Tilting of continental interiors by the dynamical effects of subduction

Abstract

A mechanism is proposed to explain epeirogenic motions of craton interiors in terms of the response of the lithosphere to subduction. The effects of changes in sea level are distinguished from subsidence of the basement by analyzing the tilt of chronostratigraphic sequences in which the bounding horizons were deposited at approximately the same elevation with respect to sea level. As an example, the Late Cretaceous subsidence and Tertiary uplift of the western interior of North America is examined, and a maximum tilt amplitude of 3 km, with a horizontal deflection scale of approximately 1400 km, is inferred. The link between platform sedimentation and subduction is tested by using numerical models of mantle convection which mimic the subduction and by examining the horizontal scale of the deflections to the overlying lithosphere. It is found that this scale is relatively insensitive to the temperature contrast between the slab and the surrounding mantle, the flexural rigidity of the lithosphere, and even the physical process assumed to govern the subduction. The most important factor affecting the scale is the dip of the subduction zone, and shallower subduction angles (less than 45 ø) can produce horizontal deflections of the •,,aer of 1000 km or more. In contrast, the vertical scale of the deflection is sensitive to all the above parameters. Using these results, two subduction models are introduced which predict both the time and length scales of the North American tilt, and it is conjectured that the process may be responsible for other regions of platform subsidence where subducted

The dynamics of laterally variable subductions: laboratory models applied to the Hellenides

“…Ultimately, this flow is excited by density variations in the mantle, and that component of the topography is often referred to as dynamic topography (Ricard et al, 1984;Hager et al, 1985;Hager and Clayton, 1989;Cazenave et al, 1989;Mitrovica et al, 1989;Gurnis, 1993;Le Stunff and Ricard, 1995). Above the anomalies of the slabs, the amplitude of dynamic subsidence can exceed several hundred metres (Mitrovica et al, 1989;Gurnis, 1993;Zhong and Gurnis, 1994;Husson, 2006;Husson et al, 2012).…”

Models of mantle convection incorporating plate tectonics: The Australian region since the Cretaceous

“…Consequently, the best proxies for continental vertical motion come from relative sea-level (RSL) change, often observed as anomalous marine inundation of one continent with respect to the mean inundation of all continents [Hallam, 1992]. One of the best examples of such motion is the anomalous subsidence of the western United States during the Cretaceous [Bond, 1976;Cross and Pilger, 1978;Mitrovica et al, 1989] which has been quantitatively linked first to a shallowing dip angle of the Farallon plate subducting beneath North America and the subsequent uplift associated with the demise of subduction [Mitrovica et al, 1989;Burgess et al , 1997; LithgowBertelloni and .…”

Eroding dynamic topography

“…Revisiting poorly understood aspects of the geological record combined with sophisticated modeling of mantle flow has recently led to renewed interest in constraining and quantifying the dynamic contribution to surface topography [Mitrovica et al, 1989;Gurnis et al, 2000;Conrad and Gurnis, 2003;Forte et al, 2007;Hartley et al, 2011]. A summary of recent investigations on the subject can be found in Braun [2010].…”

“…Consequently, the amplitude and timing of dynamic topography might be better constrained by interrogating the past, whether it is through the sedimentary [Mitrovica et al, 1989;Heine et al, 2008], geomorphological [Hartley et al, 2011] or thermochronological record [Flowers and Schoene, 2010], as the time-integrated effect of mantle flow is less sensitive to our knowledge of crustal thickness.…”