HISTORY! Universe ~14 billion years old EARTH’S AGE • Sun’s entire planetary system, formed at approximately same time. • strong evidence that Earth formed ~ same time as Moon & meteorites. • Moon dust & some meteorites (remained virtually unaltered since formation) have been dated to be ~4.56 by. THE AGE OF EARTH • oldest rocks on Earth are not necessarily the oldest because most of the rocks on Earth have been subject to a lot of geologic activity (being melted & exposed to the surface again & again) • oldest know Precambrian rock is about 4.0 billion years old. Although individual mineral grains from a sedimentary rock in Australia has been dated to be 4.4 billion years. Earth’s oldest rock: the Acasta gneiss in northern Canada was formed 4.0 billion years ago Allende meteorite, which fell in Mexico is slightly older than 4.6 billion years. LIFE ON EARTH • ~ 3.8 billion years ago 1st single-cell (simple-bacteria like) organisms formed in the oceans • Scientist believe life may have started earlier than this DETERMINING THE AGE OF EARTH & ITS ROCKS • Relative Dating Vs. Radiometric Dating • stratigraphy – science of rock layers & process by which strata are formed • strata – bands of rocks, & individual band is called stratum • relative age – younger vs. older; age of a rock, fossil, or other geologic feature relative to another feature • numerical age – age of rock or geological feature in years before present Four key principles of stratigraphy: • principle of original horizontality – all sediments were originally laid horizontally • principle of stratigraphic superposition – in an undisturbed sequence of strata, younger sediments lay on top of older sediments • principle of cross-cutting relationship – stratum must be always older than any feature that disrupts or cuts the sequence • principle of lateral continuity (unconformity) - sediments substantial gap in a stratigraphic sequence that marks the absence of part of the rock. Horizontal strata (Badlands) all these strata were originally deposited as horizontal layers all these strata were originally deposited as horizontal layers The Grand Canyon contains 2 billion years of Earth’s history The Grand Canyon FOUR UNITS OF GEOLOGICAL TIME: Eons – vast majority of Earth’s history is divided into 3 eons in which fossils are extremely rare or nonexistent. Eras – The Phanerozoic Eon is divided into three shorter units called eras, the Paleozoic (ancient life), Mesozoic (middle life), and Cenozoic (recent life). These eras were separated by major extinction events, when more of 70% of the species perished. Periods – The eras are then divided into periods. The earliest period of the Paleozoic era, the Cambrian period is noteworthy, because of the “explosion” of unparalleled diversity of life. Epochs – Periods are divided into smaller units called epochs. The Tertiary and Quaternary periods are somewhat familiar because of the emergence of humans and their ancestors. GSA GEOLOGIC TIME SCALE v. 4.0 CENOZOIC MESOZOIC PALEOZOIC PRECAMBRIAN MAGNETIC MAGNETIC BDY. AGE POLARITY PICKS AGE POLARITY PICKS AGE PICKS AGE . N PERIOD EPOCH AGE PERIOD EPOCH AGE PERIOD EPOCH AGE EON ERA PERIOD AGES (Ma) (Ma) (Ma) (Ma) (Ma) (Ma) (Ma) HIST HIST. ANOM. (Ma) ANOM. CHRON. CHRO HOLOCENE 1 C1 QUATER- 0.01 30 C30 66.0 541 CALABRIAN NARY PLEISTOCENE* 1.8 31 C31 MAASTRICHTIAN 252 2 C2 GELASIAN 70 CHANGHSINGIAN EDIACARAN 2.6 Lopin- 254 32 C32 72.1 635 2A C2A PIACENZIAN WUCHIAPINGIAN PLIOCENE 3.6 gian 33 260 260 3 ZANCLEAN CAPITANIAN NEOPRO- 5 C3 CAMPANIAN Guada- 265 750 CRYOGENIAN 5.3 80 C33 WORDIAN TEROZOIC 3A MESSINIAN LATE lupian 269 C3A 83.6 ROADIAN 272 850 7.2 SANTONIAN 4 KUNGURIAN C4 86.3 279 TONIAN CONIACIAN 280 4A Cisura- C4A TORTONIAN 90 89.8 1000 1000 PERMIAN ARTINSKIAN 10 5 TURONIAN lian C5 93.9 290 SAKMARIAN STENIAN 11.6 CENOMANIAN 296 SERRAVALLIAN 34 C34 ASSELIAN 299 5A 100 100 300 GZHELIAN 1200 C5A 13.8 LATE 304 KASIMOVIAN 307 1250 MESOPRO- 15 LANGHIAN ECTASIAN 5B C5B ALBIAN MIDDLE MOSCOVIAN 16.0 TEROZOIC 5C C5C 110 VANIAN 315 PENNSYL- 1400 EARLY 5D C5D MIOCENE 113 320 BASHKIRIAN 323 5E C5E NEOGENE BURDIGALIAN SERPUKHOVIAN 1500 CALYMMIAN 6 C6 APTIAN LATE 20 120 331 6A C6A 20.4 EARLY 1600 M0r 126 6B C6B AQUITANIAN M1 340 MIDDLE VISEAN MISSIS- M3 BARREMIAN SIPPIAN STATHERIAN C6C 23.0 6C 130 M5 CRETACEOUS 131 347 1750 HAUTERIVIAN 7 C7 CARBONIFEROUS EARLY TOURNAISIAN 1800 M10 134 25 7A C7A 359 8 C8 CHATTIAN VALANGINIAN M12 360 140 M14 139 FAMENNIAN OROSIRIAN 9 C9 M16 28.1 M18 BERRIASIAN 2000 PROTEROZOIC 10 C10 LATE PALEOPRO- M20 145 372 2050 11 C11 TEROZOIC 30 M22 TITHONIAN FRASNIAN 150 380 12 RUPELIAN 152 C12 LATE 383 RHYACIAN M25 KIMMERIDGIAN GIVETIAN OLIGOCENE 388 157 MIDDLE 2250 M29 EIFELIAN 2300 13 C13 33.9 160 393 OXFORDIAN DEVONIAN 35 15 C15 164 400 EMSIAN SIDERIAN 16 C16 CALLOVIAN 166 PRIABONIAN BATHONIAN 408 17 168 EARLY PRAGIAN C17 170 MIDDLE BAJOCIAN 411 2500 2500 37.8 170 AALENIAN LOCHKOVIAN 18 174 419 PRIDOLI 40 C18 BARTONIAN CHANGES 420 423 19 LUDLOW LUDFORDIAN 426 NEOARCHEAN C19 TOARCIAN GORSTIAN 41.2 180 HOMERIAN 427 WENLOCK SHEINWOODIAN 430 2750 20 183 433 2800 LLANDO- TELYCHIAN C20 PLIENSBACHIAN AERONIAN 439 EARLY 440 VERY 441 LUTETIAN SILURIAN RHUDDANIAN 45 190 444 JURASSIC 191 HIRNANTIAN 445 KATIAN MESO- RAPID POLARITY RAPID POLARITY CHANGES RAPID POLARITY 3000 21 SINEMURIAN LATE 453 C21 SANDBIAN ARCHEAN EOCENE 47.8 199 458 200 HETTANGIAN 460 201 DARRIWILIAN 22 MIDDLE 50 C22 RHAETIAN 467 3200 PALEOGENE DAPINGIAN 470 3250 23 C23 YPRESIAN 210 209 FLOIAN EARLY 478 480 24 ORDOVICIAN TREMADOCIAN PALEO- 485 C24 LATE AGE 10 55 NORIAN FURON- 490 ARCHEAN 220 JIANGSHANIAN 56.0 GIAN 494 3500 25 PAIBIAN ARCHEAN C25 497 THANETIAN 500 GUZHANGIAN 501 3600 26 228 Epoch 3 DRUMIAN 230 AGE 5 505 C26 59.2 509 AGE 4 60 SELANDIAN CARNIAN 3750 Epoch 2 514 237 AGE 3 EOARCHEAN 27 61.6 520 C27 LADINIAN 521 240 MIDDLE 241 AGE 2 28 TRIASSIC C28 DANIAN CAMBRIAN 529 ANISIAN TERRE- 4000 4000 65 29 247 NEUVIAN C29 PALEOCENE FORTUNIAN EARLY OLENEKIAN 250 HADEAN 66.0 250 INDUAN 30 C30 252 540 541 *The Pleistocene is divided into four ages, but only two are shown here. What is shown as Calabrian is actually three ages—Calabrian from 1.8 to 0.78 Ma, Middle from 0.78 to 0.13 Ma, and Late from 0.13 to 0.01 Ma. Walker, J.D., Geissman, J.W., Bowring, S.A., and Babcock, L.E., compilers, 2012, Geologic Time Scale v. 4.0: Geological Society of America, doi: 10.1130/2012.CTS004R3C. ©2012 The Geological Society of America. The Cenozoic, Mesozoic, and Paleozoic are the Eras of the Phanerozoic Eon. Names of units and age boundaries follow the Gradstein et al. (2012) and Cohen et al. (2012) compilations. Age estimates and picks of boundaries are rounded to the nearest whole number (1 Ma) for the pre-Cenomanian, and rounded to one decimal place (100 ka) for the Cenomanian to Pleistocene interval. The numbered epochs and ages of the Cambrian are provisional. REFERENCES CITED Cohen, K.M., Finney, S., and Gibbard, P.L., 2012, International Chronostratigraphic Chart: International Commission on Stratigraphy, www.stratigraphy.org (last accessed May 2012). (Chart reproduced for the 34th International Geological Congress, Brisbane, Australia, 5–10 August 2012.) Gradstein, F.M, Ogg, J.G., Schmitz, M.D., et al., 2012, The Geologic Time Scale 2012: Boston, USA, Elsevier, DOI: 10.1016/B978-0-444-59425-9.00004-4. .