80 University Geological Survey of Kansas. 
the first one outlined; that is, due to evaporation of sea water 
in lakes or bays. 
Through some disturbance an arm of the sea was cut off, at 
least for a time, and the water evaporating deposited gypsum. 
At the north the gypsum rock is underlaid by limestone. This 
limestone is an evidence of marine life; but no traces of life are 
found above within the gypsum strata. Life for the most part 
would be destroyed in a basin where the water was concentrated 
enough to deposit gypsum. There is thus in this area evidence 
of abrupt change in physical conditions. The gypsum contains 
clay seams irregularly distributed through the beds, showing 
that the basin received the drainage of small streams carrying 
their loads of fine sediment. These conditions remained until 
at least 8 or 9 feet of gypsum were deposited, and then the old 
connection with the sea was restored by slow depression of the 
area. ‘The gypsum formation ceased and sediment was depos- 
ited over it in the series of sandy shales now found throughout 
the area. It is not possible to say whether the evaporation 
continued long enough for the deposition of salt, but probably 
it did not, as there is no trace of salt detected near the gypsum 
in this entire region. 
The northern land was then elevated and joined to the east- 
ward land and conditions then became favorable for gypsum 
formation in the Marion epoch in the central part of the state. 
In a similar bay the gypsum was deposited almost free from 
clay seams, but intercalated with shale beds affording good evi- 
dence of alternating conditions favorable for gypsum formation 
and sedimentation. 
The gypsum rock is thicker in the southern part of the area, 
and salt deposition is indicated by presence of salt springs and 
wells, but it has now been dissolved from over the gypsum, 
where it was probably comparatively thin. The great salt beds 
just to the southwest in the direction of dip of the rocks may 
have been deposited later in the stage of gulf evaporation, after 
the waters had deposited their gypsum where we now find it 
and had retreated further to southward. 
