Postgresql MVIEW refresh from Oracle Materialized View Log
The implementation of materialized views in Oracle and Postgres is different. What you're asking would require a level of integration of Postgres into Oracle's proprietary API - to register as a known client MV so that the log correctly updates itself - that I don't believe exists. It would also require a functioning database link to the Oracle database.

This extension looks like it can help Postgres connect to Oracle; I haven't used it myself, but it looks like it should work (although it also appears to have some limitations): https://pgxn.org/dist/oracle_fdw/ 

At that point, you would need to query the source tables directly, rather than existing MV Logs. Oracle maintains those logs automatically, truncating them or removing rows when it determines that all registered MVs have refreshed a certain set of changes. If there are no registered MVs, then the logs will grow out of control forever. It won't be long before they severely impact the performance of your updates and the Oracle DB (storage requirements, backups, memory, etc.). There are also situations in Oracle where an entire MV log can become invalid and require a complete refresh of the MV to reset. My point is that without the proper client registration, the data in those logs is pretty much useless, or worse than useless: harmful to maintain.