Lecture 14: Geology of California 1) PreCambrian Craton Formation. same processes as talked about during tectonics lecture -- may be different from today Crops out in southeastern California (fig 16.26 or Rubey 1-3) WonĠt talk about this much more 2) Early Paleozoic Passive-Margin Sediment Deposition (Cambrian to Devonian) Essentially continental shelf deposits Similar to east coast today Very mature sandstones and limestones Crop out in Inyo Mts and Great Basin Now folded and, especially, thrust faulted. in Great Basin 3) Late Paleozoic Transition to Convergent Margin (Devonian to Triassic) Island arc volcanism and collisions Thrusting of continental shelf sediments (see above) Accretion of terranes now cropping out in Sierras and Klamaths roof pendents (Saddlebag Lake, Convict Lake, near Mammoth Lakes) Crustal thickening These structurally complex rocks now form the ranges of the Basin and Range 4) Mesozoic Convergent Margin (Triassic to Tertiary) [draw typical convergent margin] Formation of Sierra Nevada Batholith from many different plutons major crustal thickening roots of Mesozoic volcanoes Formation of Great Valley Sequence (a fore-arc basin) Structurally intact group of volcanic-rich sed rx Can be correlated to erosion of the Sierra volcanoes deposited on the Coast Range Ophiolite, (arc-related oceanic crust?) deoposited in fore-arc basin? Formation of the Franciscan Complex (which includes many different terranes) A complex agglomeration of oceanic terranes all in a mud-matrix melange (i.e., mixture), now very soft and landslide-prone oceanic in nature Blocks of blueschist, greeywacky, basalt, chert, and rare limestone Why does limestone not fit in? Same age as the GVS, but structurally very different this is the accretionary wedge (but very disrupted), plus various accreted terranes, like the Marin Headlands Terrane Some of the best evidence for suspect terranes Paleomagnetic evidence from limestones Laytonville limestone from south of equator Permanente limestone from north of equator Inferred history of alternating convergence and strike-slip faulting. Accretion of more terranes all along Western Cordillera 5) Cenozoic San Andreas Fault and Basin and Range Extension The Atwater Farallon Plate story [draw this, using fig 16.25 as a guide] Triple junctions Convergent volcanism restricted to the Cascades Transpression and pull-apart basins [look for good diagram] The tranverse ranges In southern California, these folds form oil and gas traps Formation of Salinian Block Piece of Sierras (? or farther south originally??) brought northward Formation of the Coast Ranges Basin and Range extension Volcanism on edges of Basin and Range 6) Glacial Ice Ages and continued faulting Formation of large glacial lakes mention ancient shore-lines These lakes are now playas. Formation of morains on east side of Sierras Volcanism on edges of Basin and Range Long Valley Caldera and associated volcanism Modac Plateau basaltic volcanism, also along faults Present-day configuration -- Physiographic Provinces Sierras - Klamaths Batholith: accreted terranes, thickened crust Basin and Range -- East side of Sierra, Death Valley, Paniment Valley Great Valley: fore-arc basin Coast Ranges: Franciscan complex Salinian Block: Piece of Sierras(?) brought north by SAF This is what weĠre standing on. Cascades Mention ocean water gets into Mt St Helens, again Modoc Platea Mojave Desert -- Garlok Fault