Modelling the influence of pre-existing brittle fabrics on the development and architecture pull-apart basins. (February 2020)

• Record Type: Journal Article
• Authors: Corti, Giacomo; Nencini, Rosa; Skyttä, Pietari
• Is Part Of: Journal of structural geology. Volume 131(2020)
• Publication Date: 2020-02
• Subjects: Pull-apart basins -- Pre-existing brittle structures -- Reactivation -- Analogue modelling; Geology, Structural -- Periodicals; Géomorphologie structurale -- Périodiques; Geology, Structural; Periodicals; 551.805
• DOI: 10.1016/j.jsg.2019.103937
• Languages: English
• ISSNs: 0191-8141

Abstract

Abstract: We use new analogue modelling experiments to analyse the development of pull-apart basins in an upper crust characterised by the presence of pre-existing discrete fabrics. As in previous models, lateral movement of rigid basal plates induced strike-slip deformation of a sand-pack. Local extension allowing the formation of a pull-apart basin was produced by the step-over geometry of the master faults; in this area, a basal silicone layer was introduced to distribute deformation and reproduced a weaker crust in the basin. Conditions of neutral, overlapping and underlapping interacting master faults were reproduced. The model upper crust, modelled by a sand mixture, was characterised by the presence of pre-existing structures; the orientation of these inherited heterogeneities was systematically varied in different experiments. Model results indicate that, depending on their orientation with respect to the strike-slip displacement, pre-existing structures can be reactivated both within and at the margins of the pull-apart basins. Inside the basin, reactivation occurs when the pre-existing structures are orthogonal or sub-orthogonal to the strike-slip displacement; in this case, the pre-existing fabrics delay the development and linkage of cross-basin faults and increase the complexity of the deformation pattern giving rise to a new set of faults characterised by an atypical trend. Pre-existing fabrics oblique to the local extension direction may be partly reactivated in the central part of the basin as segments of cross-basin faults. At the margins of the pull-apart, reactivation occurs if the fabrics spatially coincide with the lateral boundaries of the silicone layer. In these conditions, reactivation allows a faster development of the border faults, which are less segmented than in the homogenous models; this also results in a more regular final geometry of the pull-apart. Highlights: Analogue models reproduce pull-apart basins in the presence of inherited discrete brittle fabrics. Models show reactivation of inherited structures in specific conditions. Fault reactivation may occur within and at the margins of the pull-apart basins. Reactivation within the basin gives rise to faults with atypical trend. Reactivation at the margins controls the shape of the pull-apart basin.