publication . Article . 2019

Modelling the influence of pre-existing brittle fabrics on the development and architecture pull-apart basins

Giacomo Corti; Rosa Nencini; Pietari Skyttä;
Closed Access
  • Published: 22 Nov 2019 Journal: Journal of Structural Geology, volume 131, page 103,937 (issn: 0191-8141, Copyright policy)
  • Publisher: Elsevier BV
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.
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Subjects
free text keywords: Geology, Petrology, Crust, Analogue modelling, Oblique case, Geology, Structural basin, Brittleness, Displacement (vector), Lateral movement, Deformation (mechanics)
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Communities
  • EPOS
Funded by
EC| EPOS IP
Project
EPOS IP
EPOS Implementation Phase
  • Funder: European Commission (EC)
  • Project Code: 676564
  • Funding stream: H2020 | RIA
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