Veeeeeery strange. I took a look at your save, exported the map gen string (below), made a new save with it, and those ice tiles didn't generate. Maybe because I'm on 2.0.19 (experimental) and it's a base game bug that's been fixed? Can you reproduce it consistently with this string in 2.0.15, and if so what about 2.0.19?
(Remove the backslash at the start - it is there to avoid a markdown rendering error otherwise)
\>>>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<<<