Looks like dried lees/sediment. If that's in the bottom of an empty wine bottle, I'd say the wine could have used a few more racking cycles which can be accomplished by bulk aging and racking every other month. If that's in the bottom of an empty carboy after racking then it's typical but, again, I'd say it needs a little more time and another racking cycle. I just racked 2 batches of wine for the second time during the bulk aging cycle and there was nothing gunked up on the bottom of the carboy like that but there was during the first racking. It will go away gradually as sediment is removed from the wine after each racking.