Continental Deformation: Collisional Orogenesis to Passive Margin Processes



Journal Title

Journal ISSN

Volume Title



My research investigates continental deformation at opposing ends of the Wilson cycle, intracontinental collision and passive margin development. I present a map of NW Nepal river channel steepness (ksn), a proxy for rock uplift rate over 103-105 years, coupled with a seismotectonic model, and then expand this map and accompanying model to the entire Himalaya; and a subsidence analysis of the northern abyssal Gulf of Mexico (GoM), which I use to evaluate numerical models of North American dynamic topography. GPS shows southern Tibet creeps south at the same rate river terraces are deformed at the range front. The India-Asia intracontinental subduction zone, the Main Himalayan Thrust (MHT) is a lithospheric fault whose style of motion changes from seismogenic in the brittle upper-middle crust, to aseismic in the ductile middle-lower crust. I determine correlation coefficients between ksn and: MHT coupling, lithology, and precipitation using a series of cross-orogen profiles. Averaging the results reveals a strong correlation between ksn and MHT coupling (-0.6), a moderate correlation with lithology (0.3), and a weak correlation with precipitation (-0.1). This leads me to interpret the ksn map in terms MHT coupling. I use it to divide the range into 7 segments based on the size and position of clusters of high ksn rivers. At the other end of the Wilson cycle, in the post rift phase, passive margins develop, accumulate sediment, and subside. Numerical models of Mesozoic-Recent mantle circulation suggest that North America experienced a km of dynamic subsidence as the sinking Farallon slab passed beneath it. I tested this by conducting a subsidence analysis of the northern abyssal GoM, and show that it underwent three episodes of enhanced subsidence. First is early Cretaceous (142-97 Ma), second is early Cenozoic (65-49 Ma), and thirds is late Cenozoic (34 Ma – 10 ka) which correlate with thermal contraction and density driven subsidence, asymmetric basin filling, and flexure beneath a rapidly prograding shelf margin wedge, respectively. My results show that GoM subsidence can be adequately explained without the influence of the sublithospheric passage of a subducted slab.



Himalaya river channel steepness, Gulf of Mexico, Abyssal plains


Portions of this document appear in: Cannon, J. M., and M. A. Murphy. "Active lower crustal deformation and Himalayan seismic hazard revealed by stream channels and regional geology." Tectonophysics 633 (2014): 34-42.