James Hutton
Scottish physician
Principle of uniformitarianism
Processes seen in present day are same as in past
Change is slow, bigger changes needing more time
Ways of dating materials
relative- order of formation
- qualitative
- analyzes older against younger
Numerical- number of years past formation
- quantitative
relative age
principle of …
Uniformitarianism
Original horizontality
Superposition
Original continuity
Cross-cutting relationships
Baked contacts
Inclusions
Uniformitarianism
modern processes= ancient events
horizontality and continuity (relative)
horizontality sheets in rocks forms that extend continuously
Seperated by erosion
stratigraphic superposition (relative)
In layered rocks
Youngest beds are most above
Older beds are lowest
Strata twisted after deposition
cross-cutting relations (relative)
rock exsistence before it is intruded
Intrusions Are younger (dike, fault, erosion)
inclusions (relative)
fragments of rock included in another rock
Inclusion is older
Igneous xenoliths - country rock older than the magma it fell into
Weathering rubble- debris from Protoliths
igneous xenoliths (inclusions)
country rock older than the magma it fell into
weathering rubble (inclusions)
debris from protoliths
baked contacts (relative)
baked rock (older) =
Thermal meta of country rock being invaded by plutonic igneous intrusion
geologic history
Below sea level
Horizontality strata (layer) is deposited from 1 at bottom (oldest) to 8 at top (youngest)
Time complicates the order-
Igneous sill intrudes
Folding uplift and erosion
Pluton makes them wavy
Faulting cuts it down the middle, mismatching the order
Dike intrudes
fossil succession
fossils mark time
One is older than the other as time goes on
Time period = specific fossil content
Fossil range
Each fossil has range of first and last appearance that mark time when the fossils overlap in same strata layer
Strata correlates locally, regionally, globally
Unconformities
Erosion and rock creation pauses (sediment deposition) = time lost in rock record
Angular, nonconformity, disconformity
Angular nonconformity
huge gulf in time
Horizontal sediments get eroded away,
James Hutton- first realized
Hutton’ a unconformities - Siccar Point, Scotland
vertical beds of stones with another stone on top of it from a different time period (50 million gap
Nonconformity
Crystalline Meta / igneous rocks exposed by erosion then sedimentary strata deposited on top of it
Rocks are NOT the same
Discomformity
Beds parallel to each other on top and bottom of paused sedimentation
similar rocks
No deformation
stratigraphic correlation
graphical fill patterns
Seperate rock types
Divided into formations (which si decided by contacts)
Lithologic correlation
Matching rock layers in different areas based on rock types, sequence of occurence,
fossil correlation
matching rock layers based on fossils within the rocks
Arizona and Utah National park
Long distance formations that overlap rock type occurrences, and columns build composites
