Baculite Mesa
Last updated by Jerry Suchan
GESUCHAN@EARTHLINK.NET
Revision 2, 29 April 2005
This web page provides the results of the field work of the Western Interior Paleontological Society (WIPS) Field Trip to Baculite Mesa lead by Malcolm W. Bedell, Jr. on 22 May 2004. There are also plans for a second web page for the field work WIPS accomplished at nearby Tom Hollow on the same day.
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The following table of contents provides links to the indicated parts of this web page.
Introduction
and Comments
The Location
Geology
and Paleontology
Fossil Specimens
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This web page provides the field documentation of the Western Interior Paleontological Society (WIPS) Field Trip to Baculite Mesa lead by Malcolm W. Bedell, Jr. on 22 May 2004. This web page documents the results of the field work at Baculite Mesa. We also did some field work at Tom Hollow on the same day, and I plan a second companion web page to compliment this one.
All interested parties should be aware that all of the areas represented here are private property and absolutely no collecting is allowed without the permission of all the property owners involved. This permission is rarely given, and trespassing will result in problems not worth the fossils anyone might find.
These are the photos I have of the specimens. Others have other and complementing photos. All photograph were taken under field conditions. This accounts for my sunburned appearing thumb, but no, no my thumb isn't sunburned. The bright red is an artifact of compensating for the over exposure of the original photograph, an effect evident in several of the photographs on this web page.
Although I may suggest identifications for the specimens shown here, the main purpose of this web page is to document the specimens found by providing photographs of them. I have included the information I have on specimen ownership whenever possible. Besides acknowledging ownership, this also allows people conducting studies of the fossils and other aspects of the field location to ask the owner for permission to study and otherwise observe the collected material.
Please correct any errors I have made in this web page, for example in specimen identification or ownership or any other item, by e-mailing the corrections to me at GESUCHAN@EARTHLINK.NET
Many other web sites provide information on these and similar specimens, and even on Baculite Mesa. Such web sites can be found by placing the appropriate word or phrase (e.g., baculite, Baculite Mesa, Pierre shale, etc.) in your favorite search engine. Some links you may find useful:
Wayne
Itano's Colorado Pierre Shale Fossils
Paleocurrents - Fossils from Baculite Mesa
(WIPS Field Trip, May 17, 2003)
Scale: Just as it is important to keep records of the location and other information related to a fossil specimen, it is important to record the size of the fossils in some way. The best way to do this with a photograph is to include a suitable scale in the photograph, thus making it self documenting. I mostly use inches rather than the metric system. This is not the "scientific system", but the average citizen interested in fossils probably relates to inches better than centimeters. If you are uncomfortable with this, know that 1 inch = 2.54 centimeters. What scale is used doesn't matter a lot. The main idea is to give some idea of the size of the fossil specimens. Since I don't usually use a scale in the field because that is rather inconvenient because of logistics and weather (mainly wind) and so fourth, I just hold a hand sized specimen while I photograph it. Sometimes I place a coin or other object (a hammer works wonders) in the picture. That gives a sense of size that most can relate to. In any case, my thumb or fingers are usually in the photo if I use the "hold the specimen" technique to scale the specimens, and so I can estimate the size of the specimen to a useful order of magnitude.
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The Road to Fossil Heaven
Baculite Mesa is named for the plentiful baculite fossils found there. Unfortunately the preservation of these fossils is usually poor. Joshua Slattery specimens (DSCN0125 Lots of Baculites Joshua Slattery).
Searching for fossils on the flanks of Baculite Mesa
Teepee Buttes are common around and on the flanks of Baculite Mesa. This indicates we are in or just above the Teepee Buttes zone of the Pierre Shale.
Here is what appears to be a very thorough Teepee Buttes study: Tepee Buttes: Fossilized methane-seep ecosystems.
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The Cretaceous period lasted from about 144 my to 65 my ago. It was characterized in the general area of the Front Range of Colorado, and elsewhere, by swampy lowland conditions in the early Cretaceous, with a gradual transition to a marine (ocean or sea) environment, with the great Cretaceous seas covering this area during most of the remainder of the period.
As explained at Oceans of Kansas Paleontology, the Western Interior Sea, sometimes also called the Inland Sea, was probably less than 600 feet deep in most areas, and had a relatively flat muddy bottom. It is considered to be an epi-continental sea; that is one one which lies on top of a continent, and not between continents. The shallow Western Interior Sea covered most of the Midwest from the Gulf of Mexico to the Artic Circle.
The above is a generalized map of North American continent during late Cretaceous time. (Linked from Oceans of Kansas Paleontology.)
The Pierre shale is a marine formation deposited during the mid part of the Cretaceous period. As can be seen in the above geologic time chart for the Colorado Sprigs area (from "Geology of the Pikes Peak Region", Colorado by Richard L. Hubbard and Danny J. Wyatt, 1976), the Pierre shale deposition lasted from approximately 100 my to 90 my ago, a period of approximately 10 my.
According to Tepee Buttes: Fossilized methane-seep ecosystems, the stratigraphic position of the Tepee Buttes is within the Upper Cretaceous of the Western Interior Seaway, and in fact within the Pierre shale, as illustrated below.
(Chart linked from Tepee Buttes: Fossilized methane-seep ecosystems)
The Tepee Buttes occur within the Baculites scotti and Didymoceras nebrascense fossil assemblage zones. Because the Teepee Buttes are common around and on the flanks of Baculite Mesa, this provides a measure of the position of the shales of Baculite Mesa as well.
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The Fossil Specimens:
With the notable exception of Linda Soar's collection of trace fossils, the specimens found on Baculite Mesa this year are "the usual suspects". As far as I am aware, nothing new or different was found, except for the trace fossils. This does not mean these usual specimens are not interesting. They do represent the typical fauna of the this part of the Pierre shale. Furthermore everyone had a great time practicing their paleontology while they discovered wonderful specimens, perhaps some firsts for their fossil collection. I hope that everyone did a great job of curating their specimens by recording the date, geology and formation, location (by GPS if possible) and probable identification for each specimen they took from the field. This is the only way these specimens can have any future scientific significance.
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Snails (pelecypods):
All of the specimens illustrated here, except maybe the first one, are similar in appearance to the Euspira obliquata in Wayne Itano's page.
Above: Snail, Joshua Slattery specimen (DSCN0119 Snail Joshua Slattery). Specimen is about 1/8 inch long.
Above: Snail, Joshua Slattery specimen (DSCN0147 Snail Joshua Slattery). About 1/4 inch across.
Above: Snail in matrix. Dick Boucher specimen (DSCN0194 Snail Dick Boucher). Finger provides scale: specimen is about 0.75 inch in diameter at widest point and about 1.5 inches long.
Above: Snail internal cast, or steinkern. Shirley Alvarez specimen (DSCN0210 Snail Shirley Alvarez). Specimen is about 0.2 inch in diameter. Matrix is limestone and so was found in a Teepee Butte. Snails are commonly found in the Teepee Buttes. If you would like to see a picture of a complete steinkern (they are rather generic) follow this link to Gastropods: Gastropod, Steinkern-1.
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Inoceramus (extinct clams, aka pelecypods):
Inoceramus: An extinct genus of large, fossil, bivalve shells, allied to the mussels. The genus is characteristic of the Cretaceous period.
Above: Inoceramus. Joshua Slattery specimen (DSCN0121 Inoceramus Joshua Slattery). Hand provides scale, about 2.5 inches. Specimen shows typical death pose of inoceramus with both shells (aka valves) open and attached in butterfly pose.
Above: Inoceramus. Nick Betzen specimen (DSCN0179 Inoceramus Nick Betzen). Hand provides scale, about 4 inches vertically. Specimen shows both valves, but only one side is visible in the photograph because this specimen did not die in the butterfly position. Perhaps this was because it was buried in mud then it died.
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Ammonites (extinct mollusks most closely related to nautaloids):
Ammonite: The coiled, flat, chambered fossil shell of an extinct cephalopod mollusk that was abundant in the Cretaceous Period.
Above: Coiled ammonite. Tom Nelson specimen (DSCN0201Coiled Ammonite,Tom Nelson). Specimen is small, about 0.1 inch in diameter.
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Above: Didymoceras Sp. (maybe nebrascense) fragment. Steve Wagner specimen (IMG_9674resized (DSCN0198), Didymoceras Sp, Steve Wagner). Remember that the Tepee Buttes occur within the Baculites scotti and Didymoceras nebrascense fossil assemblage. That this is a didymoceras is indicated by the multiple open coils, of which three coils are evident. I did not ask where this specimen was found but they are more or less common on the Teepee Buttes limestone, and not common in the Baculite Mesa shale. This specimen appears to be preserved in limestone. This is small for a didymoceras.
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Baculites (straight ammonites):
Above: Baculite, Joshua Slattery specimen (DSCN0123 Baculite Joshua Slattery). Hand provides scale; the specimen is about 2.25 inches long.
This is, of course, the fossil after which Baculite Mesa is named. Baculites are by far the most common fossils found at Baculite Mesa. This one is a typical good specimen. The shell of the baculite is preserved only as a thin white layer visible at the top and bottom of the specimen. In life it would have had a mother of pearl sheen if the top most layer was removed. Some fossils preserve this beautiful appearance, but most of the baculites at Baculite Mesa fail in this respect. The living chamber of the animal is preserved at the left. It was the cavity the living part of the animal lived in and was filled with mud at death when the empty shell lay in the muddy sea bottom. The living chamber is typically flattened, a condition which is only slightly evident in this photograph. The suture lines visible at the right of the specimen have a kind of dendritic or leaf like appearance. These are only visible if the outside of the shell is removed. The dendritic or crinkled shape of the sutures is thought to provide strength to the baculite. In any case the patterns of the sutures are useful in identifying the species of the Baculite. They are actually the walls between each chamber of the baculite. It is thought these chambers could be filled with air to help the baculite control it's buoyancy.
What species is this? As explained by Wayne Itano, "The various species are distinguished by their suture patterns, cross-sectional shapes, degree of taper, size, and surface ornament. The book by N. F. Larson et al., which is cited on the main Pierre Shale page, has a key for distinguishing between 24 species of Baculites found in the Pierre Shale." Actually the sutures on this specimen aren't preserved very well anyway. Perhaps I will revisit this question at a later time.
Above: Very small baculites. Trick Runions specimen (DSCN0186 Small Baculite Trick Runions). These are not small enough to be juvenile baculites, but they are very small, as is evident from their preservation in the living chamber part of a much larger and yet still small specimen. Scale is provided by thumb: Larger baculite is about 0.5 inch across (diameter) and so the smaller ones, are about 0.15 inch in diameter.
Above illustration provides an idea of what a baculite might have looked like in real life. Fossil Replica - Baculite Life Reconstruction, picture linked from Black Hills Institute web site. These are "life sculptures" of the Baculites grandis. The shell is a cast replica of an original. Soft body parts were sculpted by Neal L. Larson. This is a replica of the largest specimen of the genus that has been found to date.
Of course, with no scale this picture gives no idea of the actual size of these giant baculites. It is not expected that Baculites grandis would be found at Baculite Mesa because the deposits there, the Tepee Zone, are too old. Even so, this is a great reconstruction of a baculite and gives us a feeling for the appearance of the long extinct animals. Perhaps someone is interested in buying the Fossil Replica - Baculite Life Reconstruction for $1500 ?
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Trace Fossils (aka ichno fossils):
This year Linda Soar brought a new perspective to the field trip with her search for trace fossils. While I know a little about trace fossils, and look for samples of them wherever I am investigating a field location, I learned for the first time how to find them at Baculite Besa.
As described in Ichnofossils and other traces of life, Ichnofossils are the non-body remains of organisms. This group includes burrows, borings, tracks, and any other trace formed by the life activity of organisms. Ichnofossils are very important in determining the ecology of extinct organism - although it is not always possible to link a single ichnofossil to the organism that made it. Ichnofossils are also useful in paleoenvironmental analyses, and other sedimentary problems.
Other interesting trace fossil links are:
Arthropod trackways
and
Chapter 3:
Ichnology: Trace Fossils
The following are the various trace fossils I saw during the field trip. Linda had a large sack containing several more specimens. The members of the field trip were very helpful in that they donated a number of trace fossils to Linda for her to study.
Above: Trace Fossils on baculite. Linda Soar specimen (DSCN0152 Trace Fossil on Baculite Linda Soar). The trace fossils are the small bumps on the upper right of the baculite. The baculite is typical in size, see for example specimen DSCN0123 Baculite, and this provides a scale for the trace fossils. They are small. What are they? Linda speculates "maybe fecal pellets or something".
Above: Trace fossils on baculite. I think this is a Linda Soar specimen found by Dick Bouche (DSCN0192 Trace Fossil On Baculite Dick Bouche). These appear to be some sort of etching through the shell of the animal, so they might represent some chemical or mechanical process rather than an organic fossil. Picture is about 1 inch in width.
Above: Trace Fossils on rock. Linda Soar specimen (DSCN0160 Trace Fossil Linda Soar). Scale is about 0.75 inch vertically across the specimen. Hard to say what these are, but one might again speculate they are fecal pellets "or something".
Above: Trace Fossils. Linda Soar specimen (DSCN0154 Trace Fossils Linda Soar). Thumb nail provides scale; the rock containing the yellow trace fossils is about 0.75 inch thick. What are they? One can only speculate (for now), perhaps invertebrate burrows in the ancient mud.
Above: Trace Fossils. Linda Soar specimen (DSCN0157 Trace Fossils Linda Soar). Scale is about an inch in the vertical. These differ from specimen "DSCN0154 Trace Fossils Linda Soar" above in that these traces clearly demonstrate branching. Pretty good candidates for invertebrate burrows in mud.
Above: Trace fossils on the inner cast of inoceramus. Linda Soar specimen (DSCN0165 Trace Fossils on Inoceramus Linda Soar). The suggestion for the origin of these trace fossils is that they are invertebrates which lived on the inner side of the inoceramus shell or next to the mantle.
Above: "U" shaped burrow in shale. Linda Soar specimen (DSCN0170 U Shaped Burrow Linda Soar). Speculation is that is a invertebrate burrow, such as a shrimp excavation. Thumb provides scale: the U is about an inch across. The original picture was badly washed out, and hence the lack of details.
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Above: Possible sponge. Nick Betzen specimen (DSCN0171 Sponge - Nick Betzen specimen.JPG). It is cigar shaped as illustrated, and has an apparent hole in the top, here at the left side of the picture. The bottom has marks reminiscent of a slickensides (a polished, striated rock surface caused by one rock mass sliding over another in a fault plane). Thumb provides scale: specimen is about 3.5 inches long.
There is disagreement on the identification of this as a sponge. There are no spicules (small calcareous or siliceous body found in the tissues of various invertebrate animals, especially in sponges) in the specimen to confirm it as a sponge, but not all sponges have spicules. Other suggested possibilities are: a trace fossil, such as a burrow cast; a concretion formed as a mud buildup at the bottom of the ocean floor caused by the flow of fluids or gasses upward.
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Above: Limonite concretion (a rounded mass of mineral matter found in sedimentary rock) . Steve Wagner specimen (DSCN0215 Concretion - Steve Wagner). I found a similar one, probably from the same location near the top of the shale on the east side of the mesa. These do not appear to be fossils.
Above: Annular patterns in the shale. I don't know who owns this specimen (DSCN0217 Patterns). What are these? One could speculate they might be trace fossils in ancient mud, mechanical changes, perhaps bioturbation, perhaps indications of algal growth, or some inorganic process such as chemical deposition or crystallization of salts in the mud. One story is as good as another so far.
Bioturbation is the disturbance of sediment layers by biological activity, is a significant process on the ocean floor. "Bioturbation is a key process in soft-sediment ecosystems" is also an interesting web site describing bioturbation.
Above: Annular patterns in the shale. Trick Runions specimen (DSCN0184 Round Patterns In Shale Trick Runions). What are these? Well I can repeat what I said above: One could speculate they might be trace fossils in ancient mud, mechanical changes, perhaps bioturbation, perhaps indications of algal growth, or some inorganic process such as chemical deposition or crystallization of salts in the mud. One story is as good as another so far. Scale provided by thumb.