sediments and rocks Flashcards
what are the different classes of sediments?
clastic sediments
biochemical sediments
chemical sediments
organic sediments
what are clastic sediments?
mineral grains or fragments of rocks are lithified. then crystallize into a cement. compact through burial. often by silica and quartz. sandstone is an example of clastic sedimentary rock.
what does lithification mean?
transform sediment or material into stone. compaction, burial, squeeze air or water out. cementations etc.
what does erosion involve?
involves plucking, souring, dissolution by wind and water.
what is transportation?
wind and water and ice movement. the ability of a medium to carry sediment depends on its viscosity and velocity.
what is biochemical sediment?
skeletal parts, internaal, external, opal, carbonate, calcite, aragonite, bone.
what is chemical sediment?
non-biogenic precipitate. evaporites.
what is organic sediment?
carbon-rich. remains of a once-living animal.
how do you classify rocks?
clast size: length of the diameter
clast composition: makeup of clasts of rock
angularity: degree to which grains are smooth and spherical
sorting: degree to which the clasts in the rock are the same size
nature of cement
what do ripple marks show?
preserved in sandy sediment. preserve information about flow conditions. asymmetrical ripples developed from flow in ode direction. short show deep down current. long shows gentle. used to indicate ancient sediments.
what do dunes show?
similar to ripples but larger. forms from water or wind transporting sand. occurs in streams and desers.
what is glacier sediment?
movement of ice- moves sediment underneath it, when ice melts- its drops its load and makes a pile of glacial till.
what is mountain stream sediment?
stream rush downslope in mountain avllets. fast-moving water has the power to carry large clasts.
what is alluvial fan?
mountain front. fast-moving streams. the stream deposits its load of sedimnet right at the mountain front.
what are key depoisiotnal environments?
marine delta environemnts- depositied at sea level. fine clastic- quiet water settings.
what are examples of biochemical sedimentary rocks?
limestones biochemical limestone chert biochemical chert organic chalk replacement cherk ervapories travertine dolostone dolomites
what is limestone?
sedimentary rocks, calcite or aragonite. preserves fossils.
what is biochemical limestone?
skeletal remains. warm, tropic shallow, clear, oxtgen rich. diverse organisms. when organism dies, their skeletal may stay in place. during transport, shells may break into smaller fragments.
what is ancient limestone?
massive light grey rock that breaks into chunky blocks. organism slide in it and breaks the shells up. water passes through it and creates cement.
what is chert?
rock made of crystallize quartz. after burial, silica in bottom sediment dissolves. silica in pores fluids solidifies into a gel.
what is biochemical chert?
reddish. hit with a hammer and rock cracks like glass. made from cryptocrystalline quartz. forms shell of plankton.
what is organic carbonaceous rock?
coal and oil shale. carbon in coal is pure carbon, but still a sedimentary rock, due to the make up of detritus in layers.
what are the several classes?
evaporites, travertine, dolostone, replacement chert
what is evaporites?
rocks from evaporated sea or lake water. streams brinign water into plates, carry dissolved ions. overtime, water becomes very concentrated.
what is travertine?
calcium carbonate precipitates from groundwater where it reaches the surface. dissolved calcium reacts with bicarbonate. CO2 expelled into the air.
what is dolostone?
limestone altered by Mg rich fluids. contains mineral dolomite.
what is stratification?
the formation of strata in rock.
what is strata?
sedimentary rocks are layered. arranged into beds. the boundary between 2 beds sis a bedding plate. several beds together constitute strata.
what are bedforms?
the movement of the fluids creates sedimentary structures ar the interface between sediment and fluid, these are called bedforms.
what are cross beds?
if you slice into a ripple or dune, you will find internal laminations that are inclined at an angle to the boundary of the main layer. these are called cross beds
what are rift basins?
divergent plate boundaries, the surface of the earth subsides because the crust becomes thinner as it stretches. as the rift grows, slips on the fault.
what are foreland basins?
craton side of the collision mountain belt. the form on the side of the mountains.
what is trangression and regression?
sea levels change to control the succession of sediments that we see in a basin. when sea levels rise, the coast migrates inland- this is transgression. as the coast migrates, the sandy beaches migrate with it. when sea levels fall, the cast migrates seawards- this is regression.
