CEE 1030 1st Edition Lecture 5Review QuestionWhat two factors speed up rates of chemical weathering rocks?1. low temperature, high rainfall. 2. High temperature, high rainfallSedimentary rocksproduct of mechanical and chemical weathering  ~75% of rocks at earths surface are sedimentary but only ~10% of outer 15 kmImportance of sedimentary rocks - economically important: host oil, gas, coal, gold and uranium deposits: groundwater source- source of sand and gravels for construction - preserve a record of life on earth - tell us about the environment  preserve record of earth’s climate history: evidence for past environmental conditions - verticle changes in the sedimentary rock types sedimentary rock types represent environmental changes through time - chemical composition of marine sediments tells us about changes in ocean chemistry and temperature Sediments vs. Sedimentary rocks  sediments- collection of loose, solid particles sedimentary rock- particles bound together to form a firm, coherent rock  lithification- unconsolidated sediment to rock Types of sedimentary rocks  detrital- sediment transported as solid particles ex. sandstone, shale  chemical- sediment formed from material that was once in solution in water ex. limestone: inorganic and biological  organic- remains of decayed plants ex. peat, coalDetrital sedimentary rocks - main constituents are clay, minerals, quartz, feldspar, mica, and rock fragments - particle size used to distinguish types - particles greater than 2 mm in diameter conglomerate- rounded particles places such like a river or a beach  breccia- sharp, angular particles cliffs - sand-sized particles 0.0625 to 2mm sandstone- quartz is dominant mineral- fine particles are less than 0.0625 mm mudstone/shale - siltstone and claystone- test by chewing rock - shale- shales, siltstones, mudstones difficult for water to penetrate little cementation poorly lithified and friable crumble easily Chemical sedimentary rocks-material that was once in solution (LOOK AT POWERPOINT) limestone- most abundant chemical rock, composed of mineral calcite or its polymorph aragonite  Oolitic limestone- inorganic form in warm, shallow, agitated waters  biogenic limestone- coral reefs, shell fragments, microorganisms ex. chalk, made from tiny shell fragments of plankton  conquina- poorly cemented rock of shell fragments  fossiliferous limestone- shell fragments cemented with calcite cement  chert- hard, compact, microcrystalline SiO2 nodules and layers, often in limestone beds, also known as flint  evaporates- evaportation water triggers deposition of chemical precipitates ex. halite, gypsum, carbonatemarine environment Review QuestionsSelect the answer that lists the common detrital sedimentary rocks in order of increasing particle size1. shale, conglomerate, sandstone2. sandstone, shale, conglomerate3. conglomerate, sandstone, shale4. shale, sandstone, conglomerate5. sandstone, conglomerate, shale Which of the following lists the correct sequence of steps in the formation of a sedimentary rock?1. erosion, weathering, lithification, deposition2. erosion, lithification, weathering, deposition3. weathering, erosion, deposition, lithification4. lithification, erosion, deposition, weathering5. weathering, lithification, erosion, depositionSedimentary structures- provide important information about environment of sedminenation- most common characteristic of sedminary rocks form sub-horizontal beds or strata - bedding planes separate strata - cross-bedding and current ripples graded beds- vertical change in particle size  mud cracks- evidence that sediment was alternately wet then dry. Wet mud shrinks as it dries out, forming cracks Sedimentary environments - geographic settling where sediment accumulates- determines the nature of the sediments that accumulate (grain size, grain shape, etc)  continental environments : rivers, lakes, deserts, glacial  transitional environments: delta, beach, tidal flats  marine environments: deep sea, continental shelf, organic reefs Sedimentary facies- different sediment types often accumulate adjacent to one another at the same time - composed of particular sedimentary rock