AGE PERIOD EPOCH AGE PICKS (Ma) (Stage) (Ma) Interpretive Summary of Tectonic Evolution, Blue Mts and PNW Region (B. Dorsey, 2/26/2007) PLEIST 1.8 PLIOC MESSINIAN 5.3 7.1 Post-15 Ma: Cascade arc volcanism, CW rotation, N-S shortening in Yakima etc fold belts. L TORTONIAN 10 11.2 SERRAVALLIAN 14.8 MIO- M LANGHIAN 16.4 ~ 15-?? Ma: Uplift of Wallowa Mts, delamination of dense pluton root (Hales et al., 2005). BURDIGALIAN 20 CENE E 20.5 ~ 17-15 Ma: Voluminous CRB flows followed by paired migration of YS and NB hotspots. AQUITANIAN 23.8 Models for the CRBs include mantle plume (e.g. Camp and Ross, 2004), L CHATTIAN 28.5 back-arc extension, and upper mantle convection (Humphreys et al., 2000). 30 OLIG. E RUPELIAN 33.7 ~ 38-16 Ma: John Day Formation distal backarc basin, east of Cascade arc. L PRIABONIAN 37.0 BARTONIAN 40 41.3 ~ 40 Ma: Initiation of Cascadia subduction zone and magmatic arc. M LUTETIAN ~ 45 Ma: Accretion of Siletzia oceanic lithosphere (green patch in figure). TERTIARY 50 49.0 ~ 60-38 Ma: Clarno and Challis arc magmatism, possible shallowing of subduction. EOCENE E YPRESIAN 54.8 THANETIAN L 57.9 SELANDIAN 60 Paleoc. 61.0 Late Cretaceous to Early Tertiary (~ 90-55 Ma): E DANIAN 65.0 MAASTRICHTIAN Eastward migration of Idaho Batholith, Laramide Orogeny, 70 71.3 Possible continuation of dextral transpression in the WISZ (?) Humphreys et al. (2000) CAMPANIAN 80 LATE 83.5 SANTONIAN 85.8 Giorgis et al. (2005) CONIACIAN 89.0 Cretaceous Sevier Orogeny 90 TURONIAN 93.5 (east of here): Large thrust belt and CENOMANIAN foreland basin migrate eastward onto 100 99.0 North American craton. ALBIAN 110 EARLY 112 ~ 110-90 Ma: WISZ dextral APTIAN transpressive shear zone. 120 121 ~ 135-110 Ma: Andean-type BARREMIAN subduction and magmatism. 127 inactive / CRETACEOUS extending LFTB ? inactive foreland basin ? HAUTERIVIAN OF 130 132 Wa B VALANGINIAN 137 ~ 145-135 Ma: Wallowa batholith and related plutons emplaced 140 BERRIASIAN during onset of Andean-type subduction at North American margin. deforming terranes NEOCOMIAN 144 ~ 150-140 Ma: Strong shortening, basin inversion, metamorphism, TITHONIAN 150 LATE 151 and mountain building. Initial accretion of terranes to North America. KIMMERIDGIAN 154 OXFORDIAN 160 159 migrating collisional CALLOVIAN basin SRB LFTB retroarc foreland basin 164 forebulge ?? BATHONIAN ~ 195-150 Ma: Long-lived doubly-vergent thrust S.L. MIDDLE 169 Wa 170 belt in Nevada and W Idaho. Utah-Idaho Trough B OF BAJOCIAN east of thrust belt, Izee collisional basin in west crustal thickening 176 flexural subsidence ? and loading AALENIAN 180 180 (Blue Mts). Papua N.G. - style collisional margin. TOARCIAN 190 190 JURASSIC Dorsey and LaMaskin (in review) PLIENSBACHIAN 195 inactive/waning emergent inactive/waning undeformed marine North American EARLY Wallowa arc thrust belt O.F. - B.R. arc back-arc basin craton margin 200 SINEMURIAN 202 ~ 220-195 Ma: Collision (amalgamation) of Wallowa S.L. B HETTANGIAN Wa OF 206 and Olds Ferry / Black Rock arcs, growth of flexural B B RHAETIAN ? 210 210 basins on E and W flanks of Baker Terrane thrust belt. End of “normal” subduction in the Blue Mts region. LATE NORIAN 220 221 active marine CARNIAN ~ 235-220 Ma: Wallowa volcanic arc in west, Olds active Wallowa remnant active Olds Ferry - 227 back-arc basin North American volcanic arc ocean basin Black Rock arc craton margin 230 LADINIAN Ferry / Black Rock (now in NW Nevada) arc in east. (NW Nevada) MIDDLE 234 Large Sea-of-Japan-type backarc basin east of there. S.L. Wa B B OF ANISIAN continental components 240 242 ? TRIASSIC OLENEKIAN EARLY 245 INDUAN 248 Modified from 1999 DNAG Geologic Time Scale (GSA)