Not an approval process, but a workaround could be:
1.- Restrict role permissions, so just selected roles will be able to adjust.
2.- Create Saved Searches to show Adjustments done for a specific amount ranges (i.e. <=10k, other search for >10k, etc) show the users that made the adjustment.
Per each Saved search you may create a criteria to send email alerts to a 'Supervisor' in case an user exceed the authorized adjustment amount. Example
Saved search 1 (<=10K): Authorized users are A, B and C. Condition: if the creator of the adjustment is NOT A,B or C, then send alert to supervisor.
Hope this helps.