| 제 5 장. Sedimentary Facies Model(퇴적환경모델) |
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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 |
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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 : ⓚ 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 |
confined by abandoned mud-filled meander loops(oxbow lakes)
liner
or shoestring sand body down the depositional slope
sand
body commonly|
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 |
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4. Lacustrine (호성환경)
sediment type ┌ biochemical └ terrigenous Swamp : tree Marsh : grass Bog : peat Eutrophic : high nutrients, high productivity, oxygen deficient in the hypolimnion 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
- 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
carbonate lake - saline lakes = SiO2, Ca2+, Mg2+, Na+, K+, HCO3-, CO32-, SO42-, (Playa, Sabkha) Cl- -
정출 순서: CaCO3 → Dologmite, CaMg(CO3)2 → Gypsum(CaSO4, Anhydrite(CaSO4) → Halite(NaCl) → Potash salts → Bittern salts └── Playa lakes only ──┘
* 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 |
현재 지표면의 1% 차지 - 호수, 60%의 호수 : freshwater → limnology(호수학)
분류기준 : climate - 열대, 온대, 한대
Oligtrophic : few nutrients, low productivity
Annual circulation patterns
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
chemical sediments - saline lake : 5‰ 이상 dissolved solids.
2H2O), 
biogenic sediments - pelecypods, gastropods, diatoms, oncolite-blue green algae
+ detrital nucleus
chemical sediment - pyrites|
5. Glacial (빙하환경)
- Restricted by latitude, elevation
- 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 |
cirque glacier (산정에 국한)
valley glacier (mountain or alpine glaciers)
continental glacier (ice sheet)|
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 |
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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 w/ small amount of shell material, sand, large plant fragment ⇒ supply by runoff of land washover of barriers & shelf colonization by vegetation (coarsening-upward sequence))
- 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 |
sediment - mixture of fine mud and plant debris
sea-level rise → extend marsh by providing renewed sites for sediment accumulation and related
sea-level fall → marsh decreases due to being high and dry (finig-upward sequence)
character : - well-bedded w/ wavy undulations
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제1장. 퇴적물 및 퇴적암의 일반적인 성질 |
