PRELIMINARY MAPPING AND DETRITAL ZIRCON GEOCHRONOLOGY FROM THE ERNIE LAKE REGION, CENTRAL BROOKS RANGE, ALASKA: IMPLICATIONS FOR PRE-MISSISSIPPIAN BASEMENT AND BROOKS RANGE ARCHITECTURE

The Brooks Range of northern Alaska is the result of Cretaceous arc-continent collision. Although original stratigraphic and facies relations are well characterized in the northern half of the range, the ages and primary relationships between individual map units of the metamorphosed, structurally complex southern Brooks Range are poorly known. Thus, there remain many uncertainties regarding the structural architecture and tectonic evolution of the metamorphic core, as well as whether there are any pre-Mississippian tectonic events recorded.

The Ernie Lake region is significant because it may contain the oldest rocks in the Brooks Range (the ca. 960 Ma Ernie Lake pluton and host rocks), but also the youngest rocks in the metamorphic core (rocks tentatively correlated with Mississippian Kekiktuk conglomerate). From the only work in the area (1:250,000 mapping), it is not clear as to which contacts between units are intrusive, structural, or disconformable.

We will present results of our new detailed mapping and U-Pb detrital zircon geochronology that provide new age constraints on units likely ranging in age from Proterozoic (pre- ~960 Ma) to Mississippian. In the context of this new work, we discuss implications for the crustal architecture of the Brooks Range, palinspastic restorations, and possible pre-Mississippian deformation.