Geomorphic LiDAR Mapping of Latest Pleistocene Deposits and the Western Extent of the Fickle Hill Fault, Arcata, Northern California

I incorporated high-resolution LiDAR elevation data to map the geomorphology of faulted late Pleistocene marine terraces in coastal northwestern California near Arcata. The study area is located within the onland fold and thrust belt of the southern Cascadia subduction zone. I identified multiple splays of the Fickle Hill fault, an active, northwest-striking, southwest vergent thrust zone within the broader Mad River fault zone. I identified five splays of the Fickle Hill fault within downtown Arcata. Northwest of the town I identified three possible traces in younger uplifted marine terrace surfaces. Correlation of marine formed geomorphological units to sea level curves enabled me to estimate ages for them. This in turn allowed me to approximate the age of displacement on some of splays of the fault. Preliminary assignments of ages 100 ka for a prominent fault marine terrace, and 80ka delta/fan complex and recessional platform to between 75 and 80 ka provide a regional uplift rate for the Arcata area of 0.2 mm/yr. The northern splay of the fault has not deformed the marine terrace thus has not been active in ca. 100 ka. The middle splay has had ~5 m of total vertical separation since formation of the marine terrace; about 4m of that offset occurred between 100 and 80 ka. The southern splay, an associated antithetic splay and the middle splay of the fault all have had displacement since the recessional platform was formed about 75 ka.