Rheological inheritance controls the formation of segmented rifted margins in cratonic lithosphere

M Gouiza,J Naliboff

doi:10.1038/s41467-021-24945-5

Abstract

Observations from rifted margins reveal that significant structural and crustal variability develops through the process of continental extension and breakup. While a clear link exists between distinct margin structural domains and specific phases of rifting, the origin of strong segmentation along the length of margins remains relatively ambiguous and may reflect multiple competing factors. Given that rifting frequently initiates on heterogenous basements with a complex tectonic history, the role of structural inheritance and shear zone reactivation is frequently examined. However, the link between large-scale variations in lithospheric structure and rheology and 3-D rifted margin geometries remains relatively unconstrained. Here, we use 3-D thermo-mechanical simulations of continental rifting, constrained by observations from the Labrador Sea, to unravel the effects of inherited variable lithospheric properties on margin segmentation. The modelling results demonstrate that variations in the initial crustal and lithospheric thickness, composition, and rheology produce sharp gradients in rifted margin width, the timing of breakup and its magmatic budget, leading to strong margin segmentation.

Highlights

Observations from rifted margins reveal that significant structural and crustal variability develops through the process of continental extension and breakup
Numerical modelling supports this inferred link between pre-rift structure and rifted margin architecture, with a wide range of 2-D investigations demonstrating the first-order effects of the initial thermal and rheological structure on continental rifting9–14. 2-D modelling suggests that extension velocity[12,13,14], multiphase rifting[15,16], and complex deformation network localization[17,18,19] exert a first-order control on rifted margin structure
To examine the effects of these observed variations of lithospheric thickness, composition, and thermal structure on rift segmentation and margin architecture, we have developed thermomechanical models that assimilate the unique onshore geophysical constraints for each domain (Supplementary Fig. 1)

Summary

Introduction

Observations from rifted margins reveal that significant structural and crustal variability develops through the process of continental extension and breakup. As most rift basins form along (or near) former orogens[6], inheritance is commonly invoked to explain the segmentation of both rifts and rifted margins[7,8] Numerical modelling supports this inferred link between pre-rift structure and rifted margin architecture, with a wide range of 2-D investigations demonstrating the first-order effects of the initial thermal and rheological structure on continental rifting. To date no studies have explicitly examined the effects of a heterogeneous pre-rift lithosphere, with domains of varying rheology (i.e., composition, thickness, and thermal structure), on the 3-D evolution of continental rifting and rifted margin segmentation This in part reflects that many rifted margins initiate on complex pre-rift lithosphere[6], which may be difficult to accurately reconstruct without sufficient data to connect onshore and offshore domains[28]. Magnetic[34] and seismic[5] data indicate a diachronous continental breakup younging northward, with ca. 8

Methods

Results

Conclusion