Almogave Boudins

January 23, 2006

Almogave_boudins copy

Provided by: Gabriel Gutierrez-Alonso, Universidad de Salamanca (Spain)
Summary authors & editors: Gabriel Gutierrez-Alonso

The photo above was taken from Almogarve Beach in southwestern Portugal and depicts an outstanding example of "Chocolate Tablet" boudins developed on a sandstone bed of the Carboniferous Mira Formation. Boudinage is a word (means sausage in French) coined by geologists to describe the way that layered rocks break up under extensional stress. The boudinage process causes parallel extension in a sedimentary bed or any other planar feature, like a dyke or a vein, producing sausage like features when observed normal to them or linear features when observed "face on" as in the above case. Note that the geologist taking measurements on the veins that fill the extension voids between the "boudins" is Arlo Weil, a structural geologist and paleomagneticist from Bryn Mawr College in Pennsylvania.

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