[
  {
    "type": "mapgen",
    "om_terrain": "special_deep_rock",
    "object": { "predecessor_mapgen": "deep_rock" }
  },
  {
    "type": "mapgen",
    "om_terrain": "special_rock",
    "object": { "predecessor_mapgen": "empty_rock" }
  },
  {
    "type": "mapgen",
    "om_terrain": "special_earth",
    "object": { "predecessor_mapgen": "solid_earth" }
  },
  {
    "type": "mapgen",
    "om_terrain": [ "special_field", "pasture", "special_field_highway" ],
    "object": { "predecessor_mapgen": "field" }
  },
  {
    "type": "mapgen",
    "om_terrain": [ "special_forest", "special_forest_isherwood" ],
    "object": { "predecessor_mapgen": "forest" }
  },
  {
    "type": "mapgen",
    "om_terrain": [ "special_forest_thick", "special_forest_thick_isherwood" ],
    "object": { "predecessor_mapgen": "forest_thick" }
  },
  {
    "type": "mapgen",
    "om_terrain": "special_air",
    "object": { "predecessor_mapgen": "open_air" }
  }
]
