Collaborators:  Dr. Luther Strayer (California State University Hayward)

Research Abstract:
Large-displacement thust faults can profoundly influence the migration of fluids in low-grade, foreland fold-thrust belts during orogenesis.  One commonly envisioned scenario is that thrust faults collect fluids from deeper, more hinterland parts of the orogen and channel the fluids upward and outward towards the foreland of the orogen.  Such fluids can be rich in hydrocarbons, resulting in the formation of hydrocarbon reservoirs within and on the margins of these belts.  Many aspects of fluid movement through thrust belts are well understood; much remains to be known.

This proposed work will address two issues regarding fluid movement through fold-thrust belts with priority being given to the first one.  First, how important are thrust and normal faults in transmitting fluids during development of the belt?  How narrowly confined are fluids channeled in the faults?  How much fluid moves through individual faults?  Second, what meso- and microstructural processes facilitate migration of fluids?  Were fluids confined to intensely fractured/veined zones, or in zones of intensely foliated rocks?  These questions will be investigated in the Sun River Canyon area of the Rocky Mountain foreland fold-and-thrust belt by combining the results of stable isotope geochemistry and structural analysis.  This field area was chosen because it is considered a classic example of foreland fold-and-thrust belts, its geology and kinematic histories are well known, large-displacement faults are moderately well exposed, they are comprised dominantly of carbonate hanging wall and mudstone footwalls, and the region is potentially associated with hydrocarbon reservoirs.
 

Frontal carbonate thrust in the Sawtooth Range.	Close-up of the French thrust (shale-rich footwall on left; carbonate hanging wall on right).