Mesozoic/Cenozoic Tectonics Outline
Chapters 14 (pp. 384-413; 447-448) & 15 (pp. 452-482; 503-504)

MESOZOIC/CENOZOIC TECTONICS - OVERVIEW

• MESOZOIC/CENOZOIC TECTONICS DOMINATED BY DIVERGENCE AS WEGENER'S PANGEA WAS DISMEMBERED AND THE ATLANTIC & INDIAN OCEANS OPENED (see figure 14.4)
• MOUNTAIN BELTS DEVELOPED IN MESOZOIC/CENOZOIC - ASSOCIATED WITH DESTRUCTION OF OCEANIC CRUST AROUND PACIFIC OCEAN & CONTINENTAL COLLISIONS AS AFRICA/INDIA COLLIDED WITH EURASIA, ELIMINATING TETHYS SEAWAY
  • Cordilleran Mountain System
    • SUBDUCTION & CONVERGENCE ALONG WEST COASTS OF N. & S. AMERICA
    • ACCRETIONARY TECTONICS CHARACTERIZES THIS SYSTEM (see figures 14.17 & 14.18)
  • Alpine/Himalayan Mountain System
    • COLLISION OF AFRICA & INDIA WITH EURASIA (see figure 15.29)

MESOZOIC/CENOZOIC TECTONICS - DETAILS

• TRIASSIC (~215 MY AGO)
  • Divergence leading to dismemberment of Wegener's Pangea initiates
    • CONTINENTAL RIFTING ALONG WESTERN EXTENSION OF TETHYS BETWEEN EAST COAST OF NORTH AMERICA & NORTHWEST AFRICA (see figures 14.3, 14.4, 14.5, 14.6, &14.8)
  • Convergent continental margins off western N. & S. America & Antarctica (see figures 14.21 & 14.22)
• JURASSIC (208-144 MY AGO)
  • 190 my - initial breakup of Pangea II begins
    • SEAFLOOR SPREADING IN CENTRAL NORTH ATLANTIC OFF EASTERN N. AMERICA & NW AFRICA
    • WEGENER'S PANGEA BREAKS INTO LAURASIA & GONDWANA (Florida left with N. America)
  • 165 my - Gondwana begins to break up
    • SEAFLOOR SPREADING OFF EASTERN AFRICA & ANTARCTICA
    • GONDWANA BREAKS INTO WESTERN GONDWANA (S. America/Africa) & EASTERN GONDWANA (Antarctica/Australia/India/Madagascar)
      • Jurassic seafloor off NW Australia = Indonesia rifted from Gondwana?
• CRETACEOUS (144-66 MY AGO)
  • 135 my - Gondwana continues to break up
    • WESTERN GONDWANA SEPARATES INTO SOUTH AMERICA & AFRICA
    • EASTERN GONDWANA SEPARATES INTO ANTARCTICA/AUSTRALIA & INDIA/ MADAGASCAR (now part of Africa)
  • 90 my - Laurasia begins to break up
    • SEAFLOOR SPREADING IN LABRADOR SEA & BAY OF BISCAY
      • Laurasia breaks into N. America, Eurasia/Greenland, & Spain
    • INDIA SEPARATES FROM MADAGASCAR & ACCELERATES TOWARD ASIA
    • NEW ZEALAND SEPARATES FROM AUSTRALIA
• CENOZOIC
  • Early Eocene (55 my ago) - Greenland separates from Eurasia & joins North America
  • Late Eocene (45 my ago) - Antarctica & Australia break up
  • NOTE: These 2 events were critical for Cenozoic climatic cooling

NORTH AMERICAN MESOZOIC/CENOZOIC TECTONICS

• EAST & GULF COAST
  • Mesozoic rifting (Late Triassic - Early Jurassic)
    • RIFT VALLEYS FILLED WITH REDBEDS, EVAPORITES & BASALTIC VOLCANICS
  • Mesozoic/Cenozoic subsidence (Middle Jurassic to present)
    • RESULTS FROM COOLING OF THINNED CONTINENTAL CRUST
    • ALLOWS FOR ACCUMULATION OF THICK (8 KM AV., 15 KM MAXIMUM) SEQUENCES OF PREDOMINANTLY SHALLOW-MARINE SEDIMENTS (see figure 15.34)
      • lots of limestone ( particularly in the southeast) & lots of petroleum in the Gulf Coast sediments, some localized along salt domes
    • THE COASTAL PLAIN IS THE THIN EDGE OF THIS THICK PILE OF SEDIMENTS
• WEST COAST
  • Dominated by accretion of exotic terranes (island arcs, volcanic plateaus & microcontinents) throughout Mesozoic & most of Cenozoic
  • Sonoma Orogeny
    • LATE PERMIAN THROUGH TRIASSIC ISLAND ARC COLLISION
  • Nevadan Orogeny
    • TRIASSIC THROUGH CRETACEOUS SUBDUCTION ALONG ANDEAN TYPE SYSTEM
    • GENERATED HUGE QUANTITIES OF GRANITE NOW EXPOSED IN CALIFORNIA (Sierra Nevada Batholith), IDAHO (Idaho Batholith), BRITISH COLUMBIA (Coast Range Batholith) & BAJA CALIFORNIA (Baja California Batholith) [see figure 14.23]
  • Sevier Orogeny
    • MIDDLE JURASSIC TO EARLIEST CENOZOIC (overlapped in time with Nevadan Orogeny) FORELAND THRUSTING (see figures 14.22 & 14.30)
    • RELATED TO SUBDUCTION OF NEVADAN OROGENY
  • Laramide Orogeny (see figure 15.3)
    • LATE CRETACEOUS THROUGH EOCENE
    • MOSTLY WARPING INTO DOMES & ARCHES - FINAL GASP OF SUBDUCTION
    • RELATED TO VERY FLAT SUBDUCTING PLATE (Farallon Plate)
  • Late Cenozoic tectonics is dominated by rifting
    • DEVELOPMENT OF BASIN & RANGE BY RIFTING STARTING IN LATE MIOCENE
    • UPLIFT OF THE COLORADO PLATEAU
      • Grand Canyon & other western national parks exposes lots of the Mesozoic & Cenozoic section lots of volcanism around margin of Colorado Plateau
    • CHANGE IN STYLE RELATED TO NORTH AMERICA OVERRUNNING EAST PACIFIC RISE PORTION OF MOR STARTING IN EOCENE - CONTINENTAL MARGIN CHANGED FROM CONVERGENT TO LATERAL MARGIN (see figures 15.12, 15.14, 15.15, 15.17, & 15.23)
• CONTINENTAL INTERIOR (WESTERN ONLY - EASTERN MOSTLY EXPOSED)
  • Series of transgressions & regressions
  • Triassic & early Jurassic - widespread nonmarine (redbeds & dune sands) sediments (sealevel low) [see figures 14.9, 14.11, & 14.13]
  • middle/late Jurassic & Cretaceous - transgression by Jurassic Sundance Sea & Cretaceous Interior Seaway [Zuni Sequence](rising sealevel) [see figure 14.26]
  • Eocene & Miocene - Tejas Sequence = decrease in rate of sealevel fall

Study Questions

1. What was the time of the initiation of the Mesozoic-Cenozoic Wilson Cycle?

2. What is the cause of Alpine-Himalayan Orogenesis?

3. What is the evidence indicating the timing & location of Wegener's Pangea?

4. What are the continents that formed during this initial breakup?

5. Summarize the breakup of Gondwana & Laurentia during the Mesozoic & Cenozoic.

6. How do the general characteristics of North American Atlantic & Gulf Coast tectonics differ from those western North American tectonics?

7. What are the general causes of the Sonoma, Nevadan, Sevier & Laramide Orogenies?

8. What are the general causes of Late Cenozoic western rifting, including development of Basin & Range during Late Miocene & the uplift of Colorado Plateau?

9. What are the general characteristics of the Zuni & Tejas Sedimentary Depositional Sequences?

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