Maguerit should have sent you a message, giving somewhat vague instructions on the whereabouts of a second base. In case you missed it, its in the icebergs, almost directly east of delta station.
You have finished the maguerit storyline tho there is a little bit left of the sam storyline. You need to explore the large land area, the entrance it either west or north-west of delta station i cant quite remember. bring a spy pengling. Recommend a cold suit and some flares.