Lower crustal rheological expression in inverted basins

Abstract

Although lithospheric modelling has provided extraordinary insights into the processes that shape the continental crust, considerable uncertainty surrounds the basic rheology that governs behaviour at geological timescales. In part, this is because it has proved difficult to identify the geological observations that might discriminate, or unify, models of lithospheric rheology. In particular, the relative strength of lower crust and upper mantle remains a contentious aspect of continental lithospheric rheology. We show that various models for lower crustal rheology may produce distinct patterns of inversion in extensional sedimentary basins, consistent with some of the observed natural variability of inversion styles. Inversion of basin interiors, as is common in European Mesozoic basins, is favoured by a lithospheric rheology more sensitive to lateral thermal structure than to changes in the depth of the Moho, consistent with there being little strength contrast between the lower crust and upper mantle in these settings. In contrast, inversion of basin margins, particularly involving basinward verging structures, is consistent with a rheological sensitivity to the depth of Moho as would apply for a lower crust much weaker than the upper mantle. We use an example from central Australia to demonstrate this later response, together with thermochronologic data that suggests that a relatively weak lower crust in this setting may reflect abnormally high geothermal gradients.

Tectonic History of the Kaapvaal Craton: Constraints From Rheological Modeling

“…In summary, the tectonic signatures of the KP is more compatible with an inversion type of tectonics, where the upper crust of the KP was uplifted at the basin margin (KT and KP boundary) but the precursor rift basins of the KP that are westward were significantly deformed and thickened at depth (locus of maximum inversion intensity). This interpretation concurs with the inversion models for central Australia propounded by Sandiford et al ().…”

Numerical modeling of frontal and basal accretion at collisional margins

“…As can be seen in Figure 14, the Arltunga nappe complex consists of a stack of high-grade crystalline basement nappes in which the lower crust is involved as well [Teyssier, 1985]. To the south of this complex, clastic sediments accumulated in the Amadeus Basin [Dunlap et al, 1995;Sandiford et al, 2006]. The sediments were dislocated southward in a thin-skinned manner, and their basal thrusts were deformed by the growing nappe stack beneath.…”

Identifying mantle lithosphere inheritance in controlling intraplate orogenesis

“…Among these, the study of intraplate orogenesis has generated a number of mechanisms for deformation within a plate interior (Figure ). These mechanisms include preexisting lithosphere structures, the presence of fluids, the burial of highly radiogenic material and other temperature anomalies, mantle lithosphere instability, compositional strengthening, and strain rate [e.g., Ziegler , ; Ziegler et al , , ; Sandiford , ; Nielsen and Hansen , ; Hansen and Nielsen , ; Pysklywec and Beaumont , ; Sandiford et al , ; Stephenson et al , ; Heron and Pysklywec , ]. In this study, we examine the role of deep, long‐lived inherited lithospheric structures in deformation away from plate boundaries to allow for a greater understanding of the modern view of the conventional theory of plate tectonics (e.g., Figure ).…”