▁P rec amb rian ▁cr at ons , ▁the ▁North ▁China , ▁South ▁China ▁and ▁Tar im ▁Block . ▁These ▁have ▁a ▁series ▁of ▁sed iment ary ▁units ▁over lying ▁them . ▁As ▁these ▁blocks ▁have ▁been ▁f used ▁together , ▁the ▁o ce ans ▁that ▁once ▁separated ▁them ▁have ▁been ▁com pressed ▁into ▁the ▁or ogen ic ▁bel ts , ▁that ▁are ▁now ▁between ▁them . ▁There ▁are ▁multiple ▁ways ▁of ▁naming ▁and ▁defining ▁each ▁of ▁these ▁units ▁in ▁the ▁modern ▁literature . ▁ ▁North ▁China ▁C rat on ▁ ▁The ▁P rec amb rian ▁North ▁China ▁C rat on ▁is ▁pre domin ately ▁met am orph osed ▁island - arc ▁ igne ous ▁rocks ▁that ▁formed ▁between ▁ 3 . 5 ▁and ▁ 3 ▁billion ▁years ▁ago . ▁The ▁cr aton ▁had ▁fully ▁formed ▁by ▁ 1 . 7 ▁billion ▁years ▁ago . ▁Th ick ▁sed iments ▁were ▁depos ited ▁on ▁the ▁cr aton ▁from ▁ 1 0 0 0 ▁to ▁ 5 4 1 ▁million ▁years ▁ago . ▁ ▁South ▁China ▁C rat on ▁▁ ▁The ▁South ▁China ▁C rat on ▁( also ▁Yang t ze ▁C rat on ) ▁is ▁younger ▁than ▁the ▁North ▁China ▁C rat on ▁and ▁ranges ▁in ▁age ▁from ▁ 2 . 5 ▁to ▁ 0 . 8 ▁billion ▁years ▁old . ▁The ▁South ▁China ▁C rat on ▁is ▁divided ▁into ▁three ▁parts , ▁western , ▁central ▁and ▁eastern . ▁Un like ▁the ▁North ▁China ▁C rat on ▁the ▁South ▁China ▁C rat on ▁used