Lab

Fossils and Fossilization in the National Parks

OBJECTIVES

• • To understand that fossils are naturally preserved remains or traces of once-living organisms.
  • To understand that once living organisms appear in the fossil record and can tell us about paleo environments.
  • To use index fossils to determine geologic sequences and correlate rock layers.
  • To recognize and identify the different methods of fossilization.
  • To determine the symmetry of fossils.

MATERIALS

• Graph paper, pencil, ruler, scissors, various fossils and images of fossils

INTRODUCTION

The Earth is 4.6 billion years old. Its history, secrets and stories are all written in the rocks. Geologists use clues found in the rocks from observations, radiometric age dating and proxy data to determine the ages and environmental conditions of specific rock layers and fossil evidence, thereby solving many of the Earth’s mysteries. Observational evidence such as the relative age dating law of superposition that state in an undisturbed horizontal sequence the layers at the bottom are older than the layers on top. When fossil evidence is included into this law we understand that fossils in the lower bottom layers are older than fossils in newer top younger layers. Fossils can be preserved in a wide variety of ways and Paleontologists use these methods to unravel the ancient history and condition of an organism’s life. We will explore the use of fossils to determine relative ages of rock layers and explore the many methods of fossilization in order to better understand the 4.6 billion-year history of planet Earth.

There are hundreds of National Parks that contain substantial fossil remains that have contributed significantly to our understanding of ancient life and paleo-environmental conditions in the United States: Agate Fossil Bed National Monument, Nebraska, Aztec Ruins National Monument, New Mexico, Badlands National Park, South Dakota, Dinosaur National Monument, Colorado, Florissant Fossil Beds National Monument, Colorado, Hagerman Fossil Beds National Monuments, Idaho, John Day Fossil Beds, National Monument, Oregon, Fossil Buttes National Monument, Wyoming and Petrified Forest National Park, Arizona (figure 1).

Figure 1. The orange dots represent the myriad of National Parks with paleontological resources in the United States. Image: NPS public domain https://www.nps.gov/subjects/fossils/fossil-parks-list.htm

What is a Fossil?

By definition fossils represent the tangible remains or signs of an ancient organisms’ existence. The term is derived from the Latin term fossilis meaning ‘dug up”. Paleontology is the study of preserved remains or traces of past plants and animals. They are traditionally preserved in sedimentary rocks or sediments especially marine environments. They include unaltered remains such as those found in tar pits and amber to simple evidence of life such as burrows and footprints in sandstone to atomic replacement of organic atoms by carbonate and silica minerals such as petrified wood, fossilized bones, feces and shells (figure 2). Most fossils are not original material but imprints or chemically altered hard body parts of organisms. These products can sometimes preserve exquisite details of the original organism, that allow us to understand how they lived. Today we classify fossils as remains that are older than 10,000 years. This demarcation helps to a draw line between paleontology and human or cultural Anthropology.

Figure 2. Left - Fossilized fish feces, known as coprolites from the Green River formation in Fossil Buttes National Monument, Wyoming. Coprolites give paleontologists unique insights into how an organism lived based on what it ate. Right- many C. Liops fish from Fossil lake Fossil Buttes National Monument in Wyoming. The group clustering is the result of a catastrophic fish die-off possibly due to sudden temperature or pH change in the water. Images: NPS public domain. https://www.nps.gov/fobu/planyourvisit/visitorcenterexhibits.htm

What can fossils tell us about the past?

Using the laws of relative age dating along with fossil correlation and unique index fossils, it is possible to recreate a sequence of geologic events. William Smith, in the 19^th century determined that certain fossils only existed in the fossil record for a short period of time and within a specific rock material. These unique short-lived organisms became known as index fossils. As a result, we can use these specific fossils to correlate and connect rock layers and time over great distances. For example, if you found the same fossil in Pennsylvania and then again in New Jersey you might consider that the same conditions existed at one point in both Pennsylvania and New Jersey, such as a marine or coastal environment. William Smith also discovered that fossil organisms were more complex in younger rock layers (on top) than in older rock layers (below). This increased complexity of fossils became known as fossil or faunal succession. Species change over geologic time, becoming more diverse as evolution develops. Paleontologists find simple organisms such as marine brachiopods and graptolites in older rock units and more complex organisms such as ammonites, sharks’ teeth, and marine reptiles such as ichthyosaurs in younger rock layer. More complex dinosaurs and mammal fossils are found in even younger rock layers. When several organisms are found together in a rock layer we can conclude that they must have lived at the same time and in the same environmental conditions. So, if two fossils appear together in a sequence their lifespans overlapped. By combining the lifespans of several fossils we can narrow down the time frame in which they all coexisted. Once a fossil appears in the fossil record and then disappears through extinction it NEVER reappears. Extinction is permanent.

ACTIVITY #1- Practice Sequencing Layers Using Recurring Fossils

ON THE ATTACHED PAGE AT THE END OF THE LAB, CUT OUT THE 8 CARDS with letters representing a fossil or fossil group. Using the principles of superposition, fossil correlation and fossil sequencing order the 8 cards from oldest at the bottom “TC” to youngest at the top. Look at the card with fossils T and C. Which card has a fossil letter in common with TC. This one is next in the sequence. Try to arrange the remaining cards in order from oldest at the bottom and youngest card at the top.

ACTIVITY #2 - Index Fossils and Fossil correlation

Now that you have practiced fossil correlation with letter cards let’s look at some rock/fossil layers. AT THE END OF THIS LAB FIND EIGHT CARDS WITH LETTERS AND FOSSIL IMAGES. Cut out the 8 fossil cards with letters and fossil images. Each card represents a specific rock unit containing these fossils in marine sediments. The oldest rock layer is designated as “M” with fossils Brachiopod and Trilobite. Using the 8 cards with specific fossils organize them from oldest at the bottom “M” to youngest at the top. Just like the previous activity find the overlapping fossil organisms.

What is the word spelled by this sequence? _______________

Interpretation and Determining Index Fossils

Using the grid below, write the 8 letters on the Y-axis with oldest at the bottom and youngest on the top. The oldest unit labeled letter “M” is filled-in for you.

On the X-axis write the names of the fossils in each unit. Do not repeat names, there are 13 original fossils. The fossil “Brachiopod” is filled-in.

Using the graph below shade in a bar where each fossil species existed over their letter time frame. For example, Brachiopods existed in times “M” and “S”, so shade in a bar over time frames M and S (see below).

Answer the following questions:

Which fossil would make a useful index fossil?

If I found fossils Eurypterid, Trilobites, and Horn Corals in the same rock layer, what is its age?

Is the Crinoid a good Index fossil? Why, why not?

Comment on the increased complexity of the organisms in this sequence.

If I suspected that I had layer/unit ‘O’, what fossil might be present?

How to Become a Fossil:

Not everything that has lived on Earth can become a fossil. Consider what the Earth would be like if all living plants and animals became fossils. A unique set of conditions are necessary to preserve remains. Typically, when an organism dies its remains decay, and the elements return to the Carbon and Nitrogen cycle. Think about a rotted tree in the forest, or a fish in the ocean. In order to become a fossil an organism needs to escape the traditional decay process. Rapid burial after death is needed to escape the biological breakdown that results from sunlight, water and oxygen. Having mineralized body parts such as bones and shells, shedding mineralized parts such as sharks’ teeth along with living in a marine environment increases an organism’s chance of being preserved. This uneven chance of preservation leads to bias in the fossil record. This is not scientific bias but the simple increased chance that certain organisms such as marine trilobites have of being fossilized. A jellyfish that lacks hard body parts or a land-based organism such as a reptile whose remains are most likely to be scavenged will likely miss being buried by natural events and therefore have little chance of becoming a fossil. Soft body parts such a tissue are rarely preserved while hard body parts such as teeth, shells and bones have an increased chance of being preserved. Therefore, all organisms do not have an equal chance of being preserved.

To increase the chances of becoming a fossil it is best to have:

• Hard body parts – Bones, Teeth of Shells
• Get buried very quickly in an oxygen poor environment such as a swamp or silty muds
• Stay buried
• Try not to have your rocks metamorphosed by plate tectonic movement.

PRESERVATION METHODS - Taphonomy

UNALTERED SOFT PARTS

The preservation of actual soft tissue or soft body parts is rare. Protection from bacteria, water, sunlight and scavengers is needed for this to occur. There are a few special circumstances such as subfreezing temperatures and extreme dryness that can preserve both hard and soft tissue. Examples of preservation of unaltered soft body parts include freeze dried mammoths and desiccated mummies in very cold and dry regions. Fossils have been found in the Bering Land Bridge National Preserve in Alaska which is one of the most remote National parks with its headquarters located in Nome, Alaska and preserving 2.7 million acres of wilderness (figures 3 & 4). Preservation of unaltered soft body parts is extremely rare.

Figure 3. Artist drawing of a Pleistocene aged woolly mammoth. They are related to modern elephants. Bering Land Bridge Preserve, Alaska where the remains of a freeze-dried baby mammoth was discovered. Images:

https://www.nps.gov/bela/learn/historyculture/woolly-mammoth-page-2.htm

https://en.m.wikipedia.org/wiki/File:Bering_Land_Bridge_Preserve_95.jpg

Figure 4. Wooly mammoth hair. Image: (Mammathus primigenius) hair. https://opengeology.org/historicalgeology/tools-of-historical-geology/fossil-taphonomy/

UNALTERED HARD PARTS

Some hard body parts such as shells, exoskeletons, and teeth are made of minerals that are extremely stable such as calcite (calcium carbonate), apatite (calcium phosphate) and silica. In rare occasions tree resin from ancient conifer trees (amber), can engulf an insect and preserve it without alteration. Samples of Amber are found abundantly around the world and in Chaco Culture National Historic Park in New Mexico (figure 5). Tar pits such as the famous LaBrea Tar pits Natural History museum on Wilshire Blvd in Los Angeles has spectacularly well-preserved species such as Dire wolves, Mammoths, Saber-toothed cats, Bison and many other species representing the life that existed 50,000 years ago in southern California (figure 6). The hydrocarbons in the tar or paraffin seeps into the bones and preserves them in great detail as well as making them dark black in color.

Figure 5. Chaco culture national historical Park in New Mexico showing an amber sample in situ. Image: NPS https://www.nps.gov/media/photo/gallery.htm?pg=1945673&id=9CE67B5A-155D-451F-67BFCD88A0E5F08D

Figure 6. Tar bubble seeping out of the ground at the George C. Page museum La Brea Tar Pits, Wilshire Blvd. Los Angeles CA. Animals got trapped in the tar and we very well preserved. Image: By Daniel Schwen - Own work, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=753192

ALTERED REMAINS

PERIMINERALIZATION: This is the most common form of preservation. Shells and bones are porous which allows the spaces to become filled with calcite or silica after burial preserving them in great detail. This process makes the fossil strong and preserves very fine details. Dinosaur National Monument in Utah and Colorado has well preserved dinosaur bones (figure 7). The Petrified Forest National Park in Arizona is home to large conifer type trees that existed around 225 million years ago. The forest was buried rapidly in soft sediments during a flooding event. This rapid burial protected the organic tree material from the decaying effects of sunlight and water. Perimineralization occurs as mineral laden waters seeped into the cells and replaced the organic material with dissolved minerals, preserving great details within the trees, turning the wood into stone (figures 8-10). Trace elements such as oxidized iron can add unique red rusty colors to the sample, while varying amounts of manganese, reduced iron, copper and lithium produce the varied black, green, and yellow colors.

Figure 7. Dinosaur bones on the quarry wall in sandstone. Jurassic Morrison Formation Dinosaur National Monument Utah/Colorado. Image NPS Kenneth Carpenter CC BY-SA 4.0. https://en.wikipedia.org/wiki/Dinosaur_National_Monument#/media/File:Bones_on_Quarry.jpg

Figure 8. Petrified Forest National Park, Arizona. Fosilized wood logs appear as though they have been recently felled by a lumberjack. Notice the lack of branches that were stripped by the flooding event that transported and buried the ancient forest. Image: NPS Public Domain Jacob Holgerson. https://www.nps.gov/media/photo/gallery-item.htm?pg=2160865&id=3f1aab81-0e97-4328-bec1-b5f490607a98&gid=2582B4EB-208F-47E1-8C6D-EBDA32DFA9B4

Figure 9. Close-up of a petrified log in the Petrified Forest National Park, Arizona. The many colors are a result of trace elements in the silica. Fine details such as tree rings, knots and bark texture is preserved. Image: NPS public Domain. Scott Williams. https://www.nps.gov/pefo/planyourvisit/maps.htm

Figure 10. Fine detailed tree rings and celular structures from petrified wood. Image: Wilson44691, CC 0, via Wikimedia Commons

REPLACEMENT is a process in which the original body material is replaced atom by atom, molecule by molecule with new materials. Creating a very fine detailed record of the original organism (figure 11). Typically, minerals such as calcite, silica and iron oxides replace the original material. If the process of replacement is coarse instead of fine the original fossil is destroyed and the original material is recrystallized producing a course interlocking mass with the shape of the original fossil. The preservation is course not fine in details (figure 12).

Figure 11. Ammonite very well-preserved sutures Image: r weller http://skywalker.cochise.edu/wellerr/mineral/minlist.htm

Figure 12. Recrystallized fossilization method yielding coarse textured remains. Silicified fossils from middle Permian Road Canyon Formation, Texas. Image: Wilson44691, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

https://www.nps.gov/subjects/fossils/index.htm

Carbonization occurs when high temperatures convert the original carbon-based organism, typically without hard body parts such as insects and leads to a fine scale detailed outline of the fragile organism. The chemically stable carbon remains. Leaves and wings are often preserved with this method (figures 13 & 14).

Figure 13. Large well preserved palm frond found in Fossil Buttes National Monument, Wyoming. Image NPS public domain https://www.nps.gov/subjects/fossils/fossils-through-geologic-time.htm

Figure 14. Wasp preserved by carbonization. Notice the fine details within the wings. Florissant Fossil Beds National Park in Colorado. Image: https://www.nps.gov/media/photo/gallery-item.htm?pg=1826560&id=4C0DD51A-155D-451F-67AF29C51D065C51&gid=A8B21CC3-155D-451F-67B5FEA59657006E

EXTERNAL AND INTERNAL MOLDS are impressions or shapes that preserves the outside details of the organism. The fossil itself is no longer preserved. Soft and fine-grained sediments can preserve remarkable details (figure 15). If the organism has an internal cavity such as a brachiopod or gastropod, fine sediments can fill-in the original and preserve an impression of the inside of the shell. The original fossil is no longer preserved (figure 16). Organisms with a single continuous internal cavity preserve well with this method.

Figure 15. Extinct Scallop Aviculopecten Subcardiformis from the Logan formation of Wooster Ohio. Image By Wilson44691 at English Wikipedia - Photograph taken by Mark A. Wilson (Department of Geology, The College of Wooster).[1], Public Domain, https://commons.wikimedia.org/w/index.php?curid=3797915

Figure 16. Tree mold from the Tree Molds Trail Craters of the Moon National Monument and Preserve, Idaho. Tree impression is preserved in the basaltic lava flows. It is an impression of the charred wood as the lava flowed around the fallen tree. Image: NPS public domain. https://www.nps.gov/crmo/learn/nature/fossils.htm

CASTS these are replicas of the original organism that recreates its original shape. Cavities of the original are produced and latter filled with sediment. This mimics the original organisms shape (figure 17). Casts and Molds are the most common fossilization method.

Figure 17. Left - Cast of Chisternon undatum turtle from Fossil Butte National Monument Wyoming. Right - A 20 clawed bat Onychonycteris Finneyi from Fossil Buttes National Monument, Wyoming. Images NPS public domain. https://www.nps.gov/fobu/planyourvisit/visitorcenterexhibits.htm

TRACE FOSSILS such as track, burrows, footprints or raindrop marks can be preserved telling paleontologists much about the past environment. The study of trace remains is called Ichnology (figures 18 & 19).

Figure 18. Two theropod dinosaur tracks discovered in Cretaceous rocks along the Rio Grande Wild and Scenic River, Big Bend National Park, Texas. Image:

(NPS Photo) https://www.nps.gov/articles/park-paleo-spring-2017-corrick-rio-grande.htm?utm_source=article&utm_medium=website&utm_campaign=experience_more&utm_content=small

Figure 19. Cambrian age fossil burrow. Saint Croix National Scenic Riverway. Image: NPS public domain https://www.nps.gov/articles/000/cambrian-period.htm

Coprolites are fossilized excrement can tell us about and organisms inner gut system and may contain scrapes of food that can tell us about feeding (figure 20).

Figure 20. A coprolite specimen from the Oligocene of Clark County, Oregon. Image: (collections of the Paleontological Research Institution). Photograph by Jonathan R. Hendricks.  This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

https://www.digitalatlasofancientlife.org/learn/nature-fossil-record/body-fossils-trace-fossils/

Pseudo fossils - Manganese dioxide dendrites form from a process that is similar to frost forming on a glass window. These are pseudo fossils as they are simply chemical precipitates that form a dendritic pattern. The dissolved mineral Manganese oxides precipitate out of water solutions forms branching patterns commonly on sedimentary rocks (figure 21).

Figure 21. Dendrites of manganese oxide precipitated on the surface of limestone. Width of view 10 cm. Image: Siim sepp https://www.sandatlas.org/dendritic-growth-in-crystals/

FOSSILS CAN TELL US ABOUT LIFE AND THE PALEO ENVRONMENT

Plants and animals live in specific conditions. Flamingoes and palm trees exist in warm tropical land conditions while polar bears and penguins live in cold arctic land conditions. Fish and corals live in marine settings. So, when a fossil is found paleontologists can infer that a specific environment must have existed as well. Fossils can tell us if an organism lived in a colony or as an isolated organism? Was it living in a tropical or coastal environment, was it marine or terrestrial? These are the types of questions that fossils can answer. For example, there are very well-preserved stromatolite (warm coastal water) fossils found in modern-day Glacier National Park, Montana, indicating a significant environmental, geographic change (figure 22).

Figure 22. Precambrian age Stromatolite fossils currently found in Glacier National Park, Montana. Image NPS public domain. https://www.nps.gov/articles/000/images/01-PRECAMBRIAN-GLAC-STROMATOLITES.jpg?maxwidth=1200&autorotate=false

SYMMETRY IN FOSSILS

Paleontologists often carefully draw fossil specimens as this enables them to focus on the details of the sample. One of the details is the unique symmetry of fossils. Symmetry can be the first property that enables a scientist to identify the organism.

Bilateral Symmetry: The human body has bilateral symmetry. Many modern and ancient animals have Bilateral symmetry. Many invertebrate fossils can be distinguished by their bilateral versus bivalve symmetry (across valves) (figure 23).

Figure 23. Symmetrical differences. Left: brachiopod – bilateral. Right: bivalve. Image by Jaleigh Q. Pier is licensed under a C C Attribution-ShareAlike 4.0 International License.

https://www.digitalatlasofancientlife.org/learn/brachiopoda/brachiopoda-vs-bivalvia/

Pentameral or Radial symmetry is useful in identifying the Phylum Cnidarian (class Anthozoan) in which corals belong, as the living area of the soft coral has a radiating symmetry think of the spokes in a bicycle wheel (figure 24). If the segments are in a five-portion symmetry, the term Pentameral is used. Such as in the starfish figure 25 below.

Figure 24. Radial symmetry as seen in coral. Specimen is from late Pleistocene. The specimen is from the research collections of the Paleontological Research Institution, Ithaca, New York. Image credit: Digital Atlas of Ancient Life, CC BY-NC-SA. https://uhlibraries.pressbooks.pub/historicalgeologylab/chapter/chapter7-fossils/

Figure 25. Five-part pentameral symmetry in two echinoderms. Image credit Jaleigh Q. Pier CC BY-SA https://uhlibraries.pressbooks.pub/historicalgeologylab/chapter/chapter7-fossils/

Conispiral symmetry is common in gastropods and modern-day snails. The coil is smaller at the bottom and wider at the top like a funnel (figure 26).

Figure 26. Gastropods showing spiral symmetry. Image: Scanned by Tom Meijer - Nyst, P.H., 1878-1881. Conchyliologie des terrains tertiaires de la Belgique. -- Ann. Mus. r. Hist. nat. Belg., 3: 1-262 (1878), 28 pls. (1881)., Public Domain, https://commons.wikimedia.org/w/index.php?curid=6113367

Spiral symmetry is commonly seen in Ammonites. This symmetry resembles a coiled rope (figure 27). The organism grew larger by adding new segments (septa).

Figure 27. Spiral symmetry of a well preserved pyritized ammonite. Image: https://en.wikipedia.org/wiki/Ammonoidea#/media/File:Ammoniteplit.jpg John Alan Elson - http://www.3dham.com/3dammonite2/

Trilobate symmetry is generally bilateral with three segmented body parts such as a head, thorax (middle) and a tail. This is a common Arthropod body plan. Insects and extinct trilobites are in this phylum (figure 28).

Figure 28. Two images of extinct trilobites. Three distinct body parts 1, 2 and 3 are trademark of arthropods. Images: By Wilson44691 - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=7566920

By Sam Gon III, derivative by Obsidian Soul - File:Trilobite_sections_numbered.svg, CC0, https://commons.wikimedia.org/w/index.php?curid=14909072

YOUR TASK: USING THE SAMPLES PROVIDED BY YOUR INSTRUCTOR: Try to identify the Preservation method, symmetry type and possible paleo environment of the samples. Then carefully sketch the sample.

Foraminiferan tests Public Domain, https://commons.wikimedia.org/w/index.php?curid=12515

By Alain COUETTE - Microphotographie personnelle ; http://www.arenophile.fr/Pages_IMG/P2966e.html, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=20886081

Gastropod Nepunea angulate Neptunea despecta By Scanned by Tom Meijer - Nyst, P.H., 1878-1881. Conchyliologie des terrains tertiaires de la Belgique. -- Ann. Mus. r. Hist. nat. Belg., 3: 1-262 (1878), 28 pls. (1881)., Public Domain, https://commons.wikimedia.org/w/index.php?curid=6113367

Crinoid https://commons.wikimedia.org/wiki/File:Crinoid_anatomy.png

By Vassil - Alias Collections., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3200543

Horn Coral (Credit: Bruce Avera Hunter . Public domain. https://www.usgs.gov/media/images/horn-coral-heliophyllum-halli-0

Placoderm DunkleosteusSannablePublic Domain, https://commons.wikimedia.org/w/index.php?curid=3656653

Eurypterus By H. Zell - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=9008160

Trilobite By Moussa Direct Ltd. - Moussa Direct Ltd. image archive, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=4461171

Brachiopod Devonian brach Tylothyris By Kennethgass - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=84047885

Graptolite Cryptograptus Silurian SA Specimen at Royal Ontario Museum By Grezmagro - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=63982759

Pendeograptus fruticosus Lower Ordovician Australia By Wilson44691 - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=12622126

Ichthyosaur Stenepterygius By Haplochromis - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=5825284

By Nobu Tamura (http://spinops.blogspot.com) - Own work, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=19462362 shonisaurus popularis

Pelecypod Photo is copyright free for non-commercial educational uses. 
Just credit photo to R.Weller/Cochise College.

http://skywalker.cochise.edu/wellerr/fossil/pelecypod/scallop2.htm

Sharks tooth Megalodon North Carolina By Tomleetaiwan - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=27656601

Ammonite pleuroceras solare lower Jurassic https://en.wikipedia.org/wiki/Ammonoidea#/media/File:Pleuroceras_solare,_Little_Switzerland,_Bavaria,_Germany.jpg

https://www.nps.gov/articles/fossils-of-the-2020-national-fossil-day-artwork.htm