Structural Evolution of the Gilead Syncline Area within the Northeastern Brooks Range, Northern Alaska

Rocks adjacent to Gilead Creek, within the “Gilead syncline” in the frontal part of the northeastern Brooks Range (NEBR) in Alaska were structurally altered during multiple tectonic events that likely have different directions of tectonic transport. The tectonic history of the northeastern Brooks Range has been described by multiple workers (O'Sullivan 1991, O'Sullivan 1997, and O'Sullivan and Wallace, 1998) who used apatite fission track data to document the cooling history of the area. Their work shows that tectonic events that affected the Gilead syncline area at 60, 45, 35, and 27 Ma. The purpose of this study is to determine what the structural response to each of these tectonic events was and how they can be distinguished in the rock record. To do this, the following questions will be addressed in the study: 1) How was shortening accommodated in different parts of the mechanical stratigraphy? 2) How was shortening distributed throughout the stratigraphy in faulting, folding, and strain? 3) How do forward and hindward verging structures distribute shortening? 4) What are the roles of local detachments in strain accommodation? The Gilead syncline study area is located within the foothills of the Brooks Range, adjacent to the transition between the frontal Brooks Range (Collisional orogen) and the Colville basin (Foreland Basin) deposits. The NEBR and its foothills differ from the central Brooks Range in structural style because the mechanical stratigraphy in the NEBR is significantly different than the mechanical stratigraphy in the central Brooks Range, which has caused a different structural architecture to develop in the NEBR. At this time our understanding of the structure in the Gilead syncline area is in its infancy. This study will improve the current understanding of the structural evolution of the field area the role it plays in the structural evolution of the NEBR.