Aurora R4 PCIe question

I have an Aurora R4 with the X79 chipset and an ivy-bridge E processor, which supports up to 40 lanes of pcie. It has 4 pcie slots at  x16, x1, x16, x1, and the bios gives me the option to support pcie gen 3.0. I know this works for the x16 cards as GPU-Z says that I am connecting at 3.0 speeds. I am currently using one x16 slot for my network card and one x16 slot for my graphics card, which is a dual slot  card and obscures one of the x1 slots. This leaves a single x1 slot available.

Does anyone know which generation of PCIe the x1 slots are?  I would like to install a usb3 card, and all of the cards that I can find require PCIe 2.0. I can't seem to find the specs anywhere, any knowledge would be greatly appreciated.