Does the change from the thick gray shale to the overlying sandstone indicate a transgression or a regression

regression

Explanation:

Where the gray shale was deposited is the marine environment, then there is

sandstone and mudstone in the upper unit and they are deposited in a river system. And this can be regarded as a transition which exist between the Marine and non-marine environment which is as a result of relatively drop in level of sea and this is regarded as regression.

answer ( groundwater);

the climate of each region is different from one another.