Fossilization and Fossils. So what exactly is a fossil?. ANY evidence of ancient life. Body fossil teeth or bones Trace fossil cast , track, burrow. Next question…. What is a scientist who studies fossils called? paleontologists
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So what exactly is a fossil? ANY evidence of ancient life. Body fossil teeth or bones Trace fossil cast, track, burrow
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!
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. • Preservationcan 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 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
Unaltered Soft Parts (Amber) Mosquito Scorpion Feather
Unaltered Soft Parts (Ice) Siberian Wooly Mammoth “Blue Babe” bison
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 Chesapectenjeffersonius Cretaceous Eocene Polinices sp Urosalpinx sp. Athleta petrosus
Recrystallization: Change in Crystal Structure Cyclonema Euproops Mississippian Crinoids Edrioasteroid Dalmanites
Carbonization Knightia Dragonfly larva Spider Opabinia Canadia
Permineralization Dinosaur Bone Shark Teeth Petrified Wood Brazil Permineralized Dinosaur Bone: Cell Structure Preserved Jurassic Pinecone
Altered Hard Parts (replacement) Silicified Mollusks Silicified Stromatolite Pyritization
shell shell shell Molds and Casts cast external mold shell dissolves sediment infilling interior steinkern Sediment fills void Shell dissolves
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.
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