PONS / COLLINS Großwörterbuch

@natives: Isn't "amazement" a rather positive thing?
The German phrase has a slightly negative connotation.
Normally you'd "die Hände über'm Kopf zusammen schlagen" when you're upset about something. Does "amazement" cover this gut-feeling properly?

(Langenscheidt GWB)

Tiny's suggestion should be with "hands" too, and actually I think "horror" fits much better than "amazement". Duden says it means "entsetzt sein".

Ich finde, wenn man die Hände über dem Kopf zusammenschlägt ist man nicht unbedingt überrascht, sondern eher entsetzt.

I therefore suggest: to throw one's hands up in dismay (or: in disgust, frustration - depending on the emotion involved)