A typical rock formationRelative dating: some principles to follow...Monday, October 25, 2010Principle of superpositionMonday, October 25, 2010Principle of original horizontalityMonday, October 25, 2010Principle of lateral continuityMonday, October 25, 2010Principle of cross-cutting relationshipsMonday, October 25, 2010Principle of inclusionsMonday, October 25, 2010Principles of unconformities (missing time)Monday, October 25, 2010Radiometric Age Dating•Uses unstable isotopes of naturally occurring elements. The isotopes decay: they change into different elements or different isotopes of the same element.•The rate of decay is known (has been measured in the laboratory) for a variety of isotopes.•When igneous rocks form, there is 100% parent and 0% daughter isotopes in the rock.•The ratio of the parent and daughter isotopes can be measured using a mass spectrometer.Monday, October 25, 2010Monday, October 25, 2010MethodParent isotopeDaughter isotopeHalf lifeDating rangeRubidium-strontiumRb-87Sr-8747 by10m-4.6bUranium-leadU-238Pb-2064.5 by10m-4.6bUranium-leadU-235Pb-20771.3 my10m-4.6bThorium-leadTh-232Pb-20814.1 by10m-4.6bPotassium-argonK-40Ar-401.3 by.1m-4.6bCarbon-14C-14N-145730 y100-100,000Monday, October 25, 20101999 GEOLOGIC TIME SCALECENOZOIC MESOZOIC PALEOZOICAGE(Ma)EPOCH AGEPICKS(Ma)MAGNETICPOLARITYPERIODHIST.ANOM.CHRON.5101520253035404550556065QUATER-NARYPLEISTOCENEMIOCENEOLIGOCENETRIASSIC JURASSIC CRETACEOUSPERMIANDEVONIANORDOVICIANSILURIANMISSISSIPPIAN PENNSYLVANIANCAMBRIAN*CARBONIFEROUSEOCENEPALEOCENEPLIOCENEPIACENZIANL0.011.83.65.37.111.214.816.420.523.828.533.737.041.349.054.857.961.065.0ELELMELMEELZANCLEANMESSINIANTORTONIANSERRAVALLIANLANGHIANBURDIGALIANAQUITANIANCHATTIANRUPELIANPRIABONIANBARTONIANLUTETIANYPRESIANDANIANTHANETIANSELANDIANCALABRIANHOLOCENETERTIARYPALEOGENENEOGENE1C1C2C2AC3C3AC4C4AC6C6AC6BC6CC7C8C9C10C11C12C13C15C16C17C18C19C20C21C22C23C24C25C26C27C28C29C7AC5C5AC5BC5CC5DC5E22A33A44A55B5A5C66A6B789101112131516171819202122232425282926277A6C5D5EAGE(Ma)EPOCH AGEPICKS(Ma)UNCERT.(m.y.)MAGNETICPOLARITYPERIODHIST.ANOM.CHRON.AGE(Ma)EPOCH AGEPICKS(Ma)PERIOD702602803003203403803604004204404604805005205408090100110120130140150160170180190210200 220230240NEOCOMIANLATEEARLYN.W. S.LATEEARLYMIDDLELATEEARLYMIDDLEMAASTRICHTIAN65248252256260269282296303290323327342354364370380391400412417419423428443449458464470485490500506512516495520 54371.3183.585.889.093.599.0112121127132137144151154164159CAMPANIANTATARIANUFIMIAN-KAZANIANKUNGURIANARTINSKIANSAKMARIANASSELIANGZELIANKASIMOVIANMOSCOVIANBASHKIRIANSERPUKHOVIANVISEANTOURNAISIANFAMENNIANFRASNIANGIVETIANEIFELIANEMSIANPRAGHIANLOCKHOVIANPRIDOLIANLUDLOVIANWENLOCKIANLLANDOVERIANASHGILLIANCARADOCIANLLANDEILIANLLANVIRNIANARENIGIANTREMADOCIANSUNWAPTAN*STEPTOEAN*MARJUMAN*DELAMARAN*DYERAN*MONTEZUMAN*SANTONIANCONIACIANTURONIANCENOMANIAN ALBIANAPTIANBARREMIANHAUTERIVIANVALANGINIANBERRIASIANTITHONIANKIMMERIDGIANOXFORDIANCALLOVIANBATHONIANBAJOCIANAALENIANTOARCIANPLIENSBACHIANSINEMURIANHETTANGIANNORIANRHAETIANCARNIANLADINIANANISIANOLENEKIANINDUANC31C32C33313233M0M1M5M10M12M14M16M18M20M22M25M29M3169176180195190202206210221234227248245242111444567788888888899999101233.2311RAPID POLARITY CHANGESPRECAMBRIANPROTEROZOICARCHEANAGE(Ma)EON ERABDY.AGES(Ma)75090016002500300034003800?100012501500175020002250250027503000325035003750LATEEARLYMIDDLELATEEARLYMIDDLELLMEEEEDCBALLLM30C3030C30C3434543Monday, October 25, 2010PaleomagneticsEarth has a dipole magnetic field, with the direction in line with the axis of spin.When rocks form, they are permanently magnetized in the direction of the current magnetic latitude. Monday, October 25, 2010Monday, October 25, 2010Plate TectonicsMonday, October 25, 2010Monday, October 25, 2010Monday, October 25, 2010Monday, October 25, 2010FossilsMonday, October 25, 2010A fossil is any recognizable evidence of preexisting life.Types of fossils:! (1) Trace fossils! (2) Preserved materialFossils are our only direct evidence ofwhat organisms looked like in the past.The fossil record is a biased one.Monday, October 25, 2010Where is the time?Monday, October 25, 2010Taphonomy: The study of the process of fossilization, from death of the organismto discovery by the paleontologist.Monday, October 25, 2010Types of biases in the fossil record•Fossils with no hard parts are rarely preserved. Fossil record is mostly a record of shells and bones.•Organisms that lived in areas where they are likely to be preserved.•Time averaging of fossil beds.•Post-mortem transport, scavenging, Monday, October 25, 2010Diatoms ForaminiferaMicrofossilsMonday, October 25, 2010“Invertebrates”Monday, October 25, 2010VertebratesMonday, October 25, 2010StomatolitesMonday, October 25, 2010TransitionalFormsMonday, October 25, 2010Basilosaurus hind legMonday, October 25, 2010Ankle bones of the archaeocetes Rodhocetus (Eocene)on the left, a pronghorn (middle) and Artiocetus (right).Note the double-pulleyed astragalus. Other features in common are a notched cuboid and a prominent fibular facet.Monday, October 25, 2010Tiktaalik roseae (late Devonian)Monday, October 25, 2010Monday, October 25, 2010Monday, October 25, 2010Microfossils from the Apex Chert, North Pole, AustraliaAbout 3.465 billion years old, resembling filamentous cyanobacteriaMonday, October 25, 2010Stromatolite, North Pole deposits, Western Australiaabout 3.5 billion years oldMonday, October 25, 2010Extant stromatolite showing closeup of cyanobacteriaMonday, October 25, 2010Proterozoic (2.5 bya to 544 mya). Evolution of organisms with oxygenic photosynthesis caused an increase in oxygen levels. Rising oxygen levels in the world’s oceans caused the formation of iron oxide, often preserved in the banded iron formation. Monday, October 25, 2010Eukaryotic milestones•2.7 bya: chemical traces of eukaryotic-type lipids in fossil organic matter (controversial).•2.1 bya: Grypania spiralis, the first fairly well-accepted fossil eukaryote•1.6-1.8 bya: origin of single-celled algae of unknown type, known as acritarchsMonday, October 25, 2010Grypania spiralis from MichiganMonday, October 25, 2010acritarchMonday, October 25,
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