Page 297 - Carbonate Facies in Geologic History

284 Shoaling upward Shelf Cycles and Shelf Dolomitization
- -320'--

yellow ~I® CI ® 0 well sorted
buff ("' 01" @
<;) - <;) - X-bedded
-1r C!)~ grainstone
red €I 0 0 <;)
~1'Ir -
0 :;) <;)
0* 00 poorer sorted
:!II " - I'" grainstone
I!}
IS) ~ 0
10 0*
~ -
red 1(:)
o (. * - spherulites Oolite 'Subphase
of clear water
,.. X-bedded shoaling phase
:JI IC!J III'
10
0 0
. (0 I .... grainstone
~
r* 0 * .
1 ~10 0
'II!'
,G ~
red ., ~ Co X-bedded
,* *1 grainstone
'JIll" !) 'II"
::>_~~I
(;j *** 290'--
. . thin bedded
•
. • . • lam pelleted
1"'\
· . bioclastic Normal
mudstone
. • . MOrine

Phase
•
'1Vr -28~'--

buff Beginning Clastic
.L~ silty mud stone ) Phase
280'--
,.
.. *'
gray 00*
brn. * * grainstone
'*
*
Fig.X-2. Upward shoaling cycle at Timber Creek, Big Snowy Mountains, Montana, in Mis-
sissippian Lodgepole Formation. Numbers indicate footage in measured section-about
13 m thick. Contacts between cycles are probably marine hard grounds because no evidence
of subaerial cementation exists in the oolite

the Central Montana high and in the Bridger Mountains to the south. Figure X-2
illustrates a typical Lodgepole oolitic cycle. Smith's detailed petrographic work
and tracing of the cycles across the Central Montana high from north to south
adds regional knowledge to the facies pattern (Fig. X-3). He recognized five cycles
in the formation, the lower of which (the Paine Member) in the Big Snowy and