Development of topography in 3-D continental-collision models

• Published in: Geochemistry, geophysics, geosystems : G3 Vol. 16; no. 5; pp. 1378 - 1400
• Main Authors: Pusok, A. E., Kaus, Boris J. P.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01.05.2015; John Wiley & Sons, Inc
• Subjects: Active margins; Amplitude; Banks (topography); Buoyancy; continental collisions; Dynamics; Evolution; Fronts; India-Asia collision; Lithosphere; Loads (forces); Mathematical models; Modes; mountain building processes; numerical modeling; Numerical models; Numerical simulations; Plateaus; Scaling; scaling analysis; Shape; Slope; Subduction; Topography; Topography (geology); Uplift; Upper mantle; Tibet; China, People's Rep., Xizang, Tibetan Plateau; Pakistan, Himalayas; China, People's Rep., Xinjiang, Tarim Basin
• DOI: 10.1002/2015GC005732
• ISSN: 1525-2027

Understanding the formation and evolution of high mountain belts, such as the Himalayas and the adjacent Tibetan Plateau, has been the focus of many tectonic and numerical models. Here we employ 3‐D numerical simulations to investigate the role that subduction, collision, and indentation play on lithosphere dynamics at convergent margins, and to analyze the conditions under which large topographic plateaus can form in an integrated lithospheric and upper mantle‐scale model. Distinct dynamics are obtained for the oceanic subduction side (trench retreat, slab rollback) and the continental‐collision side (trench advance, slab detachment, topographic uplift, lateral extrusion). We show that slab pull alone is insufficient to generate high topography in the upper plate, and that external forcing and the presence of strong blocks such as the Tarim Basin are necessary to create and shape anomalously high topographic fronts and plateaus. Moreover, scaling is used to predict four different modes of surface expression in continental‐collision models: (I) low‐amplitude homogeneous shortening, (II) high‐amplitude homogeneous shortening, (III) Alpine‐type topography with topographic front and low plateau, and (IV) Tibet‐Himalaya‐type topography with topographic front and high plateau. Results of semianalytical models suggest that the Argand number governs the formation of high topographic fronts, while the amplitude of plateaus is controlled by the initial buoyancy ratio of the upper plate. Applying these results to natural examples, we show that the Alps belong to regime (III), the Himalaya‐Tibet to regime (IV), whereas the Andes‐Altiplano fall at the boundary between regimes (III) and (IV). Key Points: Three‐dimensional numerical models of India‐Asia‐like collision zone and plateau buildup External forcing and strong crustal blocks favor development of high topography Scaling arguments to predict different modes of surface expressions