Gap is possible when you have size of section alignment larger than page size.
Example can be found here: c:\Windows\SysWOW64\ntdll.dll section alignment is 0x10000 but size of committed header is 0x1000 so first section starts at 0x10000 and there is gap between 0x1000 and 0x10000 but you can't access that memory in any way since it's not committed and you can't commit it manually. Use VmMap to see how it looks like there are no protection flags and so on...