Time, Cratons, and Voyageurs NP

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Brachiopods (lamp shells) are marine invertebrates which superficially resemblebivalves (clams) even though they are not closely related. Some groups, such as theLingulata, have been present throughout the Phanerozoic. Others, however, such asObolellida, have restricted ranges.If a rock contains an assemblage of more than one group, such as both Pentameridaand Spiriferida, this limits its possible age to the narrower span when both coexisted.
Correlation of rock units over greatdistances becomes much moreconvincing if those rocks sharesimilar fossil assemblages. Here,a limestone exposed at the top ofthe Grand Canyon has beenidentified as the same materialfound near the base of Zion.Similarly, a sandstone at Zion isalso exposed at Bryce Canyon.Oftentimes it is possible toestablish correlation on the basisof similar lithologies (rock types)and similar sequences of layers,but one could argue that theseenvironmental conditions maysimply have occurred at differenttimes in different places.
Page 2 and 3: Today’s Lecture• Geologic Time
Page 4 and 5: PrinciplesofStratigraphy• Origina
Page 6 and 7: Layered sedimentary rock is typical
Page 8 and 9: The Principle of Superposition stat
Page 10 and 11: The mudcracks shown above formed ov
Page 13 and 14: The Principle of Cross-Cutting Rela
Page 15 and 16: Complex sequences of events can be
Page 17 and 18: Unconformities• Nosinglelocationo
Page 19 and 20: Intrusive igneous rocks and metamor
Page 21 and 22: Note the abrupt interruption of the
Page 23: Both “sides” of this angular un
Page 26: The Grand Canyon has several unconf
Page 29: FaunalSuccessionandCorrelation• W
Page 33: DivisionsofTimeScale• Eons(larges
Page 36 and 37: SpontaneousRadioactiveDecay• Some
Page 38 and 39: RadiometricDatingofRocks• Inorder
Page 40 and 41: Potassium-Argon dating can be used
Page 42 and 43: The steep front of this Hawaiian ba
Page 44 and 45: Organic samples are prepared for ra
Page 46 and 47: Radiocarbon dating is useful for as
Page 48 and 49: OtherAbsoluteMethods• Severalothe
Page 50 and 51: Varves: Lakes which freeze overduri
Page 52 and 53: Cosmogenic (surface) dating: If a r
Page 54 and 55: Formation of Continental CratonsMet
Page 56 and 57: Terrane AccretionMarshak, EARTH (No
Page 58 and 59: Pillow basaltscraped off theocean f
Page 60 and 61: NORTH AMERICAN CONTINENT~500 Millio
Page 62 and 63: Voyageurs National Park• Establis
Page 64 and 65: Voyageurs National ParkRecent Histo
Page 66 and 67: Voyageurs National ParkGeologic His
Page 68 and 69: Voyageurs National ParkAn example o
Page 70 and 71: Voyageurs National ParkGeologic His

Time, Cratons, and Voyageurs NP

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