An interesting question would be, if there is carbonate, what would be the ratio of lime to the carbonate; and the ratio of sulfate to sulfite? This might help to establish how strong was the oxidatizing environment when the minerals were laid down. It doesn't seem they have the instruments to determine these ratios on the rovers.
Calcium sulfate (gypsum, hemihydrate, or anhydrate) on earth are formed by precipitation from liquid water. Which form predominates depends on temperature and saline/pH of the ionic soup.
It's interesting to extrapolate from what they have already found out. I look forward to MORE info and explanations. Too bad the networks do not place more importance on this tremendous advance in knowledge of our universe. (Perhaps if NASA "sexed it up", they would cover it....she says snidely.)
Oops. "anhydrate" ==> anhydrite