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

Abstract

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River terrace development in the NE Mediterranean region (Syria and Turkey): Patterns in relation to crustal type

“…6). The pattern of the modelled uplift history here is compatible with a thin mobile lower-crustal layer (~5-7 km thick), consistent with the known presence of the aforementioned thick layer of mafic underplating at the base of the crust beneath the Arabian Platform (Westaway, 2012;Westaway and Bridgland, 2014). In contrast with the Euphrates, and indeed with the Don (see above), the history of vertical crustal movement indicated by the Tigris sequence ( Fig.…”

“…These preservation types are as follows: (1) typical terrace staircase archives on dynamic (Phanerozoic) crust with a mobile lower layer, (2) stacked sequences in subsiding areas, in which accumulation of sediment is a significant positive-feedback driver of the subsidence, (3) sequences in ultra-stable cratonic regions (coincident with Archaean crustal provinces), which (as noted above) show evidence for neither uplift nor subsidence, but instead for the lateral accretion of sediments of different ages , and (4) records intermediate between patterns 1 and 3, showing alternations of uplift and subsidence, as seen in areas with thin mobile crustal layers, often of Proterozoic age (Westaway, 2012;Westaway and Bridgland, 2014; see above). The preservation patterns within archive type 1 are divisible into systems that have formed terraces in approximate synchrony with glacial-interglacial climatic fluctuation, those that have formed terraces less often than that and those (rare) systems in which terrace formation has occurred more frequently than once per glacial-interglacial cycle .…”

“…3). The records from these rivers were synthesized by Matoshko et al (2004) and further reviewed by Westaway (2008a, 2014), with detail of the prevailing crustal properties and their relation to the fluvial archives was further discussed by Westaway and Bridgland (2014). All three rivers have excellent fluvial archives, benefitting from research over very many years and well constrained by biostratigraphy, loess-soils overburden sequences and geochronology (Matoshko et al, 2004).…”

“…The preservation patterns of fluvial archives developed in the Arabian Platform would seem to belong to Pattern 4, since they show alternations between incision and aggradation, presumably in response to alternating uplift and subsidence (Figs 4-6; 8B). This is thought to be a consequence of the interaction between isostatic compensation by lower-crustal flow and by mantle processes (Westaway, 2012;Westaway and Bridgland, 2014). To clarify, it can be anticipated that isostatic compensation for surface processes can be generally accommodated in weak layers in the upper Earth (mantle and/or lower crust).…”

“…Thus the characteristic river terrace staircases observed in areas such as NW Europe have formed on relatively hot, dynamic Phanerozoic crust. It has also been shown that rivers on crust of an antiquity intermediate between Archaean and Phanerozoic (i.e., Proterozoic), which generally has a limited thickness of mobile lower crust, have produced fluctuating patterns of terrace formation and accumulation, suggesting oscillations between uplift and subsidence (Westaway, 2012;Westaway and Bridgland, 2014).…”