What could explain the existence of coal deposits in antarctica?

Antarctica once belong of the Gondawa that was called a super continent, at that time the Antarctica was surfaced with forest and had coastal warm currents on its shores. And when the Antarctica detach from the continent Gondwana and moved to the south, it begin to change the waters cooled, the temperatures dropped, the forest disappeared, and the snow begin to covered the land then was compacted into ice over time, all combining to create coal deposits.