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A Field Guide to Fossils of the Smoky Hill Chalk

Part 5: Coprolites, pearls, fossilized wood and other remains.


Copyright 2004-2012 by Mike Everhart

Page created 08/12/2004; Last Updated 09/09/2012



LEFT: Several views of a giant fossil pearl found in the Smoky Hill Chalk, Gove County, Kansas (Click to enlarge).  The specimen is the size of half a golf ball.

Continued from Part 4; Pteranodons, Birds and Dinosaurs


1. Coprolites:  The remains of feces / excreta are often found in the chalk and sometimes contain well preserved vertebra and other fish bones. They are white and chalky in appearance, and since they are composed largely of calcium phosphate, they are more resistant to erosion than is the surrounding chalk. For more information, see my Coprolite webpage.

copro01z.jpg (18959 bytes) LEFT: A large shark or mosasaur coprolite found in the lower Smoky Hill Chalk. The mass includes small pieces of bone and fish scales.

RIGHT: Shell coprolites - Small, compacted masses of oyster shell fragments are found only in a limited zone in the lower 1/3 of the chalk. These appear to be the coprolites from a fish or other predator that fed exclusively on oysters. At this point, only the plethodid Martinichthys is a candidate.

2. Fossilized Wood - Pieces of logs and branches floated out into the Western Interior Sea where they became water logged and sank to the bottom.

Professor B. F. Mudge (1877, p. 283-284) was among the first to note the presence of “an occasional fragment of fossilized wood.  … This wood was, in a few instances, bored before fossilization by some small animal. This might have been done by the larva of an insect (a “borer”) when the tree was living, or later by a teredo when the trunk floated in water. In either case it shows that the Cretaceous vegetation was subject to the same enemies as that of the present period. Some of this wood was in charred condition [carbonized] and would burn freely. Other specimens were changed into almost pure silica, the cavities studded with quartz. In one case a log, weighing about 500 pounds, had all conditions of the transformation; a portion had the appearance of soft decayed wood, which crumbled in handling, and other parts ringing like flint under a hammer. Occasionally specimens were converted into chalcedony, but the annual growth of the wood distinctly remained. In a single instance we detected the fibrous structure of the palm.”

LEFT: A fragment of the outer surface of a petrified log wood from the Fairport Chalk Member (Middle Turonian) of the Carlile Shale in Ellis County. The small round circles are abandoned borings that were later filled with chalk.  Note that the shipworm (Teredo sp.) borings in wood that Mudge referred (above) to would now be called Teredolites longissimus.... and that a "shipworm" is a actually a small clam, not a worm.

RIGHT: A closer side view of the same specimen showing the closely packed chambers where the clams were living. It almost looks like a bee's honeycomb but is not organized.... it was literally "every clam for himself"

LEFT: A closer side view of the same specimen showing the closely packed chambers where the clams were living.

RIGHT: A closer side view of the same specimen showing the closely packed chambers where the clams were living. Note the fibrous appearance of the surrounding wood; it appears that this log was preserved.. and not necessarily "petrified."


The remains of a tree nearly 30 feet long were reported by Williston in 1897 from near Elkader, KS. Often flattened, the wood had become carbonized (or in some cases, crystallized with calcium carbonate) and will burn poorly. Sometimes oysters and other invertebrates attached themselves to the wood before it was covered by the bottom mud. Most fossilized wood in the Smoky Hill Chalk is black in color but retains the grain of the original wood.  (NOTE

carbwooa.jpg (26199 bytes) LEFT: A section of carbonized wood from a large log in the lower Smoky Hill Chalk.

RIGHT: Detail of the carbonized wood at left, showing the fibrous, barely altered texture of some areas in the specimen. This wood is about 85 million years old.

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treebara.jpg (25399 bytes) LEFT: A small piece of preserved (calcitic?) wood where calcite crystals are covering it in a pattern that looks very much like bark.

RIGHT: A gnarly piece of wood (pine?) that was preserved in the Smoky Hill Chalk.

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3. Pearls - Sometimes small round nodules are found attached to inoceramid shells. They are the remains of pearls that were fossilized along with the clam shell. The nacre or "mother of pearl" luster is not preserved in inoceramid pearls.  This is because the pearly, nacreous color associated with true pearls is made up of a mineral called aragonite. In the Smoky Hill chalk, the aragonite is not preserved. Inoceramid shells and pearls have lost the thin inner pearly aragonite layer, and are solely composed of calcite. This also means that some kinds of shells, like those of ammonites, were not preserved because they are composed entirely of aragonite.  An 1940 article in the Hays Daily News noted that George Sternberg had donated 50 pearls from the Smoky Hill Chalk to the Smithsonian Institution, and a scientific paper was published on their occurrence (Brown, 1940).

LEFT: Two free pearls and three that are attached to fragments of inoceramid shells from the lower Smoky Hill Chalk. Click here for a close-up of the pearl at upper left.  The layers showing how the pearl was formed over time are visible.

RIGHT:  A side view of an inoceramid pearl showing the underlying inoceramid shell, most likely Volviceramus grandis.

Click here for pictures of a giant hemispherical pearl from the Smoky Hill Chalk.

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LEFT: Two small pearls (4-5 mm) from the base of the Lincoln Limestone Member of the Greenhorn Limestone Formation (Upper Cenomanian) in Russell County, Kansas.

RIGHT: A cross section of the larger pearl shown at left showing. the concentric layers.

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4. Borings: Many invertebrates that were living in the inland sea are represented indirectly by casts, burrows and other evidence.

cirripia.jpg (19349 bytes) In some cases, the damage done by cirripids as they bored into inoceramid shells is preserved while the actual animal is not. In addition, the bottom muds of the inland sea may have been relatively low in oxygen and may have not supported large numbers of smaller invertebrates. There is still much work to be done in defining the somewhat limited invertebrate community of the inland sea.

5. Burrows - Burrow structures from worms and other invertebrates were not generally preserved in the soft mud of the inland sea but can be found indirectly in some chalk strata. Currently, it is believed that the harder layers of chalk are evidence of thorough mixing (bioturbulation) by bottom dwelling organisms. It is likely that much of the evidence was simply not preserved due to the consistency of the mud and other, adverse chemical conditions as such lower levels of dissolved oxygen.

6. Bentonites - These are the remains of the ash (usually rust red in color) from volcanic eruptions that fell on the surface of the ocean. There are more than 200 bentonites in the Smoky Hill Chalk, each of which represents the eruption of a fairly large volcano (larger than Mt. St. Helens in May of 1980) to the west of present day Kansas. Some are an inch or more in thickness. Hattin (1982) used several of these bentonites as part of his stratigraphic marker units in the chalk.

7. Iron concretions: Iron concretions are found through out the Smoky Hill Chalk, but most often in the lower one-third. These concretions can form in many shapes and sizes and are composed primarily of iron sulfide (jarosite). In some cases they may form around bits of inoceramid shell or other debris. When freshly exposed, they are often shiny and exhibit various metallic colors on the surface. They tend to degrade fairly rapidly into splintery marcasite when exposed to moisture and often shatter or become piles of rust-red debris.

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LEFT:  The smaller, oval forms are referred to as "pop-rocks" locally.  They may be relatively smooth or have a definitely rough, crystalline surface. Small cubical pyrite nodules are found at some levels.

RIGHT: A large concretion formed on an inoceramid shell fragment, and roughly shaped like an animal.

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8. Silicified chalk - Variously referred to as Smoky Hill or Niobrara jasper, silicified chalk was formed after eroded and exposed chalk was covered by the sand of the Ogallala Formation.  Silica leaching from the sand permeated the chalk and hardened it. 

"Smoky Hill jasper, also known as Niobrara, Graham, or Republican River jasper, is derived from the Smoky Hill Formation of the Central Plains. This formation outcrops over a fairly widespread area across Kansas, Nebraska, Colorado, and Wyoming, although the highest quality chert-bearing deposits are limited primarily to locations from west-central Kansas to southwest Nebraska (see Hattin 1982). Smoky Hill jasper is a highly siliceous material that varies in color from caramel to dark brown, tan, black, white, green, yellow, and red. These materials frequently occur as flat, tabular cobbles banded with several of the above colors. Concentrations of quarries have been located in Graham, Trego, and Gove counties in Kansas (see Banks 1990:96; Stein 1997)." Excerpt from pages 183-184 of Brosowske, S.D. 2005. The evolution of exchange in small-scale societies of the Southern High Plains. Unpublished Ph.D. Dissertation, University of Oklahoma, 526 pp.  

"Nodular, usually stratiform masses of chert occur within the Smoky Hill Chalk at several places, e.g., at Locality 23, at several places in Graham County (Prescott, 1955, p. 47), and at Norton (Logan, 1897a, p. 220). At locality 24, the nodules reach thicknesses as great as 15 cm (0.5 ft). Smoky Hill chert is associated with highly weathered chalk and occurs in the uppermost part of the exposure. According to Frye and Leonard (1949, p. silicification took place at the same time as the silicification in adjacent Ogallala (Miocene and Pliocene) beds." Excerpted from Hattin, 1982, p. 19. 

"In a few places the chalk beds carry large amounts of chert which seem to be interstratified with the chalk. This is well represented at Norton, along the Prairie Dog Creek. Northwest of town about a mile the chert is quarried to a considerable extent. Plate XXVIII shows this, and Plate XXIX shows the same chert capping a chalk bluff at the old mill, Norton." Excerpted from Logan, 1897, p. 220-221, Volume II of the University Geological Survey of Kansas.

"From the bluffs south of the Smoky a large quantity of clayey limestone has been brought to fill the well. I found in these pieces of rock very good specimens of common opal. They are white and look like porcelain, and were formed by the infiltration of siliceous springs into the cretaceous strata; the magnesia contained in the latter caused the silica to assume the opaline rather than the agate or chalcedonic form." Excerpted from From LeConte 1868, page 11.

LEFT: A piece of silicified chalk from the contact between the Smoky Hill Chalk and the Ogallala Formation above Marker Unit 9 in Gove County. This piece contains at least three fish scales but is hard enough to ring when hit with a hammer. 

RIGHT: Another piece of silicified chalk from southern Gove County shown in side and top view. In this case, coarse sand, probably carried by flowing water,  infiltrated a space under a piece of loose chalk before being lithified by the silica leached from overlying sediments.

LEFT: A piece of banded silicified chalk from eastern Gove County.

Blade: A blade made from silicified chalk by a contemporary flint napper. The Plains Indians used silicified chalk as a source of tool making material, and as trade goods (Brosowske, 2005). Up to 40% of stone tools found in some areas of the Midwest are made from Smoky Hill Jasper. 

For additional background information on Kansas geology, Smoky Hill Chalk, marine fossils of the Late Cretaceous and paleontology in general, see my Late Cretaceous Marine references about Marine reptiles and Fish and other fossils.