Fossilization and Fossils

ANY evidence of ancient life. So what exactly is a fossil? ANY evidence of ancient life. Body fossil teeth or bones Trace fossil cast, track, burrow So what exactly is a fossil?

What is a scientist who studies fossils called? paleontologists Next question… What is a scientist who studies fossils called? paleontologists Archaeologists study the remains of ancient humans and their cultures. Write this down; it is an IMPORTANT distinction! Archae – beginning or ancient Paleo – old; the term was originally used by Charles Lyell 1838

Fossils If the layers of sedimentary rock are the pages that tell the story of the Earth, fossils are the words. Literally, the word fossil means “dug up”. Technically speaking fossils are remains of life that are at least 15,000 years old. Preservation can include both altered and unaltered hard and soft parts. Fossils can also be casts and molds. Found in shales, sandstones, limestones, amber, ash, nodules, tar, and ice. The study of an organism from death to fossilization is called taphonomy (can include post-fossilization events as well).

Process of fossilization Talk about the process

Process of fossilization Fossilization depends on two critical steps: • rapid burial by sediment • mineralization Helpful conditions: • anoxia (lack of oxygen following burial) • minimal disturbance subsequently • mineral-rich water in sediment

Types of Fossilization Unaltered Remains Original material, including soft parts preserved Rapid burial in ice, tar, or mummification Recrystallization Original material dissolved New mineral deposited simultaneously Permineralization Minerals infill pores and holes Molds and casts Infilling with other material Often, sedimentary infill Carbonization Preservation as thin films of carbon Outline and sometimes detailed structures preserved Permineralization: Minerals dissolved in water fill in the open spaces in bone. This makes the bone harder and heavier, but some original bone material may be retained.

Unaltered Soft Parts (Amber) Mosquito Scorpion Feather

Unaltered Soft Parts (Ice) “Blue Babe” bison Siberian Wooly Mammoth

Unaltered Hard Parts: Tar and Anoxic Silt Beetle in tar LaBrea Tar Pit Avitelmessus, NC Fish from Messel, Germany

Unaltered Hard Parts (skeletal) Smilodon Ashfall Park Columbian Mammoth

Recrystallization: Aragonite to Calcite Pliocene Busycon carica Pterorhytis conradi Chesapecten jeffersonius Cretaceous Eocene Polinices sp Urosalpinx sp. Athleta petrosus

Recrystallization: Change in Crystal Structure Cyclonema Euproops Mississippian Crinoids Edrioasteroid Dalmanites

Carbonization Knightia Spider Dragonfly larva Opabinia Canadia

Carbonization Sphenopteris

Permineralization Dinosaur Bone Shark Teeth Petrified Wood Brazil Jurassic Pinecone Permineralized Dinosaur Bone: Cell Structure Preserved

Altered Hard Parts (replacement) Silicified Mollusks Silicified Stromatolite Pyritization

Molds and Casts shell external mold cast interior steinkern shell shell dissolves sediment infilling interior steinkern shell shell Sediment fills void Shell dissolves

Casts and Steinkerns

Trace Fossils Reflect the activity, or behavior, of organisms on land and in marine settings. Exogenic – on the surface. Endogenic – within the substrate. Shape of the trace fossil does not always mirror the animal. Trace fossils are named for their particular shape and form and not for the animal that made the trace.

Same animal may make several different types of trace fossils.

Trilobite resting trace

Trilobite trackway

Grazing trace

Other trace fossils include trackways on land (mostly dinosaur, reptile, and amphibian) and coprolites (fossilized feces, “poop”).

Dinosaur Ridge, CO Glen Rose, TX

Coprolites Dinosaur Turtle Mammal Crocodile Remember that feud between Cope and Marsh? Mammal Crocodile

Factors that Affect Fossilization Animal contains hard parts Death without scavenging or decomposition Rapid burial after death