PEBBLE PHOSPHATE DEPOSITS. 
63 
lies near the top of the phosphate beds throughout the whole field, 
indicates a change of conditions during the time of the deposition of 
the phosphate beds, a slight uplift having brought about a second 
concentration resulting in deposits of greater thickness and richer 
in the percentage of pebble phosphate to the matrix than would 
otherwise would have accumulated over this area. 
In pit No. 3 of the Prairie Pebble Phosphate Company near Mul¬ 
berry the following section was observed: 
1. Incoherent sand- 2 to 4 feet 
2. Indurated gray sand grading below into phosphate matrix-12 to 16 feet 
3. Workable phosphate stratum -- 10 to 12 feet 
4. Yellow clay marl, “bed rock” (exposed) - 5 feet 
The following section was observed in the pit of the Medulla 
Phosphate Company at Christina : 
1. Incoherent pale yellow sand and soil--- 2 to 5 feet 
2. Gray sand, iron stained near surface_ 8 feet 
3. Phosphate bearing matrix--12 to 20 feet 
4. Yellow clayey marl, “bed rock” (exposed) - 4 feet 
The gray sands of the overburden pass gradually into the work¬ 
able phosphate bed, the upper one or two feet of which is a coarse 
pebble conglomerate, while that beneath contains considerable clay. 
The stratification lines in this pit are well marked. 
IRREGULARITIES IN THE TOP SURFACE OF THE BED ROCK. 
That the top surface of the bed rock is extremely irregular is a 
fact observed in practically all pits that have been worked, the rock 
presenting in fact all of the irregularities of an original land sur¬ 
face. This is to be expected since it is believed that the bed rock 
marl was subjected to erosion for a time previous to the deposition 
of the phosphate. 
ABSENCE OF FORMATIONS OF THE MIOCENE PERIOD. 
The bed rock marl is believed as has already been noted to rep¬ 
resent deposits accumulated during the upper Oligocene time. The 
formation holding the land pebble phosphates on the other hand was 
formed as shown by the fossils which it contained either very late 
in the Miocene period or more probably early in the Pliocene. There 
is thus an almost if not complete absence of Miocene formations. 
