Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1937-04-24

DR.. Del6S befan rechecklng the CambY1an
/ nomenclature which resulted when subsequent
OF the formations as defined BY ". H. Weed
AZ the turn OF the century.
! Geoloslsts have tried for years 20 clarity
/ this confusion By a study OF the literature
alone, or q study Of fossils only. But the
Inaccuracies in the field work Of investigators
and the "a lurc Of these investigators 70 as
sign the fossils they collected 70 the correct
formations left Cambrian paleontologie liter
allure practically MEANINGLESS" Or, Deiss
says.
After checking his fossils collected in Mon
tana directly with the type Of Cambrian fos-
siis In the United States national museum
Dr.. Deiss Was able to answer the i've major
questions which had confronted him at shs
beEinninE Of his study;
Five Major Questions
l. Where are the original type CambFian
sections and type localities Of the described
formations located?
? Are the formations. as oriEinaliy defined
readily recognizable in the field-that IS. are
must they Be amended or discarded
B. are the thickneSses originally given rea-
Sonably accurate. and are they uniform
throughout the area7
g. What are the exact styatigraphio horizons
within each formation from which fossils
are known
S What are the most important published
species that may be used indiees TO the
AAAActtut AolHAIpuhf
where Exposed
The AREA under consideration Is IN CEN
trail and southern Montana Just west OF the
central part OF the state and Ia the north
western part Of Yellowstone park The Cam
brian rocks within the area form a consid-
cradle part OF the Bic and Little Belt, Castle
and Biz Snowy mountains and OF the BridgeF
Madison and Oailatin RANGES These rocks are
also exposed in the Absaroka and Beartooth
ranGes. and IN the Horseshoe hills lying be-
mn he - asnA fha
missouri and Oalntln rivers on the west
and south. The southern end Of the Gala
TIN rance extends into the northwestern
corner Of Yellowstone park.
Measures Sections
Dr. Deiss examined II sections OF Cam
brian rock In detail in order TO evaluate the
original field work and definitions Of forma-
tons. In those sections direct measurements
OF the beds with q steel tape we're made
wherever possible. steel tape was also used
for transverse distance In obtaining field
data Tor the computation OF thicknesses where
direct measurements we're impossible A Rich /
ARDS model OF a Brunton comrass was used
FOR obtaining the altitude OF the strata and
slope angles and for traverse bearings Slope
angles were read directly in order to elm /
nate errors. Computations OF thicknesses I
we're checked to within a 5-percent limit OF I
error. In addition. fossils we're searched for 4
m. and collected only from the measured /
sections. thus ELIMINATING any possibility Of I
opinion or Interpretation as TO their exact
Itrategic position
DR. Deiss WIS able To keep constant snd
progressive check on the relative positions
y the same faunas IN different sections Con-
ilusions developed from his study he lists
lnder six heads;
Il. All but one OF Weeds ORIGINAL names
Y the Cambrian formations in the Little
3elt mountains must be retained as the
tandard for central and southern Montana
nd Yellowstone park. The reasons for this
onclusion are: The names we're taken cor
ectly from geographic features the forma-
ions are apparently natural iithoioRic units,
nd are persistent and readily RECOGNIZABLE
vervwhere In the area. From the base up
ard. these formations are: F1athead sand
tone Wolsey shaie. MeaEher limestone, Park
hale Ptlgrim limestone and Dry Greek shale
Fellows Weed Names
"a. Pesle's ORIGINAL nomenclature for the !
hree Forks Cambrian section must be dis
eRarded. The name F7athead formation IL
ow restricted TO the basal arenaceous sun
~ formation OF the series. The use OF Weeds
ames to denote formations invaiidates the 4
anne Gailatln for thet rank II future workers I
re the term oallatin. they should do so to !
anne Eroup and not a formation, and J
louid apply the term only 10 Upper Cam
Ran sediments. Peale's members Of the Cal
tin formation fTriloblte limestones OboI- G
lie shales. Notified limestones Dry Greek | 4
tales and Pebhly limestones). with the exc {
ption OF the Dry Greek. were discarded In 5
100. The Htholosic units referred to By
lese names are all present IN the Three
orks area except one the Pebbly lime q
ones. and are now correlated respectively s
lth the Measher, Park. Pilgrim and Dry 2
-eek formations
Each Section Amended
D. Discrepancies between the original de- y
riptions and the conditions observable in +
e field are so great that each section had
be amended. The errors and ambiguities in
e original definitions Of the type forma- =
,ns likewise necesstated their revislon q
ReauiFes New ZonInR n
- Satisfactory faunal lists cannot be n