Historical Geology Lecture 3 Fossilization

Historical Geology ITaphonomy IIThe Fossil Record A)Controls on Fossil Record Completeness B)Mineral Composition of Hard Parts C)Fossil Preservation 1)Body Fossils a) Altered Hard Parts b)Unaltered Remains c)Preserved Soft Tissue 2) Trace Fossils 3)Chemical Fossils IIIInformation from the Fossil Record A)Paleoecology B)Paleoclimate C)Paleogeography D)Biodiversity Outline

Historical Geology Taphonomy the study of all that has happened to organisms from the moment of death to final preservation as a fossil. Taphonomic Processes  necrolysis  biostratinomy  diagenesis

Historical Geology Fossilization Controlling Factors  body construction (hard parts)  environment  predation Death Scavenging Decay of soft tissues Decreasing probability 100% ?% Continuous removal of “ potential ” fossils The probability of preservation depends on the anatomy and habitat of the organism — marine organisms with hard parts are most likely to be preserved Abrasion And transport Burial Final Preservation

Historical Geology Fossilization Common Mineral Compositions of Hard Parts  calcium carbonate CaCO 3  aragonite  calcite  silica SiO 2  calcium phosphate Ca 3 (F, Cl, OH)(PO4) 3

Historical Geology The Fossil Record  Body Fossils  Altered Hard Parts  Unaltered Remains  Preserved Soft Tissue  Trace Fossils  Chemical Fossils Trilobite Tracks

Historical Geology Fossil Preservation Altered Hard Parts  permineralization  replacement  recrystallization

Historical Geology Fossil Preservation Permineralization permineralization - the process of fossilization wherein the original hard parts of an animal have additional mineral material deposited in their pore spaces.

Historical Geology Fossil Preservation Replacement replacement - substitution of inorganic matter for the original organic constituents of an organism during fossilization. Florissant Fossil Beds National Monument, Colorado Petrified Wood

Historical Geology Fossil Preservation Replacement Brachiopod Sponge Silicification Pyritization Ammonite replacement by FeS replacement by SiO 2 Phosphatization replacement by Ca 3 (F, Cl, OH)(PO 4 ) 3 shark vertebrae

Historical Geology Fossil Preservation Recrystallization Same minerals New mineral structure Loss of detail AragoniteCalcite Increasing crystal size Rugose coral

Fossil Preservation Unaltered Remains Historical Geology  amber  tar  freezing  mummification

Historical Geology Fossil Preservation Unaltered Remains amber tar freezing

Fossil Preservation Preserved Soft Parts Historical Geology  mineral plating  impressions  replacement  carbonization

Historical Geology Fossil Preservation Preserved Soft Parts phosphatization - replacement of low phosphate apatite with high-phosphate apatite Markuelia secunda phosphatized embryo Bengston and Zhao, 1997 Aphaesia DickinsoniaSpriggina fern leaf soft tissue impression mineral plating

Historical Geology Fossil Preservation Preserved Soft Parts carbonization - the conversion of the organic material of a plant or animal to a thin film of carbon. Didymograptus Isograptus Insect Palm frond

Historical Geology Fossil Preservation Trace Fossils  tracks  trails  burrows  borings  eggs and nests  gastroliths  fossilized feces (coprolites)  root paths  casts and molds (?) ichnology - the study of plant and animal traces. Implicit in this definition is that the traces made by plants and animals reflect some sort of behavior while living (biogenic).

Historical Geology Fossil Preservation Trace Fossils Advantages Long Time Range Abundance Common In-situ Occurrence Preservation Potential Excellent Environmental Indicators Disadvantages One trace maker can make multiple traces Many trace makers can make identical traces

Fossil Preservation Trace Fossils on Bedding Planes Historical Geology track - a set of discrete footprints Australopithecus afarensis Dinosaur Tracks

Fossil Preservation Trace Fossils on Bedding Planes Historical Geology trail - continuous trace, usually formed by the whole body of a travelling or resting worm, mollusc or arthropod Trilobite A : crawling trace B : resting trace C : dwelling trace D : grazing traces E : feeding traces

Historical Geology Fossil Preservation Trace Fossils within Sediment burrow - structures formed within soft sediment by moving grains out of the way, either for locomotion, dwelling, protection or feeding vertical burrows ichnofossil Paleocastor

Historical Geology Fossil Preservation Trace Fossils within Sediment horizontal burrows

Fossil Preservation Trace Fossils within Sediment Historical Geology boring - structures formed in hard substrate by cutting right through the grains, either for protection, dwelling, carbonate extraction or even for feeding purpose (bioerosion). Ordovician ichnofossil Trypanites Cretaceous ichnofossil Gastrochaenolites

Historical Geology Fossil Preservation Trace Fossils - Excrements fecal pellets (or strings) - small pellets or strings of excrement, usually of less than 10 mm length coprolite - fossil feces, probably an amalgamation of pellets in many cases

Historical Geology Fossil Preservation Trace Fossils - Other Plesiosaur gastroliths ( “ stomach stones ” ) root paths Nest and eggs of a Therizinosaur or Segnosaur

Historical Geology Fossil Preservation Molds and Casts

Historical Geology Fossil Preservation Molds mold - an impression made in the earth or rock material by the exterior or interior of a fossil shell or other organic structure. Subprionocyclus normalis Gastropods Internal MoldsExternal Molds Bivalves

Historical Geology Fossil Preservation Casts secondary rock or mineral matter that fills a natural mold, producing a replica of a fossil shell or skeleton. Coleoptera curulionidae Keichousaurus hui Tree trunk

Step a: burial of a shell Step b: dissolution leaving a cavity, a mold Step c: the mold is filled by sediment forming a cast Historical Geology Fossil Preservation Casts and External Molds Trilobite Brachiopod

Historical Geology Information from the Fossil Record  Paleoecology  Paleoclimate  Paleogeography  Biodiversity

Historical Geology Information from the Fossil Record Paleoecology and Paleoclimate

Historical Geology Information from the Fossil Record Paleoecology and Paleoclimate

Historical Geology Information from the Fossil Record Paleoclimate

Historical Geology Information from the Fossil Record Paleogeography

Historical Geology Information from the Fossil Record Biodiversity