The Pacific is the oldest of the existing ocean basins, its oldest rocks having been dated at about 200 million years. The major features of the basin and rim have been shaped by the phenomena associated with plate tectonics. The coastal

The mid-oceanic ridge, in the youngest part of a growing ocean basin, is usually free of sediment. Passing off the ridge, calcareous sedimentation, caused by microorganisms, is found. Clays and chert (silica rock) occur in deeper parts.

As the ocean widens, arkoses, sandstones, and shales may accumulate in clastic wedges along the continental margin, and marine limestones may be deposited. The successions on the coasts of Brazil and West Africa record symmetrically the change from nonmarine clastic sandstones and shales, via evaporites (about 120 million to 110 million years old), to marine sandstones and limestones. This sequence records the incoming of seawater into a continental rift valley, widened via a Red Sea-type narrow ocean into a mature ocean.

Some topics in this essay:
Plate Tectonics, Pacific Nazca, Red Sea, Red Sea-type, West Africa, Australia Turbidity, Pacific Rise, Gulf California, South America, plate tectonics, Bahama Banks, continental plates, major features, pacific rise, east pacific, ocean basins, continental margin, sandstones shales, east pacific rise,