A typical rock formation Relative dating some principles to follow Wednesday October 26 11 Principle of superposition Wednesday October 26 11 Principle of original horizontality Wednesday October 26 11 Principle of lateral continuity Wednesday October 26 11 Principle of cross cutting relationships Wednesday October 26 11 Principle of inclusions Wednesday October 26 11 Principles of unconformities missing time Wednesday October 26 11 Radiometric Age Dating unstable isotopes of naturally Uses occurring elements The isotopes decay they change into different elements or different isotopes of the same element rate of decay is known has been The measured in the laboratory for a variety of isotopes igneous rocks form there is 100 When parent and 0 daughter isotopes in the rock ratio of the parent and daughter The isotopes can be measured using a mass spectrometer Wednesday October 26 11 Wednesday October 26 11 Method Parent isotope Daughter isotope Half life Dating range Rubidiumstrontium Rb 87 Sr 87 47 by 10m 4 6b Uranium lead U 238 Pb 206 4 5 by 10m 4 6b Uranium lead U 235 Pb 207 71 3 my 10m 4 6b Thorium lead Th 232 Pb 208 14 1 by 10m 4 6b Potassium argon K 40 Ar 40 1 3 by 1m 4 6b Carbon 14 C 14 N 14 5730 y 100 100 000 Wednesday October 26 11 1999 GEOLOGIC TIME SCALE C5A C5B C5C C5D 5E C5E 6 M 16 4 11 12 C11 C12 13 C13 15 C15 16 C16 17 40 18 20 C20 C21 22 50 C22 23 C23 RUPELIAN C25 26 C26 27 C27 65 C28 29 140 M18 PRIABONIAN M29 170 41 3 180 M LUTETIAN 190 49 0 E 200 C29 30 C30 Wednesday October 26 11 EARLY THANETIAN 220 57 9 L SELANDIAN 61 0 E 230 DANIAN 240 65 0 4 1 300 112 320 2 APTIAN 121 3 127 3 132 4 137 4 144 5 340 BARREMIAN HAUTERIVIAN VALANGINIAN 360 BERRIASIAN TITHONIAN KIMMERIDGIAN OXFORDIAN CALLOVIAN BATHONIAN MIDDLE 380 151 154 6 7 159 7 164 8 169 8 400 420 BAJOCIAN AALENIAN 176 8 180 8 440 TOARCIAN PLIENSBACHIAN EARLY LATE 190 8 195 8 SINEMURIAN HETTANGIAN RHAETIAN YPRESIAN 54 8 93 5 280 ALBIAN LATE 160 1 99 0 M22 M25 89 0 202 8 206 8 210 8 MIDDLE 460 480 NORIAN 221 9 227 9 CARNIAN 500 LADINIAN 234 9 242 245 248 9 9 10 520 ANISIAN EARLY OLENEKIAN INDUAN PERMIAN CHRON HIST M12 M14 M16 150 BARTONIAN PALEOCENE 25 M10 1 1 CENOMANIAN M20 E C24 28 130 210 55 M0 M1 M3 M5 37 0 24 60 120 CHATTIAN 28 5 C18 C19 21 L C17 19 45 23 8 L EOCENE 35 20 5 33 7 PALEOGENE 30 OLIGOCENE 10 C10 110 AQUITANIAN TERTIARY C8 C9 14 8 LANGHIAN C6A 6B C6B 6C C6C 9 34 C34 100 TURONIAN 83 5 85 8 540 E MOSCOVIAN 900 282 290 1000 296 303 311 1250 BASHKIRIAN SERPUKHOVIAN 323 327 1500 VISEAN 342 TOURNAISIAN 354 L LATE 750 SAKMARIAN GZELIAN KASIMOVIAN E BDY AGES Ma 269 ASSELIAN L ERA 543 248 252 256 260 ARTINSKIAN S SERRAVALLIAN E 6A 25 ANOM 11 2 BURDIGALIAN C6 7 7A C7 C7A 8 90 SANTONIAN CONIACIAN TATARIAN UFIMIAN KAZANIAN KUNGURIAN W C5 TORTONIAN LATE L EON 1750 FAMENNIAN FRASNIAN 364 370 GIVETIAN M PROTEROZOIC 20 80 260 CAMPANIAN C33 C4 L 1 AGE Ma MIDDLE 1600 EARLY 2000 380 EIFELIAN 391 2250 EMSIAN PRAGHIAN L LOCKHOVIAN PRIDOLIAN LUDLOVIAN WENLOCKIAN E L M 400 412 417 419 423 428 LLANDOVERIAN ASHGILLIAN LLANVIRNIAN 449 458 3000 464 470 ARENIGIAN E D C B TREMADOCIAN SUNWAPTAN STEPTOEAN MARJUMAN DELAMARAN DYERAN MONTEZUMAN LATE 2750 443 CARADOCIAN LLANDEILIAN 2500 2500 485 490 495 500 506 512 516 520 3250 ARCHEAN 5D 33 5 3 7 1 C4A 71 3 PRECAMBRIAN PICKS Ma AGE N 5B 5C C3A 2 MAASTRICHTIAN 32 C32 3 6 MESSINIAN 65 AGE PERIOD EPOCH Ma PENNSYLVANIAN 15 C3 70 PICKS UNCERT m y Ma MISSISSIPPIAN 5A E ZANCLEAN 30 C30 31 C31 AGE CARBONIFEROUS 5 PIACENZIAN 0 01 1 8 PERIOD EPOCH PALEOZOIC DEVONIAN 10 L PLIOCENE C2A CALABRIAN AGE Ma NEOCOMIAN 4A HOLOCENE PICKS Ma RAPID POLARITY CHANGES 4 PLEISTOCENE MIOCENE 3A QUATERNARY NEOGENE 3 AGE CRETACEOUS C2 EPOCH JURASSIC C1 2 PERIOD TRIASSIC 1 2A 5 CHRON HIST ANOM AGE Ma MESOZOIC MAGNETIC POLARITY CAMBRIAN ORDOVICIANSILURIAN CENOZOIC MAGNETIC POLARITY 3000 MIDDLE 3400 3500 EARLY 3750 3800 A 543 Paleomagnetics Earth 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 Wednesday October 26 11 Wednesday October 26 11 Plate Tectonics Wednesday October 26 11 Wednesday October 26 11 Wednesday October 26 11 Wednesday October 26 11 Fossils Wednesday October 26 11 A fossil is any recognizable evidence of preexisting life Types of fossils 1 Trace fossils 2 Preserved material Fossils are our only direct evidence of what organisms looked like in the past The fossil record is a biased one Wednesday October 26 11 Where is the time Wednesday October 26 11 Taphonomy The study of the process of fossilization from death of the organism to discovery by the paleontologist Wednesday October 26 11 Types 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 Wednesday October 26 11 Microfossils Diatoms Wednesday October 26 11 Foraminifera Invertebrates Wednesday October 26 11 Vertebrates Wednesday October 26 11 Stromatolites Wednesday October 26 11 Transitional Forms Wednesday October 26 11 Wednesday October 26 11 Wednesday October 26 11 Basilosaurus hind leg Wednesday October 26 11 Ankle 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 Wednesday October 26 11 Tiktaalik roseae late Devonian Wednesday October 26 11 Wednesday October 26 11 Wednesday October 26 11 Microfossils from the Apex Chert North Pole Australia About 3 465 billion years old resembling filamentous cyanobacteria Wednesday October 26 11 Stromatolite North Pole deposits Western Australia about 3 5 billion years old Wednesday October 26 11 Extant stromatolite showing closeup of cyanobacteria Wednesday October 26 11 Proterozoic 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 Wednesday October 26 11 Eukaryotic milestones 2 7 bya chemical traces of eukaryotic type lipids in fossil organic matter controversial 2 1 bya Grypania spiralis the first fairly wellaccepted fossil eukaryote 1 6 1 8 bya origin of single celled algae of unknown type known as acritarchs Wednesday October 26 11
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