With all oil leaks, it's best to 'Gunk' the engine, then wash down with a hose (protecting the alternator). Then after a few days you will be able to see fresh oil. With your leak don't rule out the oil filter being slightly loose. Also check the cam cover gasket. It may have a slight leak which is running down the engine. Finally, you may need to look at the camshaft oil seal. If there's a leak there, the oil will be running down the inside of the cambelt cover and escaping near the alternator. The oil seal isn't too difficult to replace, but the leaking oil could have contaminated the belt, in which case, you should change the belt.