I. Geologic time Relative dating A. Relative Dating - One unit is older than the other 1. Law of Superposition 2. Law of crosscutting relationships - The crosscutting unit is younger 3. Law of faunal succession - Each fauna or flora is succeeded by a different species through time a) - Fossil - The preserved remains, impressions or casts of plants and animals b) - Index fossil - Fossil that has a distinct morphology, wide ranging, the species was present for a short period of time. 110 m.y. S5SS55S11 °~180:: ͣɣSÍriÍSS m • y • í" 180 m.y. I l l I I I I I I I I I I l l I I FIGURE 1-20 Igneous rocks that have provided absolute radiogenic ages can often be used to date sedimentary layers. (A) The shale is bracketed by two lava flows. (B) The shale lies above the older flow and is intruded by a younger igneous body. (Note: m.y. = million years.) ^ Age of shale between 450 and 490 m.y. (Ordovician index fossils) Section A Some radioisotopic dates obtained Shale known to be Ordovician in age by fossils, now known to be 450-490 m.y. old by correlation to Section A FIGURE 1-21 The actual age of rocks that cannot be dated isotopically can sometimes be ascertained by correlation. Section B No radioisotopic dates obtained Radiometrie Dating - geochronologic units B. Absolute Dating -Absolute dating give an age of the sample in years - Technique used is Radiometric dating - Involves measuring the amount of unstable radioactive isotope (parent) and the amount of isotope that the parent decays into (daughter) - Rate at which parent isotopes decay into daughter isotopes is constant - The amount of time it takes for half of the parent to decay into daughter isotopes is a half life - Graph to determine age and number of half lives, Fig. 2.5 p. 15 lab manual and Fig. 8.12 Use different isotopes with different kinds of rocks and also depends on approximate age of the sample , Table 8.1 Geochronologic units (time units) - time intervals in the history of Earth (e.g., Late Devonian Epoch). Also, time intevals during which corresponding time-rock units (i.e., chronostratigraphic units) formed a. isotope: same number of protons, different number of neutrons b. radioactive isotopes disinegrate & radiate particles at a fixed rate c. half life: time it takes to disintegrate half of original amount Selecting a dating method - duration of half life - chemical composition - closed system Age Dating with Half-Lives • Half-life of a radioactive isotope is the time it takes for one half of the atoms of the original unstable parent isotope to decay to atoms of a new more stable daughter isotope • The half-life of a specific radioactive isotope is constant and can be precisely measured Radiometrie Dating One Half Life = 50%> of the isotope has decayed Half Life differs for each isotope. Two Half Lives = 25% remains (75% decayed). Three Half Lives = 12.5% remains (87.5% decayed). Geometrie Radioactive Decay 100 e d) o i-U) c C 'ÍĎ E a) i— E o +-• ic c 0) n Q. r 12.5- ŠL 6.25-g 3.125 Mineral at time of crystallization Atoms of parent element Atoms of daughter element Mineral after one half-life Mineral after two half-lives Mineral after three half-lives Time Units During each half-life, the proportion of parent atoms decreases by 1/2 (b) ©2001 Brooks/Cole Publishing/ITP Determining Age • By measuring the parent/daughter ratio and knowing the half-life of the parent, geologists can calculate the age of a sample containing the radioactive element • The parent/daughter ratio is usually determined by a mass spectrometer - an instrument that measures the proportions of atoms with different masses Determining Age For example: - If a rock has a parent/daughter ratio of 1:3 , the remaining parent proportion is 25% -25% = 2 half lives Mineral at time of crystallization • Atoms of parent element • Atoms of daughter element Mineral after one half-life If half life is 57 million years then the rock is 57 million years x 2 = Mineral after two half-lives Mineral after three h a If-1 i ves 114 million years old Time Units (b) ©2001 Brooks/Cole Publishing/ITP What Materials Can Be Dated? • Most radiometric dates are obtained from igneous rocks • As magma cools and crystallizes, radioactive parent atoms separate from daughter atoms - Parent and daughter fit differently into the crystal structure of certain minerals • Geologists can use the crystals containing the parent atoms to date the time of crystallization TABLE 1-3 Some of the More Useful Nuclides for Radioisotopic Dating Parent Nuclide* Half-Lifet Daughter Nuclide Source Materials Carbon-14 5730 years Nitrogen-14 Organic matter Uranium-238 4.5 billion years Lead-296 Zircon, uraninite, pitchblende Uranium-235 704 million years Lead-207 Thorium-232 14 billion years Lead-208 Rubidium-87 48.8 billion years Strontium-87 Potassium mica, potassium feldspar, biotite, glauconite, whole metamorphic or igneous rock Potassium-40 1251 million years Argon-40 (and Muscovite, biotite, hornblende, (1.251 billion years) calcium^O)* whole volcanic rock, glauconite, and potassium feldspar** 'Nuclide is a convenient term for any particular atom (recognized by its particular combination of neutrons and protons). ^Half-life data from Steiger, R. H., and Jäger, E. 1977. Subcommission on geochronology: Convention on the use of decay constants in geo- and cosmochronology. Earth and Planetary Science Letters 36:359-362. * Although potassium-40 decays to argon-40 and calcium-40, only argon is used in the dating method because most minerals contain considerable calcium-40, even before decay has begun. Relative dating Stratigraphic record can be subdivided according to a variety of criteria including lithology (lithostratigraphy), fossils (biostratigraphy, ecostratigraphy), seismic profiles (sequence stratigraphy), magnetic polarity (magnetostratigraphy), event deposits (event stratigraphy). Types of Rock units 1. Chronostratigraphic units (time-rock units) - all strata in the world deposited during a given time interval (example: Upper Devonian Series) 2. Biostratigraphic units - stratigraphic units of rocks defined by their fossil content 3. Lithostratigraphic units - stratigraphic units (usually spatio-temporally restricted, three dimensional rock bodies) defined by lithology and/or physical and chemical characteristics of rocks (Group, Formation, Member, Tongue, Bed) (Event Stratigraphic Units - Units based on short-term events that had widespread depositional effects, that is,events that produced an isochronous event deposit; useful in regional (basin-wide) stratigraphic correlations) 4. Magnetostratigraphic units (polarity time units) - stratigraphic units based on magnetic reversals of the Earth's poles 5. Sequences (Sequence Stratigraphy) - basin wide stratigraphic sequences that are separated by regional unconformities or their correlative conformities Table 1 Summary of Categories and Unit-Terms in Stratigraphic Classification* Strati graphic Categories Principal Stratigraphic Unit-terms Uthostratigraphlc Group Formal ion Member Bed is). Fiowisj Unconformity-bounded Synlhem Bioslraligraphic Biozones: Range zones Interval aoňes Lineage zones Assemblage rones Abundance zones ú"'--: s hinds oľ brazones Magnetostratigraphic polarity Polarity zone Olher (informal) slraligraphtc categories (mineralogie, stable isotope, environmental, seismic, etc.) -zona (with appropriate prefix) Equivalent Gcochronologic Units -------------------------------------------------- Cnronostratigraphic ■ Eonothem Era them System Seiles Stage Sutalage (Chronozone) Eon Era Parioct Epoch A&e Subage (or Age) fChrůn) * it addilionai ranks are needed, prefixes Sub and Super may be used with unit-terms when appropriate, although restraint is recommended to avoid complicating the nomenclature unnecessarily. 1. Lithostratigraphy a. description of unit properties (e.g. color, texture, particle shape, stratification, lithology) b. named after dominant grain size fraction c. hierarchy of lithostratigraphic units (1) group: consists of 2 or more formations (2) formation: a main unit that has considerable lateral extent (3) member: a named unit within a formation; names are geographical d. lithostratigraphic units of Wisconsin (WGNHS handout) Biostratigraphic Zones Biozones - the most fundamental biostratigraphic units. A zone is a body of rock whose lower and upper boundaries are based on the ranges of one or more taxa (usually species or phena) (see this Figun for graphic examples of the major types of biostratigraphic zones) -■■ Last appearance Taxon Range Zone First appearance Concurrent Range Zone Interval between two first appearances interval between two last appearances Figure 17.3 Diagram illustrating the principal kinds of interval zones as defined by the North American Stratigraphic Code (1983) and the International ■Stratinranhir Guide H QQ4^____________________ Index Fossils Guide Fossils (other terms used: Zone Fossil, Index Fossil) A good index fossil must be: 1. Independent of environment 2. Fast to evolve 3. Geographically widespread 4. Abundant 5. Readily preserved 6. Easily recognised Examples: Graptolites, Ammonites, Foraminiferans, Pollen, Nannoplankton Correlation of strata using fossils • Identical fossils mean strata are same age Universityof Geology 101 Environmental Geology Lecture 4 Slide 12 Connecticut *' Ray Joesten Grafické znázornění příkladů biozón (upraveno dle Chlupáč & Štorch 1997) v__ a 7/ a V v S Y 1 é v A v v A Lfcc 1 - zóna rozsahu taxonu a 2 - zóna společného rozsahu taxonů b, c A v i , A b yr A~ - - _ a V A A a V A intervalová zóna mezi prvním výskytem taxonů a, b v v v zóna rozsahu společenstva se čtyřmi vůdčími taxony (a, b, c, d) zóna hojného výskytu taxonu a Vysvětlivky: A, B, C - stratigrafické profily a, b, c, d - vůdčí taxony (znaky) Y- nejvyšší výskyt taxonu (znaku) /^ - nejnižší výskyt taxonu (znaku) A - hojný výskyt taxonu hranice biozón Chronostratigraphy Lithostratigraphy - only local lithostratigraphic units. To compare the strata of the same age deposited in different regions biostratigraphy is used. Its use enables to determine chronostratigraphic units (time-rock units) - all strata in the world deposited during a given time interval (example: Upper Devonian Series) číselné datování magnetostratigrafie chemostratigrafie í biostratigrafie biozóny litostratigrafie skupina souvrství člen (vrstvy) vrstva Obr. 5. Vztahy stratigrafíckých metod a vznik Mezinárodní stratigrafické stupnice (upraveno podle Hollanda 1992). globální standardní stratigrafie eonotem e rate m útvar oddělení stupeň . Ze shrnutí nejrůznějších dat z profilů (místní stupnice) a jejich korelací se vynořuje syntéza významných etap vývoje zemské kůry ve formě chronostratigrafických jednotek a Globální stratigrafické standardní stupnice. Tyto jednotky jsou založené na horninách vznikajících během určitého intervalu geologické historie a jejich hranice jsou odvislé od vybraných konkrétních bodů na spodních hranicích stratotypových profilů. Slouží k sjednocování a řazení událostí a jevů v historii planety a představují členění této historie podle mezinárodně dohodnuté hierarchie. Základní jednotkou je stupeň, který v dnešní etapě stratigrafického poznání má většinou jen regionální platnost a proto korelace stupňů v celosvětovém měřítku skýtají těžkosti. Jeho rozsah je dán stratotypy spodní a svrchní hranice (mají mít co nejvýraznější a na velké vzdálenosti sledovatelnou charakteristiku), jeho jméno většinou geografickým názvem typické oblasti (např. givet, baden). Vyšší jednotkou je oddělení, jehož hranice jsou definovány spodní hranicí jeho nejstaršího stupně a horní hranicí nejmladšího stupně. Jeho znaky přesahují většinou již hranice oblastí a mají interregionální ráz. Názvy jsou dány pozicí uvnitř útvaru (např. spodní, střední, svrchní devon) nebo vzácnej i geografickým jménem. Oddělení skládají vyšší jednotku - útvar. Útvary mají většinou již značný časový rozsah, celosvětovou platnost a jsou odrazem celosvětově sledovatelných evolučních kroků. Jejich hranice jsou analogicky dány hranicemi nejstarší a nejmladší nižší jednotky. Jejich názvy jsou v literatuře tradovány mnohdy již od úsvitu geologie a vyjadřují vztahy etnografické (např. silur), geografické (např. perm), litologické (křída), či pozici ve stratigrafickém sledu (např. kvartér). Jednotkou vyšší je eratem, který vymezuje velmi významné etapy života na naší planetě (např. paleozoikum) a nejvyšší pak eonotem odrážející nejvýznamnější kroky historie Země (např. fanerozoikum). Spodní hranice mezinárodních stratotypů (vybraných typických, co nejúplnějších a chráněných profilů) je definována jedinečným (standardním) bodem v profilu (tzv. „golden spike"), který zaujímá jistou konkrétní polohu v geologické historii vyjádřenou např. stupněm vývoje organického světa, radiometrickým stářím, polaritou etc. Príklad : Chronostratigrafícké jednotky Geochronologické jednotky Oblastné litostratigrafické jednotky Rýdzo bi os t rati grafické jednotky f an* r dz oik um mezozoikum jura lias t oar k Htldoceras bitrons e o n o t e m eon era perioda epocha věk chron Skupina S ú vrstvi e člen vrstva l horizont) rôme druhy bi ost rati grafických zón Isubzóno] ( biohorizont) er a t e m ú t v a r o d d e 1 e n i e stupeň chronozóna Obr. 23a. Přehrad hlavných stratigrafických jednotiek. Chronostratigrafícké a geochronologické jednotky si vzájomne zodpovedajú a ich obsah je presne stanovený. Oblastné Jitostrati grafické a biostratigrafické jednotky sú nezávislé od iných stupníc a hierarchické usporiadanie je relatívne 31 Mass Extinctions Punctuate Geologic Record il-C'G 600 ■í 200- 0 Largest global mass extinctions Paleozoic Era 1 Mesozoic Era SOD 500 400 300 200 Millions of years ago 100 Mass extinctions mark the end of Paleozoic and Mesozoic Eras, Ordovician, Devonian, & Triassic Periods University of Connecticut Geology 101 Environmental Geology Ray Joesten Lecture 4 Slide 16 Litho-stratigraphy Ash Silt b Sand Sand Silt b Sand Laua Silt ^ fc7 Chrono-stratigraphy Radiometric Magneto-dates stratigraphy 1.G t 0.1 million years Bio-stratigraphy 3.2 ± 0.2 million years Three essential components of the studu of fossils in context: Lithostratigraphu Chronostratigraphu Biostratigraphu F. Paleomagnetism 1. Movement of magnetic pole 2. Chron: major and complete reversal; last about 1,000,000 years •last major reversal 780,000 YBP • Brunhes - normal • Matuyama - reversed 3. Subchron: shorter-lived reversals within a chron 4. Allows correlation of isolated stratigraphic sections over broad regions Magnetic polarity of liva _±_U J iV. -.--■■ rtvtrsal time tcafc Millions of years, jgp 0.0 Brunhfrs normal epoch E*e >■ I- h ■■ ,. ■! -' [If *•+ f h *■ - n. L -. »r k ' , * -r F * P ř U H [l-ŕ< ť | I » F F- -M----K----1 Migrietic-rtvť-rsil time 5-caľc - Brunhfrs norrnjl epcth Evcnu / - / Matuyanfta neversjl epoch Gaus-s normal epoch - ■ Millions of years, ago -i 0.0 1.0 2.0 3.0 Subdivision & interpretation of sedimentary record using a framework surfaces seen in outcrops, well logs, & 2-D and 3-D seismic. Include: Surfaces of erosion & non-deposition (sequence boundaries) Flooding (trangressive surfaces [TS] &/or maximum flooding surfaces [mfs]) This framework used to predict the extent of sedimentary fades geometry, lithologic character, grain size, sorting & reservoir quality Any package of sedimentary strata bounded above and below by an unconformity (of any kind) is a sequence. Sequence stratigraphy makes sequences the fundamental units of the rock record, and hence emphasizes periods of deposition and nondeposition (closely related to episodes of rising and falling sea level) as the essential information. Sequence stratigraphy grew out of seismic stratigraphy; unconformities are easily distinguished in seismic records, but lithology is often unknown. Sequence Stratigraphic Interpretation of sedimentary strata as products of "relative sea level change" Correlations based on Lithology - Lithostratigraphic Sand Unit Correlations based on Bounding Surfaces - Atlostratigraphic mis SB LST TST HST Key (Maximum Flooding surface) (Transgressive Surface) (Sequence Boundary) Lows!and System Tract Transgressive System Tract Highst an d System Tract Relative sea level is the depth of water relative to the local land surface. Relative sea level can change due to local vertical tectonic motions or due to eustatic sea level variations (i.e. global changes in the volume of ocean water or of the ocean basins). In both sequence and traditional stratigraphy, the critical events that determine the locations of environments and unconformities are transgressions and regressions. A transgression is a landward shift in the coastline, and hence a landward shift in all marginal marine environments. A regression is a seaward shift in the coastline. The second and often co-incident step in the interpretation of well logs and cores is the use of parasequence stacking patterns (the vertical occurrence of repeated cycles of coarsening or fining upwards sediment) of to identify the lowstand system tracts (LST), transgressive system tracts (TST) and highstand system tracts (HST) that are enveloped by the mfs, TS and SB. These parasequence cyclic stacking patterns are commonly identified on the basis of variations in grain size and when these fine upwards are indicated by triangles whose apex is up while those that coarsen upwards are indicated by inverted triangles whose apex is down. The repeated stacking patterns for LST cycles are: - •Cyclic fill of incised depressions that tend to fine upward. •Cyclic sand to shale bodies of basin floor fans that tend to fine and thin upward. •Cyclic sand to shale bodies of shelf margin clinoforms that tend to coarsen and thicken upward. The repeated stacking patterns for TST cycles are: - •Regressive cyclic shale to sand bodies ofthat tend to coarsen and thin upward. Seismic stratigraphy Interpreting how the Earth's sedimentary layers have formed, is difficult. Cores taken on land and from the ocean are not only expensive to retrieve, but represent a small percentage of the Earth's surface. Methods using seismic waves developed in the 1960's help to observe the crust's layers in detail. Seismic stratigraphy is when energy waves are used to bounce off the different layers of the Earth. These layers provide us with data that a seismic stratigrapher can then interpret. For example, in the seismic profile below we show the results of waves bouncing off the different layers and then recorded on the surface of the Earth. These "wavy" images can then be used to reconstruct the area in rock units, as shown in the interpretation of the seismic profile. These advances have allowed geologists to map more area than ever before. Prior to these advances, only outcrops and geologists walking and recording on their maps could be used. Chemostratigraphy . Oxygen Isotopes 1. 3 Oxygen Isotopes; 160 and 180 most common 2. Fractionation a. 160 lighter so evaporates preferentially; 180 heavier so condenses preferentially b. ratio at which these isotopes enter chemical compounds is temperature dependent c. most widely used proxy for: •changes in global ice sheet volume •changes in global temperatures 3. Measurement a. measure how much 180/160 ratio deviates from isotope proportions found in modern oceans b. 8180 %o is zero for standard marine ocean water 4. During Glacials: • 160 preferentially evaporated from oceans • 160 deposited on ice sheets & concentrated there •ice sheets relatively depleted in 180 so 8180 is negative • 180 concentrated in seawater; ice age oceans have 8180 values of about +5 •marine shells also enriched in 180 during glacials 5H. Other Dating Methods 1. Dendrochronology 2. Lacustrine Sediments - varvites 3. Lichenometry ľ\ INSIDE THE TREE L---------1. Cumtiiu* Tree ring width Variability of tree ring width and climatic conditions Seasonal patterns: Early wood Large, thick-walled cells Late wood Small, densely-packed, thin-walled cells Together = an annual growth ring Mean width of rings dependant on: tree species tree age availability of stored food climate (precipitation, temperature, humidity, sunshine, windspeed, humidity) Trees as filters and sources of palaeoclimatic data ' LOTtitaed i tö»iy»wd 4JuCl Lichenometry 0 Most used to date glacial deposits in tundra environments 0 Also used to date lake-level, sea-level, glacial outwash, trim-lines, rockfalls, talus stabilization, former extent of permanent snow cover 0 Assumes constant growth rate of lichen so that the largest diameter lichen will be the oldest Liehen Dates Species Diameter Age Location Alectoria minuscula 160mm 500-600 yrs Baffin Island Rhizocarpon geographicum 280mm 9,500+/-1500 yrs Baffin Island Rhizocarpon alpicola 480mm 9,000 yrs Swedish Lapland Ecostratigraphy is the stratigraphy of ecosystems, a powerful tool for high-resolution cyclic and sequential stratigraphy, based on biostratigraphy. It is founded on the application of ecological knowledge to the reconstruction of past ecosystems and their succession, in relation to global external forcing agents such as sea level oscillations, climate changes, etc. The ecostratigraphic techniques used in this study (mainly palynocycles and ecologs) have provided regional chronostratigraphic correlation frames from 2nd order cycles (3 to 50 million years duration) to periodic cycles within the Milankovitch band (around 100,000-year period), for Paleocene, Eocene, Oligocene, and Miocene stratigraphic sequences. fairly high energy -> coarse textured deposits (pebbles/sand); offshore -> progressively lower energy environments -> progressively finer textured deposits - medium sand - fine sand - silt/mud - clay - carbonates (beyond land-derived sedimentation in shallow tropical oceans). a) Quartz sandstone - predominantly quartz grains ("clean sandstone"). Long transportation (quartz survives long transportation because it is relatively hard). Distant from mountainous regions, tectonically stable. Often form at coastlines, in deserts, on higher energy coastal plains and river floodplains (e.g. Padre Island). Quartz grains make up 90%+ of rock and the grains are well rounded. Cross beds and ripples are common. Arkoses Lake shales b) Arkose - terrestrial; derived from granitic highlands, contain > 25% feldspar grains (implies fairly short transportation, because feldspar is relatively soft and erodes over long distances). Commonly pink-red color. Meta m orphic c) Graywacke - mixture of sand, clay and rock fragments ("dirty sandstone"). Indicates tectonic activity, rapid erosion/sediment accumulation, short transportation. Often deposited as turbidites (submarine landslide deposits). Matrix is usually 30%. Beds are often graded (sorted by size - coarse at the base, finer at the top). Deltaic coastal plain Subgraywacke Ocean —■ ■j ,. FIGURE 3-2 9 Deltaic environment in which lithic sandstones may be deposited. d) lithic sandstone - typical of deltaic deposits e.g. Mississippi delta. Matrix < 15%. Transitional between quartz sandstones and graywackes. SHALES: Form in similar environments to sandstones, only deposited under lower energy conditions (i.e. "quieter" locations) -> finer particles (clay, silt). Shallow marine, marshes, lakes, lower energy coastal plains and fioodplains. Finely layered, often fissile. Common fossils. CARBONATES: Most common = limestone (calcium carbonate). Formed by abundant marine organisms and the precipitation of calcium carbonate from sea water. Warm, clear, shallow tropical oceans - particularly common in platform areas. (b) FIGURE 3-31 Carbonate mud accumulating on the sea floor in che shallow warm waters of the Bahama Banks carbonate platform. Green algae of the genus Penicilius form the tuftlike growths in the background. These algae produce fine, needlelike crystallites of calcium carbonate (aragonite) rhat contribute to the production of carbonate sediment. Other algae, such as Halirňeáa, produce similar calcium carbonate particles. {Cuurttsy of i-'inestone Terms for Marine (i.e. Ocean) Environments and some characteristic sediment facies -PbbsiĽ l\\\ih lick = 2151.1 ni IňVi fn IINU m iJi.üMIfil httNi m, 11 i.i.'i.n'u K» m nv.Mwm ILnial sin.-1 Subnariií* ShůS-slopů bratá canvwi ten 100 A* íurbfdiřy curraŕvl ElDW-a. Iflrngsl pgflide« settle t&llůwrd by smaller purtiĽluä A ^ratted b*d ©1999 Wadsworth Publishing Company/ITP CONE BATHYAL deep sea ten) canyon chenal avec levées distributaire X O f in plaine abyssale (decantation) CLASSICAL TURBIDITE Divisions Pew« Mgilivl Or grůdid Turbidif« Upper poroltel kinrnnoe Ripples, wovy or convoy red lorn nice Plön* pa rail«! laminae Massive, graded Interpreta'on Pelagic sed im emotion Fine grained, low density lurbidtty airfient deposition ? ? ? Lower pgrT of Lower Flo* Reqme Upper Flow Regime Plane Bed ? Upper f low Reg tne Rapid deposition and Quick bed P) DISTRIBUTION OF DEEP-SEA SEDIMENTS sedimentaci vápnitých nebo křemitých bahen je karbonátová kompenzační hloubka (CCD). Obr. 21. Křivky závislosti nasyceni mořské vody vzhledem k aragomtu a kalcitu na hloubce mořské vody pro současný Atlantik. Vlnovkou jsou vyznačeny kompenzační hloubka aragorutu (ACD) a kalcitu (CCD), lyzoklina je hloubková úroveň, ve které rychle vzrůstá rychlost rozpouštění kalcitu ale ve které se ještě vyskytuji pelagické karbonáty. Upraveno podle Broecker (1974). increasing fertility 2 - 3 - u 5 — 5 _ sapropelic subtropical convergence diatom j and terrigenous mud oceanic divergence diatom ooze upwelling area Distribution of modern sediment facies in the contesii of depth and ocean fertility, based on sediment patterns hi the eastern central Pacific. Numbers are Lypieal sedimentation rates in mm/1000 yrs •Marine »- Continental Shelf - Continental Slope - Continental Rise »Turbidite Deposits shelf slope Figure 5.11, p. 115 Deap sea mud Laminated mud Ripple cross-laminated sand Laminated sand Graded bed Erosional base marked by flute cast River Facies changes due to rising sea level - Water Getting Deeper Direction of migration of shoreline, and landward shift of sedimentary facies Deposited at time A Deposited at time B Comparison of sediments deposited •Delta •Progradation Coarsening Upwards Sequence Delta Front Pro delta Sand Silt Clay t—■.—.....i; .........^^ ---------------------------1 »Mississippi Delta