Minecraft wiki entry for Configured_surface_builder, associated text:  type:[needs testing] The type of surface builder to use, must be one of "default", "mountain", "shattered_savanna", "gravelly_mountain", "giant_tree_taiga", "swamp", "badlands", "wooded_badlands", "eroded_badlands", "frozen_ocean", "nether", "nether_forest", "soul_sand_valley", "basalt_deltas", or "nope". These choices change the generation of patterns of surface materials, and in the case of "frozen_ocean" and "eroded_badlands", add generated icebergs and buttes, respectively. For example, the mixed patterns of stone in mountains and the striped terracotta of mesas are coded for through these options.
 config: Configuration for the surface builder.
 top_material:[needs testing] The block to use for the topmost layer of the terrain.
 Name: The namespaced id of the block to use.
 Properties: Block states
 state: A block state key and its value.
 under_material:[needs testing] The block to use directly under the topmost layer of the terrain.
 Name: The namespaced id of the block to use.
 Properties: Block states
 state: A block state key and its value.
 underwater_material:[needs testing] The block to use under bodies of water.
 Name: The namespaced id of the block to use.
 Properties: Block states
 state: A block state key and its value.