Alluvial Architecture of the Late Cretaceous Prince Creek Formation, North Slope, Alaska

Peter P. Flaig¹, Paul J. McCarthy¹, Erik Brandlen¹, and Anthony R. Fiorillo^2
1University of Alaska-Fairbanks, Fairbanks, AK
²Museum of Nature and Science, Dallas, TX

The Late Cretaceous Prince Creek Formation is exposed in bluffs along a 50 km stretch of the Colville, Kogosukruk, and Kikiakrorak rivers on the North Slope of Alaska. Complex alluvial architecture within bluffs was captured by means of careful photography along with the production and interpretation of photomosaics. Photomosaics were graphically coupled with measured stratigraphic sections for comparison of stratigraphy with alluvial architecture. Photomosaics/stratigraphy indicate that the alluvial architecture is laterally/temporally variable and includes (1) vertical and lateral accretion within classic ribbon sandbodies, (2) predominantly lateral accretion and heterolithic fill within sheet sandbodies, and (3) accretion of floodplain fines. Siltstone, mudstone, and shale are common in this system while medium-to coarse-grained material is extremely rare. Sandstones are predominately fine-grained, with ripples being the most common bedform. Root-traces are nearly ubiquitous within sandbodies, suggesting seasonally dry conditions. Heterolithic fill in channels may suggest a marine influence on the system. Non-channelized, finer-grained facies are interpreted as crevasse splays, levees, lakes, peat-bogs, and paleosols. Laterally stable ribbon sandbodies are interpreted as anastomosed channels while tabular sheet sandstones with prominent lateral accretion surfaces are interpreted as low-energy meandering streams. Ribbon sandbodies and sheet sandstones are often found stratigraphically at the same level, though they may be separated by floodplain fines. Meandering and anastomosing channels coexist in this fine-grained system, suggesting large evolving splay complexes adjacent to meandering trunk channels. This view is consistent with a paleoenvironmental interpretation of the region as a low-relief coastal plain containing a widespread, low-energy alluvial system.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas