The Coconino sun., 1927-01-21
FOSSILS AT GRAND
CANYON
BY G. E. STURDEVANT
: !. !. -. i. -. !. ]. :

one hundred and forty thousand peo-
pie yearly to see the Worlds Most
Sublime of Earthly Spectacles, il
serves as one of Natures greatest
museums where the successive life
forms of the Paleozoic are beautifully
portrayed. Many laymen as well as
scientists take keen interest in the
& various phases of past life found in
the thick horizontal strata that make
up the greater part of this enormous
cash in earth's crust.
The former representatives of life
IN this region are known as fossils.
Popular Interpretation Of a fossil
] generally means something ancient.
This IS only partly correct. A Roman
coin is quite ancient yet it is not a
! fossil. likewise the dodo bird, which
has become extinct in the life of man,
IS often regarded as ancient since no
| living person has ever seen a live
/ specimen. By definition a fossil is
ANY trace of organism preserved IL
a deposit in some past geological
! period"
Fossils are preserved in several
ways. The original material is some
/ times found such as the hairy MAN.
/ AiID5iA II CcSA NCd III lIG IclStO ice
| fields of Siberia. Carbonization of
the original plant material is another
mode of preservation. All plants
contain certain amounts Of carbon.
Pressure, due to the accumulation Of
sediments, drives out the water and
volatile gases from the plants caus-
ing concentration Of the carbon.
| Thus, by mining the coal millions of
years after it is formed, one can view
the carboniZed remains of plants ages
after they have become extinct. Areas
are encountered occasionally where
the original material is encrustated
by calcareous material which is chem
icaly the same as limestone. This is
especially true around former calcar-
eous springs. Such process can be
seen taking place today around the
hot springs of Yellowstone National
Park. Another method, of preserva-
ton Of fossils, is by impression. FIRE.
quently leaf drops in the soft mud
or an animal walks along leaving his
trail. Later the mud or wet sand /
may become hardened by superim-
posed sediments preserving the traces |
Of life-forms as impressions for thou /
sands of years. Perhaps the most |
u
petrification or replacement by stone /
The original material is removed in |
fine particles and replaced generally I
by silica. Petrified wood is not wood I
turned to stone but wood replaced by |
stone. Replacement or substitution |
OF chemical for the woody material |
takes place at the same rate as the |
removal Thus petrified wood often
times reveals the actual cellular struc-
ture of the species. The most COM
mon modes Of preservation of the fos-
sils found at the Grand Canyon are by
impression and petrification.
The animal tracks, invertebrate fos-
sils, and fossil ferns, at the Grand
Canyon, are especially rich in species. +
Each species has it's individual his
tory such as its geological range and
as well as its source Of
origin. Some of the species are SO
they can be treated as in
dividual subjects.
The tracks in the rocks are Of espe-
cial interest. Three successive forma-
tions along the Hermit trail contain
animal tracks. At present three gen
era and three species have been clas-
sified from the Supai formation, eight
genera and ten species from the Her
NIT shale, and fifteen genera and
twenty-five species from the Coconino
sandstone. The Coconino sandstone
is regarded by geologists as the best
Permian fossil track horizon in the
world. DR.. c. w Gilmore of the Ma s.
tional Museum, who has done most of
the work on the animal tracks, be-
lieves the total of twenty-six genera
and thirty-five species will be consid-
erably increased by further collec- |
tions.
A great many species Of inverte-
brate fossils are found in the walls of
the canyon. Some are large being
four or five inches in length while
others are microscopic in size. Some
are worldwide in their distribution
while others are exceedingly limited. ;
Some Of the forms lived for millions
If years without any perceptible
change while others became extinct
after very short vertical range
Among the fossil forms, one or
more species of the following genera
occur in the Hermit shale: Calliptoris,
Glenopteris, Pecopteris,
Neuropteris, Tinyppterris, Spheno-
Dhyllum, and Walchia. DR.. David !
hlte, senior geologlst OF the geOlog- ,
cal survey, is preparing a paper on
he above plants collected at thief
Grand Canyon during the past sum
ner
Fossils are not mere curiosities of
past forms of life that were once
prevalent upon the earth They give
| vivid account Of the life present at
hat particular time In addition
some fossils serve as an invaluable
lid for geologists in classifying the !
lge of bezds.' Such fossils are known
IS Index" fossils or ''horizon mark
,rs." These fossils have a wide dis
with short vertical range.
Cor instance Callipteris conferta lived
exclusively in Permian time Two
,eds of rock exposed in valleys sew {
raj miles apart may appear as the
anne bed yet to establish conclusive t
roof it is necessary to find the fos- I
lis. If oil is discovered in a field at t
me locality the presence or absence 7
f fossils determines if the same form
ltion is present in an area some dis
ance removed. Fossils tell us of the I
nvasions of ancient seas, their extent,
nd how long before they withdrew. II