Hashing algo in Sia blockchain

Hi
Does anyone know what the hash function that Sia blockchain uses to hash the previous block header? My understanding is that Blake2d is used as a PoW function, but a different function might be used for hashing. Bitcoin uses SHA-256 for both, but zcash for example uses Equihash for PoW, but SHA-256 for hashing.
Thanks!

Sia uses BLAKE2b everywhere – for PoW, Merkle trees, transactions IDs, etc.