DEFORMATION ASSOCIATED WITH THE LITTLE SALMON AND YAGER FAULTS IN THE YAGER CREEK-WOLVERTON GULCH AREA, NORTHWESTERN CALIFORNIA

Three strands of the WNW-striking, NE dipping, Little Salmon fault cut Paleocene to Quaternary rocks and sediments at the northeastern margin of the Eel River basin between Yager Creek and Wolverton Gulch. The northernmost Yager fault thrusts Paleocene-Eocene Yager Complex sandstone and Miocene-Pliocene lower Wildcat Group sediments over late Pliocene Scotia Bluffs Sandstone and Plio-Pleistocene Carlotta Formation conglomerate and sandstone. The central Little Salmon fault thrusts late Pliocene Scotia Bluffs Sandstone and Plio-Pleistocene Carlotta Formation conglomerate and sandstone over Carlotta Formation conglomerate and sandstone. The newly identified southernmost strand forms an arcuate, north-side-up scarp in Holocene alluvial fan deposits. Patinopecten sp. and ?Pandora sp. in silty mudstone on the upper plate of the Yager fault, and Macoma sp., ?Spisula sp., Clinocardium meekianum, Siliqua sp. cf. S. oregonia, and Compsomyax sp. cf. C. subdiaphana in sandstone on the upper plate of the Little Salmon fault provide biostratigraphic control for previously undifferentiated Wildcat Group sediments, and show that the Yager fault has significantly greater stratigraphic throw than the Little Salmon fault. Two large overturned folds, an anticline in the hanging wall and a syncline in the footwall of the Yager fault, record additional fault-related deformation. Sets of deformation bands measured at three locations in the syncline are more tightly clustered in their current orientations than they are when rotated by returning associated bedding dips to horizontal. This observation suggests that folding preceded formation of the deformation bands and is consistent with interpretation of the overturned folds as fault-propagation folds. Additional investigation is needed to determine the stratigraphic throw and other characteristics of the southernmost, potentially active, strand of the Little Salmon fault in this area.