Sedimentary rocks Fossil Fuel Resources Exam next Tuesday February 14 Bring Scantron and Review Questions Weathering About 75 of all rock outcrops on the continents Important to reconstruct much of Earth s history Sediment is derived from weathering Mechanical Weathering Two kinds of weathering Mechanical Chemical Chemical weathering Chemical changes of minerals Removing or adding elements Most important agent is water Rates of weathering Important factors Rock characteristics Climate 1 Sedimentary Rocks Two main types Clastic or detrital Deposition of particles Chemical Precipitation from water includes rocks formed by organisms Shale Types of Clastic Rocks Shale most abundant Sandstone Conglomerate Shale with plant fossils Most common type of clastic rock Very fine grained sediment Usually gray Tendency to split along planes fissile Sandstone Sandstone Composed of sand size particles Environments include Beach River Shallow sea Dunes 2 Conglomerate Conglomerate Particles larger than 2 mm Usually rock fragments Chemical rocks Dissolved material precipitates to form sedimentary rock Physical processes Life processes biochemical origin Coquina Chemical rocks Limestone calcium carbonate 90 precipitated by organisms Most common type of chemical rock Close up of coquina 3 Fossiliferous limestone Chalk Chemical rocks Rock salt Direct precipitation from water Chert flint jasper opal or agate Evaporites Salt Gypsum Hotspring deposits Features of sedimentary rocks Bedding and bedding planes Size shape and distribution of grain sizes Fossils Porosity Permeability Economic importance Coal Petroleum and natural gas Sources of iron and aluminum 4 Petroleum Requirements Hydrocarbon System Source Cooking Reservoir Trap http www priweb org ed pgws systems systems home html SOURCES Shale with organic material Gooey sludge on ocean floor Diatoms Planktonic organisms Probable source of petroleum http www priweb org ed pgws systems energy capture capture html http www priweb org ed pgws systems source source html COOKING Just right temperature Just right pressure Just right time RESERVOIR Permeable Porous Usually a sedimentary rock 5 PERMEABLE POROUS Permits fluid throughflow Nylon scrubbie RESERVOIR Permeable and Porous Has open space Sponge TRAP Impermeable Shale commonly Usually not source shale http www priweb org ed pgws systems reservoir reservoir html Trap Almost no permeability or pore space STYLES OF TRAPS Structural Stratigraphic http www priweb org ed pgws systems seal seal html 6 STRUCTURAL TRAPS Anticline Fault Overthrust Salt Dome ANTICLINE TRAP Reservoir sand Capping shale Arched fold Plummer McGeary Physical Geology 2nd Wm C Brown Co 1979 FAULT TRAP Reservoir exists Fault creates trap OVERTHRUST TRAP Reverse fault Both fold and fault traps Plummer McGeary Physical Geology 2nd Wm C Brown Co 1979 SALT DOME TRAP Plummer McGeary Physical Geology 2nd Wm C Brown Co 1979 SALT DOME TRAP Rising dome deforms beds Salt and shale impermeable Plummer McGeary Physical Geology 2nd Wm C Brown Co 1979 Plummer McGeary Physical Geology 2nd Wm C Brown Co 1979 7 STRATIGRAPHIC TRAPS Sand pinch Lens Unconformity Reef SAND PINCH TRAP Deposition of sand Shale deposited above sand Deltas Invading seas Plummer McGeary Physical Geology 2nd Wm C Brown Co 1979 SAND LENS TRAP Channel sand Shifting channel of river Shale above Ganges Delta Plummer McGeary Physical Geology 2nd Wm C Brown Co 1979 http eol jsc nasa gov debrief STS066 rep2 htm Sand lens Traps from meandering streams UNCONFORMITY TRAP Reservoir rock tilted and eroded Impermeable rock deposited above erosion surface Plummer McGeary Physical Geology 2nd Wm C Brown Co 1979 http www priweb org ed pgws systems traps strat strat traps html 8 REEF TRAP Alberta Reef deposit Porous reef core Flanks also porous Impermeable shale cap Plummer McGeary Physical Geology 2nd Wm C Brown Co 1979 LOCATIONS OF FUELS American Oil Fields MAJOR OIL FIELDS IN NORTH AMERICA Middle East North America Plummer McGeary Physical Geology 2nd Wm C Brown Co 1979 TITUSVILLE PA Oil Creek Valley in the 1860s Phillips well rt 4000 bbl day Woodford well lt 1500 bbl day Origin of Pennsylvania Oil Delta deposits of gooky mud with organics Overlain by river sand Sea invades and covers all with shale Pennsylvanian Period http www priweb org ed pgws backyard pennsylvania pennsylvania oil html http www priweb org ed pgws history pennsylvania tarr farm html 9 Texas Oil Boiler Avenue Lucas Gusher 1901 Initial production 100 000 bbl day Salt dome traps On Spindletop salt dome at Beaumont Texas http www priweb org ed pgws history spindletop spindletop html http www priweb org ed pgws history spindletop spindletop html Signal Hill Long Beach CA Drilling on the North Slope 1932 http www priweb org ed pgws history signal hill signal hill2 html Plummer McGeary Physical Geology 2nd Wm C Brown Co 1979 Drilling in the North Sea Top 10 Countries Oil Statistics Reserves http www nationmaster com graphT ene oil res int 10 Comsumption http www nationmaster com graphT ene oil con int 10 Rocks and Fossils Busbey Doenraads Willis and Roots Fog City Press 1997 10
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