Whiting claims there is a new interval below the middle Bakken and above the upper Three Forks. The lower Bakken silt is prospective Whiting's Hidden Bench leasehold.At the link, there is a Whiting graphic which shows this additional interval.
I linked this graphic just the other day from the Whiting presentation, but I missed this interval; it just shows how good Mike Filloon is in noting details.
The Lower Bakken Silt sits between the lower Bakken shale and the Pronghorn Sand in the Hidden Bench prospect and is considerably thicker than the Pronghorn Sand based on the graphic, up to 7 - 10 x thicker based on the graphic.
See also this link (at the link, scroll down).