Constraining the onset of orogenic contraction in fold-and-thrust belts using sedimentary stylolite populations (Umbria-Marche Apennines, Italy)
Résumé
Stylolites are pressure solution structures, the roughness of which yields quantitative information about the magnitude of the normal stress applied to the stylolite plane. The stress magnitude is calculated from the cross
over length (Lc) determined using the signal analysis of a 2D track. For a sedimentary, bedding-parallel stylolite
(BPS), Lc scales to the magnitude of the vertical maximum principal stress σ1, hence to the burial depth at the
time the roughness of the stylolite froze. We present a dataset of nearly 200 BPS from Meso-Cenozoic folded
carbonates across the Umbria Marche Apennine Ridge. The BPS population is used to address the discrepancies
between Lc values obtained by using different signal analysis methods. Assuming that in compressional settings
burial-related pressure-solution more probably halts because of the switch of σ1 from a burial-related vertical
attitude to a tectonic-related horizontal attitude, the vertical stress magnitudes derived from the inversion of the
BPS roughness were combined to burial models at each investigated fold to reconstruct the absolute timing at
which the orogenic stress started to prevail. The results indicate that the onset of horizontal compression started
at ~10 Ma and ~8 Ma in the innermost and outermost folds, respectively, and predated fold development as
indicated by the age of growth strata. These results establish Stylolite Roughness Inversion Technique as a
reliable depth gauge that enables refining the timing of the onset of contraction in fold-and-thrust belts.
Origine : Publication financée par une institution
Licence : CC BY - Paternité
Licence : CC BY - Paternité