1. Glacial sediments either pushed onto the continental margin by the bulldozer-like action of glaciers (moraines) or dropped there by melting icebergs. In either case the sediments would be angular and poorly sorted.
2. Turbidites - a form of terrigenous sediment
3. Calcareous ooze
4. Pelagic clay
5. Siliceous ooze
6. Changing the Pacific margins from active to passive would eliminate the trenches that collect sediments and the subduction the carries them back into the mantle. This would widen the continental shelf and slope - both primarily composed of terrigenous sediments (neritic sand, mud and turbidites) - and allow formation of a continental rise and abyssal plain. Without the trench to stop them, turbidity currents could carry turbidites much farther from land, thus reducing the area covered by oozes, pelagic clay and hydrogenous deposits.
7. When the Atlantic was new, it was narrow, shallow and prone to drying up. Evaporites (gypsum and rock salt) could form, and if covered by terrigenous sediments, would not re-dissolve when the sea once again invaded the rift between the continents. Sea-floor spreading widened the Atlantic, but the buried evaporites remain on the margins of the separated continents. Salt domes in the Gulf of Mexico are evidence of such an event.
Last Updated: 01/13/2015
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