The Mesozoic began 248 mya and ended 65 mya

The Mesozoic began 248 mya and ended 65 mya

• The Mesozoic began 248 mya and ended 65 mya

• Three periods - Triassic, Jurassic, Cretaceous
• breakup of Pangaea was the major geologic event
• tectonism and sedimentation are used to classify the Mesozoic in N. America
• Note the overlap in three styles of Cordilleran Orogeny

The movement of continents during and after the breakup affected global climates

• The movement of continents during and after the breakup affected global climates

• Sea-level changes due MOR heating and growth, then cooling

• Carbonates (for example the stable isotope ratio C)reveal large concentrations of carbon dioxide present in the Mesozoic atmosphere.

• This suggests a greenhouse climate.

• No glaciers, no coal, so CO2 abundant.

• Greenhouse gasses pass sunlight which hits the land and sea. Re-radiate heat (IR)

• Greenhouse gasses hold the heat, not lost to space as quickly. Warmer equilibrium.

Cretaceous : global rise in sea level until 75 -70 mya, vast MOR

• Cretaceous : global rise in sea level until 75 -70 mya, vast MOR

• Jurassic:

• Atlantic opens E,
• began building the Cordillera W,
• Gulf of Mexico begins to form and experiences evaporite deposition

• Late Triassic: Begin rifting in East

The Newark Supergroup documents the rifting of Pangaea to form the Atlantic

• The Newark Supergroup documents the rifting of Pangaea to form the Atlantic

• Early Triassic saw coarse detrital sediments deposited from the erosion of Appalachian highlands

• fault-block basins developed as N. America separated from Africa and filled with nonmarine sediment plus dikes and sills
• eroded to a flat plain by the Cretaceous

First, as continents separate, restricted basin, thick evaporites formed in the Gulf

• First, as continents separate, restricted basin, thick evaporites formed in the Gulf

• Normal marine deposition returned to the Gulf by Late Jurassic, with transgressions and regressions

• thousand of meters of sediments were deposited

Building the western margin of North America and the Cordillera

• Building the western margin of North America and the Cordillera

Cordilleran Orogeny

• Cordilleran Orogeny

• Laramide – Vertical blocks-built the present day Rockies K-Tertiary
• Sevier – J-K thrust faulting to the east
• Nevadan - Jurassic batholith intrusion in the Sierra Nevada and elsewhere on the western edge

• Cretaceous

• extensive marine deposition until 70mya, thins to the east

• Jurassic

• clean cross-bedded sandstones
• marine sediments in the Sundance Sea

• Triassic

• shallow-water marine clastics
• red beds