퇴적학 - (정대교 교수) 강원대학교

[Minera]

층서를 다루는 퇴적학 강의 요약본입니다.

원작의 권리는 강원대학교 지질학과 정대교 교수님과 이를 최초 개재한 KorEArtH NET에 있습니다.

Copyright ⓒ KorEArtH NET. All rights reserved.

제 1 장. 퇴적물 및 퇴적암의 일반적인 성질

정대교 (강원대학교 지질학과)

Texture(조직)

• 입도(grain size) : Udden & Wentworth 분류체계 : Φ = -log₂d
• 입도상수 (grain size parameter)

              Median         

              Mean          

              Sorting         

              Skewness      

              Mode : 최빈값

              Moments : n 번째 value(25, 75 or 16, 84)

              

              

                            

          · Skewness(왜도) :     

              + (positive) : fine-skewed - fluvial sand (다량의 점토와 silt 함유)

              - (negative) : coarse-skewed - 해안의 sand ( wave 에 의해 세립질 제거)

          · Kurtosis(첨도) :       leptokurtic - peaked curves      ┐

                                           platykurtic - flat curves                ┘  Kurtosis ( Folk)

                                         

• Grain Shape

          - Roundness : 0～6 rho(ρ) scale (Folk, 1955), 0～1 (Wadell : 1933)

          - Sphericity : oblate(disk), equant, bladed, prolate(roller)

                             Ψ = s/S (Wadell : 1933) (s: 같은 부피의 sphere로 환산한 표면적, S: 실제 표면적)

                             CSF = S/(LI)½ (Corey : 1949)

                             (S: short diameter, L: lond diameter, I: intermediate diameter)

• Surface Texture : SEM을 이용한 표면 긁힘 연구 (주로 석영 모래 입자에 적용)

          ① Concoidal fracture - outwash fan

          ② Smooth  rounded - v_shaped percussion - beach

          ③ Frosted, pock-marked & concoidal fracture - desert

• Fabric : packing  ┌ cubic - least stable

                             ├ rhombic - most stable

                             ├ point - contact

                             └ concave - convex contact, sutured contact, preferred orientation,                                              (imbrication)

                                grain-supported & matrix- supported

• Porosity & permeability (moisture content)

  - cubic : 47.6%. - rhombic : 26%

• Textural maturity

          immature ＞5% clay, poor sorting, angular grains.

          submature - little or no clay, poor-sorting, angular grains.

          mature - good sorting, angular grain.

          supermature - good sorting, well-rounded.

• Textural inversion: well-rounded but poorly sorted sediments

           → two environments or sources에서 유래된 퇴적물의 mixing(예: 하천의 본류와 지류의 합류지점,                조간대에서 storm wave 또는 bioturbation에 의한 상하 퇴적층의 교란)

           → 퇴적암 기원의 recycled퇴적물의 경우.

  ** Selective transport : 퇴적물의 초기 이동에 영향을 주는 요소

   ① pivot angle

       

  ② 기타 : size, shape, density(hydraulic equivalence)

              fluid viscosity, turbulence intensity concentration of particles

      기타변수 : particle flocculation - clay mineral : - charged

                    transport : 두 요소의 상호작용  ┌ fluid drag velocity

                                                               └ bed stress

제 2 장. Mineralogy

(1) Terrigenous - quartz, feldspar, rock fragments, clay minerals, heavy minerals.

      * provenance - source rock composition 반영 → kyanite, staurolite (변성암기원)

                             tectonic terranes 추정(Ingersoll : 1983) → Great Valley Basin 연구로 잘 알려짐

                             Potassium feldspar → granite 기원

(2) Chemical and miscellaneous sediment

    - biogenic - micrite, skeletal - aragonite, calcite, high-Mg calcite

    - pyroclastic - tephra (화산분출 모든물질)

    == physico-chemical - evaporites, chert(volcanic-origin), zeolite.

                                     phosphates, non-skeletal carbonates.

    - pellet - sand-sized aggregates

    - ooids - medium-coars sand sized, shallow - intertidal 환경

    - phosphates - replacement of carbonate particles

    - chert - microcrystalline, cavity-filling (fibroradiating) chert

    - zeolite - hydrous aluminosilicates. volcanic origin

    - Fe-rich sediments - banded, cherty Precambrian formations.

(3) Cementation - silica, carbonate

   Silica : deep diagenesis : microcrystalline chert, fibrous chert(chalcedony) hydrous form(opal),

                                        overgrowth

   Carbonate : CaCO₃, provided by ground water

                    Siderite (FeCO₃)

   Iron Oxide (hematite)

** Volcaniclastic - 화산기원 모든 sediments

  Pyroclasitc - 특별히 화산폭발에 의해 직접 분출 생성된 물질만을 지칭

64  mm	bomb(blocks)	volcanic breccia, agglomerate
	lapilli	lapilli - stone
2 mm
	ash	tuff   -vitric         -lithic         -crystal
0.06 mm
	dust

* accretionery lapilli → 성장력

Volcaniclastic 의 3 types deposits

① pyroclastic - fall deposits →  air fall, block, bomb

② volcaniclastic flow deposits → ignimbites (fludized ash flow)

                                                base-surge deposits (ash-laden steam flow)

                                                lahar deposits - mud flow

③ hyaloclastite → fragmented and granulated lava through water-contact (수성기원 응회암)

                           : 수중분출, 빙하주변 용암 분출 시 생성

(4) Classification

   Folk's classification - sandstone

   Mudrock

   Carbonate

     - Dunham's  :  mudstone → wackestone   →   packstone    →   grainstone → boundstone

                          10%〉mud-supported 10%〈     grain-supported no mud

     - Folk's : - allochem → intraclast

                                      Ooid

                                      fossil

                                      pellet

                   - orthochem - micrite, sparite(cement)

                   - reef rock

제 3 장. Sedimentary Processes

  - Fluid : gas, liquid

  - Shear force : stress(pressure) parallel to the surface

  - Body force : gravity, inertia

  - Dynamic viscosity (μ)mju : coefficient of the shear to its rate of shear

                                            (=molecular viscosity) : 분자간 작용하는 힘

                                            (두 판사이의 얇은 film layer가 가지는 tangential force)

  - Kinematic viscosity (ν)nu = 

           = 

 

      Laminar flow   : Re <    0.1 ┐ normally  Re 〈 2000

      Turbulent flow : Re ～ 1000 ┘     Re 〉 2000

  - Fr : Fr 〈   1 : tranquil flow . wave can not pass upstream (subcritical flow)

       Fr      〉 1 : rapid flow   . wave can not pass upstream (supercritical flow)

  - Hjulstrom's diagram

  - Hydraulic sortion - sliding, rolling, saltation, intermittent suspension or continuous suspension

  - Hydraulic equivalence : depending on intensity of the flow

  - Competence

  - Capacity

1.Biological Processes

  1) degradation : 미생물에 의한 다른 생물체의 crushing, scraping, site reduction

                         caused by consumption, burrowing, boring (해삼, gastropod, sea urchins, 소화)

  2) pelletization : 배설에 의한 pellet - filter feeder, deposit feeder

  3) organism - enhanced sedimentation

      sediment baffles → energy 감쇠 (marine grass)

      sediment trapper → blue green algae → stromatolites

2.Physical Processes

  1) Fluid flow ┌ Turbulent, laminar

                               └ Rapid, tranquil

                 force per unit area (pressure) : normal to surface : gravity

                 stress(shear) : parallel to surface

        Shear Stress : maximum at base

        (τ)      zero at free surface

     Renold number : 

             (1883, 1884 : 영국수학자)

             ν(nu) : Kinematic viscosity

             η(eta) : morecular viscosity

             ρ : density

             μ : viscosity

             U : velocity

             L : unit length (pipe diameter) (mean flow depth)

       * Open channel에서

         ┌ Re  〉 2000 : tubulent flow (turbulent eddies)

         └ Re 〈  2000 : laminar

       * Flow 내에 towing sphere가 있을 때

             Re = 24 → eddies in the wake

             Re 〈 1 : under laminar flow

     Froude number : 영국조선설계사

            Fr = 

            U=관성 (유속), D=depth of water, g=gravity acceleration

           ┌ Fr 〈 1.0 : tranquil or subcritical

           └ Fr 〉 1.0 : supercritical, rapid flow

     * boundary layer : zone of shear stress

         → downstream (velocity increase)

                                                                                      thicker - turbulent

     * flow separation : Figure 2-6

         change in diameter

     * flow (natural current)의 구분

        ┌ Steady : 일정한 지점에서만 flow velosity (방향 속도) 가 일정 (하류 방향은 속도 감소)

        └ unsteady : 일정만 지점에서만 flow velocity 가 일정하지 않음 (river →계절)

        ┌ uniform : 흐르는 방향을 따라 속도가 항상 같음 (streamline 이 평행)

        └ non - uniform : 흐르는 방향을 따라 속도가 항상 다름 (강굽이에서 처럼)

         streamline : flow 의 세기 방향의 변화를 묘사 ( 밀집 → velocity 증가)

  2) Settling of particles

       Stoke's law : for single particle

        

       W_S : settling velocity

       d   : diameter

       ρs-ρ : density difference

       μ : viscosity

       * effect of shape ⇒ equivalent diamater (ex : shell)

  3) Sediment entertainment

   : threshold velocity - 임계속도 for moving

      Hjulstrom diagram : clay, silt size grain의 침식 이동이 fine sand 에 비해 어려움

       

      Cc : 임계조건

      d : 입도

      g(σ-ρ) : 잠수중력 

      τ_o : shear stress    

      ν  : kinematic viscosity

      f   : Reynold 수

     * grain movement

         - two mechanism : ① fluid drag on grains in contact with fluid

                                    ② hydrodynamic lift force

         - 방해 요소: 입자의 무게, 입자간 점착력

         - motion type: ① traction - slide, roll     ┐ bed load

                             ② saltation - hop, boune ┘

                             ③ suspended or wash load

                              Mississippi          전세계

             뜬짐                65%                300억t

             녹은짐             29%                 36억t

             밑짐                 6%                  30억t

  4) Hydraulics and sediment texture

      hydraulic sorting, abrasion

       - Competence - 일정한 유속의 유체가 운반할 수 있는 최대 입자 크기

       - Capacity: 일정 유체가 운반 가능한 퇴적물 총량

      Saltation population : 90～95% 의 총 bedload (figure 2-9)

      *입자모양 : flow에 가장 적은 저항을 갖는 자세로 퇴적

3.Bedforms

  * Flow regime : fluid flow, bed configuration, dissipation of energy, phase(bed and water surface)

                           의 관계들의 총체로서 표현

     Upper flow regime Fr   〉1.0

     Lower flow regime Fr 〈 1.0

  * ripple → sand wave → megaripple(dune) → plane(flat) bed → antidune → chutes and pools

    ----------------Lower F. R..------------╂------------ Upper F. R..---------------------

  * bedform은 turbulence of flow와 grain 의 interaction에 의해 형성

    (flow power :: product of velocity(V) × boundary shear stress(τ_o))

   Figure 2-9, 2-10, 2-11 참조

4.Sediment gravity processes (mass flow)

 ⓐ turbidity current : density currents - turbidite

 ⓑ liquified sediment flow : upward flowing 에 의해 supporting

 ⓒ grain flow : grain to grain collision: dry grain flow

 ⓓ debris flow : mixtune of fine coarse -matrix strength & buoyancy

 ⓔ slump/slide

  Figure 2-14 참조

5.Tides and tidal currents)

 ┌ spring tide : 사리

 └ neep tide : 조금

  micro tidal range : 〈 2m

  meso tidal range : 2-4m

  macro tidal range : 〉4m

  * unequal high and low tidal velocity - currents

                                 └→ time - velocity asymmetry

    ┌ flood slack : 만조

    └ ebb slack : 저조

  * maximum flood tidal current : after mid tide

     maximum ebb tidal current : near low tide

     flood-dominated or ebb-dominated

6. Waves

     Surface wave = gravity wave → height period

 ┌ sea wave

 └ swell wave

                          f(W.F.D)

                          W : wind velocity

                          D : duration of wind

                          F : fetch, distance of water surface

   surf : mean coast

  * water motion in waves

             

                      ordital motion : effective depth = 1/2 of wavelength

  * longshore current : parallel to shore

  * rip current : after breaking surf : back-flowing currents

      

제 4 장. Sedimentary Structures

1. Stratification

  ① bedding and lamination(few millimeter thick)

  ② Cross-stratification

  ③ Irregular stratification - sliding(slumping)-folding

                                   - convolute, load structure escape

                                   - bioturbation - burrow, roots

2. Bedding Plane Structure

  A. Tool mark

  B. Scour mark

  C. Bed form - ripple, sand wave, dune, antidune

  D. Biogenic mark

  E. etc : grading

             coarsening-upward

             fining-upward

             massive

- Ripple migration and cross-bedding

- Flaser bedding - wave bedding - lenticular bedding

───────→ mud content increase ───────→

┌ Physical (inorganic)

└ Biogenic (organic)

┌ primary (pre-lithification)

└ secondary (chemical)

3. Physical structure(inorganic)

 1) Bedding structure

  ① horizontal bedding

      : lake, beach, deep marine - parallel, continuous rather uniform, monotonous

    ⓐ rhythmites

         thin, repetitious sequence(cyclic) - texture, composition 의 교호

         * seasonal charge (varve) - glacial lake

         * beach bed - uprush and backwash (grain size, composition)

    ⓑ upper flow plane bed or flat bed (no movement of sediment)

         fluvial - braided, alluvial fans, glacial outwash

         →sand, gravel horizontal bedding for a few meter scale.

  ② Bedforms and their internal stratification

   ⓐ current - generated structure (lower flow regime)

         * foreset stratification : influenced by sediment texture, velocity, bed shear stress.

                                                         by depth ratio

         → angular contact (increasing depth, increasing suspension load) → tangential → concave

         * plan view

          ――――――――――― increasing flow strength ――――――――→

          linear → undulatory → cuspate → rhomboid(planed off) → flat bed

	Ripple	Megaripple(dune)	Sandwave
Spacing	〈 60cm	60cm-6m	〉 6m
Height/Spacing	variable	large	small
Flow velocity	low (25～50cm/s)	high (70～150cm/s)	moderate (40～80cm/s)
Geometry	high variable	high variable	straight to sinous

* trough cross-bedding ← lenticular & trough shaped sets의 측방 이동 누적에 의해 형성.

* tabular cross-bedding ← linear bedforms의 수평적 이동 누적에 의해 형성

      ◎ Reactivation surface : interruption in migration or erosional surface.

              caused by flow rates, tidal stage, tidal current direction

* Climbing ripple cross-stratification : 다량의 부유 퇴적물 유입

    (ripple in drift): 측방 이동 + 상향 누적

    (ripple in phase: 주로 상향 누적 by rapid sediment input)

* Hummocky cross-stratification

    low-angle and gently undulation cross-stratification

    (dip : 3～6°)

    wavelength : ～ a few meters

    height : up to 30～40cm (보통 수 centimeter)

    caused by storm waves on shelf

   ⓑ current - generated structures (upper flow regime)

         * upper plane bed

         * antidune - stream, tidal inlet, gentle-sloping beach

            (line-crested) → low preservation

                                    (뒤따르는 waning flow에 의해 대개 상쇄되어 보존 가능성은 낮음)

   ⓒ wave - generated structures

         wave ripples : symmetrical (peak-crest, round-trough)

         - wave ripple crest - straight/slightly sinuous with common bifurcations

         - wave ripple - chevronlike cross-stratification

                               controlled by wave size, grain size, wave period, depth of water

         * ripple index (R.I.) : ripple length/height

         * ripple symmetry index (R.S.I.) : length of horizontal projection of

                    (R.S.I.) ( 2.5 〈 current ripple )

                               ( 2.5 〉 wave ripple )

                    (R.I.)    ( 0～4 wave ripple )

                               ( 15〈 current ripple )

   ⓓ other bedding type

      ① flaser and lenticular bedding : tidal, streams, intertidal beach

          altermating of energy 또는 sand mud availability

         ┌ flaser : thin mud + sand - 비교적 high energy

         └ lenticular : discontinuous sand lens - 비교적 low energy

      ② wavy bedding : continuous mud (undulating)

      ③ graded bedding (inverse drading) : a few centimeters

          - distribution grading - no fine in lower part

          - coarse-tail grading - all size but grading in only coarse part

          * by turbidy currents, shallow water, intertidal - sudden decrease of competence

            flooding (waning) 또는 hurricanes에 의해 형성 가능

      ④ imbrication and internal fabric

       * preferred orientation by gravitational field with current flow

          : gravel, fossils on bedding surface

       *imbrication : overlapping arrangement → dip current 지시

          : long axes parallel to flow

                           normal to flow : rolling of clasts in bed load

       * parting lineation : thin sandstone → flow parallel to lineation

 2) Bedding plane structure

   (1) Bottom mark (sole mark) : 퇴적층 층리면 하부에 imprint로서 보존, 상하 퇴적층은 조직이

                                                     상이함

                                                  : by current and gravity 

     ⓐ flute or flute cast - by current (sediment accumulation : rapid high turbulent flow)

                                         up down stream

                                         turbidite에서 많이 산출

                                 indicator of current direction and paleoslope

     ⓑ scour mark(transverse)

           - ridgelike transverse to paleocurrent direction

           - a few cm in scale

     ⓒ flute rill mark : long, narrow scour(anastomosing shape)

                                   parallel to current direction (tidal flat에서  형성)

     ⓓ longitudinal furrows and ridges

           : straight, long, spaced closed ridge and furrows

     ⓔ tool mark : by downcurrent transport of pebbles, shells, twigs, branches, fishbone

          * Groove cast (striation cast) : linear 긁힘(물체에 의해 파인 흔적)

          * Brush marks

        * Skip casts

        * Chevron marks

        * Prod marks

        * Bounce marks

   (2) Surface marks : all not related to current

                                   a few millimeter ～ a centimeter in scale

     ① current generation features

          * current crescents (obstacle mark) : 장애물 주위에 생기는 구조

                                                                    (stream, foreshore beach, tidal flat 환경)

          * sand shadows : aeolian setting 의 current crescents

                                                                ( low preservation )

          * rill marks : small, bifurcation dendritic erosional feature

                                                                    ( low preservation )

     ② climate - related features

          * raindrop impressions : mud or muddy sand surface

                                                 (a few millimeter) - arid, semiarid.

                                                 (not always symmetric <by falling oblique rain>: ripple-like)

         * mud cracks : polygonal, V-shaped-supratidal, floodplain, playalake, sabkhas.

     ③ 기타

         * swash marks : up-backwash on foreshore area

              (Figure 3-35) : extensive, concave seaward

              - diagnostic indicator of shoreline(기울기에 따라 간격 달라짐)

         * adhesion ripple : wind blowing sand over a wet substrate.

                                       (eolian 환경)(3-36)

         * pit and mound structure : volcano - shaped or pitlike by water/gas escaping

         * crystal impression : ice, halite, gypsum, pyrite in tidal flats, sabkhas, lagoons

 3) Penecontemporaneous deformation structure

  (1) Load structure by mass of overlying sediment unit (coarse sand over mud)

        * Load cast : flute caster 유사 but not distinct linear alignment, no regular display

        * Flame structure : mud intruding the overlying coarse unit

  (2) Ball and pillow structure : elliptical or pillow-shaped (pseudo-nodule)

                                                   by slumping or downslope sliding(?)

                                                   (liquefaction of the mud and mobilization of mud)

                                                   a few centimeter ～ 1 meter

  (3) Dish structure : discountinuous, concave-upward laminations in sandstones

                                * dish and pillar - water escape structure

                                   dewatering → columns or pillars of massive sands.

                                                       (upward flow of water)

  (4) Convolute bedding : complex folding in mud or fine sand,

                                          remarkable continuity of individual bed in convolute unit

                                          (slump structure 와 혼동

                                          - due to gravity only, soft sediment faulting 와 함께 발생)

                                          → (liquefaction, turbidite 층에서 많이 산출)

  (5) Slump structure : rapid sedimentation + slope instability

                                    complicated, toothpaste-type folding w/

                                    overturned folds and faults

                                    from glacial, point bar, dune, delta, tidal flats turbidite

  (6) injection structure : a few cm ~ several m

                                         sandstone sill - concordant   ┐ by liquefaction + loading

                                         sandstone dike - discordant  ┘

                                         (jnjection from mostly below, some above)

4. Biogenic Structure

  : 퇴적환경의 주요정보 제공 ( intrabasinal structucture → epifaunal(in faunal))

    ichnology

    trace fossil(lebenspurren)

    bioturbation ← sediment reworking by organism

 (1) Boring & Burrows

   1) Boring : penetrating of a hard substrate(shell, rock : carbonate) for food protection

       (3-43)      fungi, algal, sponges, worms, gastropods, bivalves, echinoids

                     indicate ┌ ancient shoreline in beach rock

                                 ├ marine substrate

                                 └ framework of reefs

   2) Burrows :┌ shelter, locus for feeding, dwelling, escape

       (3-44, 45)  └ single, vertical tube ┐

                           u-shape burrows    ┘

 (2) Tracks, trails, resting traces - epifaunal

   1) tracks : vertebrates, arthropod (3-46)

   2) trail : gastropod in low-energy : tide flat, lagoon, shallow shelf, deep ocean n(3-47)

   3) resting trace : somewhat like mold starfish

   4) feeding, escaping, grazing, dwelling structures

 (3) fecal pellets - gastropod, bivalves, echinoids, holothurians, polychaete, arthropod, fish

                               fine sand ~ pebble size. avoid shape

                                    (sand ~ mostly)

                               occurs in terrigenous, carbonate

               low energy : lagoonal, estuarine, lake, tidal flat, shallow marine

                                 - flaser, lenticular bedding을 형성키도 함

5. Late diagenetic or Chemical structure

 1) Mineral segregation → concretion, nodule, septaria, geodes, sand crystals.

        * concretion, nodule : amorphous mass of various mineral composition

           radial, concentric

           ~ up to several m

        특정 층준에 형성 - chert, iron oxide, pyrite, calcite, gypsum, others

                핵             - fossils(insects, plants, fish)

              기원            - microgeochemical 환경 from tissue decay

        * septarian structure : shrinking mass → mineral precipitation(calcite, quartz 가 흔함)

              - solution → crack, pocket을 유발 in carbonate rocks

                            →tepee(calcite에 물의유입 또는 결정화 작용,  의해 “∧” 모양으로 부풀어오른 구조

              - groundwater → ion을 공급

              - geode

 2) Solution structures

          - Pressure - soultion at carbonates(evaporite, quartz arenites)

            Stylolite : marble 에 흔함 : insoluble concentration on the stylolitic surface

 3) Coloration → Fe-Oxide 에 의한 Color change (FeS₂, Fe₂O₃, FeO) → liesgang banding

 4) Diapiric structure - salt, mud

제 5 장. Sedimentary Facies Model(퇴적환경모델)

1. Alluvial Fan → Humid

    (선상지환경)     Arid

                              Glacial

    - 평면도

    - 수직단면도

    - Tectonic Setting - fault bounded

    - Process - debris flow, mud flow, sieve deposit, sheet flow

    - Sediments - no organic, oxidiging, lateral and vertical, facies change

    - Sequence characteristics

    - Pooly sorted, immature

    - Lenticular patterns - radiating

    - associated w/ eolian, fluvial, lacustrine marine

  기후에 따라 ┌ Humid - flanks of Himalaya (Modern)

                                   Alaska, Iceland (Ancient)

                   └ Arid - more steep, forming pediment

                              oxidation high permeability

                              small overlapping lobes and channels

                              felspathic and mafic minerals

                              Death valley, California

주요 facies 특성 요약:

  ① fossils and carbonates rare, evaporites

  ② poorly sorted, a great range in grain sizes, poor-stratified

  ③ poorly rounded, immature composition

  ④ major changes in lateral, vertical facies particularly in the downfan direction

  ⑤ rapid downfan decrease in clast size

  ⑥ oxidizing feature on sediments - red, brown, yellow, orange

  ⑦ No organic matter, not many fossils-vertebrate bones & plant fragments

  ⑧ most commonly medium to large-scale

      cross-strata and planar stratification, graded and inverse- graded bedding

  ⑨ lenticular, wedge-shaped geometry

  ⑩ sediment body-channelized(channel deposits) little lateral continuity

  ⑪ fault-bounded-grabens, half-grabens strike-slip fault-bounded basins

  ⑫ associated w/ eolian, lacustrine, marine facies

  ⑬ containing soil profiles and terrace surfaces

  ⑭ Paleocurrent patterns-radiating outward, complex, radiating patterns

  ⑮ sieve deposits

2. Fluvial(하성환경)

    경사에 따른 분류┌ Straight

                           │ Fluvial

                           └ Meandering

                            * Anastomosing

    평면도 - meandering

              - crevasse - splay

              - point bar

              - levee

              - flood plain

     Channel migration

                  Point bar sequence - fining-upward

     Sediment ┌ Various Characters

                  └ red color, cross-bedding, 토양층(calcrete)

     Fossil - fish, gastropods, pelecypods, trails on flood plains, plant, pollen

     Paleocurrent - imbrication, cross-bedding

     Process   - normal, gravity(debris flow, stream flood, sheet flood)

     ┌ Sand dominated - Trollheim, Scott, Donjek type

     └ Gravel dominated - Sask atchewan, platte, Bijou type (p.246)

     Climate, regional geology, geomorphology, relief, discharge, substrate composition

       ==> controlling factors for fluvial sedimentary facies

  1) Braided channel

      a. 특징 : 1. numerous channel separated by bars, small islands

                   2. low sinuosity, coarse sediments w/ bedload, suspended load

                   3. deposition : shifting of channels and bar aggradation

                   4. steep slope, bankful discharge

                   5. overloaded channel로 불림

      b. process

         1. fan(humid)의 distal part와 유사한 process를 보임

         2. temporal variation in discharge --> coarser grains를 계속 운반할 수 없음

      c. sediment and sedimentary structures

         1. planar, trough cross-stratified, massive

         2. crudely-bedded gravel facies, matrix-supported

         3. small lenses of sand, mud w/ ripple, imbrication of pebble

         4. sediment bodies : longitudinal bars(linguoid bars)

  2) Meandering channel

     ① two types - coarser grained meander belt : sand gravel.

                          fine-grained meander belt : highly sinuous

     ② lateral accretion : fining-upward(point-bar)

     ③ flow velocity variation through depth

     ④ deposits : channel lags

         point-bar deposits - scroll bars, swale, well-sorted, pebbles-common

         channel sequence - regular, cyclic sequence

         overbank deposits : natural levee-coarser

                                      flood plain - finer

         crevass-splay - coarser than levee deposits, locally, fan-shaped

         channel-fill deposit : abandoned organic-rich

주요 facies 특성 요약:

 ⓐ fluvial sands range from very coarse, through fine to medium-grained

     well-sorted examples to silty or muddy sands

 ⓑ channel, point bar, braided bar sands-well-sorted, cyclicity

 ⓒ electric log - fining-upwards

 ⓓ trough cross-bedding, planar cross-bedding

 ⓔ meandering channel - cross - stratification

 ⓕ oxidizing environments - red colors

 ⓖ paleontology- ① very restricted - fish, gastropods, pelecypods, trails on floodplains

                        ② most common-plant fossils-large logs, plant debris, fossil pollen

                           ┌ large amount of pollen        ┐ confirm‎ fluvial facies

                           └ lack of marine microfossils ┘

 ⓗ paleocurrent structures : imbrication, cross-bedding

 ⓘ braided river : sheet or wedge-shaped sandstone, conglomerate w/thin, persistent

                         shale enclosed within coarser sediments

                         great thickness(〉200m) clast-supported gravels from channels and bars

                         (long axes transverse to flow)

 ⓙ meandering river :   confined by abandoned mud-filled meander loops(oxbow lakes)

                                 liner or shoestring sand body down the depositional slope

                                 sand body commonly

 ⓚ anastomosing river : peaty silts are dominant

                                  sand or gravel bodies are very marrow to the thickness

 ⓛ braided rivers

    ① ┌ inter mediate axis :upstream imbricated ┐↔deep sea conglomerate

        └ long axis : transverse to flow               ┘  (long axis : imbricate and  paralleled w/ flow)

    ② no cylicity

    ③┌ trough, tabular crossbeds by migration of gravelly dunes

       └ or flat topped bars, horizontal bed

    ④ rough fining-upward sequences

    ⑤ from base to top

        horizontally bedded or cross-stratified→roughly cross-stratified gravelly sand

           →irregular sandy tabular crossbed sets or parallel laminations and

           capped by fine-grained rippled sand and muds

    ⑥ ** Planar tabular crossbed sets within sand body

            → Briaided nature of the sequence

             * more irregularities in grain size trends, less fine overbank material

 ⓜ meandering rivers

    ① floodplain deposits-muds containing roots or caliches

    ② classic fining-upward sequences : by lateral river

        migration : lag gravel→intraclast conglomerate→sand→mud

 ⓝ anastomosing rivers:

    ①thick peat-rich silts and clays laterally to coarse grained channel facies

    ② little fining-upward sequence

3. Aeolian or Desert (풍성환경)

   Dune - interdune + dune (well sorted, rounded, generally fine-to-medium supermature sand size)

   Wadis- imtermittent streams

   Barchan - 초승달모양 사구

   Seif - longitudinal 사구

   대개 Playa, Subhka 와 연결되어 있음

   기후 - hot & dry(250mm이하/year) : 20% 의 사막 : dune-covered

   현생 - Basin and Range of U.S.A on active tectonic setting

            Sahara 사막 of the stable craton

   Erg - 모래로 덮인 사막

   Pediments - 기반암이 노출되어 있는 사막

   Desert Pavement - deflation, mud crack, residual(lag) coarse grains

   Loess: 사막에서 기원한 이질 퇴적물 (황사)

   Draas - extremely large bed forms with l km 이상 wavelength

   Dreikanters - 삼릉석 - deflation pavement

   Sediments -  large scale cross-bedding

                      raindrop imprints

                      bimodal sand lag

                      clay coating (hematite coating)

                      tabular beds

                      quartz(most) feldspar(mineral)

                      Not much fossils- pollens, spores some algae

주요 facies 특성 요약:

 ⓐ large-scale(tabular wedge), planar cross-strata(dip : 20-30°)

     overlain by smaller scale trough cross-strata(climbing ripples)

 ⓑ sand flow toes, forming tangential contact of cross-beds w/ lower bounding surface

 ⓒ raindrop imprints (raised rim, depressed centers)

 ⓓ evenly distributed bimodal sand lags along erosional surfaces

 ⓔ high ripple index : oriented up and down leeside deposits & desiccation cracks

 ⓕ graded deposits, probably related to grain fall processes

     inverse graded produced by migrating ripples

 ⓖ Texture : ① moderately sorted to well-sorted, fine-to medium-grained inland dune sand

                      rounded, generally supermature

                  ② well-sorted fine-grained coastal dune sand

                  ③ moderately to very poorly sorted interdune or serir(stony desert) sands

                  ④ rapid textural change and permeability contrasts on a bed within cross-bed sets

                  ⑤ many eolian sand grains have clay coatings probably responsible for the reddening of                       dune sand

 ⓗ geometry : tabular bodies

     composition : quartz, feldspar

 ⓘ not much paleontology pollen & spores, some algal -common

4. Lacustrine (호성환경)

    현재 지표면의 1% 차지 - 호수,  60%의 호수 : freshwater → limnology(호수학)

    분류기준 : climate - 열대, 온대, 한대

                    sediment type ┌ biochemical

                                        └ terrigenous

      Swamp : tree

      Marsh : grass

      Bog : peat

    Oligtrophic : few nutrients, low productivity

      Eutrophic : high nutrients, high productivity, oxygen deficient in the hypolimnion

    Annual circulation patterns

      ① temperature driven: once or twice overturn in a year

         ┌ spring overturn

         └ fall overturn

      ② density driven:  influx of suspended sediment ┐ → overflow  ┐

                                             of cold water           ┘ interflow      │로 분리

                                                                                 underflow ┘

      ③ upwelling and sinking

            - wind blowing across the epilimnion

  * Lake sediments : Fig 5-16

     수평적 퇴적상 배열 순서 alluvial fan → mud flat →interdeltaic marginal lacustrine →open lacustrine

     mostly thin : (200m 〉 ), cirular in plan view, lenticular

     terrigenous sediment - river input

        - a single, large source of sediment → delta (coarsening-upward sequence)

        - pelagic sediment - silt, mud(clay) through settling from suspension (varve structure)

        - turbidite : cold runoff + dense turbid water → underflows or turbidity currents

     chemical sediments - saline lake : 5‰ 이상 dissolved solids.

                                      carbonate lake

        - saline lakes = SiO2, Ca2+, Mg2+, Na+, K+, HCO3-, CO32-, SO42-, (Playa, Sabkha) Cl-

        - 정출 순서: CaCO3 → Dologmite, CaMg(CO3)2 → Gypsum(CaSO4, 2H2O),

           Anhydrite(CaSO4) → Halite(NaCl)  →  Potash salts → Bittern salts

                                                                └── Playa lakes only ──┘

     biogenic sediments - pelecypods, gastropods, diatoms, oncolite-blue green algae + detrital                                      nucleus

     chemical sediment - pyrites

         * Marl - typical of freshwater lake sediment (calcareous + detrital mud)

 기타 특징

    1. fining-outward

   2. coarsening-upward as the basin fills

   3. thin, continuous bedding varves

   4. diverse paleontology - algae, mulluscs, ostracods, vertebrate,

   5. 석유 근원암 역할: 미국 Utah의 Uinta 분지, 중국 서부 - Qaidam Pendi 유전

 주요 facies 특성 요약:

  ⓐ common fossils : aquatic vertebrates, ostracods, palynomorphs, mollusks, bivalves, gastropods,                                charophytes(blue green algae), diatoms, algae, plants,

                               conchostracans(brachiopods), burrowing

  ⓑ abundant lipid-rich organic sediment, horizontally laminated

  ⓒ even and continuous varve-like laminae

  ⓓ polygonal pull-apart or desiccation cracks, bird tracks(trace fossils)

  ⓔ loop-bedding : disrupted thin beds and laminae broken by low-and

      high-angle, small-scale fault and boudinage pull-apart structures.

  ⓕ salt-crystal molds in nodular chert, mud-supported carbonate rock

      -'lumpy' texture or wavy, irregular bedding

  ⓖ Graded Bouma sequence of thin bedded sandstone and interbedded mudstone

      including sole mark, rip-up clast, burrowing, ripple mark

  ⓗ desiccated algal mats and crusts of evaporite minerals,

      fossiliferous coal bed w/mullusk wackstone

  ⓘ low-angle cross-strata, interbedded sandstone w/ mollusk-bearing mudstone.

  ⓙ climbing-ripple lamination, cross-laminated sandstone and siltstone beds

  ⓚ Burrowed rock(bioturbation) w flat bedded sandstone underlying coal and lime wackestone

  ⓛ sandstone grading upward from large-scale, low=angle tabular to trough cross-strata

      near base to medium-scale trough cross-strata to small-scale cross lamination

  ⓜ stromatolitic algal boundstone overlain by an ostracods,

      curviplanar, laminated to small-scale cross-laminated calcareous sandstone

  ⓝ ① some what circular in plan view and lenticular in cross-section

      ② fining-outward trend into the basin and coarsening-upward stratigraphic trend

      ③ marl, evaporite minerals some zeolite mineral especially analcime

      ④ thin continuous bed(varve) small ripple and ripple cross-strata

5. Glacial (빙하환경)

   - Restricted by latitude, elevation

        cirque glacier (산정에 국한)

        valley glacier (mountain or alpine glaciers)

        continental glacier (ice sheet)

   - Plastic behavior at depth

   - Rate of movement : a few to 100 meter per year

                                 slide over the bed rock surface (50 %) + ice itself flow (50%)

 * Erosion

   - glacial striation and glacial groove by sediment-laden ice, crescentic gouge

   - polish or smoothed surface by fine-grained sediment at the base of the ice mass

 * Deposition : characteristics : sorting, grain size, particle shape, fabric, lithologic composition size                                              and geometry of the unit.

   - lateral moraine(측퇴석), terminal moraine(종퇴석)

   - subglacial sedimentation: 빙하 하부에 포함되어 운반

   - englacial sedimentation : within the ice mass

   - proglacial sedimentation : in front of the glacial termination and by discharging meltwater

   - drift (glacial-deposited sediments.)

    ┌ till → unsorted, unstratified, fine-matrix → tillite, polymictic conglomerate(diamictite)

    └ outwash deposits → sand, gravel w/ silt, clay

   - 호주의 Cooper 분지, Oman의 Marshal Field 에서는 fluvial, lacustrine 환경과 연계되어 석유 산출

 주요 facies 특성 요약:

  ⓐ similar deposits to fluvial, unidirectiontional flow structures

  ⓑ abrupt particle change

  ⓒ very poor sorting - pebble, cobble size, coarse grain

  ⓓ well-imbrication to upstream dips

  ⓔ gravel bars, transverse ribs or clast stripes

  ⓕ large-scale cross-bedding antidune and standing wave structures some ripples and

      megaripples, structureless for drift sediments

  ⓖ geometry : tabular or linear

      composition : heterogeneous

  ⓗ pollen, spore - Pleistocene deposits

  ⓘ 주요 퇴적 시기 - Precambrian(middle-late),

          Carboniferous-Permian(Gondwana)-Africa, India, Australia, Antarctic, South America

6. Delta (삼각주 환경)

     - 3 main parts - delta plain, delta front, prodelta

   1. interaction between sediment yield and energy flux.

   2. large delta in trailing-edge coast and marginal sea coasts

   3. constructional phase - progradational, river-dominated

       destructional phase - wave, currents, tidal dominated

   4. deltaic process의 주요 지배 변수

      주변수 - riverine processes

      종변수 - climate, relief in the drain age basin, sediment yield, water discharge regime

   5. three primary forcess in riverine process

       - inertial forces - homopycnal - no density contrast between river and sea water

                               (turbulent jet)

       - bed friction

       - buoyancy

     ① inertia-dominated effluent

         Gilbert's delta model : topset, foreset, bottomset.

         (deep lake or where tide homogenizes the water mass) ← high gradient streams

     ② bed friction - dominated outflow

                         - bifurcation of the outflow

                         - substantial shoaling just behind the mouth

                         - lateral spreading - homopycnal flow

     ③ buoyant outflow

         density contrast ┌ fresh water : 1.0

                                └ sea water : 1.026～1.028 g/㎤

                                     hypopycnal flow

   6. marine processes

     ① tide - Amazon, Gangls-Brahmaputra(bangladesh) Ord(Australia)

                 linear shoals with their long axes parallel to flow

     ② wave - broad, gently-sloping shelves → well-developed deltas

     ③ coastal currents - channel mouth migration을 초래 sand spit

   7. deltaic sediments

     ① distributary channel  - coarsest sediment

                                         migrating laterally - X - bedding

                                         abandoned channel filled w/ mixed. silt, clay, organic material

         natural levee - subaerial or subaqueous

                                 fine-grained settling from suspension

     ② interdistributary bays and marshes - most silt and clay

                                                             scattered shell debris, thin sand lenses,

                                                             parallel laminations and burrow mottling

     ③ mud lumps - diapiric masses of deformed muds

                           (3～4m above sea-level)

     ④ delta front : depth - ~10m or less

                                     sand-sized sediment-by winnowing

                                     X-stratification, low bioturbation

                                     highest energy environments

                                     progradation - common

                                     elongate or crescentic sand bodies

           * distal bar : near outer limits of the delta front

                              interbedded fine sand and mud

                              several meter high

                              rotational slump blocks

     ⑤ prodelta - widespread & homogeneous silt & clay

                       fining-seaward

                       grade into shelf mud

                       deposition from suspension → thin lamination

                       shell-scattered

                                   ──────→ fluvial process

           * straind plain → cuspate → lobate → elongate

                                  ←────── marine process

           * size : few 1000 ㎢ - area

                       few 1000m - thick

 주요 facies 특성 요약:

  ⓐ geometry : thick lens, wedge

      Texture : coarsening-upward trend, sand and mud

  ⓑ lithology : coal and peat seams, abundant micaceous particles, numerous woad fibers

  ⓒ sedimentary structures: convolate bedding, diapiric features, loading structures (slump, growth       fault structure)

  ⓓ freshwater-brackish water-saltwater transition on paleontology

  ⓔ ① distal marine & destructional phase : mud & silt : gray, black

                       pyritic nodules, ironstone concretions, plant fossils,

                       marine limestone, black, hard, fissile 'slaty'

                       containing large black spheroidal concretions

      ② delta slope & prodelta : muds and silts gray

                       sandy, marine fossils, ironstone concretions

      ③ alluvial plain     ┐  sandstone, fine-grained, micaceous, siltstone

          distributary and │ argillaceous : variable massive to thin-bedded

          barrier channel ┘ usually w/an uneven lower surface

        (proximal-prograding delta) irregular bedding and burrowed structure, contorted bedding,

                                              climbing ripples

      ④ delta plain (swamp and marsh over bank and levee)

             : silt and mud, coal, underclay, gray to dark gray, noncalcareous-argillaceous occurs in

               nodules or discontinuous bed

          non-fossiliferous, sand shale : gray

  ⓕ growth fault(rollover structure) from seismic record in the subaqueous delta plain

7. Tidal flat or intertidal (조간대 환경)

  1. ┌ flood tide : 밀물 (high tide)

     └ ebb tide : 썰물 (low tide)

     ┌ spring tide : 사리

     └ neap tide : 조금

      - macrotidal - tidal range 4m 이상, mesotidal: 2-4m, microtidal: 2m 이내

  2. supratidal - intertidal - subtidal

      └─  peritidal  ─┘

  3. salt marsh - grass vegetation, mangrove(swamps) including levee, tidal creek, low relief

       sediment - mixture of fine mud and plant debris

        w/ small amount of shell material, sand, large plant fragment

        ⇒ supply by runoff of land washover of barriers & shelf

       sea-level rise → extend marsh by providing renewed sites for sediment accumulation and related

        colonization by vegetation (coarsening-upward sequence))

       sea-level fall → marsh decreases due to being high and dry (finig-upward sequence)

       character : - well-bedded w/ wavy undulations

                        - severe bioturbation

                        - small channel - fill structure

                        - marine or brackish organism

  4. mangrove swamp - tropical region peat low current and wave energy

  5. sediments - terrigenous mud+sand

                      (예: 한국 황해 조간대 - 최대 25km wide, lower relief,

                             flood current(120cm/sec) > ebb current(70cm/sec))

     ① bioturbation, burrows pelletization, herring-bone-cross-bedding

         flaser, lenticular bedding, desiccation cracks. wrinkled algal mats.

         * time - velocity asymmetry → development of reactivation surfaces.

     ②  sand-dominated - meso-tidal, macro-tidal, muddy-widespread

           ┌ low tidal flat - sand 우세, ripple mark, long wave action and winnowing의 결과

               mid tidal flat - bed load + suspension load 즉 sand와 mud의 교호층, starved ripple

           └ high tiddal flat - mud 우세

            - cross-bedding by migration of megaripples by sand waves

               tidal current in macro tidal area

  - 기타 특징:  tectonic setting - move extensive on broad stable coast

                         shape          - tabular, perpendicular to the paleo-shoreline orientation

                       thickness      - few meters

                        texture          - fining-upward sequence by progradation thin bedding

 주요 facies 특성 요약:

  ⓐ geometry : tabular or elongate, few meters in total thickness(thin-bedded)

  ⓑ texture : general fining-upward by progradation of a decrease in grain size from low tide to high                    tide

  ⓒ lithology : terrigenous tidal flat-quartz, feldspar, rock fragments, clay minerals

                    carbonate tidal flat-biogenic calcite, aragonite debris some dolomite

                    marshes : plant debris, clastic particles w/ some biogenic carbonate

  ⓓ sediment structure :

                             ┌ marsh : thin bedding various bioterbation by roots,

                             │            invertebrates burrows

                             │ terrigenous flat :

       microtrough     │    ① various bioturbation by mollusks, worms, ripple bedding

  ripple stratification │    ② common small-scale ripple X-stratification, flaser

     scour base w/   │        bedding wavy

  coarse lag, shells │        bedding. lenticular bedding channel bottom layered w/

                             │        eroded shells

                             │    ③ desiccation features in the muds. isolated sand and mud

                             │        filled

                             │        channels w/ longitudinal oblique beds

                             └ carbonate tidal flat : similar terrigenous, but w/ less physical

                                                              structures algal mats are common in ther

                                                              upper supratidal portion

  ⓔ paleontology : abundant & relatively diverse

     ┌ marsh : much plant material as peat or coal oysters and burrows of  crabs and worms

     └ tidal flat : some scattered plant debris in the upper strata, iron oxide

                       cement various burrow structures, gastropals, pelecypods

  ⓕ overlying sand, X-stratified tidal delta or subtidal esturine deposits

  ⓖ tidal channel deposits

     ┌ clean, well-sorted, very fine grained, nearly uniform grain size

     │ small and medium, scale high-angle cross-beds

     └ burrows rare, some opposed. X-bedding directions

     ┌ reworked skeletal fragments of contemporaneous shallow marine fossils

     └ many fragments oolitically coated, some well-preserved

     ┌ Elongate, sharp and erosional at sides and bases,

     └ possibly interbedded with oolitic limestones

      shoreline : ┌ gradational contact, conformably overlies oolitic limestone,

                    : └ grade upwards into tidal flat, horizontal lamination w/ s-scale

                          X-lamination. burrows rare, festoon X-beds