This script looks at X$KSQST, which contains a breakdown of enqueue gets and enqueue waits by lock type. Unfortunately, there is no indication of the relative duration of these waits, so care must be taken when interpreting the output.
select
q.ksqsttyp type,
q.ksqstget gets,
q.ksqstwat waits
from
sys.x_$ksqst q
where
q.inst_id = userenv('Instance') and
q.ksqstget > 0
/