I'm a little alarmed that your water coming from the tap is brown or black in the first place.
Yeah...it's gross. I hate to even bathe in it, when it's really really brown.
But that black was alarming! It wasn't a lot, it just gushed out black for a second...
We just live in an old part of town with old pipes. I suspect that because of the drought, the ground heaved during that cold snap and caused the release of the black sediment. It coincided with that cold weather and there were ruptured pipes all over Tulsa due to the ground heaving.