What word describes keeping something for purposes of reference, and tracking history?

Context: At a Town council meeting, one policy was rescinded, and a new policy was presented. One councillor requested that a record be kept of the old policy for reference so the new policy could be better understood. Like a breadcrumb trail, so people who read the new policy could know where it came from and how it evolved.

I'm trying to fill in the blank:

Councillor [...] requested that the intent of the old policy be preserved in the new policy for _________ purposes...

Solution 1:

Perhaps "archival" is appropriate here.

According to Webster's Dictionary:

Archival, adj.
Pertaining to, or contained in, archives or records.

Solution 2:

Councillor [...] requested that the intent of the old policy be preserved in the new policy for historical reference...

reference - (noun) the act of looking at or in something for information