Continental Consequences of Plate tectonics - Deformation of the Continental Crust

[Chapter 21 of the text; and some of 20]

Basic structure of continents.

Interior platforms (covered with flat-lying sediments) and shields - stable, old (pre-cambrian) crust not deformed for 1000's of lillions of years

Continental shelves

Mountain belts

Opening of an ocean

If oceans are opening, how does the opening start? Have to break apart an existing continent

Thinning of lithosphere

Formation of initial rift

Sedimentation in rift: Significance of salt deposits;

Sedimentary sequences before rifting are same on both continents; salt formed in small ocean stage; after rifting sed sequences may be very different on each continent.

Mountain Belts (Orogenic zones) and collisions

Features of mountain belts:

linear nature,

deformed metamorphosed rocks,

ophiolites - fragments of basaltic and ultramafic rocks with pelagic (deep sea) sediments

continental margin sediments (migeosyncline), shallow water limestones

volcanic rocks of island arcs (eugeosyncline).

Closure of oceans and collisions: during subduction plates are only converging - a continuous process; collision is an event that interupts or stops convergence- an attempt to subduct buoyant lithosphere

continent-continent,

arc-continent,

arc-arc

Wilson cycle

Opening and closing of oceans

Micro plates and terranes

Evolution of the Appalachian orogenic belt - a case history of the complex evolution in a mountain belt

Plate Evolution

Ocean history, continental paleomagnetism, and geology can be combined to obtain a picture of Phanerzoic plate evolution of the Earth

Gondwanaland

Pangea

Ancient oceans - Iapetus, Tethys