I visited Spain and SW Portugal last week and couldn't resist a short visit to the folded and boudinaged Carboniferous turbidites near Almograve, SW Portugal. Chocolate boudinage structures are not all that common, but here there are a few superb examples right on the beach. Chocolate boudinage implies uniform flattening, with extension along both X and Y strain axes (Figure 14.17a in my textbook).
Brittle and ductile: The boudinage is primarily a brittle process, as portrayed by quartz-filled fractures (white), while the folding is ductile (although very low temperature, probably <300 C). What a beautiful area to study cleavage formation, folding, fracturing and boudinage!
See Reber et al. (Tectonoph. 2010, v 493, 187-195) and Marques (Tectonics 2010) for more information.
Chocolate boudinaged fold limb.
Axial planar cleavage in metasandstone.
Folded turbidites.
