I'd guesstimate around 700-800 but it's hard to tell. For example, according to MFP, a slice of Cheesecake Factory "Oreo Dream Extreme" Cheesecake is 1630 per slice but some homemade oreo cheesecakes come out at 300 or so per slice so it could be way more or less depending on the recipe.
I hate it when places don't make the nutritional info available.