Lecture 7: Fossils and Fossilization PDF

Lecture 7: Fossils and Fossilization ©JoAnna Wendel Reminder Quiz 3 now available Find it under ‘quizzes’ on UM Learn Unlimited attempts Objectives Understand how fossils form Understand the types of fossil preservation Identify the best places for f...

Lecture 7: Fossils and Fossilization ©JoAnna Wendel Reminder Quiz 3 now available Find it under ‘quizzes’ on UM Learn Unlimited attempts Objectives Understand how fossils form Understand the types of fossil preservation Identify the best places for fossils to form National Geographic Fossils are prehistoric remains or traces usually preserved in sedimentary rocks Fossils and Body fossils: shells, bones, and teeth Traces: tracks, trails, burrows, nests, and feces Fossilization Fossils provide information on ages, depositional environments, and evolution Fossils provide relative ages of strata in separated columnar sections of rocks- Biostratigraphy  Taphonomy The study of all factors that affect an organism from the time of death to the time of discovery as a fossil Death and decay → burial→ after burial Did the animal die where it was living? How Do Fossils Form? Crinoids Favorable conditions for fossilization Organism had a durable skeleton Lived where burial in sediment was likely Avoided decay, scavenging, and metamorphism Good fossil record of corals, clams, and brachiopods Have hard shells Poor fossil record of jellyfish and bats Have lots of soft or delicate parts Soft tissue is rarely preserved Hair, feathers, scales Eomaia Images: Stanley (2009); commons.wikimedia.org How Do Fossils Form? Basic requirements: Oxygen-poor environment Low-energy setting Rapid burial in fine-grained sediment Image: © Davide Bonadonna via davidebonadonna.it  How Do Fossils Form? Not the best place to be for preservation! Factors that affect preservation: Scavenging Depth Salinity pH Oxygenation Climate (temperature, moisture) Depositional environment: materials and rates Wave or current action: transport and abrasion Image: funny.co.uk The impact of each of these factors is in part determined by the length of time between death and burial Types of Fossil Preservation Body Fossils: prehistoric remains Fig 5.10 Royal Tyrrell Museum  Fig 5.12 Body Fossils: unaltered remains Body Fossils: altered remains Fig 5.13  Trace Fossils: indication of organic activity Fig 5.11 © Davide Bonadonna via davidebonadonna.it  Trace Fossils Jonathan R. Hendricks Dinosaur-universe.com digitalatlasofancientlife.org Trace Fossils Bioturbation Molds and Casts Fig 5.14  continental shore Best places to become a fossil? Sedimentary environments marine Fig. 6.9 Continental Shore Reefs Marine wikipedia marinesanctuary.org  Oxygen-poor environment Best places to become a fossil? Low-energy setting Rapid burial in fine-grained sediment  Oxygen-poor environment Best places to become a fossil? Low-energy setting Rapid burial in fine-grained sediment  Oxygen-poor environment Best places to become a fossil? Low-energy setting Rapid burial in fine-grained sediment Domingo et al., 2013 PLOS  Oxygen-poor environment Best places to become a fossil? Low-energy setting Rapid burial in fine-grained sediment Domingo et al., 2013 PLOS  Oxygen-poor environment Best places to become a fossil? Low-energy setting Rapid burial in fine-grained sediment Domingo et al., 2013 PLOS