If I had to make stuff up:
Steal the left half of the commerce tree:
+1 Movement and +1 sight range for naval combat units. A Great Admiral appears. +2 Movement for all Great Admirals.
+3 Production in coastal Cities
Starter: Doubles benefits/discovery bonuses from Natural Wonders
Speed production of Archaeologists
+ 1 sight for all units (this would stack with America's ability and stacks with the naval units)
Reduced unhappiness for cities settled on different continents
Finisher: Hidden Archaeological dig sites revealed
That's completely random and made up. I could probably make up more if I thought about it some more.
So, if you are on a Pangea map, do you think this tree is a worthwhile investment? I don't think so.
Most of the arguments I have seen so far for a late availability of the Exploration tree have pretty much come down to the name being related to the "Age of Exploration", without much thought about how the tree would work.
I assume btw that you give Spain a different UA with that opener, otherwise they would be rather overpowered with 6 food 15 gold tiles and the like.
My Exploration tree would be something like this:
Opener: Can build Scouts. One free Scout.
+1 culture for each Natural Wonder discovered
Ancient ruins yield two bonuses to Scouts.
City state discovery bonuses doubled.
+1 Movement and +1 sight range for naval combat units. A Great Admiral appears. +2 Movement for all Great Admirals.
Archeologists unaffected by Closed Borders
Finisher: as already confirmed