Jamaica: Pakistan ended day three of the first Test on 201-4 in reply to 286 all out, the bulk of their runs coming in a dogged third-wicket stand of 131 between Younis (58) and Babar Azam (72).
West Indies were ultimately grateful to Gabriel (2-37), who ousted both set batsmen in successive overs just when Misbah-ul-Haq's side were threatening to carve out a position of dominance.
Yet the day undoubtedly belonged to Younis as the 39-year-old, who intends to retire following this three-match rubber, joined the elite club of batsmen to have scored 10,000 runs in cricket's premier format.
Having begun his innings needing 23 to reach the landmark, Younis took his career tally into five figures in the first over after tea and celebrated joyously in front of Pakistan's dressing room.
After he and Azam departed, Misbah and Asad Shafiq dug in to see their side through to stumps. Both men will resume on five.
The Windies began Sunday on 278-9 in their first innings - following a second day severely truncated by rain - and added just eight runs to that total before Mohammad Amir cleaned up Gabriel to finish with career-best figures of 6-44 and leave Jason Holder stranded on 57 not out.
There was an early setback for Pakistan in reply when Azhar Ali was caught behind for 15, slashing at a short, wide delivery from Alzarri Joseph.
Ahmed Shehzad then fell lbw to Holder for 31, having prospered with a series of pull strokes, but Azam and Younis each overcame early scares in a patient partnership that gave their side the upper hand.
Azam was fortunate to survive an appeal for lbw from Holder on two, as replays showed West Indies should have called for a review.
Younis, meanwhile, saw a thick outside edge off Devendra Bishoo land safely between three converging fielders, yet it was not long before both batsmen were looking secure.
Younis took tea with 9,999 Test runs to his name, but a swept four off Roston Chase brought up the milestone he had yearned for and he duly lifted his tempo, striking Kraigg Brathwaite for six over long-on.
Gabriel eventually came to West Indies' rescue, a slower ball inducing a drive to cover from Younis before the previously assured Azam chopped on playing an indecisive defensive stroke.
Neither Misbah or Shafiq appeared comfortable in the overs that remained, but West Indies were unable to find a fifth breakthrough, Pakistan's captain surviving two wildly optimistic reviews late in the day.
Brief scores
West Indies - 286 (Chase 63, Holder 57*, Dowrich 56, Amir 6-44)
Pakistan - 201 for 4 (Babar Azam 72, Younis 52, Gabriel 2-37)
Status - Pakistan trail by 85 runs