Plate Tectonics and Sedimentation: Where do sediments accumulate?
How and why do continents break-up and new ocean basins form?
• what are the principal steps involved?
• where do sediments tend to accumulate and what types of sediments
• how long does it take for a new ocean basin to form?
• how is oceanic crust formed?
Over time heat builds-up under large continents
• upwelling limb forms in the Asthenosphere
• result: series of "hot spots"
Rift Stage (Continental Break-Up)
• crust heated from below, thermally expands and thins
• creation of tension fractures (= normal faults)
• extension causes collapse of thinned crust (= horsts & grabens)
• creation of long, narrow, fault-bounded central rift valley
• thick sequences of continental deposits due to rapid subsidence and high relief
alluvial fans and alluvial plains; braided streams and lakes or playas
• intrusion of diabase sills and extrusion of basaltic lava flows
Commonly, each hot spot produces 3 arm rift (triple junction)
• rifts propogate, those that hook-up become the incipient ocean basin
• others become aborted pull-apart basins or "failed rifts"
Hartford/Deerfield Basin, Newark Basin
Drift Stage (Opening of New Ocean Basin)
• rifting continues, basalt forms in the central axis of the rift valley (= new oceanic crust)
• the ocean invades the graben
• seafloor spreading begins (= divergence)
• oceanic crust cools, contracts, and subsides as it moves away from the active spreading center
• rifted (thinned) continental margins subside and a passive continental margin is born
How and why do continents break-up and new ocean basins form?
• what are the principal steps involved?
• where do sediments tend to accumulate and what types of sediments
• how long does it take for a new ocean basin to form?
• how is oceanic crust formed?
Over time heat builds-up under large continents
• upwelling limb forms in the Asthenosphere
• result: series of "hot spots"
Rift Stage (Continental Break-Up)
• crust heated from below, thermally expands and thins
• creation of tension fractures (= normal faults)
• extension causes collapse of thinned crust (= horsts & grabens)
• creation of long, narrow, fault-bounded central rift valley
• thick sequences of continental deposits due to rapid subsidence and high relief
alluvial fans and alluvial plains; braided streams and lakes or playas
• intrusion of diabase sills and extrusion of basaltic lava flows
Commonly, each hot spot produces 3 arm rift (triple junction)
• rifts propogate, those that hook-up become the incipient ocean basin
• others become aborted pull-apart basins or "failed rifts"
Hartford/Deerfield Basin, Newark Basin
Drift Stage (Opening of New Ocean Basin)
• rifting continues, basalt forms in the central axis of the rift valley (= new oceanic crust)
• the ocean invades the graben
• seafloor spreading begins (= divergence)
• oceanic crust cools, contracts, and subsides as it moves away from the active spreading center
• rifted (thinned) continental margins subside and a passive continental margin is born
