@EventHandler
    public void init(FMLInitializationEvent event){
        ......
        if(ConfigDivergentUnderground.enableFossils){
              GameRegistry.registerWorldGenerator(new FossilGenerator(), 0);
        }
        ......
    }

/\/\/\\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\\/\/\/\/\/\/\/\/\/\/\/\/\/\/


public class FossilGenerator implements IWorldGenerator{

    @Override
    public void generate(Random random, int chunkX, int chunkZ, World world, IChunkGenerator chunkGenerator, IChunkProvider chunkProvider) {
        if (world.provider.getDimension() == 0) {
            generateOverworld(random, chunkX, chunkZ, world, chunkGenerator, chunkProvider);
        }
    }

    private void generateOverworld(Random random, int chunkX, int chunkZ, World world, IChunkGenerator chunkGenerator, IChunkProvider chunkProvider) {
        generateOre(ModBlocks.FOSSIL.getDefaultState(), world, random, chunkX * 16, chunkZ * 16, 0, 48, 1 + random.nextInt(2), ConfigDivergentUnderground.fossilTries);
    }


    private void generateOre(IBlockState ore, World world, Random random, int x, int z, int minY, int maxY, int size, int chances) {
        int deltaY = maxY - minY;

        for (int i = 0; i < chances; i++) {
            BlockPos pos = new BlockPos(x + random.nextInt(16), minY + random.nextInt(deltaY), z + random.nextInt(16));

            WorldGenMinable generator = new WorldGenMinable(ore, size);
            generator.generate(world, random, pos);
        }
    }

}