Curtin's title is unnecessarily clickbaity, so try mine: Nonoceanic water cycle at 4Gya. This merits promotion to the Timeline.
They have water underground reacting with rocks. They say that would be delivered from water on the surface, not from some deeper vent. So I guess they couldn't find any oceanic salts in the vein. That means: freshwater on the surface.
They mention life... several times. But Earth had no life then. Stromatolites are datable a few hundred million years later. I'd have left "life" off the title and maybe mentioned it only once in the main body. Better speculations would go toward other planets at ~550 My of age and, especially, the 70% insolation range.
Also missing on Earth at the time: a magnetic field. Before the 550 My mark, gradual release of water from internal sources should have boiled off. Why not after?
Did a big post-Theia comet or Cereslike deliver this water all at once? or volcanoes? A sudden steamcloud might deluge the whole planet before salts got into the basins. I get the impression that space rocks tend salty already when they get within 1.6 AU. I bring to witness Mars' perchlorates - and for that matter Europa's ocean; given its own heat-sources, radiation, and low-G. The salts don't however make it back into atmo to rain down on the plateaux. Or for that matter to snow down.
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