Lecture 10 Time and Geology

Lecture Outline IDefinitions IIRelative Time A)Principles i.Original Horizontality ii.Superposition iii.Lateral Continuity iv.Cross-Cutting Relationships v.Inclusions B)Unconformities i.Disconformity ii.Angular Unconformity iii.Nonconformity C)Correlation i.Physical Continuity ii.Similarity of Rock Types iii.Fossils D)Standard Geologic Time Scale Lecture 10 i

Lecture Outline IIIAbsolute Time A)Isotopes B)Radioactive Decay i.Types of Decay a)Alpha Emission b)Beta Emission c)Electron Capture ii.Decay Systems a)Uranium C)Isotopic Dating D)Uses of Isotopic Dating i.Radiocarbon Dating ii.Transport Tracing iii.Paleoclimatology IVUsing Relative and Absolute Age VConclusions Lecture 10 ii

Definitions Lecture 10 I Uniformitarianism the fundamental principle that geological processes and natural laws now operating to modify the Earth's crust have acted in much the same manner and with essentially the same intensity throughout geologic time, and that past geologic events can be explained by forces observable today; "The present is the key to the past.” The doctrine does not imply that all change is at a uniform rate and does not exclude minor local catastrophes.

Definitions Lecture 10 I Group Formation Member Contact

Relative Time Lecture 10 II.A Original Horizontality (Steno) Superposition (Steno) Lateral Continuity (Steno) Cross-Cutting Relationships (Lyell) Inclusions (Lyell)

Principles of Relative Time Original Horizontality Lecture 10 II.A.i

Principles of Relative Time Superposition Lecture 10 II.A.ii

Principles of Relative Time Lateral Continuity Lecture 10 II.A.iii

Principles of Relative Time Cross-Cutting Relationships Lecture 10 II.A.iv

Principles of Relative Time Inclusions Lecture 10 II.A.v

Unconformities Lecture 10 II.B.1 unconformity - (1) a break or gap in the geologic record, such as as interruption in the normal sequence of deposition of sedimentary rocks, or a break between eroded metamorphic rocks and younger sedimentary strata. (2) the structural relationship between two groups of rock that are not in normal succession. conformity - (1) the relationship between adjacent sedimentary strata that have been deposited in orderly sequence with little or no evidence of time lapse; true stratigraphic continuity (2) a surface that separates younger strata from older ones, along which there is no physical evidence of erosion or nondeposition.

Unconformities Lecture 10 II.B.2 Disconformity Angular Unconformity Nonconformity

Unconformities Disconformity Lecture 10 II.B.i an unconformity between beds that are parallel. The tendency is to apply the term to erosional breaks that are represented elsewhere by rock units of at least formational rank.

Unconformities Angular Unconformity Lecture 10 II.B.ii an unconformity in which younger sediments rest upon the eroded surface of tilted or folded older rocks.

Unconformities Nonconformity Lecture 10 II.B.iii an unconformity between stratified rocks above and unstratified igneous or metamorphic rocks below.

Correlation Lecture 10 II.C Physical Continuity Similarity of Rock Types Fossils

Correlation Physical Continuity Lecture 10 II.C.i

Correlation Rock Type Lecture 10 II.C.ii

Correlation Fossil Assemblages Lecture 10 II.C.iii

Deep Time

Standard Geologic Time Scale Lecture 10 II.D Divisions of Time Eon Era Period Epoch Age Chron Phanerozoic Eon -"Eon of Evident Life" Paleozoic Era -"Era of Old Life" Mesozoic Era -"Era of Middle Life" Cenozoic Era -"Era of Modern Life"

Lecture 10 II.D The Standard Geologic Time Scale Chronostratigraphic Units ChronologicChronostratigraphic Unit _ _Unit Era Erathem Period System Epoch Series Age Stage Chron Zone

Absolute Time Lecture 10 III Isotopes Radioactive Decay

Absolute Time Isotopes Lecture 10 III.A isotopes - atoms of the same element that have different numbers of neutrons but the same number of protons

Absolute Time Radioactive Decay Types Lecture 10 III.B.i

Half-Life

Radionuclides Radioactive (parent) Radiogenic (daughter) Radioactive and Radiogenic Cosmogenic

Radioactive Decay Systems

238 U 206 Pb

Absolute Time Uses of Isotopic Dating Lecture 10 III.D Radiocarbon Dating Transport Tracing Paleoclimatology

Half -life: 5,730 years Effective Range: ,000 years Source Materials: Organic Matter Uses: Radiocarbon Dating Absolute Time Radiocarbon Dating

Absolute Time Transport Tracing Lecture 10 III.D.ii

Lecture 10 III.D.iii 18 O/ 16 O (interglacial) < 18 O/ 16 O (glacial) Absolute Time Paleoclimatology

Lecture 10 IV Using Absolute and Relative Dating