A numerical modelling technique that can account for alternations of uplift and subsidence revealed by Late Cenozoic fluvial sequences

Relation between alternations of uplift and subsidence revealed by Late Cenozoic fluvial sequences and physical properties of the continental crust

“…Similar behaviour is also observed in younger crustal provinces with thick mafic underplating, such as parts of South America and the Arabian Platform in Syria and SE Turkey (e.g, Bridgland & Westaway, 2008b;Westaway, 2012). This behaviour contrasts with Archaean cratons, in which the combination of thick lithosphere and low radioactive heat production results in the absence of any mobile layer, leading to great stability and, as a result, the absence of terrace staircases (e.g., Westaway et _ al., 2003) or minimal vertical movement, as observed in the lower Dnieper (Matoshko et _ al., 2002;see above).…”

“…Westaway (2012) has suggested that these reversals represent phases of deformation of the mantle lithosphere that were induced by the preceding phases of LCFF and the 35 resulting crustal thickening and associated loading of the mantle lithosphere. They are thus only directly observable in regions where the mobile lower-crust is relatively thin, so its response to a phase of LCFF is correspondingly rapid, and the mantle lithosphere is relatively thick and stiff, so its response to the same phase of LCFF occurs significantly more slowly than that of the mobile lower-crustal layer.…”

“…Platform, a region of Late Proterozoic crust with thick mafic underplating, from the rivers Euphrates, Tigris, and Orontes, and support the deductions made in the present study regarding the relation between this effect, crustal and lithospheric properties, and climatic forcing (e.g., Demir et _ al., 2007Westaway, 2012).…”

“…(2012) and Donohue et al (2013) have not considered the possibility that lower-crustal flow might be induced by the pressure variations at depth caused by the evident lateral variations in erosion, or that erosion rates in any locality have varied over time in response to climatic forcing. There is no modelling technique that can explore all the various effects simultaneously; i.e., including the complex perturbations that develop to the thermal state of the crust as a result of the induced lower-crustal flow, and which act as a regulating feedback mechanism (Westaway, 2002a(Westaway, , 2007a, and the complexity of the deformation to the mantle lithosphere that may result (Westaway, 2012), as well as effects of independent preexisting lateral variations in the thickness and thermal state of the continental crust and of independent thermal and buoyancy effects within the sub-lithospheric mantle. We therefore draw the principal conclusion apparent from the empirical evidence, which is that the observed abrupt variations in uplift rates indicated by the fluvial incision, and the evidence for reversals between uplift and subsidence, are consistent with a thin mobile lower-crustal layer.…”

Quaternary fluvial archives and landscape evolution: a global synthesis

“…Similar mafic layers, added to the base of the crust by magmatism associated with mantle plumes, may likewise constrict the thickness of the mobile lower crustal layer in younger crustal provinces. Westaway (2012) has suggested that the occurrence of reversals in vertical crustal motion, as are observed in the Dnieper and Don (see above; Fig. 2), results from the interaction between isostatic compensation of erosion by lower-crustal flow and by deformation within the mantle lithosphere.…”