Gaia means earth

so Sasuke has a heaven seal and Kimimaro has an Earth seal

by the way, Orochimarus arms wernt sealed up anything else but materially - whos to know that souls even have arms. The reason why he probably wanted to get Tsunade to heal his arms is to avoid all the pain, and he probably wanted to keep his current body.
But he cant do that anymore and had to reincarnate.