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UI373 OUTLINE
TOOLS AND CONCEPTS
Introduction -What is Historical Geology? -Why is it important? -Academic, extraction, global change The Scientific Method and Historical Geology -What is the scientific method? -General structure -Hypotheses/multiple working hypotheses
- Falsifiable? -Make predictions -Test prediction -Reproducible -Clarify assumptions -Comparisons between Historical Geology and other sciences regarding application of the scientific method -Falsifiability, experimentation, reproducible -Consilience -An observational science. -Basic principles and procedural assumptions in historical geology -Catastrophism -Abraham Gottlob Werner and “Neptuneism” -Sediments on the surface were laid during catastrophic
floods. -Uniformitarianism -James Hutton 1788 Theory of the Earth -Processes have always operated much the same way and at much the same pace as today -Actualism -Present is the key to the past -Based on the premise of uniformitarianism -Gradualism vs. Catastrophism -Gradualism -Processes occur slowly over long periods of time. Concept of Hutton championed by Charles Lyell “Principles of Geology” (1830's) that displaced Catastrophism -Short comings -Sedimentary events and biotic events are typically abrupt -Catastrophism -Has regained credit after being panned by Lyell The Concept of Geologic Time -Absolute vs relative time -Relative time -Steno's Laws - named for Nicholas Steno (1700's) -Original horizontality -Tilting
-Spontaneous radioactive decay of isotope
- 147 Sm = 143 Nd + 2p + 2n -^143 Nd is the daughter product; 2p +2n alpha particle -Half-life -Assumptions -System is closed -No previous daughter products present -Clock wasn't reset -Some commonly used isotopes -^14 C - 14 N hl=5700yrs (good to 40,000yrs); young organic-rich -^235 U - 207 Pb hl=700ma; old rocks of all types -^87 Rb - 87 Sr hl=48ba; very old rocks of all types -^40 K - 40 Ar hl=1.3ba; mostly sediments Major Physical Earth Systems and Cycles -Introduction -Uniformitarianism, Actualism -Concept of spheres -Lithosphere -Hydrosphere -Atmosphere -Biosphere Plate Tectonics -Introduction History of Plate-Tectonic Theory
-Alfred Wegener and continental drift/Pangaea (1915) -Published two main lines of evidence in On the Origin of the Continents and Oceans (1915)
- Bullard fit after a contemporary of Wegener
- Distribution of Glossopteris flora -Alexander Du Toit added other lines of evidence in the two decades to follow
- Similarities in rock sequence in Gondwanan continents
- Late Paleozoic Gondwanaland glaciation and orientation of groves
- Divided endemic taxon (e.g., Mesosaurous)
- Continuity of Mt. Belts -Early arguments against Wegener's theory -No mechanism for plate movement -Couldn't move continents through solid ocean crust -Basic structure and composition of the outer earth was already established -Continental crust (felsic; 36km+36km), oceanic crust (mafic; 10km), lithosphere and asthenosphere and lower mantle (ultramafic; divisions at 100km and 350km respectively), outer core (liquid Fe), inner core (solid Fe) -Wegener's time line did not stand up to the fossil record -Pangaea break up in Cenozoic Vs Mesozoic -1950's and 1960's revival -Mid-Jurassic sea floor -Ocean floor topography -Polar wander paths
-Andean-type -Backarc compression and the fold and thrust belt -Isostatic loading and the foreland basin -Japanese-type -Back arc tension and divergence -Convergent (Continent-Continent) -Continents are buoyant so suture zone -Compression of margins and generation of highly deformed mountain chain -Folded and thrusted shelf and accretionary prism sediments -Foreland basin -Metamorphism -Ophiolites The Rock Cycle -Introduction -Rocks groups -Igneous -Metamorphic -Sedimentary -Why and how rocks change over time/rock cycling -Role of tectonics and other cycles The Water Cycle, Heat Energy, and Global Climate -Introduction to the hydrosphere and the unique nature of planet earth -Water through the spheres
-Reservoirs and Fluxes -Reservoirs -Ocean, glaciers, groundwater, lakes, soils, atmosphere, rivers, land plants -Fluxes -Evaporation/transpiration, precipitation, glaciers, infiltration, runoff, groundwater Global Climate (Heat Energy, Atmospheric/Oceanic Circulation, and Variations in the Water Cycle) -Heat and phase change -1g water heated one degree C requires one Calorie -Latent heat of fusion is 80 cal/g & latent heat of vaporization is 600 cal/g -Heat energy variation and variation in the intensity and style of water cycling -Temporal variation -Short term -Seasonal and yearly -Long-term -Proterozoic snowball Earth verses tropical Eocene -Geographic variation/Atmospheric circulation patterns -Convection cells -A non-tilted earth -Two-cell model -The tilted earth and the differential heat absorption because of continents -Current six-cell model
-Evidence Carbon and Oxygen Cycles -Introduction -Short-term C (Carbon) and O (Oxygen) cycling through the Biosphere -Photosynthesis and Respiration -CO 2 (Carbon dioxide) + H 2 O(Water) = CH 2 O(Sugar) +O 2 (free oxygen) -Sugar cycling -Storage of organic C -Biomass -Impact of atmosphere -Burial and removal from short-term cycle -Coal from cellulose (mostly on land) -Oil from soft tissue (mostly aquatic) -Variation in rate and carbon isotope (C^13 , C^12 ) ratios -Reading the limestone (Calcite CaCO 3 ) -Storage in the Carboniferous -Relationship of atmospheric oxygen to organic carbon burial -Long-term C and O cycling -Carbon and oxygen removed from the atmosphere and placed in the lithosphere -Burial of organics on land and in oceans -Carbonates (mostly CaCO 3 ) -Ca+2^ (calcium)+ HCO 3 -^ (bicarbonate) = CaCO 3 (Calcite)+ H+
(Hydrogen) -Volcanism and metamorphism -Continents Vs ocean floor -Hydrosphere and acid rain -CO 2 + H 2 O = H 2 CO 3 (carbonic acid) -Chemical weathering and the neutralizing of carbonic acid to bicarbonate -H 2 CO 3 = HCO 3 -^ + H+ -Weathering consumes the H+ -Bicarbonate is also introduced as these acids attack carbonate rocks -CaCO 3 + H+^ + HCO 3 -^ = Ca+2^ + 2HCO 3 - -Buried organics finally oxidize, releasing CO 2 which makes more acid -Same reaction as respiration -Aquatic organisms and return of C and O to the lithosphere -CO 2 used for body tissue from the hydrosphere -Photosynthesis reaction -CO 2 and formation of calcite skeletons, mostly in the oceans -Ca+2^ + HCO 3 -^ = CaCO 3 + H+ -Variation with time of atmospheric CO 2 -Computer models predict a general decline of CO 2 over the Phanerozoic -Greenhouse Vs icehouse effects and negative feedback in long-term carbon cycling -Greenhouse effect and the role of CO 2 -Icehouse effect and the role of CO 2 -Other factors impact icehouse (e.g., land at poles, ocean circulation, etc.)
-Vestigial structures -Ontogeny and phylogeny -Artificial selection -Floral/faunal succession -Evidence for natural selection -Young inherit traits from the parent -An oversupply of young are produced by parents -Young struggle to survive and only the fittest win -The young that survive pass their traits to the next generation -Evolution and natural selection also proposed synchronously by Alfred Russell Wallace -Mechanism clarified through gene research (Mendel, late 1800’s ) and DNA discovery (early 1900's)
- Modern Synthesis of evolution -The DNA (deoxyribonucleic acid) molecule as a blueprint -Consists of two strands spun into a double helix -Nucleotides (sugar (deoxyribose), a phosphate group, and a nitrogenous base (Thymine, Cytosine, Adenine, Guanine)) -DNA and reproduction -Sexual vs asexual reproduction -Microevolution -Point mutation -Macroevolution -What is a species? -Biological definition Vs morphological definition -Processes
-Speciation -Phyletic gradualism -Punctuated equilibrium -Extinction -Background extinction -Mass extinction -Adaptive radiations -Convergence -Size and specialization trends Introduction to Paleontology -What is Paleontology/Paleobiology? -Why study Paleontology? -Evolution; environments (paleoecology); paleogeography -What is a fossil, and what fossil types exist? -Body fossils; trace fossils (burrows, etc.); pseudofossils -Inorganic phenomenon which resemble fossils -Preservation potential -Preservational biases -Biological (decay, scavenging, etc.); physical and chemical (abrasion and breakage, chemical dissolution, etc.); diagenetic (replacement, diagenetic masking, etc.); alteration (metamorphism, igneous activity, etc.); age bias; exposure -Conditions favoring preservation -Sedimentary rocks; quick burial; low oxygen levels; hard parts; low energy; non-terrestrial environment -Modes of preservation -Ecological classification
-Mechanical weathering -Physical braking of bedrock -Root wedging; ice wedging, etc. -Products -Grains -Chemical weathering -Chemical brake down of bedrock -Solution -Products -Ions(Ca+, K+, (CO 3 )-2); residuals(Clays, etc.) -Order of resistance -Favored conditions -Acid rain and temperature -Transportation of sediment from source to deposite -Media -Gravity (e.g., landslides); wind (e.g., dunes); ice (e.g., till); water (e.g., river deposit) -The solutes -Saturation, undersaturation, and precipitation -The solid particles -Kinetic energy and deposition -Interpreting characteristics of clastic sediments/clastic sedimentary indicators -Mineralogy; grain size; sorting; shape (roundness vs sphericity); color (dark vs red)
-Fabric (planar bedding, dunes/ripples and cross bedding, mudcracks) -Solute deposition -Carbonates (mostly limestone (calcite; CaCO 3 )) -Role of CO 2 and CO 2 sequestering -Role of skeletons -Tropics; shallow ocean -Micrite (algae); allochems (ooids, bioclasts, pellets) -Clastic indicators above still apply -Evaporites -Where's and why's -Important evaporites -Halite (NaCl); anhydride (CaSO 4 ); gypsum (CaSO 4 + 2H 2 O) -Lithification -Burial; compaction; cementation (calcite; silica (SiO 2 ); iron oxide) Environmental interpretation -Interpretation of depositional environment -Identify the target strata; divide rocks into packages (lithofacies vs biofacies); infer a depositional environment -Role of environmental indicators -Physical indicators -Fossil indicators and the biological niche Depositional Environments -General principles
-Mostly coarse to medium sand; poor to good sorting; angular to rounded; many bars separating small channels; cross-bedded sand and cross-bedded to planar bedded gravel; channel scours; ripples and mudcracks on bars -Meandering streams -Subenvironments and their characteristics -Channel -Point bar -Gravel lag -Backswamp/floodplain -Levee/splays complex -Abandoned channel fill Paralic environments -Fluvial to marine transition zone -Deltas -Progradation -Delta plain (distributary, natural levee, interdistributary bay, swamp, backswamp/marsh) -Delta front (mouth bar) -Prodelta (prodelta muds) -Fossils -Beaches -Beach (shoreface, foreshore, back-beach)
-Lagoon -Tidal inlets -Tidal flat -Marsh -Fossils Marine environments -Submerged -Shelf (below fair-weather wave base) -Siliciclastic -Pelagic sedimentation -Storm sands -Carbonate -Reef-dominated -Reef core and flat -Talus -Back Reef -Lagoon -Platform -Shoal -Channels -Ramp flat -Slope -Turbidity currents -Canyons, submarine fans
