This is one set of world gen data that did this on a freshly installed copy of 40.2:
[WORLD_GEN]
[TITLE:MEDIUM REGION]
[SEED:123Doom123]
[HISTORY_SEED:123Doom123]
[NAME_SEED:123Doom123]
[CREATURE_SEED:123Doom123]
[DIM:129:129]
[EMBARK_POINTS:10000]
[END_YEAR:330]
[BEAST_END_YEAR:200:-1]
[REVEAL_ALL_HISTORY:1]
[CULL_HISTORICAL_FIGURES:0]
[ELEVATION:1:400:1200:401]
[RAINFALL:0:100:200:200]
[TEMPERATURE:25:75:200:200]
[DRAINAGE:0:100:200:500]
[VOLCANISM:0:100:3200:3200]
[SAVAGERY:0:100:300:200]
[ELEVATION_FREQUENCY:1:1:1:1:1:1]
[RAIN_FREQUENCY:1:1:1:1:1:1]
[DRAINAGE_FREQUENCY:1:1:1:1:1:1]
[TEMPERATURE_FREQUENCY:1:1:1:1:1:1]
[SAVAGERY_FREQUENCY:1:1:1:1:1:1]
[VOLCANISM_FREQUENCY:1:1:1:1:1:1]
[MINERAL_SCARCITY:500]
[MEGABEAST_CAP:25]
[SEMIMEGABEAST_CAP:50]
[TITAN_NUMBER:10]
[TITAN_ATTACK_TRIGGER:400:1000000:1000000]
[DEMON_NUMBER:30]
[NIGHT_TROLL_NUMBER:14]
[BOGEYMAN_NUMBER:14]
[VAMPIRE_NUMBER:0]
[WEREBEAST_NUMBER:0]
[SECRET_NUMBER:0]
[REGIONAL_INTERACTION_NUMBER:28]
[DISTURBANCE_INTERACTION_NUMBER:28]
[EVIL_CLOUD_NUMBER:14]
[EVIL_RAIN_NUMBER:14]
[GENERATE_DIVINE_MATERIALS:1]
[GOOD_SQ_COUNTS:200:300:800]
[EVIL_SQ_COUNTS:200:300:800]
[PEAK_NUMBER_MIN:20]
[PARTIAL_OCEAN_EDGE_MIN:2]
[COMPLETE_OCEAN_EDGE_MIN:1]
[VOLCANO_MIN:200]
[REGION_COUNTS:SWAMP:260:1:1]
[REGION_COUNTS:DESERT:260:1:1]
[REGION_COUNTS:FOREST:1500:3:3]
[REGION_COUNTS:MOUNTAINS:1500:2:2]
[REGION_COUNTS:OCEAN:1000:1:1]
[REGION_COUNTS:GLACIER:0:0:0]
[REGION_COUNTS:TUNDRA:0:0:0]
[REGION_COUNTS:GRASSLAND:1500:3:3]
[REGION_COUNTS:HILLS:1500:3:3]
[EROSION_CYCLE_COUNT:1000]
[RIVER_MINS:300:100]
[PERIODICALLY_ERODE_EXTREMES:0]
[OROGRAPHIC_PRECIPITATION:1]
[SUBREGION_MAX:5000]
[CAVERN_LAYER_COUNT:3]
[CAVERN_LAYER_OPENNESS_MIN:0]
[CAVERN_LAYER_OPENNESS_MAX:100]
[CAVERN_LAYER_PASSAGE_DENSITY_MIN:0]
[CAVERN_LAYER_PASSAGE_DENSITY_MAX:100]
[CAVERN_LAYER_WATER_MIN:0]
[CAVERN_LAYER_WATER_MAX:100]
[HAVE_BOTTOM_LAYER_1:1]
[HAVE_BOTTOM_LAYER_2:1]
[LEVELS_ABOVE_GROUND:15]
[LEVELS_ABOVE_LAYER_1:13]
[LEVELS_ABOVE_LAYER_2:5]
[LEVELS_ABOVE_LAYER_3:5]
[LEVELS_ABOVE_LAYER_4:5]
[LEVELS_ABOVE_LAYER_5:5]
[LEVELS_AT_BOTTOM:3]
[CAVE_MIN_SIZE:5]
[CAVE_MAX_SIZE:200]
[MOUNTAIN_CAVE_MIN:30]
[NON_MOUNTAIN_CAVE_MIN:60]
[ALL_CAVES_VISIBLE:0]
[SHOW_EMBARK_TUNNEL:2]
[TOTAL_CIV_NUMBER:40]
[TOTAL_CIV_POPULATION:-1]
[SITE_CAP:-1]
[PLAYABLE_CIVILIZATION_REQUIRED:1]
[ELEVATION_RANGES:0:0:0]
[RAIN_RANGES:0:0:0]
[DRAINAGE_RANGES:0:0:0]
[SAVAGERY_RANGES:0:0:0]
[VOLCANISM_RANGES:0:0:0]
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