And no, Faith, there is no 'front' in this photo. It is like a cross section.
I can't read the photo any other way. Please mark the photo so I can see what you mean.
As for your correction of "in front of" as "below," yes the Vishnu is literally beneath the sandstone but it's also in front of it as I read the photo.
As I see that photo, the top of the sandstone is actually about twice as far up as where you drew the upper yellow line. The top is the redder material at the upper-left corner. The part between the yellow lines is more or less vertical, and the part between the top yellow line and the redder top is more beveled back, thus the shadow difference. I'm guessing that a few inches of sandstone thickness is being shown there, and that it is thicker further back, outside the photo frame.
The sandstone left there is an erosional remnant - The sandstone used to cover the entire area of the photo. It's NOT that the sandstone stopped being deposited at that point, with the larger quartz clasts being pushed at the front. There are most likely more large quartz clasts still conceiled in the sandstone. OR PERHAPS the quartz chucks are the remains of vein material, still in place. Hard to say without looking at it in person, and also without seeing the larger context.