CGmesozoic
MESOZOIC ERA IN CALIFORNIA
I. NW Trending Mountain Systems
a. Klamath-Sierra Nevada--Peninsula Ranges
b. Coast Ranges
c. Lesser Ranges in Basin Range and Mojave (N-NW)
d.Transverse Ranges
II. Overwhelming event of the Mesozoic Era was the initial Building of the structural Framework of California
a. By the end of Mesozoic (about 63 m.y) all elements of Mts. and Great Valley were established
b. Limited mountain building in late Triassic to middle Jurassic time
c. Major mountain building period occurred near close of Jurassic
*best known in Sierra Nevada--so it is called the NevadanOrogeny
d. Nevadan orogeny continued and renewed into Late Cretaceous--evidenced by massive intrusions of granite rocks, volcanic activity, folding faulting and uplift.
III. Mesozoic Rocks
a. Widespread throughout state
(1) elevated areas
(2) sandwiched between Paleozoic and Cenozoic strata
b. 5 of 11 rocks in California map are Mesozoic
(1) oldest--sedimentary and volcanics older than Nevadan Orogeny
TR--Early late Jurassic
(2) younger--late Jurassic through Cretaceous divided into 4 units (collectively cover largest portion of state)
(a)Sierra Nevada; Klamaths; and Coast Ranges (west of San Andreas fault); in all provinces of southern California
(b) ultamafic rocks (peridotite, serpentine) - Widespread in Klamath's and along major fault zones in Sierran Foothills Coast Ranges
V. Mesozoic Rocks (detailed)
*Most important geologic period as far as California History
1. Widespread throughout state
2. primarily two N-NW trending belts, sandwiched between Paleozoic and Cenozoic rocks
a. East most belt (red and brown on state map)-extends into Southern California
(1) Granitic rock (Plutonic) oldest Mesozoic rocks
(2) older sedimentary rocks than the Granite rocks
b. western most belt (green and yellow colors on state map)
(1) Eugeoclinal, sedimentary rocks (graywacke, cherts, shale): igneous rocks; basalt, ultramafic rocks (Serpentrine):Metamorphic rocks; Gneiss, schist (Melange) mixture of all rocks
(2) shelf and slope sedimentary rocks
3. 5 or 11 rocks on California map are Mesozoic
4. Tectonics and mountain building culminated in Mesozoic: This is the initial building of structural framework of California
a. by the end of Mesozoic (63 my ago) all elements of mountains and Great Valley were established
b. limited mountain building in Late Triassic to middle Jurassic time
c. Major mountain building period occurred near close of Jurassic
(1) best known in Sierra Nevada Region--hence called the Nevadan Orogeny
(2) Nevadan Orogeny continued and renewed into the Late Cretaceous
Evidenced by:
(a) massive intrusion
(b) volcanic activity
(c) folding, faulting
(d) uplift
(regional Metamorphism)
d. By end of Mesozoic to Early Cenozoic Mountainous regions reduced to Lowlands and a peneplain.