The Burlington Formation
By: Richard Gottfried

The Burlington Formation is a marine limestone, found in rock layers
laid down during the Mississippian Period (325-360 million years ago).
The Mississippian Period was relatively short-lasting only 35 million
years-and its fossil record is almost entirely marine (Thompson, 1982).
This is due to the flooding of North America called the Kaskaskia
transgression, which began during the Devonian Period (380-450 million
years ago). This was interrupted at the end of the Devonian Period by
partial regression, but deposition continued uninterrupted into the
Mississippian Period. The Kaskaskia Sea reached its greatest extent
about the middle of the Mississippian Period, and late Mississippian
sedimentary rocks of the basins mark its recession. This recession
also marks the boundary between the Mississippian and Pennsylvanian
Periods in the North America (Clark and Stern, 1960).

The Mississippi Valley was covered by this clear, shallow, warm inland
sea that advanced from the south. During this period, limestone was
deposited to a total thickness of more than 2,000 feet in some areas.
These limestone deposits occur almost continuously from Iowa to
Alabama. The high bluff along the Mississippi River north of St. Louis
are typical of this deposit (Shourd and Wegenek, 1969).

The Kaskaskia Sea extended from the west, eastward into the Mississippi
Valley. The Early Mississippian marine deposits are far thicker in the
west and they seem to represent a much longer record of the limestone
deposition than anywhere else on the continent (Moore, 1958). From
Kansas, eastward to the Ohio Valley, the Early Mississippian deposits
are relatively thin and lithologically somewhat variable. The prevailing
lack of course sediments indicates that the adjacent lands were low.
Shifting seas, oscillating sea level, and instability of the sea floor at the
close of the Devonian time and the beginning of the Mississippian resulted
in a sequence of rock units that are complexly interlayered and vary from
one to another. As a result, geologists have found it difficult to make precise
correlations between regions. Some beds with definite characteristics in
one locality are considerably different even a short distance away. Also,
some beds lack distinctive fossils, and some have no fossils, making age
determinations difficult (Unklesbay and Vineyard, 1992). Thompson (1986)
has completely revised the Mississippian succession with new definitions
of some old units and the introduction of the newly named ones.

Throughout most of the mid-continent, the Mississippian is divided into
four series--the Kinderhook, Osage, Meramec and Chester. In the
Mississippian of Missouri, the oldest. Kinderhook is followed by a thick
limestone section comprising the Osagean Series. The Burlington
Limestone is its most prominent formation. It was recognized in the mid
1800's and named by James Hall (Moore, 1928) for its occurrence in the
bluffs along the Mississippi Valley at Burlington, Iowa, to include the beds
which had been called the "Encrinital group of the Burlington" and the
reddish brown Encrintal group of Hannibal."

Present in nearly all major Mississippian outcrop regions in Missouri,
the Burlington Limestone is widespread throughout the mid-continent
region. It is known from Iowa to northwestern Arkansas and from western
Illinois to western Kansas. It is present throughout Missouri, except in
the Ozark uplift, where it has been removed by erosion. Differentiation
of the Burlington with the overlaying, lithologically similar Keokuk
Limestone is often difficult or impossible, so the sequence of Osagean
limestones is sometimes identified as "Burlington-Keokuk Limestone"
(Thompson, 1986).

In Missouri, the Burlington appears at the surface in Lewis and Knox
counties, covers the larger portion of Shelby and Marion counties, and
is exposed in numerous places in Monroe, Ralls, Pike, Lincoln and St.
Charles counties. On the south side of the Missouri River, the formation
is found in the vicinity of St. Louis and southward into Jefferson, Ste.
Genevieve and Perry counties. North of the Missouri River, the Burlington
forms an almost continuous south-facing escarpment. The outcrop of the
Burlington in Warren, Montgomery, Callaway and Boone counties is
irregular, and there are numerous outliers. The formation makes high
bluffs along both sides of the Missouri River a short distance west of
Jefferson City, extending up-stream to a point 2-3 miles south of Glasgow
in western Howard County, and is found in numerous other areas within
the state (Moore, 1928).

As observed in most exposures, the Burlington Limestone is unusually
course-grained, crystalline, crinoidal limestone. Its texture is sufficiently
distinctive and persistent to permit recognition of the formation commonly
on this basis alone. The Burlington Limestone is made of almost entirely
on the remains of various fossils, by far the most important of which are
crinoids. Some portions of the Burlington, however, are not so evidently
crinoidal, as for example, the so-called "white ledge" quarried in the
northeastern part of Missouri. Parts of the Burlington formation also
consist of thin, uneven cherty beds and cherty nodules (Moore, 1928).

A large proportion of the crinoid species are restricted to the Burlington
Formation. The crinoids began to assume a front rank in the beginning
of the Osage, as shown by the rich crinoid faunas of the Fern Glen and
other beds. The Burlington contains a record of the continuation and
acceleration of crinoidal development; the clear, shallow waters of the
Mississippi Valley being apparently a region of maximum differentiation
and dispersal of crinoids exhibit evolution along several lines-species of
Burlington age being broadly distinguished from those of the Keokuk
and both of these from Warsaw types.

The Osage epoch marks the culmination of the great division of the
crinoids known as the Camerata, and it is remarkable that immediately
following this maximum deployment the group vanished.

Crinoids flourished because they were filter feeders, and most of the
particles in the clear oceans would have been bits of food. They also
needed warm water to produce their elaborate skeletons, since warm
water can hold more dissolved calcium carbonate than cold, making it
easier to precipitate (Thompson, 1982).

One can imagine the crinoids growing in extensive marine meadows,
rippling in the waves on their long, thin, graceful columns, like garden
flowers in the wind. On rare occasions, they were preserved whole,
flattened to the bottom by a storm and quickly covered with lime mud.
Unfortunately, the organic matter connection the plates and columnals of
the stem nearly always rotted in the water and plates were scattered and
sorted by the waves to form crinoidal limestones (Clark and Stearn, 1960).

The Burlington contains more species of crinoids than any other
formation in the Mississippi Valley. About 260 species have been
identified, some of which may be descriptions studied only casually.
Brachiopods are next in abundance. About 110 species have been
identified. Bryozoa are abundant but only a few species have been
recognized. Blastoids are more abundant in the Burlington than any
other formation in Missouri. Thirty-three species have been listed,
mostly in northeast Missouri near Louisiana (Branson, 1944). Colonial
corals declined in some areas, but solitary corals were diversified and
abundant. Gastropods, pelecypods and cephalopods are rare. Sharks
greatly increased their numbers and variety, which may have contributed
to the decline of the trilobites, (Shroud and Wagenek, 1969), as only a
few specimens of trilobites have been found. Shark's teeth are widely
distributed, but rare. About 100 species have been described from the
Burlington of the Mississippi Valley, but of these, not more than 20
are known from the Burlington of Missouri.

Branson, E.B., (1944), The Geology of Missouri, Vol. XIX, The University
of Missouri Studies No. 3, Columbia.

Clark, Thomas H. and Stearn, Clint W., (1960),
Geological Evolution of America, 2nd edition, The Ronald Press Co.,
New York.

Moore, Raymond C., (1928), Early Mississippian Formations in
Missouri, Missouri Bureau of Geology and Mines, Rolla, Mo.

Moore, Raymond C., (1958) Introduction to Historical Geology,
2nd edition, McGraw-Hill Book Co., New York

Parker, Steve and Bernor, Raymond L., (1960), The Practical
Paleontologist, Simon and Schuster, Inc., New York, 1990

Shourd, Melvin L., and Wegenek, Leonard R., (1969), Fossils
A Student Reference Book, Alfred A. Knopf, New York

Thompson, Thomas L., (1986), Paleozoic Succession in Missouri:
Part 4 Mississippian System, Missouri Department of Natural
Resources, Division of Geology and Land Survey, Rolla, MO, 1986

Unklesbay, A. G., and Vineyard, Jerry D., (1962), Missouri
Geology, Three Billion Years of Volcanoes, Seas, Sediments, and
Erosion. University of Missouri Press, Columbia and London

Burlington Formation

Mississippian Fossils of Missouri

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