Geologic Map of the Christian Quadrangle, Alaska

Geologic Setting

Most of the Christian quadrangle is in the Porcupine Plateau; the northwestern part is in the southern Brooks Range, and the southern quarter is in the Yukon Flats. Outcrops of bedrock are poor or lacking, except in the Brooks Range. Although large valley glaciers have moved through the Porcupine Plateau, along the East Fork Chandalar and Vanticlese Creek, most of the upland areas in the Porcupine Plateau have not been eroded by ice. Consequently the rocks are deeply weathered and many outcrops in the low hills east of the East Fork are only soil and rubble. The southern quarter of the quadrangle in the Yukon Flats is covered with unconsolidated glacial and alluvial deposits.

The Christian quadrangle is at the east end of the southern Brooks Range schist belt. Here three geologic terranes that originate well south of the Brooks Range intersect the subterranes of the southern Brooks Range along northward-directed thrust faults and northeast-striking strike slip faults. The displaced terranes from the south have been mapped by Jones and others (1987), as the schist of the Ruby terrane, the mafic rocks and phyllite of the Tozitna terrane, and the graywacke of the Venetie terrane. The typical rocks of the southern Brooks Range Arctic Alaska terrane at this intersection are the carbonate and clastic rocks of the Hammond subterrane, and the schist of the Coldfoot subterrane. The Coldfoot schist ends at a probable strike-slip fault about 10 miles west of the Christian quadrangle. At that place the mafic rocks and phyllites of the Angayucham terrane that form the south flank of most of the Brooks Range veer sharply northeastward across the Coldfoot subterrane schist and terminate it. A small fragment of the Endicott Mountains subterrane of the Arctic Alaska terrane also lies within the Christian quadrangle, but the main body of this subterrane lies north of the quadrangle.

First posted November 24, 2000