Possible Clues:

• Oil spilt on journey produces powdery deposit
• In North Africa I entered another port and left before one
• Mediterranean site to ripen olives, with final losses increasing
• City in Libya — city in Lebanon
• Journey from Oxford to Long Island with Mediterranean port
• Chief Libyan port
• North African city in the lyrics to the 'Marines' Hymn'
• The largest city in Libya - or second largest in Lebanon
• Oea is the ancient name of this city and port in Libya
• Foreign capital excursion on oil rig, occasionally