Lecture 2: Fossils & Fossilization PDF

LECTURE 2: Fossils & Fossilization From Ch 1, p 8-12; Ch 2, 28-33 of Dinosaurs (4th Ed.) Charles Knight Photo: RTMP  LECTURE 2: Fossils & Fossilization From Ch 1, p 7-12; Ch 2, 27-32 of Dinosaurs (4th Ed....

LECTURE 2: Fossils & Fossilization From Ch 1, p 8-12; Ch 2, 28-33 of Dinosaurs (4th Ed.) Charles Knight Photo: RTMP  LECTURE 2: Fossils & Fossilization From Ch 1, p 7-12; Ch 2, 27-32 of Dinosaurs (4th Ed.) Part 1: Introduction to Fossils and Fossilization Part 2: Fossils and Fossilization (Nat. Geo video) Part 3: Collecting Fossils Part 4: Sedimentology & Fossil Dating  LECTURE 2: Fossils & Fossilization From Ch 1, p 7-12; Ch 2, 27-32 of Dinosaurs (4th Ed.) Objectives Understand what a fossil is and how it forms Understand the principles of sedimentology and how the age of a fossil is determined  Fossils Dinosaurs: that we even know about them is near miraculous! Dependent upon fossils (buried remains of organic life) Organisms most commonly destroyed after death (scavenged; decomposed); by luck, rare individuals are preserved fossils Image: Public Domain  Fossils Fossils are the preserved remains, or traces of remains, of ancient animals and plants From Latin ‘fossillis’ - ‘to have dug up’. Fossils are > 10,000 years old Fossils do not include human artifacts (that’s archaeology)  Fossilization Replacement - molecular replacement of the calcium-sodium hydroxyapatite or conversion to fluorapatite. Permineralization – pore spaces in the bone are in-filled with minerals Photo: M Ryan Fossilization has been going on throughout Earth History FASTOVSKY fig. 1.8  Where Are Fossils Found? Fossils can be found anywhere in the world, but the right type (sedimentary) must be present 1. Not in Igneous Rocks - crystalline rock from molten mineral matter 2. Not in Metamorphic Rocks - crystalline and sedimentary rock changed by heat, pressure and chemical fluids 3. Only in Sedimentary Rocks Sedimentary rocks can inform us of the local environment that a fossil was deposited in coal SS MS Photo: D. Eberth Paintings: Gov’t of Alberta  Types of Fossils Body Fossils Hard tissues (skeletal part); typically undergoes replacement or permineralization. Soft tissues (unaltered full body to bio-molecules) Trace Fossil (Ichnofossils) Ichnos = ‘track or trace’ Body or body part impressions (casts and molds) Traces of behaviour (footprints, burrows) Other Fossil Types Coprolites Gastroliths  Body Fossils Burial generally leads to fossilization of bones and teeth (hard parts) A. Fast burial helps preserve articulated skeletons B. Slow burial usually leads to disarticulated  Body Fossils: Articulated Skeletons Saurolophus from The Dragons Tomb, Nemegt Fm, Mongolia Photos: M Ryan Body Fossils: Articulated Skeletons PROTOCERATOPS & VELOCIRAPTOR Photo: P. Currie  Art: Mike Skrepnick Body Fossils: Bonebeds DP Fm: Centrosaurinae Centrosaurus bonebed Dinosaur Provincial Park, Alberta  Trace Fossils Trace fossils are imprints or marks left by organisms; Inferences about behaviour & biology can be obtained: Locomotion (speed, gait) Metabolic rate Family units? Predatory styles FASTOVSKY fig 1. 6  Trace Fossils For dinosaurs, the most common trace fossils are footprints MOLD CAST CAST  Coprolites Photo: Gov’t of Saskatchewan Tyrannosaurus rex coprolite – Eastend, SK  Gastroliths Photo: Gov’t of Saskatchewan Acta Palaeontol. Pol. 52 (1): 1–16, 2007 The horned dinosaur Psittacosaurus with gastroliths  Ancient Soft Tissue Preservation Biomolecules Mummies Photo: Yale University Skin impressions are not Fossilized skin Dinosaur blood vessel with cell ‘Zhur’, 57,000 year old wolf pup mummy 30,000 year old Cave lion (Panthera spelaea) cub mummies Photo: Government of the Yukon Ancient Soft Tissue Preservation: Feathers Sinosauropteryx prima sp., Early Cretaceous (110 Ma), China (Jehol biota) First non-avian dinosaur identified with feathers (1996)e Fiann Smithwick, et al. 2017. Countershading and Stripes in the Theropod Dinosaur Sinosauropteryx Reveal scales Heterogeneous Habitats in the Early Cretaceous Jehol Biota. Current Biology 27, 3337–3343.  Ancient Soft Tissue Preservation: Ornamentation Psittacosaurus sp. from the Early Cretaceous (110 Ma), China Ceratopsia: Psittacosauridae 6 feet long; < 300 lb. Bristles on tail Vinther ,et al. 2016. 3D Camouflage in an Ornithischian Dinosaur. Current Biology 26, 2456–2462. dio:10.1016/j.cub.2016.06.065 Amber is classified as a mineral Photo: Phys.org Oculudentavis – A reptile of uncertain affinities  Finding & Collecting Fossils Planning Prospecting Collecting Preparation & Curation Research & Education Planning ost important part of the expedition – getting it right to look – four criteria: ght rocks – rocks must be sedimentary ght age –preserve the time when non-avian dinosaurs lived rrestrial – dinosaurs were terrestrial beasts ood exposure – need to be able to see the ground to find fossi ics (permissions & permits; support for your crew; Health & S Prospecting No fancy technology Search head down Luck and experience Collecting Making a plaster jacket: Clean fossil off; Pedestal Cover with damp toilet paper Jacket with strips of burlap soaked in water and plaster (2 layers min) Let harden Flip over Top jacket & transport back to camp Preparation and Curation Preparation - time-consuming, expensive work of freeing the fossil from its matrix Curation – taking care of the specimens; storage; protection; loans Display – casting/scanning the originals for exhibition and study Research and Education The fossils aren’t of any use stored away unseen in collections. They are used for research – typically undergrad, grad, and professional levels, but citizens can contribute, too. Publication of research in peer-reviewed journals & presented to the public through social media and public presentations Displays from the basis of educational programs  Sedimentology & Fossil Dating What is Sedimentology? How do we know how old Fossils are? By: Susan Montoya Bryan (https://www.vicnews.com/news/buy-your-own- dinosaur-fossil-for-as-low-as-7/) GEOLOGY is the science that deals with the earth's physical structure and substance, its history, and the processes that act on it. SEDIMENTOLOGY is the study of sedimentary rocks and the processes by  Geological Time Scale Most Recent Chart:  Geological time – geologists’ temporal toolbox Numerical time – geochronology – ages in numbers Relative time – litho- and biostratigraphy – age relative to something else  Numerical time - geochronology Measures years before present; for dinosaurs, millions of years before present (Ma) Dinosaurs lived ~230 Ma – 66 Ma How do we know this? We date How to date a rock: rocks! Look for rocks with minerals that contain unstable isotopes so that RADIOMETRIC DATING can  Radiometric Dating Using radioactive material to determine the age of a rock Sedimentary rock cannot provide us with an age We need to determine the age of nearby volcanic rock, We or associated charcoal use minerals or fossilsisotopes (atoms that with unstable decay spontaneously) in the following universal decay reaction: Unstable “parent” isotope (decays to) stable “daughter” isotope + nuclear products + energy (generally, heat) Sedimentary Rock (no useful unstable isotopes) Ash Layer (can be dated!) Sedimentary Rock (no useful unstable isotopes) The decay reaction is the dating key; if you know: 1. The original amount of parent isotope; 2. How much of the parent isotope is left; and The 3. halfThe liferate of decay of the isotope, is a handy You can estimate estimator of its age. the rate of decay of any unstable isotope; you must choose the right Common isotopic systems and their half- lives available to geochronologists: Unstable Stable Half life “Parent” “Daughter” (years) Carbon 14 Nitrogen 14 5730 Potassium 40 Argon 40 1.25 X 109 Uranium 238 Lead 206 4.47 X 109 Uranium 235 Lead 207 700 X 106 Rubidium 87 Strontium 87 48.8 X 109 Only the three fully blackened ones have half lives appropriate for dating dinosaurs.  The Right Isotope Carbon-14 has a half-life of 5730 years Good for modern fossils Only goes back 50,000 years, does not work for dinosaurs! Potassium – Argon Dating Potassium 40 has a half-life of 1.3 Billion years Great for dating dinosaur bones Uranium – Lead Dating Uranium has many isotopes half-lives between 700 million – 4.5 Billion years Excellent for dating oldest rock By: James King-Holmes (https://www.nature.com/articles/d41586- Relative time – age in relation to something else Relative Dating – rocks are dated in relation to each other, no absolute dates are used Lithostratigraphy – younger sediments are deposited on top of older sediments Biostratigraphy – distinctive assemblages of organisms characterize particular time intervals  Lithostratigraph y Sediments accumulate naturally Dust, Sand, Silt, Mud etc. Geological processes cause this accumulation Ocean currents, rain, rivers, wind, volcanic activity, gravity etc. STENO’S LAWS can be used to age the rock By: Paul Preuss (https://www2.lbl.gov/Science-Articles/Archive/sabl/2007/Apr/05- erosion.html) STENO’S LAWS Principle of Superposition Principle of Original Horizontality Principle of Lateral Continuity Principle of Cross-cutting relationships  Principle of Superposition Sedimentary rocks are A deposited over time, stacking on top of each A other B Younger layers of rock sit on top of older layers of rock IsfjordenSuperposition.jpg B A: Young B: Old Principle of Superposition Slightly younger than 85 million years old Dated at 85 million years old Slightly older than 85 million years old  Principle of Original Layers of Horizontality sedimentary rock were originally deposited flat Geological processes can deform the rock after deposition, but the layers keep the By: Bradley Deline (https://openpress.usask.ca/geolmanual/chapter/overview-of-relative- and-absolute-dating/) same relationship to each other Principle of Layers of Original Youn sedimentary rock Horizontality were originally g deposited flat Old By: Bradley Deline (https://openpress.usask.ca/geolmanual/chapter/overview-of-relative- and-absolute-dating/) By: Pearson Scott Foremans (File:Anticline (PSF).png)  Layers of Principle of sedimentary rock Lateral extend Continuity continuously along the surface of the earth By: Alan Majchrowicz (https://alanmajchrowicz.com/galleries/arizona/colorado-river- from-desert-view-point-grand-canyon-national-park/)  Erosion can cut into the Principle of rock after deposition, Lateral separating outcrops, but the layers remain the Continuity same By: Alan Majchrowicz (https://alanmajchrowicz.com/galleries/arizona/colorado-river- from-desert-view-point-grand-canyon-national-park/)  Principle of Cross-Cutting Relationships A geological feature which cuts another is the younger of the two features e.g., A river cutting into a rock formation will deposit sediments, eventually creating rocks much younger than the surrounding formations Youngest By: J Merck 2000 (https://canvas.instructure.com/courses/1326949/pages/principle-of-cross-cutting- relationships)  Biostratigr aphy Fossil assemblages can be used to determine the age of other fossils INDEX FOSSILS: fossils that indicate a particular period of time There are many common fossils (usually invertebrates) with wide ranges that are useful over continental or even global scales Ammonites are excellent index fossils because they By: Sinclair Stammers (https://www.sciencephoto.com/media/171457/view/amm onite-fossils) To determine the age of a fossils a savvy geochronologist uses a mix of numerical and relative dating to ultimately construct a Parts complete of rock GEOLOGICAL TIMESCALE formations can be numerically dated Biostratigraphy and lithostratigraph y can be used to fill in the gaps  GEOLOGICAL TIMESCALE: The part of the timescale shown here highlights when non-avian dinosaurs roamed the Earth, showing the three relevant Periods of the Mesozoic Era, as well the Epochs and Stages that make up each Period.  Each period, epoch and stage has an absolute date determined through numerical dating Stages are usually the smallest numerically dated division Each stage is divided into many different regional or global Biozones