"That must've been a lot of work--thanks."

You're welcome. Nothing compared to what you do here.

"Given that the stratigraphy is based on a "standard" one cubic kilometer of seawater, would the stratigraphy we actually find somewhere scale to tell us the depth of the water?"

In the abstract, yes. On a real planet, not really. If Nick is right about the sabkha, or it's a playa, then it becomes alot more complicated. For example, the evaporite Castile Formation (Permian) of Texas and New Mexico has a max thickness of 1200 m. How deep would that sea have been?

Thick evaporite deposits are created with a continued influx of sea water into a shallow evaporative basin which is slowly subsiding. It has been said that this unit is a few hundred meters thick (was it 200?). Is that the entire package? With an evaporative basin, the stratigraphy is similar, but there is a component of lateral zoning as well. I'll draw that up, too, but this is a busy week.

As for the rest of your questions, I think we have to try and assume the martian seawater based upon the rocks that eroded up-stream. I assume someone has a grant to research this, I'll keep my eye open. I'm not sure what would result, a change in the thickness, and total mineralogy. Other clues? I'll think on it. The water may be dense, but what with? The rocks will tell us, hopefully.

Also, there are evaporite deposits that never saw much of a sea, like the White Sands in New Mexico.

You are so right: ?'s to the Nth power.

jms