LIME CREEK FAUNA OF IOWA IN SOUTHWESTERN UNITED 
STATES AND NORTHERN MEXICAN REGION. 
BY CHARLES R. KEYES. 
Twenty years ago one of our most prominent Iowa scientists, Mr. 
Frank Springer, announced the discovery, of a typical Lower Burlington 
fauna at Lake Valley, in southern New Mexico. A year ago I had occa- 
sion to state before this Academy that this Lake Valley limestone; is of 
wide extent. Now, at Lake Valley there exists beneath the limestones 
carrying he abundant crinoids of the Lower Burlington a massive, yel- 
low, magnesium limestone very much like the Chouteau limestone of 
Missouri, and beneath this green and then black shales in all respects 
like the Kinderhook shales at Burlington. Beneath this section there is 
in southwestern New Mexico and southeastern Arizona a limestone for- 
, mation which is Highly fossiliferous, and which carries the common fos- 
Y sils, many forms which we are very familiar with in Iowa. The most 
abundant forms are those unique types which collectively are known as 
the Lime Creek fauna, now famous the world over through the discus- 
sions and descriptions of Professor Calvin. 
It is now pretty well agreed by Tschernychew, Williams and other 
authorities, that this Lime Creek fauna is Mid Devonian in age, and that 
it appeared earlier in the West than in the East. In New York it is 
found in the Late Devonian portion of the section. Its recent discovery 
in the Southwest is of great interest. 
In' southwestern United States the Paleozoic sequence has been little 
understood. Of the five great systems which constitute it in the general 
section only the Carboniferous rocks have become familiar. Until within 
the past two or three years Cambrian, Ordovician, ^Silurian, and Devon- 
ian rocks have been practically unknown in New Mexico. Now all four 
/ systems are found to exist here. Peculiarity of areal distribution has 
been the chief cause for their escaping notice. They form a narrow' belt 
of tilted beds striking northwestw^ard from El Paso. 
In the Franklin Mountains north of El Paso where magnificent sec- 
tions, 4,000 feet in height are to be seen the entire Paleozoic succession 
is finely exposed. The Carboniferous limestones appear to rest directly 
upon the Silurian and Ordovician. Thus far no Devonian beds have been 
recognized. Farther westward the Devonian formation begins to appear 
^ and by the time the Arizona line is reached it has attained a thickness of 
over 300 feet. Although not yet reported the Devonion beds no doubt 
occur in a score or more of the mountain ranges of southw'estern New^ 
Mexico and southeastern Arizona. 
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