Fossils evidence of past life Petrified Petrified Cavities and pores are filled with precipitated mineral matter Formed by replacement Cell material is removed and replaced with mineral matter Cast Carbonization Remains or traces of prehistoric life Mold Hollow space of a mold is filled with mineral matter Shell or other structure is buried and then dissolved by underground water http www ammonoid com Manning html Shape is preserved in the surrounding sediment Impression Replica of the fossil s surface preserved in fine grained sediment Preservation in amber Hardened resin of ancient trees surrounds an organism Organic matter becomes a thin residue of carbon This is a compression of the original organism Indirect Evidence Includes Tracks Burrows Coprolites fossil dung and stomach contents Gastroliths stomach stones used to grind food by some extinct reptiles http www lfbuffalo org exhibitions map t 1 Tracks Dinosaur footprint in fine grained limestone near Tuba City Arizona Fossils and correlation Types of fossils Petrified Formed by replacement l t Mold Cast Carbonization Impression Preservation in amber Indirect evidence Principle of faunal succession Principle of faunal succession Index fossils http www lfbuffalo org exhibitions map a Conditions favoring preservation Rapid burial Possession of hard parts Archean through Devonian Proposed by William Smith late 1700s Fossil organisms succeed one another in a definite and determinable order order therefore any geologic time interval can be recognized by its fossil content http rst gsfc nasa gov Sect2 Sect2 1b html Carboniferous through Quaternary http rst gsfc nasa gov Sect2 Sect2 1b html Cambrian Marine Life Trilobite http www ststephens it biology fossils html http www handprint com PS GEO geoevo html 2 Ordovician Invertebrates http www handprint com PS GEO geoevo html Silurian reef Crinoid 380 ma http www lsa umich edu exhibitmuseum exhibits temporary exhibits Silurian Landscape Ordovician sea floor http www uwsp edu geo faculty hefferan Geol106 CLASS6 MAIN 20PAGE htm Devonian Sea Silurian Reef http hoopermuseum earthsci carleton ca camex 1rpaleoreef html http www nasa gov worldbook earth worldbook html Mid Paleozoic http www tufts edu as wright center cosmic evolution docs text text bio 4 html Late Paleozoic http www tufts edu as wright center cosmic evolution docs text text bio 4 html http www handprint com PS GEO geoevo html Carboniferous Fern Forests http www handprint com PS GEO geoevo html 3 Permian Sea Permian Reptiles Permian Extinction Link to hypotheses of the Permian Extinction http en wikipedia org wiki Permian extinction 80 95 of marine species died out 70 70 off tterrestrial t i l vertebrates t b t Largest extinction episode in geologic record http www handprint com PS GEO geoevo html Geologic time scale Divides geologic history into units Originally created using changes in organisms representing that time interval Eras of the Phanerozoic eon http www handprint com PS GEO geoevo html Subdivisions Eons Eras Periods Epochs Geologic Time Scale Eon Greatest expanse of time 4 eons Phanerozoic visible life the most recent eon started 543 Ma Proterozoic 2500 543 Ma Archean 3800 2500 Ma Hadean oldest eon 4500 3800 Ma Mesozoic Cenozoic recent life 65 Ma now Mesozoic middle life 248 65 Ma Paleozoic ancient life 543 248 Ma http geography berkeley edu ProgramCourses CoursePagesFA2002 Geog40 Geog40 Week7 html 4 Mesozoic http serc carleton edu introgeo earthhistory dinosaur html Mesozoic http geography berkeley edu ProgramCourses CoursePagesFA2002 Geog40 Geog40 Week7 html Archeopteryx Mesozoic Mammal Mesozoic http www tufts edu as wright center cosmic evolution docs text text bio 4 html Mesozoic Mammal Eomaia Repenomamus http www researchcasting ca sculpt 20miami htm Jurassic http www worldbook com features dinosaurs html world mesozoic html http www amnh org exhibitions dinosaurs diorama Cretaceous http www worldbook com features dinosaurs html world mesozoic html http www amnh org science papers mesozoic mammal php Mesozoic Sea http geography berkeley edu ProgramCourses CoursePagesFA2002 Geog40 Geog40 Week7 html 5 Mesozoic sea Cretaceous Extinction Cenozoic mammals Perhaps 60 of species died Result of radical change in environment Perhaps Earth encountered a large meteorite t it 10 km in diameter 90 000 km hr Equivalent to 100 megatons of TNT exploding http www uky edu AS Geology webdogs time mesozoic mesozoic htm Cenozoic http www handprint com PS GEO geoevo html http www handprint com PS GEO geoevo html Cenozoic Cenozoic http www uky edu AS Geology webdogs time cenozoic cenozoic htm http www copyrightexpired com Heinrich Harder cenozoic html Relative dating Lateral Continuity Placing rocks and events in proper sequence of formation Deciphering Earth s history from clues in the rocks Principle of Original Horizontality Sediment is deposited horizontally http cse cosm sc edu hses RelatDat pages lateral htm http faculty icc edu easc111lab labs labf orig horizontality jpg 6 Principle of Superposition Oldest rock A Younger rocks above E is i th the youngest Principle of Cross cutting Relationships Cross cutting relationships Younger feature cuts through an older feature Something must exist first to be cut by another thing The things cutting may be things such as igneous intrusions Or they may be events like fault breaks folding or erosion periods http cse cosm sc edu hses RelatDat pages superpos htm Folding occurred after deposition Unconformities A break in the rock record Three types of unconformities Angular unconformity Disconformity strata on either side are parallel Nonconformity Angular Unconformity Tilted rocks are overlain by flat lying rocks Remember the principle of original horizontality http rst gsfc nasa gov Sect2 Sect2 6 html Formation of an angular unconformity Simple angular unconformity http www grisda org colorado index htm Folding erosion deposition folding http rst gsfc nasa gov Sect2 Sect2 6 html 7 Nonconformity Nonconformity Metamorphic or igneous rocks below Younger sedimentary rocks above Disconformity Gap in sedimentation that may have erosion also Represents an interval in geologic time without rock deposited Most difficult of the three unconformities to detect Strata on either side are parallel Several unconformities are present in the Grand Canyon Principles of Relative Dating Leaves of History Original Horizontality and Lateral Continuity Superposition of sedimentary layers Faunal Sucession
View Full Document
Unlocking...