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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 • • • • • • • • 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%) 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) + 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 • 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 • • • • 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