QQ in a funny spot

[stu-unger]

villain in this hand is semi thinking player. i havent seen him do anything too out of line, but he is a little too loose pf.

50nl 6max
effective stack 80
dealt to hero Q [img]/images/graemlins/club.gif[/img]Q [img]/images/graemlins/heart.gif[/img] is SB

pre flop: MP calls, CO calls, button calls, hero raises to 3.5, BB calls, CO calls.

flop (11):J [img]/images/graemlins/diamond.gif[/img]10 [img]/images/graemlins/diamond.gif[/img]4 [img]/images/graemlins/club.gif[/img]
hero bets 10, BB calls...

turn (31):5 [img]/images/graemlins/diamond.gif[/img]
hero checks, villain checks...

river (31):K [img]/images/graemlins/spade.gif[/img]
hero checks, villain bets 20, hero folds...

what should i do on this turn? is this a standard fold on the river?