well, testing on MP and DEPT demo tables, without any index, I get the explain plan :

Operation Option Obj Name
----------------------------------- ----------- --------------------
SELECT STATEMENT
MERGE JOIN
SORT JOIN
TABLE ACCESS FULL DEPT
SORT JOIN
TABLE ACCESS FULL EMP

that is to say : FULL on EMP, FULL on DEPT where LOC=3 and DEPTNO=10, and then merge join the 2 temporary results on deptno ...