Header Image Overlap in Safari

Hi there,

I have an issue where my header image is being overlapped by my logo and navigation bar in Safari and on mobile devices only. The page looks correct in any other browser. I tried using z-index with some success, but I still cannot get the banner image to sit beneath my nav and logo. Not sure if I should continue to try a variation of z-index or something else.

I am using a child theme of the Twenty-Eleven theme. Any possible solutions will be very appreciated.

Website

Thanks,
Matt