"Analyses of Raft and Squeezing Salt Geometries in Permian Zechstein on and offshore northern Netherlands"

Dr. Frank Strozyk

Dr. Heijn van Gent

Picture_135 - FrankLogos

Picture_129 - Frankproject2
Top Salt (white mesh) and the Z3 stringer in the northern Dutch onshore (view from N).
The brittle Z3 intra-salt stringer (anhydrite and dolomite) is investigated on its structural features on different scales (regional, local, intra-, inter-, and well-scale). First results show that (1) the overall stringer geometry correlates to the intensity of halokinesis, (2) the stringer geometry locally strongly differs from Top Salt, (3) halokinesis and stringer deformation are strongly influenced by tectonic movements in the pre-salt (e.g. along the boundary of the Louwerszee Trough).
Picture_130 - Frankproject1
Seismic cross-sections and interpreted Z3 stringer in the less deformed Friesland area (western onshore). Note the smooth and continuouse, but wavey and locally broken (boudins) stringer surface. The study implies that this geometry may reflect earliest stages of stringer deformation during initial/low halokinesis. Furthermore, the observed structural features (i.e., fold frequency, boudin frequency) can be found back in hardly deformed and fragmented stringer parts in major salt structures. While the fold amplitude of the stringer highly increases with halokinesis, the fold frequency appears to remain the same...
Picture_131 - Frankproject3
E-W seimsic section northern Dutch onshore, highlighting that the stringer geometry is disharmonic to the Top Salt. Furthermore, the stringer/the salt is only locally effected by tectonics in the underburden ('corner flow'). This implies that the stringer and salt deformation is somewhat decoupled from under- and overburden tectonics, and vertical throws in the salt section much larger than expected from Top Salt geometry.
Picture_132 - Frankproject4
Finally, the stringer imaged in the 3D seismic volumes is of very complex geometry. This is most likely base on superimpoised, polyphase patterns of folds and boudins with offsets and stacks of stringer fragments. Interpretation of the structures implies that only one part of the stringer is visible in seimsic data (i.e., isolated fragments may represent the seismically resolved fold hinges, while the steep and thin fold limps are invisible), and that compressional and extensional (or complex sharing?) deformation mechanisms may have changed during time.
Picture_138 - SaltminevsSeismikFrank1
The big questions is: which part of the stringer is seismically imaged, and which structures can be interpreted from that?
Comparing  interpretations of the internal structure of salt diapirs from mining literature (Seidl, 1923; left image) with  the interior of similar structures in seimsic data (right image) implies that a large part of the stringer may be invisible. A model of a more or less connected stringer with isoclinal folds comes to mind. However, breaking of the brittle intra-salt stringers is not considered in the mining literature from the early last century. Consequently, their interpretations may be wrong.
Picture_140 - InterpretationFrankPicture_860 - Stringermodelsfoldsvsfloaters
Left: if we compare the seimsic data (top) with our initial interpretation (centre) and one based on salt mining literature (bottom), which interpretation is better? Right: Based on the seimsic data (top) there could be strong differences in the stringer and the salt deformation. The stringer could either be broken up and single fragments are sunken down, while the salt layers could be less deformed (centre), or the stringer is (more or less) connected and heavily folded, while the salt layers are strongly deformed (bottom). Note that stringer fragments in the first model sink into the lower salt section, while the stringer in model two still traces the boundary between both salts.
 
 
 


 

Movie of a rotating fold in the Zechstein.

Animated Illustration of van Gent et al (2011). The internal geometry of salt structures -. Journal of Structural Geology  33, 292-311.

Other articles in the category "salt deformation"

 

Publications

 

Theses

Heijn van Gent
Stress and strain from reflection seismic data. PhD-thesis. Geologie - Endogene Dynamik, RWTH Aachen. 198 pages (2010)
 

Nonreviewed

Peter Kukla, Janos Urai, John K. Warren, Lars Reuning, Stephan Becker, Johannes Schoenherr, Markus Mohr, Heijn van Gent, and several additional authors .
An Integrated, Multi-scale Approach to Salt Dynamics and Internal Dynamics of Salt Structures. AAPG Search and Discovery Article #40703, February 25, 2011, 87 pages. (2011)
 

Papers

Stefan Back, Heijn van Gent, Lars Reuning, Juergen Groetsch, Jan Niederau, Peter A. Kukla
3D seismic geomorphology and sedimentology of the Chalk Group, southern Danish North Sea. Journal of the Geological Society 168(2), 393-406. doi: 10.1144/0016-76492010-047 (2011)
 
Heijn van Gent, Janos Urai, Martin de Keijzer
The internal geometry of salt structures - a first look using 3D seismic data from the Zechstein of the Netherlands. Journal of Structural Geology - Special Issue: Flow of rocks: Field analysis and modeling - In celebration of Paul F. Williams' contribution to mentoring 33, 292-311. (2011)
 
Markus Mohr, John K. Warren, Peter A. Kukla, Janos Urai, Anton Irmen
Subsurface seismic record of salt glaciers in an extensional intracontinental setting. Geology, 35(11),963-966 (2007)
 
Markus Mohr, Peter A. Kukla, Janos Urai, G. Bresser
Multiphase salt tectonic evolution in NW Germany: seismic interpretation and retrodefromation. International Journal of Earth Sciences 94(5-6),917-941 (2005)
 

Abstracts

Heijn van Gent, Frank Strozyk, Janos Urai, Martin de Keijzer
Seismic interpretation of the internal geometry of the Zechstein evaporites - Large scale structures and internal stability. EGU General Assembly. Geophysical Research Abstracts, 13, pp. EGU2011-2265. Room 22 / Wed, 06 Apr, 13:30-17:00, / Room 22 / Wed, 06 Apr, 13:30-17:00. (2011)
 
Janos Urai, Peter Kukla, Heijn van Gent, Steffen Abe, Shiyuan Li, Guillaume Desbois, Johannes Schoenherr, Zsolt Schléder, Lars Reuning, and several additional authors .
Internal Dynamics of salt structures. Alpine Salt 2011: A workshop on Alpine Evaporites, Salzburg, Austria. 31 March. Invited Talk (2011)
 
Heijn van Gent, Janos Urai, Martin de Keijzer, Frank Strozyk
The internal geometry of the Zechstein - Seismic interpretation of coeval extension and compression. GeoDarmstadt 2010, Darmstadt, Germany, 10-13 October 2010, Hoppe, Röhling, Schütz (eds) Schriftenreihe der Deutschen Gesellschaft für Geowissenschaften, v (2010)
 
Janos Urai, Peter Kukla, Heijn van Gent, Steffen Abe, Guillaume Desbois, Johannes Schönherr, Zsolt Schléder, Lars Reuning, Stephan Becker
Internal Dynamics of Salt Structures. GeoDarmstadt 2010, Darmstadt, Germany, 10-13 October 2010, Hoppe, Röhling, Schütz (eds) Schriftenreihe der Deutschen Gesellschaft für Geowissenschaften, vol. 68, E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, 5 (2010)
 
Heijn van Gent, Janos Urai, Martin de Keijzer
The 3D geometry of the Zechstein Z3 carbonate/anhydrite member: implications for the study of salt structures and hydro-carbon production. AGU 90, Fall Meet. (2009)
 
Heijn van Gent, Janos Urai, Martin de Keijzer
The 3D geometry of the Zechstein Z3 carbonate/anhydrite member: implications for the study of salt structures and hydro-carbon production agu san francisco 2009. Eos Trans. AGU, San Fransisco, CA, USA, 90 (52) Fall Meet. Suppl., T33C-1931. (2009)
 
Heijn van Gent, Janos Urai, Peter A. Kukla
The 3D Geometry of the Zechstein Z3 Carbonate/Anhydrite Member: Implications for Salt Dynamics and Hydrocarbon Production. AAPG International Conference & Exhibition, Cape Town, South Africa, October 26-29, 2008. (2008)
 

Salt deformation Gallery

 

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