Looks like botched generation, but it isn't, because if you actually walk there and get within normal exploration range you'll see how it actually looks:
I'm not sure what RSO has to do with the map display, but I've never seen this happen without RSO, so I'm posting here.
Factorio 0.13.10, RSO 2.0.5, custom config with
Code: Select all
region_size = 20
absolute_resource_chance = 0.80
global_richness_mult = 2
global_size_mult = 2