Mechanical analysis of a natural example of onland gravity gliding: The role of river incision and deposition

Abstract

Gravity gliding implies rigid translation of a body down a slope where displacements are parallel to a tilted detachment plane. Although large-scale gravity gliding is commonly observed offshore, under conditions of high fluid overpressure and abundant upslope sedimentary supply, its occurrence on land is debated. We investigate the mechanical feasibility of such a process as well as the role of fluvial incision and sedimentation down the slope in the initiation of the gliding. We use a two-dimensional (2-D) finite element model combined with a 2-D failure analysis approach. The numerical models simulate the deformation and provide quantitative estimates of the failure criteria at the head and toe of the overburden. Analytical solutions approximate the numerical results by taking into account the fluvial incision and sedimentation, the internal friction angle, and the thickness and length of the overburden. Our models are based on a field example in the Andean foothills of Argentina, where gravity gliding of a 1000 m thick section is suspected above a crustal-scale anticline. The incision and sedimentation reduce and strengthen, respectively, the downslope resistance to contractional failure. The critical slope at which the gliding is initiated is reduced by fluvial incision and increased by sedimentation. We show that tectonic uplift may lead to large-scale gravity gliding on land where the overburden thickness is less than 2000 m. Incision facilitates and localizes the frontal shortening. Incision greater than 1000 m may trigger gliding for overburden up to 4000 m thick, while sedimentation thicker than 1000 m inhibits gliding. These results show that thin-skinned onland gravity gliding could be common in tectonically active regions where incision is important.

Topographic controlled forcing of salt flow: Three‐dimensional models of an active salt system, Canyonlands, Utah

“…The contribution of salt flow into the canyon [ Potter and Mcgill , ; McGill and Stromquist , ] versus shortening of the overburden due to gravity gliding [ Huntoon , ; Messager et al ., ] as mechanisms for the formation of the Meander Anticline has yet to be clearly defined. The models present evidence that indicate that the Meander Anticline is a combination of both salt flow and overburden gliding, but when salt is confined or even exposed on a 100 m scale, salt flow predominantly contributes to the formation of the Meander Anticline (Figure b).…”

“…The 1–2°NW regional dip, indicated by surface measurements [ Huntoon et al ., ] and subsurface interpretation [ McCleary and Romie , ; Condon , ], has been frequently called for to accommodate strain via gravity gliding [ Huntoon , ], downdip salt flow [ Mcgill and Stromquist , ], or a combination of the two [ Ely , ]. Results of numerical modeling indicate that gravity gliding could be initiated under the conditions of the Needles District, where the salt dip is 2°, overburden thickness is 0.5 km, and the length of the sliding sheet is 6–10 km [ Messager et al ., ]. Huntoon [] attributed the Meander Anticline primarily to shortening of the overburden due to gravity gliding at the Colorado River Canyon.…”

“…As the Colorado River continues to incise from the top to the base of the Paradox Formation, salt response and overburden spreading patterns will continue to evolve, much like the Kebenawa Ridge, Ethiopia [Mège et al, 2013], and dissolution along with shifts in salt flow patterns and rates may provide feedback on the river system such as changes in longitudinal profile, sedimentation, and incision rates [Benito et al, 2000;Pederson and Tressler, 2012]. Furthermore, recent numerical modeling experiments of active salt systems show that surface processes are a major influence on structural expression [Messager et al, 2014;Collignon et al, 2015]. Although our models do not simulate the evolution of an eroding landscape, we show that the current landscape can have a large impact on deformation patterns of both the salt and overburden and can negatively or positively influence the effect of other driving forces (e.g., salt geometry and overburden rheology).…”

“…Topography, salt geometry, rheology, and evolving structures contribute to this spatial complexity and can each individually influence regional deformation patterns. External forces that initiate salt-related deformation include tectonics [Daudré and Cloetingh, 1994;Vendeville and Jackson, 1994;Letouzy et al, 1995], sedimentation [Ge et al, 1997;Gemmer et al, 2004;Hudec et al, 2009;Trudgill, 2011;Goteti et al, 2012], hydrology and dissolution [Aftabi et al, 2010;Gutierrez et al, 2012;Guerrero et al, 2014], and differential unloading due to erosion [Mège et al, 2013;Messager et al, 2014;Collignon et al, 2015]. The structural expression is dependent not only on these external forces but also on internal conditions such as salt and overburden rheology, topography and relief, and salt geometry [Poliakov and Podladchikov, 1992;Letouzy et al, 1995;Ter Heege et al, 2005;Allken et al, 2013;Collignon et al, 2015;Kettermann et al, 2015].…”

Geomorphologic evidence for Plio‐Quaternary shortening in the southern Neuquén basin (40°S, Argentina)

“…Moreover, extensional structures in the basin have recently been reinterpreted as non‐tectonically driven by Messager et al . (,b). They hypothesized that normal faults observed on top of the Chihuido anticline, a basement‐cored anticline to the north of the study area, are not related to an extensional stress regime as proposed by Ramos (), but rather correspond to gravitational gliding of the thin‐skinned cover in response to a current uplift of the anticline.…”