Passive margins getting squeezed in the mantle convection vice

Abstract

[1] Passive margins often exhibit uplift, exhumation, and tectonic inversion. We speculate that the compression in the lithosphere gradually increased during the Cenozoic, as seen in the number of mountain belts found at active margins during that period. Less clear is how that compression increase affects passive margins. In order to address this issue, we design a 2-D viscous numerical model wherein a lithospheric plate rests above a weaker mantle. It is driven by a mantle conveyor belt, alternatively excited by a lateral downwelling on one side, an upwelling on the other side, or both simultaneously. The lateral edges of the plate are either free or fixed, representing the cases of free convergence, and collision (or slab anchoring), respectively. This distinction changes the upper mechanical boundary condition for mantle circulation and thus, the stress field. Between these two regimes, the flow pattern transiently evolves from a free-slip convection mode toward a no-slip boundary condition above the upper mantle. In the second case, the lithosphere is highly stressed horizontally and deforms. For a constant total driving force, compression increases drastically at passive margins if upwellings are active. Conversely, if downwellings alone are activated, compression occurs at short distances from the trench and extension prevails elsewhere. These results are supported by Earth-like models that reveal the same pattern, where active upwellings are required to excite passive margins compression. Our results substantiate the idea that compression at passive margins is in response to the underlying mantle flow that is increasingly resisted by the Cenozoic collisions.

Coastal staircase sequences reflecting sea-level oscillations and tectonic uplift during the Quaternary and Neogene

“…Such a widespread geomorphic record of long lasting uplift (i.e. Miocene and older) represents convincing long-term evidence of the global compression against coastal margins so well exhibited through sequences including the MIS 5e benchmark Yamato et al, 2013).…”

“…We previously advocated that this apparent uplift could result from an increasing generalized compression of continents during the Cenozoic . This would result in the compression of any margin, and uplift would be symptomatic (Yamato et al, 2013). We dismissed alternative mechanisms, such as dynamic uplift as a response to mantle flow or post-glacial rebound.…”

“…Tectonic inversion of the rifted margins is probably the most important aspect generating uplift at passive margins but this aspect requires a kinematic reorganization at the plate tectonics scale that may result in ubiquitous uplift (see Pedoja et al, 2011). During the Cenozoic, changes in plate tectonics, in particular the disappearance of the Tethys and Farallon slab, the anchoring of the Nazca slab in the deep mantle (Husson et al, 2012) and the Alpine collision, increased the overall compression in the lithosphere, which in turn could have triggered deformation and uplift not only at both active and passive margins (Yamato et al, 2013).…”

Break-up and seafloor spreading domains in the NE Atlantic

“…Doré & Lundin 1996;Japsen & Chalmers 2000;Lundin & Doré 2002;Ritchie et al 2003;Gomez & Verges 2005;Doré et al 2008;Stoker et al 2010;Tuitt et al 2010;Japsen et al 2012;Yamato et al 2013;Døss-ing et al 2016). Cenozoic compressional domes have been described on the Vøring, Faroe -Shetland and Hatton margins, in the Rockall Basin (for a short summary see Kimbell et al 2016), and in the NE Greenland margin (Price & Whitham 1997;Hamann et al 2005).…”

Rifts and Rifted Margins: A Review of Geodynamic Processes and Natural Hazards

“…Additionally, passive margin deformation may be influenced by far-field plate boundary forces such as ridge push [Bott, 1991], basal drag [Yamato et al, 2013], or compressive stress resulting from a lateral buoyancy gradient between continents and ocean [Artyushkov, 1973]. These forces manifest in the interior of the plate and activate zones of intraplate weakness [Hillis et al, 2008].…”