université de Fribourg: J. Mosar, D. Egli, M. Diem, M. Gruber

Geological Institute Universität Jena: J. Kley, A. Malz

Geoexplorers (Liestal): S. Schefer

Gruner Böhringer AG (Oberwil): P. Jordan, D. Arndt, J. Pietsch

Proseis AG (Zürich Oerlikon): B. Meier, P. Roth, P. Kuhn, S. Heuberger, S. Muff, B. Steiner

Nagra: W. Albert, J. Becker, P. Birkhäuser, P. Blaser, G. Deplazes, L. Kiefer, B. Kunz, M. Ruff, M. Schnellmann, T. Vietor

Ackknowlegments (contributing & supporting colleagues)

Geological Setting: The bigger picture

Nagra 2014

Geological Setting: Central Northern Switzerland

Tectonic map & synoptic stratigraphic profile (Nagra 2014)

Presentation concept:

Modified from Müller et al. 2002

«A journey through time»

1 Late Palezoic structures

2 Mesozoic stratigraphy

3 Late Cenozoic tectonics

Late Paleozoic structures

Late Paleozoic: Crystalline basement

Polyphase deformed gneisses & granitic intrusions

Crystalline Rocks are only exposed in the southern Schwarzwald Massif

Major Late Variscian fault zones

(Franzke in prep.)

Filename 9

Late Paleozoic: Permocarboniferous Trough

Carboniferous & Clastic sediments (coal bearing) Compilation of Permocarboniferous sediments (Leu 2008)

Late Paleozoic wrench faulting let to the formation of Permocarboniferous troughs


Top Basement map of northern Switzerland with compilation of Permocarboniferous sediments (Leu 2008)

Tectonic model of the trough

Diebold et al. 1991


Diebold et al. 1991 Marchant et al. 2000

Tectonic Model of the trough: wide range of possible interpretations


Modified from Naef & Madritsch 2014

Aided by the high quality new seismic data the tectonic map of the trough was updated (> see follow-up presentation by B. Meier)

Mesozoic stratigraphy

Triassic: Evaporites

Anhydrite of the Lower Keuper

Early Triassic Mesozoic transgression Shallow marine to terrestrial environment Evaporites in the Lower & Middle Muschelkalk and the Keuper Formation Future detachment horizons during compressive Alpine foreland deformation

Ductile deformation of anhydrites in the Folded Jura

Triassic: Aquifers

Limestones & Dolomites of the Upper Muschelkalk Well cores of Upper Muschelkalk from the geo-thermal well Schlattingen-1 (see Frieg et al. 2015)

Early Triassic Mesozoic transgression Shallow marine to terrestrial environment Limestones & Dolomites of the Upper Muschelkalk Potenitally important aquifers!

Triassic: Marls

More details on tomorrow’s excursion!

Keuper sediments exposed in the clay pit of Frick

Liassic: Staffelegg-Formation

Homogeneous claystones of the Frick Member Frequent «hard beds» within the Gross Wolf Member

Revised stratigraphy by Reisdorf et al. (2011) Strongly condensed section (thickness of 20 – 50 m) Consituted of several different members containing clay-, lime and / or sandstones Characterized by lateral facies transistions

(e.g. Wetzel et al. 2003)

?


According to Nagra’s host rock definition the Staffelegg Formation consitutes to the «lower confining units» of the Opalinus Clay

Significant for site selection in SGT-E2

(e.g. Wetzel et al. 2003)

Facies distribution of the Staffelegg Fm. in northern

Switzerland (Kiefer et al. 2015)

?


Overview of the Frick clay quarry


Dogger: Opalinus Clay

Clay stone deposited in a shallow epicontinental sea (70-130 m thick) Very high clay content (> 45 %) Regarded as the prioritory host rock for the disposal of radioactive waste in Switzerland

?

Paleogeographic situation at beginning of Opalinus Clay deposition (after Allia 1996)

Opalinus Clay in cores of the Benken well (Nagra 2002)


Main advantage over other host rock candidates: Very homogenous over several scales

Nagra 2002


Main advantage over other host rock candidates: Very homogenous over several scales

Further key properties very high sorption very low permeability self sealing properties

More details on Monday’s excursion to the Mont Terri rock laboratory

Upper Dogger: inkl. the «Brauner Dogger»

Comparatively complex stratigraphy between the Opalinus Clay & Base Malm Characterized by dramatic lateral facies changes due to increasingly differential subsidence On a regional scale, a western and an eastern facies area can be distinguished

Cross bedded limestone of the Hauptrogenstein Fm.

Western facies area Eastern Facies area

Sandstone intercalated clays of the Wedelsandstein Fm.


Upper Dogger: inkl. the «Brauner Dogger»

The «Brauner Dogger» sequence in the east was proposed as potential host rock for LLW during SGT-E1 (Nagra 2008)

Intercalated hard beds suggest smaller scale facies changes within the sucession Key issue for seismic exploration (> see follow-up presentation by B. Meier)

Sandstone intercalated clays of the Wedelsandstein Fm. Seismofacies in the «Brauner Dogger» succession

Lower Malm: The Effingen Member

Part of the Wildegg Fm. deposited in an epicontinental basin Sandy marls intercalated by successions of limestone beds Strongly varying thickness across northern Switzerland (SW to NE: > 200m to < 50m) In the southwest the units was proposed as potential host rock for LLW

Deplazes et al. 2013

Upper Effingen Member with 3 distinct limestone beds successions & the

underlying very calcareous Gerstenhübel beds in the

Jakobsberg Quarry


Limestone bed successions with strongly decreased clay content can be correlated over several 100 m using various geological & geophysical data sets

Nagra 2014

Well correlation of the Wildegg Fm. incl the

Effingen Member using quantitative clay content

curves derived from geophysical logs


These continuous «hard beds» make the Effingern Member disadvantageous compared tow other nominated host rocks in particular Opalinus Clay


Tectonic outcrop-scale fracture systems as observable in limestone beds within the Effingen Member (Madritsch, 2015)

Upper Malm: Villigen Formation

Dominated by micritic limestones of varying thickness

Facies distribution & paleogeography of Effingen Wildegg & Villigen Fm. (compiled by Nagra 2014 based on Gygi 2000, 1990)

Massif, micritic limestones of the Villigen Fm.


Molasse sandstone (Early Miocene)

Siderolithic clay (Eocene) Carstified limestone (Upper Malm)

The Upper Malm represent the youngest Mesozoic sediments The Top Malm / Base Tertiary is marked by regional unconformity representing

~100 Ma of stratigraphic hiatus Very important seismic marker horizon (> see follow up presentation by B. Meier)

Late Mesozoic & Early Cenozoic: Uplift & erosion

Late Mesozoic & Early Cenozoic: Uplift & erosion Thermochronological data suggests approx.

800 m of uplift & erosion (Mazurek et al. 2006)

Most likely related to the developement of the Alpine forebuldge

Widely observed dilational mode-I type fractures most likely formed as a consequence.


Late Cenozoic tectonics

Miocene: Molasse basin formation & normal faulting

OMM clastics dissected by a normal fault USM marls intercalated by sandstones

The area of Northern Switzerland becomes affected by flexural bending

Miocene: Molasse basin formation & normal faulting

Seismically expressed normal fault cutting through

the Mesozoic succession and rooting in a deep-seated

basement fault

(> see also follow-up presentation by B. Meier)

Reactivation of late Paleozoic basement structures (cf. Diebold & Noack 1997)

Miocene: Hegau tectonics & volcanism

Egli & Mosar 2014

Kinematics of faulting & relation to volcanic activity are still poorly understood

Ongoing collaborative research with the Université de Fribourg

Late Miocene: Jura Folding

Folded of Mesozoic strata

The Lägern Anticline

Ductile deformation of Triassic evaporites

caused by «Distant-push»

Buxtorf 1916, Laubscher 1961


Late Miocene: Jura Folding

Indications for a secondary «thick-skinned» deformation phase underneath the Jura Mountains are increasing (e.g. Ustaszewski & Schmid 2007)

Possibly involving a reactivation of deep seated basement structures (Permocarboniferous Trough?)

Modified from Burkhard & Sommaruga 1999

Jura Folding: Defining today’s tectonic units

Nagra 2014

Late Miocene structures: Mandach-Thrust

Alternative interpretation approaches (Madritsch et al. 2013)


Jura Folding: Defining today’s tectonic units

Nagra 2014

Late Miocene structures: Baden-Irchel-Herdern Lineament

Alternative interpretation approaches (Madritsch et al. 2013)

Triangle structures proves to be restorable and be geometrically valid (Malz et al. 2015a)

Late Miocene structures: Baden-Irchel-Herdern Lineament

Late Miocene structures: Implications


Secondary detachments appear to have strong influence on the structural style

Malz et al. 2015b

The Paleozoic basement structures were reactivated multiple times

Late Miocene structures: Implications

Naef & Madritsch 2014 (> see also follow-up presentation by B. Meier)

Post-Pliocene: & what about Neotectonics?

Counterclockwise rotation of Central Italy with shortening in the southern Alps & Dinarides Instrumentally recorded recent shortening

across Swiss Alps: < 0.5 mm/a Time series are yet rather short (measurements close to error margin) &

may not be representative for the period of concern of a repository (1 Ma)


Quaternary deposits can be used as geomorphic markers to eventually detect or exclude subtle active deformation that might have occured over long time scales

Late glacial gravels in the Lower Aare Valley

Morphology of Early Pleistocene «Deckenschotter» Gravels



Morphologic analysis of the Mandach Thrust east of the Beznau Isle (Nagra 2014)

The potential of these geomorphic approaches has

increased significantly due to the availabilty of high resolution digital

elevation models

(e.g. based on LiDAR data with vertical accuracy ~ < 50cm)

Geological overview: Resume

Northern Switzerland has a fascinating geological history

Highlights include:

− Complex facies transitions developed during Mesozoic sedimentation

− World class type examples of thin-skinned deformation structures

− Evidences for polyphase reactivation tectonics

Nagra’s exploration activities have continuously contributed to a better understanding of the region’s geology

The gained knowledge is of relevance for both, the geoscientific and the geoeconomic community.

besten dank für ihre aufmerksamkeit

Thank you for your attention!

«See you tomorrow in the Jura Mountains»

Geology of Northern Switzerland€¦ · Nagra (Geologist / Project Manager Field Investigation)...

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