Tectonic Development of the Alaska Range Suture Zone

We are studying a series of late Mesozoic and Cenozoic sedimentary basins in central Alaska that record the evolution of a major suture zone. A database for all the basins is being established by reconstructing the depositional systems; construction of a series of cross sections through the basins; and compositional analysis of sandstones and conglomerates. Currently, we are focused on Neogene sedimentary basins located along the north-central flank of the Alaska Range that contain the record of uplift of the highest mountain range in North America, extensive low-sulfur coal reserves, and potential petroleum reservoirs. The east-west trending basins were filled by fluvial and lacustrine deposits and consist of the Miocene Usibelli Group (~ 800 m thick) and the Pliocene Nenana Gravel (~ 1000 m thick). The general questions we are addressing include: (1) How do basins form within the interior of collisional/accretionary orogenic settings? Can a conceptual model be developed for basin formation along suture zones? (2) What can the synorogenic deposits contained in these basins teach us about the Neogene uplift of the Alaska Range? Does the detrital record contain information on how deformation and uplift changed along strike and through time for this orogenic belt? What was the influence of paleoclimate on detrital composition during unroofing of the Alaska Range? (3) Coal from the Usibelli Group is becoming an increasingly important energy source for Alaska and for export to Pacific Rim countries. What were the depositional, tectonic, and climatic controls on coal deposition in these basins? Major goals of this ongoing research include documentation of the long term evolution of sedimentary basins along suture zones; delineation of along strike variations in the uplift history of the Alaska Range; and analysis of the distribution of potentially commercial coals for future exploration.

Digital relief map of the central and eastern Alaska Range. Thick coals of the Usibelli Group. Person (red shirt) in lower right corner.