Sticherus sp. Closer photo of branched fronds, and close-up of sori, a single row on each side of midvein. Pinnules entire, glabrous, with fine scales.
Hell's Bells! That looks like Sticherus! I'll have to work on that. It's most definitely not a Blechnum. I'm almost certain it's a new species for the ACT region. The only question is whether it's a known native species or an introduced escape. Stay tuned.
Perhaps not surprising, given that we found both Gleichenia dicarpa and G. microphylla in the same region and a little higher up, and G. microphylla occurs nearby.