"Head" on conditioning Barleywine

I brewed an English Barleywine 3 or 4 months ago. Sat in primary for 4 weeks, then racked to secondary on oak cubes. It's been on the oak for about 2 months or so now. I noticed foam on the top of the beer that resembles beer head and airlock activity. The oak cubes were on vodka for the 4 weeks of primary. I'm a stickler for sanitizing, but I'm hoping it's not an infection. Should I be worried? Sampled it, tastes fine. Any insight appreciated.

 

I was thinking nucleation on the oak. But the last time I put a beer on oak cubes, the bottles were gushers. So I worry about oaking. It was probably overcarbed. Tasted great though. With this being a Barleywine, it's gonna be there for a while.