Tschingelhörner with Glarus thrust in the Glarus Alps seen from the Southeast near Sengnas Sut.
More pictures of Glarus thrust.

This is an old homepage - updated until November 2004

Bas den Brok
Senior Lecturer Structural Geology and Tectonics
Geologisches Institut ETH, Sonneggstrasse 5, CH-8092 Zürich
Tel. +41 1 632 3664, Fax. +41 1 632 1080, denbrok@erdw.ethz.ch

Education || Professional Experience || Publications || Teaching etc ...

Structural Geology? What is Structural Geology?

Who is NOT interested in geological structures?

My Scientific Interests

• Understanding/modeling Rock deformation mechanisms in nature, theory and experiment.
• Role of water: Pressure solution, stress-corrosion micro cracking, grain boundary migration, force of crystallisation.
• Ductile deformation of quartz (mechanisms, microstructures, crystallographic preferred orientation development).
• Mechanics of thrust motions (Glarus nappe in Glarus Alps, Tuscan nappe in Apuane Alps).
• Low angle thrusts and extensional detachments.
• Regional geology of Glarus Alps (Switzerland) and of Alpi Apuane (Italy).
• Deformation mechanisms leading to oil- and gas-production induced reservoir compaction.

Effect of elastic strain on dissolution and growth microstructures on very soluble salts (K-alum, sodium chlorate, KDP) (DFG financed PhD study of J. Morel) [abstract]. Literature: (i) S.W.J. den Brok, J. Morel (2001) The effect of elastic strain on the microstructure of free surfaces of stressed minerals in contact with an aqueous solution. Geophysical Research Letters 28 (4), 603-606 [view at publisher]. (ii) J. Morel and S.W.J. den Brok (2001) Increase in dissolution rate of sodium chlorate induced by elastic strain. Journal of Crystal Growth 222, 637-644 [view at publisher].

Temperature-driven fibre growth in wet salt aggregates (part of diploma thesis M. Sieber) [abstract]. Literature: S.W.J. den Brok, C.W. Passchier, M. Sieber (1998) Fibre growth in wet salt aggregates in a temperature gradient field. Mineralogical Magazine 62 (4), 527-532 View at IngentaConnect || View at Publisher || Abstract and some pictures.

Pressure solution compaction of sodium chlorate aggregates (part of diploma thesis M. Zahid) || [abstract]. Literature: S.W.J. den Brok, M. Zahid, C.W. Passchier (1999) Pressure solution compaction of NaClO3 and implications for pressure solution in NaCl. Tectonophysics 307, pp. 297-312 doi:10.1016/S0040-1951(99)00103-1

In-situ microscopic study of microcracking in wet sodium chlorate single crystals (part of diploma thesis M. Zahid) || [abstract]. Literature: S.W.J. den Brok, M. Zahid, C.W. Passchier (1998) Cataclastic solution creep of very soluble brittle salt as a rock analogue. Earth and Planetary Science Letters 163, 83-95 doi:10.1016/S0012-821X(98)00177-0

In-situ microscopy study of ductile shear zone development by cataclastic solution creep in sodium chlorate aggregates (DFG financed PhD study of M. Zahid) [abstract] [abstract-2].

Pressure solution indentation experiments on K-alum single crystals (diploma thesis of G. Melisa) [abstract] || [abstract2-html] [pdf] We indented potassium alum single crystals with metal pistons in the presence of saturated potassium alum solution. In these experiments the indentation is driven by a chemical reaction rather than by stress. The pistons oxidise in the weakly acid alum solution. Pistons were coated at the side and could only react at the contact with the alum. Indentation rate appeared to be inversed proportional to the stress. Our experiments show that chemical reactions may drive deformation, leading to a very different mechanical behaviour where stress would play an only minor role.

The Glarus Alps are a fascinating part of the Swiss Alps, especially because of the famous Glarus Thrust and the Lochseiten Limestone, over which it thrusted. Here, Conrad and Arnold Escher von der Linth (probably) were the first to recognise that huge masses of older rocks (Permian "Veruccano") unconformably rested on younger Mesozoic and Tertiairy rocks and proposed the existence of an overthrust. This idea was abandoned, and Arnold Escher later proposed the existence of a complicated fold structure with flat-lying overturned limbes to explain the observations (the so called "Glarner Doppelfalte", see Figure above).

We study deformation microstructures related to the overthrusting of Glarus nappe (diploma thesis of O. Jagoutz) [abstract1] || [abstract2] || [abstract3] [pdf]

Pictures of Glarus thrust.

The Glarus thrust at the American Museum of Natural History:
http://www.amnh.org/rose/hope/creatinghope/expeditions/q2_ex8_main.html


FURTHER PROJECTS

• Mitigation of oil- and gas-production induced surface subsidence (post-doctoral project Dr. P. Wanten) [abstract].

• In-situ microscopic study of grain growth in wet sodium chlorate aggregates (part of diploma thesis M. Zahid). || [abstract]. Literature: S.W.J. den Brok, M. Zahid, C.W. Passchier (1999) Stress induced grain boundary migration in very soluble brittle salt. Journal of Structural Geology, VOL. 21, pp. 147-151. doi:10.1016/S0191-8141(98)00112-6

• Construction of pressure controller for in-situ microcopy experiments (diploma thesis of G. Buchholz).

• Gravity-driven motion of fluid inclusions in very soluble salt (K-alum) (diploma thesis of M. Sieber).

• Crystallisation force of gypsum. Development of fibrous gypsum veins (diploma thesis of Nynke Keulen). Keulen, N. T., den Brok, S.W.J., Spiers, C.J. (2001) Force of crystallisation of gypsum during hydration of synthetic anhydrite rock. 13th DRT conference Deformation Mechanisms, Rheology, and Tectonics, Noordwijkerhout, The Netherlands 2001. || Abstract

  

  Thin sections of natural fibrous gypsum veins (crossed polarisers). Note "static" recrystallisation of fibrous aggregate in right two pictures. Samples from Ober-Ehrendingen, Aargau.

• Measurement and interpretation of Quartz C-axes fabrics. Literature: den Brok, S.W.J. (1996) Influence of crystallographic orientation on pressure solution in quartzite. Journal of Structural Geology 18, 859-860. Bons, P.D., den Brok, S.W.J. (2000) Crystallographic preferred orientation development by dissolution precipitation creep. Journal of Structural Geology 22, 1713-1722.

  

• Microstructural study of meso-scale folds in the Namurian strata at the Namur Citadelle to find out whether these are of "tectonic" or of "sedimentary" origin (together with Dr. M. Sintubin and Prof. N. Vandenberghe from Leuven University, Belgium). || [pictures]. Literature: S.W.J. den Brok, M. sintubin, N. Vandenberghe (1997) Early "soft-sediment" and Late "hard-rock" Varsican deformation features in the Namurian strata at the Namur Citadelle (Belgium). Aardkundige Mededelingen 8, 69-72.

• Set up of a Griggs solid medium apparatus in the rock deformation laboratory and start a first series of deformation experiments on dry quartz single crystals to study the crystallographic orientation dependence on orientation of deformation lamellae (diploma thesis of D. Witmer). In 2001 start of PhD project: Experimental study into the effect of recrystallisation on lattice preferred orientation development in quartz (den Brok / Kunze).

  

  Examples of experimentally recrystallised natural quartzite (left two pictures) and natural single crystals of quartz (right two pictures).

Quarz grain approximately 0.5 mm in size deformed by pressure solution from above and below, and broken in parts. Fractures were filled in with fibrous chlorite aggregate. The quartz fragments were slightly rotated. Example from Olympic Mountains, Washington State.


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4 November 2004