Stratigraphy (GEOL 4/54070)
Dr. Joseph D. Ortiz; Office: McGilvrey 336
Phone: 330-672-2225; E-mail: jortiz@kent.edu
Introductions
• Name, class, expected degree
•
Phone and email
•
Geology experience
Classes? Field camp?
•
Soft Rock or Hard Rock?
•
Why this class?
Class Topics
• 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)
• Three Midterms (each worth 15%) 45%
• Average Grade on Lab Assignments 15%
• Average Grade on Field Trip Reports 20%
• Cumulative Final Exam 20%
• Total 100%
What is “Soft Rock” Geology?
Sedimentary Geology =
Sedimentology
(Study of the character of sediments and sedimentary rocks, their transport and deposition)
+

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?
•
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
•
Paleoceanography
•
Paleoclimatology
•
Paleogeography
•
Paleontology and
Evolution
• Major repositories for
• 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?
•
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 1
• Pyroxene 2
• Amphibole 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
•
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 blanket