Briton Jack Clarke initially set the pace during the 30 minute session, becoming the first driver this weekend to dip below the 1m28s barrier to hold provisional pole at the halfway point ahead of title protagonist Jolyon Palmer.
However, a second run for the drivers on fresh tyres prompted a flurry of fast times, with the top ten places changing hands numerous times.
Friday practice pace-setter Benjamin Lariche was the first person to better Clarke's time with a 1m26.720s, only for the Frenchman to be quickly deposed by De Marco, whose quickest time of 1m26.548s was sufficient to secure pole position for this afternoon's race - although the Italian stopped out on track at the end of the session.
Behind Lariche, who secured a front row starting berth for the first time in F2, Armaan Ebrahim clinched his best qualifying result of the year in third - the Indian driver working his way solidly through the field in the first part of the session before posting the third quickest time in the final stages.
Will Bratt enjoyed a strong qualifying to clinch fourth at the chequered flag, ahead of Sergey Afanasiev and Philipp Eng - two of the drivers that he is battling against for third in the overall standings.
In the main championship fight, Jolyon Palmer proved the title pace-setter as he qualified seventh after being as high as second on the grid early on. Dean Stoneman finished just outside the top ten in 11th place.
Benjamin Bailly was eighth fastest, with Ivan Samarin ninth and Kazim Vasiliauskas rounding out the top ten - who were separated by only seven tenths of a second.
Ramon Piñeiro will start his first Formula Two race from 13th position, less than four hundredths of a second ahead of early pace setter Jack Clarke.