OK, so the package is definitely there.

First, connect as sys and create a public synonym.
connect sys/sys_password@db
create public synonym DBMS_LOGMNR_D for sys.DBMS_LOGMNR_D;


Then, grant execute privs to system:
grant execute on sys.DBMS_LOGMNR_D to system;

Next, connect as system and try to see the package:
connect system/system_password@db
describe DBMS_LOGMNR_D
describe sys.DBMS_LOGMNR_D

If both of these succeed, you should be able to execute the function you were looking for...