Structural analysis of the Mystery Bay area, New South Wales

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Abstract
The Ordovician sedimentary rocks of the southeastern Lachlan Fold Belt in the Mystery Bay area are folded into two approximately coaxial and subhorizontally plunging fold series: F1 and F2. Regional domains with internally consistent F1 and F2 trends are juxtaposed along strike‐slip faults. Locally developed kink bands commonly have a close spatial relationship with the domain boundaries. A faulted domain boundary is exposed in coastal rocks at Mystery Bay between north‐northeasterly trending turbidites and northwesterly trending complexly deformed cherts and pelites of the Wagonga Beds. South of the boundary fault, F1 and F2 trends in the turbidite succession exhibit a segmented 75° counterclockwise rotation about a near‐vertical axis within a 750 m wide zone parallel with the coast, relative to regional trends preserved farther south. The rotation zone hosts prolific subvertical kink bands and crenulations. The turbidite succession youngs towards the east and hence its present position is incompatible with its projected along‐strike position on the western limb of a major anticline exposing the older Wagonga Beds. At least three generations of faulting are recognized. Within the coastal Wagonga Beds, a set of post‐F1 faults is subparallel to the tectonic grain and probably had vertical motion. Two systems of post‐F2 strike‐slip faults include a conjugate system in coastal outcrops, with offsets indicative of layer‐normal shortening; and a series of northerly trending faults, with probable sinistral displacements, recognized from inland exposures.

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