ES 105 Lab FOSSIL FUELS AND SEDIMENTARY ROCKS Week of February 6-10 (next week) Lab Classroom NS 116 Reading: Earth Science Read Appendix of Lab Manual Tarbuck and Lutgens Must have completed ‘Safety Agreement’ for Chapter 3: pages 52-54, 61-69 your lab instructor before beginning this lab. (Prelab 3) Rock cycle Rock cycle diagram • Igneous • Sedimentary • Metamorphic Sedimentary rocks Weathering About 75% of all rock outcrops on the • Mechanical continents • Chemical Important to reconstruct much of Earth's history Sediment is derived from weathering 1 Mechanical Weathering Chemical Weathering • Breaks into smaller pieces • Equilibrium with conditions • Frost most important agent • Forms new minerals and releases ions to solution • Oxidation, acidosis • Enhanced by mechanical weathering Sedimentary rocks Sediment clasts Two main types • Particle loosened from pre-existing rock • Rocks formed by deposition of sediment— • Transported and rounded to place of Clastic (or detrital) deposition • Rocks formed by precipitation from water-- • Shape, size, and sorting of clasts can tell Chemical (includes rocks formed by about the environment of deposition organisms) Lithification Cement Process of becoming stone • Brought in by water • Burial and compaction • Mineral material between clasts • Precipitation of cement • Fills in pore spaces • Each reduces ‘pore space’ • Commonly calcite, silica, and sometimes iron oxide 2 Types of Clastic Rocks Shale • Shale (most abundant) • Composed of very fine grained sediment • Sandstone • Shows obvious tendency to split along • Conglomerate planes (fissile) • Usually gray • Most common type of sedimentary outcrop Shale with plant fossils Sandstone • Composed of sand-size particles – Between 1/16 mm and 2 mm diameter – Particles may be individual mineral grains or rock fragments – Quartz most common type of grain • Environments include •Beach, •shallow sea, •river, •sand dunes Sandstone Conglomerate • Composed of particles larger than 2 mm • Usually particles are rock fragments • When describing conglomerate, refer to shape of the clasts it is composed of, not the overall shape of the rock 3 Conglomerate Detrital (clastic) rocks • Shale is the most common one • Made from solid particles • Classified by particle size Chemical rocks Chemical rocks Material was once in solution and • Limestone precipitates to form sediment – Composed of the mineral calcium carbonate • Directly precipitated as the result – Much of this calcite was precipitated by of physical processes, or organisms • Through life processes • Considered an ‘organic sediment’ if from (biochemical origin) organisms • Second most common type of sedimentary rock—most common type of chemical rock Coquina Close up of coquina 4 Fossiliferous limestone Chalk Chemical rocks Rock salt • Direct mineral precipitation from water – Microcrystalline quartz (precipitated quartz) known as chert, flint, jasper, opal or agate – Evaporites such as rock salt or gypsum – Travertine (calcite) and sinter (silica) from hotspring deposits Classification of sedimentary rocks Sedimentary rocks Features of sedimentary rocks • Strata, or beds (most characteristic) • Bedding planes separate strata • Fossils 5 Sedimentary rocks Fossils Features of sedimentary rocks • Traces or remains of prehistoric life • Bedding and bedding planes • Are the most important inclusions • Size, shape and distribution of grain sizes • Help determine past environments • fossils • Used as time indicators • Used for matching rocks from different places Features of sedimentary rocks Sedimentary rocks • Porosity Economic importance • Permeability • Coal • Petroleum and natural gas • Sources of iron and aluminum 6.