My little hill north of Las Vegas - the ground cover and geology

Unfortunately, I am posting in reverse order. So I have already been writing about this place. Here is a one little "instructional video".

It took a while to conclude that the black shiny material is volcanic [nah! it is marine], and a bit like obsidian. It is a bit more crystalline and, actually, reddish underneath the dark brown desert varnish. The darker, the older - a convenient chronological metric. I found it was in layers between the gray "garbage" material. These must, in turn, be volcanic ash. It took a while to realize both soft and hard materials are layered together in the bedrock. I wish I photo'd one of the sandwiches of material. Here is a cliff of it:

Perhaps a geologist could tell me if nodules of "chert" can accrete inside volcanic ash.

Update: Apparently yes, and in sedimentary layers too. So chert it is.

Update 2: I cannot be sure it is volcanic. It could be an old ocean bed.