Download Stratigraphy (GEOL 4/54070)

Stratigraphy (GEOL 4/54070)
Dr. Joseph D. Ortiz; Office: McGilvrey 336
Phone: 330-672-2225; E-mail: [email protected]
Introductions
• Name, class, expected degree
• Phone and email
• Geology experience
Classes? Field camp?
• Soft Rock or Hard Rock?
• Why this class?
Class Topics
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Sedimentary environments: Terrestrial, coastal, marine
Geochronology and chronostratigraphy
High resolution stratigraphic methods (e.g. core and well logging, chemostratigraphy)
Sequence Stratigraphy and Basin Analysis
Sedimentary rocks – genesis, types, distribution, and alternation
Siliciclastic versus biogenic sedimentation
Clastic transport and fluid flow
Lithostratigraphy and facies relationships
Class logistics
• Website:
http://www.personal.kent.edu/~jortiz/Strat/
• Students with special needs?
• Conflicts with field trip or exams?
• Prerequisites:
Petrology and Invertebrate Paleontology
Grading Policy
(see http://www.personal.kent.edu/~jortiz/Strat/grading.html)
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Three Midterms (each worth 15%)
Average Grade on Lab Assignments
Average Grade on Field Trip Reports
Cumulative Final Exam
Total
45%
15%
20%
20%
100%
What is “Soft Rock” Geology?
Sedimentary Geology =
Sedimentology
(Study of the character of sediments and sedimentary rocks, their transport and
deposition)
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Stratigraphy
(Assessment of the temporal and spatial relationships of sediments and rock
strata)
Russian R., CA
What Sedimentary Geology Processes do you see?
Questions of interest?
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How are geologic units related?
Has sea level varied through time?
If so, by how much?
How have the Earth’s regional environments changed through
time?
• Has climate varied?
• Where can Earth’s geologic resources be found?
Importance of Sedimentary rocks
• Record the story of
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Paleoceanography
Paleoclimatology
Paleogeography
Paleontology and
Evolution
• Major repositories for
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Groundwater
Oil and Gas
Coal
Iron
Agricultural Fertilizer (phosphates, nitrates)
Building materials
Sedimentary Geology is a broad,
interdisciplinary, science
• Enormous range of temporal scales
Events (e.g. landslides, turbitites)
Eons (e.g. erosion and sediment transport)
• Enormous range of spatial scales
Single depositional layers (e.g. tsunami deposits)
Global sedimentary horizons (e.g. sea level onlap)
• Mechanical
• Chemical
Weathering processes
Working with another student
Make lists of physical (mechanical) and chemical weathering
processes.
Mechanical
Chemical
Mechanical Weathering
• Thermal stress
(Response to heating/cooling
• Exfoliation
(Large scale pressure release)
• Freeze-thaw (Ice wedging)
• Abrasion
• Salt wedging
• Wet/dry cycling
• Biotic processes
Abraded Coral, Taiwan
Chemical Weathering varies with
Eh, pH, surface area
Classes of reactions:
• Simple Solution
(Complete Hydrolysis)
• Partial Hydrolysis
• Hydration/Dehydration
• Oxidation-Reduction
• Ion Exchange
• Chelation
Carbonate dissolution
What
determines
the rate of
weathering
at an
outcrop?
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Sedimentary Composition
Biological activity
Climate
Drainage
Topographic relief
Exposed Surface area
Sort the following lists in terms of susceptibility
to weathering
Mafic Minerals
• Pyroxene
• Olivine
• Amphibole
Felsic Minerals
• Quartz
• Ca Plagioclase
• Na plagioclase
Susceptibility to weathering
Mafic Minerals
• Olivine
• Pyroxene
• Amphibole
1
2
3
Key
• 1= Least Stable
• 3 = Most stable
Felsic Minerals
• Quartz
3
• Ca Plagioclase 1
• Na plagioclase 2
Chemical weathering and
Bowen’s reaction series
• High Temperature - High Pressure mineral phases are more
susceptible to weathering under surface conditions.
• Most susceptible minerals are thus Olivine and Ca- minerals.
• Least susceptible mineral is quartz
Biotic processes can enhance weathering rates
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Lichen growth
Root or tree trunk wedging
Burrowing activity
Impact on both physical and chemical weathering
Geographic influence on weathering
• Mechanical weathering dominates in cool, dry, and high latitude (or
altitude) regions
• Chemical weathering dominates in warm, moist, and low latitude (or
altitude) regions
The Rock Cycle
Next Lecture: Properties of the sedimentary
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