I agree with @DallonF. I read from your description (you mentioned "app") that you are targeting touch devices (mobile, tablet)? So first to go would be to keep consistency with the running OS on the device. Think of the native interactions (e.g. swipe on tables to move a screen back on iOS) too. So the user has only the effort to learn navigation and interactions once. If you invent a new way for navigation, you add some effort. So if you HAVE TO make a new way of navigation, keep close the native one.
If you need "munition" for discussions, refer to current browsers. Safari, Chrome, Firefox have their nav buttons on the upper left corner.
hope this helps