Geology of the Pacific Ocean . The Pacific Ocean developed from the Panthalassa, a vast global ocean, following the breakup of the supercontinent Pangaea in the Mesozoic Era, gradually forming Gondwana and Laurasia, which in turn divided. There is no firm date for when the changeover occurred, as the replacement of the sea bed is a continuous process, though reconstruction maps often change the name from Panthalassic to Pacific around the time the Atlantic Ocean began to open. The Panthalassic Ocean first opened around 750 million years ago at the breakup of Rodinia, but the oldest Pacific Ocean floor is only around 180 Ma old.
South China (continent) Ocean. By the Late Carboniferous (300 million years ago), while North China collided with Siberia and Kazakhstania, completely closing the Proto-Tethys Ocean, South China became an independent continent. For much of the Permian Period, South China remained in the tropical latitudes. And also, while most of the giant lycopods of the Carboniferous disappeared, giant lycopods remained in South China, since its isolation from the now formed Pangaea. Cimmeria, a microcontinent that consisted of today's Tibet, Iran, Turkey, and parts of Southeast Asia rifted away from Gondwana (just as North and South China did earlier), and was heading towards Laurasia. Paleo-Tethys