Palaeocene faulting in SE Sweden from U-Pb dating of slickenfibre calcite

• Estimating the timing of faulting is crucial to modelling tectonics, palaeoseismicity, landscape evolution and fault mechanics. Four slickenfibre calcite samples from a conjugate strike-slip fault set in a platformal limestone, SE Sweden, were dated using U-Pb. Three of the samples yielded an average age of 64.8 +/- 6.5Ma, while the fourth yielded a marginally younger age of 54.7 +/- 5.5Ma. Precipitation of the fibres is interpreted as syn-deformational. Age uncertainty and dispersion reflect incorporation of common Pb and tiny host-rock components into the dated calcite and/or possible fault reactivation through ca. 55Ma. We infer from crystal characteristics, stable isotopes (O-18 and C-13) and rare-earth elements that fibres formed in an environment rich in deep-seated fluids, at temperatures of 40-200 degrees C, with shear stresses exceeding 10 MPa and at a maximum burial depth of c. 4km. This Palaeocene faulting may reflect far-field stresses from shortening in the Alps.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geology (hsv//eng)

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