Do faults trigger folding in the lithosphere?

Abstract

A number of observations reveal large periodic undulations within the oceanic and continental lithospheres. The question if these observations are the result of large- scale compressive instabilities, i.e. buckling, remains open. In this study, we support the buckling hypothesis by di- rect numerical modeling. We compare our results with the data on three most proeminent cases of the oceanic and continental folding-like deformation (Indian Ocean, Western Gobi (Central Asia) and Central Australia). We demon- strate that under reasonable tectonic stresses, folds can de- velop from brittle faults cutting through the brittle parts of a lithosphere. The predicted wavelengths and finite growth rates are in agreement with observations. We also show that within a continental lithosphere with thermal age greater than 400 My, either a bi-harmonic mode (two superimposed wavelengths, crustal and mantle one) or a coupled mode (mono-layer deformation) of inelastic folding can develop, depending on the strength and thickness of the lower crust.