Any idea what made this formation?
Q – This is in the Utah desert, south of Green River. I keep hearing that it might be clastic dikes? I have sent this pic to the USGS and they are kinda stumped too but plan to send some paleontologists to check it out.
A – The clastic dike explanation looks quite probable. As I understand it, when a fluid (typically water) saturated body of sediment is overlain by another thick layer of sediment the weight of the overlying sediment overpressures the fluid in the saturated sediment body, resulting in the fluid forcing its way toward the surface, where the pressure is lower, and entraining the accompanying sediment as it rises. Probably looks like a lava lamp, though the processes are distinctly different.
My Masters Thesis was clastic dikes of the Panoche Hills (central) California.
And yes, the features seen in these photographs from Utah and seen in the recent issue of the Newsletter do look somewhat that they could be associated with clastic dikes. However, I would want to view them up close and personal before saying anything more. For one, the fracture system of the area is a strong clue as to their origins, something difficult to determine with the information at hand.
I don’t remember any of my dike structures being evenly truncated at their tops. Obviously at some point in their history there was significant erosion that planed the top of the structure off as well as the surrounding area; and the structures were durable enough to resist subsequent erosion and weathering enough so to persist, as we see them, to present. To make them as durable as they appear to be I would speculate that they were injected from below and into their existing cracks by sediment overlying a fluid rock unit (unconsolidated and wet sediment).
Norman Smyers