Structural syntaxes, tectonic aneurysms, and fault-bounded fore-arc slivers are important tectonic elements of orogenic belts worldwide. In this study we used high-resolution topography, geodetic imaging, seismic, and geologic data to advance understanding of how these features evolved during accretion of the Yakutat Terrane to North America. Because glaciers extend over much of the orogen, the topography and dynamics of the glaciers were analyzed to infer the location and nature of faults and shear zones that lie buried beneath the ice. The Fairweather transform fault system terminates by obliqueextensional splay faulting within a structural syntaxis, where thrust faulting and contractional strain drive rapid tectonic uplift and rock exhumation beneath the upper Seward Glacier. West of the syntaxis, oblique plate convergence created a dextral shear zone beneath the Bagley Ice Valley that may have been reactivated by reverse faulting when the subduction megathrust stepped eastward during the last 5-6 Ma. The Bagley fault zone dips steeply through the upper plate to intersect the subduction megathrust at depth, forming a fault-bounded crustal sliver capable of partitioning oblique convergence into strike-slip and thrust motion. Since ca. 20 Ma the Bagley fault accommodated more than 50 km of dextral shearing and several kilometers of reverse motion along its southern fl ank during terrane accretion. The fault is considered capable of generating earthquakes because it is suitably oriented for reactivation in the contemporary stress fi eld, links to faults that

The Saint Elias Mountains in southern Alaska are located at a structural syntaxis where the coastal thrust and fold belt of the Fairweather plate boundary intersects thrust faults and folds generated by collision of the Yakutat Terrane. The axial trace of this syntaxis extends southeastward out of the Saint Elias Mountains and beneath Malaspina Glacier where it is hidden from view and cannot be mapped using conventional methods. Here we examine the surface morphology and flow patterns of Malaspina Glacier to infer characteristics of the bedrock topography and organization of the syntaxis. Faults and folds beneath the eastern part of the glacier trend northwest and reflect dextral transpression near the terminus of the Fairweather fault system. Those beneath the western part of the glacier trend northeast and accommodate folding and thrust faulting during collision and accretion of the Yakutat Terrane. Mapping the location and geometry of the structural syntaxis provides important constraints on spatial variations in seismicity, fault kinematics, and crustal shortening beneath Malaspina Glacier, as well as the position of the collisional deformation front within the Yakutat Terrane. We also speculate that the geometrical complexity of intersecting faults within the syntaxis formed a barrier to rupture propagation during two regional Mw 8.1 earthquakes in September 1899.