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A sample from the Breakaway Shale in the Lake Moondarra area north of Mt Isa with an Australian one dollar coin, 23 mm in diameter, as scale. The central part shows a thrust duplex comprising seven horses, some of them internally folded. The roof thrust is very well defined, separating the shortened layers from the upper layers that do not record any contractional deformation. The basal decollement, on the right side, becomes a low-angle normal fault toward the centre, whereas on the left, it is faulted by a right-dipping, high-angle normal fault that is partially overturned (rather than inverted) by contractional deformation. Together, these two faults define a graben. In the bottom right corner, a series of domino-style faults and two antithetic, low-angle faults are also accommodating extensional deformation.

Published as Photograph of the Month in the Journal of Structural Geology.

PhotoID573

A sample from the Breakaway Shale in the Lake Moondarra area north of Mt Isa with an Australian one dollar coin, 23 mm in diameter, as scale. The central part shows a thrust duplex comprising seven horses, some of them internally folded. The roof thrust is very well defined, separating the shortened layers from the upper layers that do not record any contractional deformation. The basal decollement, on the right side, becomes a low-angle normal fault toward the centre, whereas on the left, it is faulted by a right-dipping, high-angle normal fault that is partially overturned (rather than inverted) by contractional deformation. Together, these two faults define a graben. In the bottom right corner, a series of domino-style faults and two antithetic, low-angle faults are also accommodating extensional deformation.

Published as Photograph of the Month in the Journal of Structural Geology.

PhotoID573

Photograph: Arne F. Scherrenberg

Reference: For more information see: Scherrenberg, A. F., and Rosenbaum, G. (2009). Photograph of the Month: Thrust duplex, low-angle normal faults and domino-style faults in laminated shale, Mt Isa, Australia. Journal of Structural Geology 31, 475.