Characterizing Strain Between Rigid Crustal Blocks In The Southern Cascadia Forearc: Quaternary Faults And Folds Of The Northern Sacramento Valley, California

Topographic profiles across late Quaternary surfaces in the northern Sacramento Valley (California, USA) show offset and progressive folding on series of active east-and northeast trending faults and folds. Optically stimulated luminescence ages on deposits draping a warped late Pleistocene river terrace yielded differential incision rates along the Sacramento River and indicate tectonic uplift equal to 0.2 +/- 0.1 and 0.6 +/- 0.2 mm/yr above the anticline of the Inks Creek fold system and Red Bluff fault, respectively. Uplift rates correspond to a total of 1.3 +/- 0.4 mm/yr of north-directed crustal shortening, accounting for all of the geodetically observed contractional strain in the northern Sacramento Valley, but only part of the far field contraction between the Sierra Nevada-Great Valley and Oregon Coast blocks. These structures define the southern limit of the transpressional transition between the two blocks.