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Geosclence Canada. Volume 3. Number 2. May. 1976 101

hydrocarbon reservoirs, themeandering builds laterally and downstream across systems depositing elongate shoestring the plain. stratigraphically bounded by The floor commonly has a shales, and the sandy braided systems coarse "lag" deposa of material that the forming thicker and laterally more can only move at peak flood time. extensive bodies. This material would include the gravelly component of the clastic load, together handerlng Systems with water-logged plant material and The main elementsof a modern partly consolidated blocks of mud meandering system lexemplified by the eroded locallvfrom the channel wall. ~ississi~~ior~razoi exi is) ~iveis] Above the lag, sand is transported Fades Models are shown in Figure 1. Sandy through the system as bedload. During IS normally restrlctea to the maln average , tne typlcal bedlorm

3. Sandy Fluvial channel or to oart~alv or Comoletelv on the cnannel floor cons~sls~ ~ ~ ol slnbo~s-~ ~~~~ abandoned 'loops; deposition crested (Fig. I)ranging in height systems of fines ( and ) occurs on from about 30 cm to one metre. and in flood basins. It is surprising that Preservation of these dunes results in there are so few integrated studies of trough cross-stratification. In shallower Roger G. Walker modern meandering systems in the parts of the flow, higher on the point . Department of Geology laeralure of the last twenty years. The the is commonly ripples McMaster University most important papers include those of (preserved as trough cross lamination; Hamilton, Ontario LBS 4Ml Sundborg (1956; River Klaralven). Fig. 1). As a broad generalization, we harms et a1 (1963. Red River). Bernara may propose that the preserve0 lntmductlon et a1 i 1970: Brazos River). McGowan oeoos~tsof the act ve~~- channel - w~lloass This article will follow the pattern ?-~-- and darner' [t 970; colorado (Texas) from trough cross-bedded coarsesands established previously in thisseries. I will and Amite ] and Jackson (in to small scale, trough cross-laminated describe in general terms the press; Wabash River). Although the fine sands upward (Fig. 1). depositional environments of modern meandering river model is well The development of a plane fluvial systems, and attempt to formulate

established. its basis is somewhat dated, (without riooles or dunes)~ ~~ is favoured bv a general model. I will then show how the , ~ ~ ~~ -- ~, Further integrated work (not just on one higher ve~bcitiesand shallower depths. model acts, 1 ) as a norm for purposesof ) would seem important. and deposition on the plane bed results comparison. 2) as a framework and in horizontal lamination. The particular guide for future observations, 3) as a a) The Main Channel Meandering in the combinations of depth and velocity prediclor in new geological situations. channel is maintained by on the required to produce plane bed can and 4) as a basis for hydrodynamfc outer banks of meander loops, and occur at various river stages, and hence fnferprelalion. deposition on the inner parts of the parallel lamination can be formed both For reasons of space, I will consider loops. The main depositional lowand high on the point bar. It can here only the sandy systems. Gravelly environment isthe point bar, which therefore be preserved interbedded with and bouldery systems are less well understood, although their deposits are abundant in Canada and locally are economically important (e.g., the uraniterous conglomerates in the Elliot Lake area are generally considered to be fluvial). Sandy rivers can be straight, meandering or braided, although natural straight rivers are very uncommon. There would appear to be a spectrum of types from meandering to braided: meandering systems are fairly well understood, and sandy braided systems less well understood. At the moment R Seems best toconsiderthem separately, and use two models Comparison ol new situations with the meandering Flgum 1 norm and the braided norm should help Block djagram showrng major morphological point bar - the dunes and ripples in the toestablish the range of variation elements 01 a meanderingriver system. channel give rise to trough cross-bedding and ripple cross-lammation, respectively between the two types of system. Erosron on the oulsrde bendofmeander loops leads lo lateral accretion on the opposile (inset, lower right), which are preservedm a Sandy fluvial deposits are known from lining-upwardsequence. See text for detarls. all geological systems. Archean to recent. They form important trough cross-bedding, or small Scale I I trough cross-lamination (Figs. 2.3). BATTERY POINT The preservation of all of these WARY SEQUENCE $ 'MEANDERING" leatures is basically due to the lateral 8 FINING-UPWARD and downstream accretion of the point SEOUENCE bars. Channel-floor dunes may be driven slightly diagonally onto the lower I partsof the point bar, thus helping the BAR point bar to accrete laterally on topof the TOP* channel-floor lag. The upper part of the point bar may be composed of a series of ridges and swales (Fig. I),the swales acting to funnel flood waters across the point bar wlth a much straighter thatweg i POINT BAR lhan the normal low-stage meandering TOP . If coarse is funnelled lhrough theswalesat high flow, itmay be oeposlted at the downstream end n rne I formof chL1e oars" lF~a1 McGowan POINT BAR and Garner, 1970).~heiechutebarsact to lengthen the point bar in the I downstream direction, hence constricting the llow and causing CHANNEL CHANNEL FLOOR increased erosion immediately FLOOR downstream. Pure meandering rarely have ngum 2 exposed bars in the middle of their Comparison of a summary sequence of from data m Allen, 1970 lmpl~cal~onsof the channels, and hence the sandy active- facies for the Devonjan Baltery Porn1 comparjson are d~scussed~nthe text Letters channel deposits can all be termed (Gasp6, Quebec: Can1 and besrde 1heBafleryPornt sequence refer to the LATERAL ACCRETION deposits, Walker, 1976) with the meandering river facres 01 Can1 and Walker (1976) V A related to lateral migration of point bars model. The model is redrawn to correct scale rndrcates vertlcal accrellon (Fig. 1). c) Verlical Accrelion Deposits. Outside During rising flood stage,the levees b) Channel Abandonmenl. Meander the main channel, deposition in the flood can be breached, causing the formation loops can be abandoned gradually basins, ox-bows and levees takes place of a "crevasse-splay" (Fig. 1) - a wedge (chutecut-off)orsuddenly(neckcut-Off) by addition of during flood of sediment suddenly washed into the (Allen, 1965, p. 118-9.156). During stage when the river overtops its banks flood basin, and commonly containing chute cut-off, Ihe river gradually re- (Fig. 1). In contrast lo the lateral some of the coarse bedload portion of occupies an old swale, and accretion within the main channel. the river sediment. The simultaneously flow gradually overbank deposition causes upbuilding deposit may resemble a classical decreases in the main channel. Gradual ofthe flood plain, hence the term in having a sharp base, overall abandonment thus results in gradual VERTICAL ACCRETION. Near to the . and a sequenceof flowdecrease, and this could be main channel, where the flood walers sedimentary structures indicative Of reflected in the by the sweep along as a , the vertical decreasing flow during deposition. development 01 a thick sequence of low- accretion deposits tend to be silty, and The only other deposits that may flow sedimentary structures - are commonly cross-laminated. Farther rarely be preserved as part of the vertical essentially ripple cross-lamination (Fig. from the river, flood waters may stagnate accretion sequence are windblown, and 4). Aner complete abandonment. and only mud is deposited. Alter retreat may be either loess, or coarser sandy forming an ox-bow lake, of the flood, the mud and silt commonly deposits blown in as large dunes. would be restricted to fines (silt. mud) dry out, and dessication cracks are introduced into the ox-bow during formed. The flood basins and levees of d) Meandering River Facies Sequence. overbank flooding from the main most river systems (post-Silurian) tend The distillation of observations from a stream (Fig. 1). to be abundantly vegetated, and hence large number of modern meandering Neck cut-off involvesthe breaching01 the deposits contain root traces (Fig. 5). streams. and from many ancient a neck between two , and the In semi-arid or arid environments, the formations interpreted as meandering- sudden cut-olf of an entire meander fluctuating water table and drying at the fluvial, allows a general facies sequence loop. Both the entrance to and exit from surface favour the formation of caliche- to be formulated. One version of this the loop tend to be rapidly plugged with like nodules within the vertical accretion sequence is shown in Figure 2; it was sand. Flow diminishes to zero very deposits. distilled by Allen (1970) and is redrawn quickly and the resulting sequence of to scale here. In its simplest form. the deposits is dominated by later, flood- sequence is FINING-UPWARD and ~ntroducedsilts and muds (Fig. 4). Geoscience Canada. Volume 3. Number 2.May. 1976 103

consists of in-channel deposits (lateral accretion), followed by overbank tines (vertical accretion) (Figs. 6.7). In this particular sequence, the facies relationships were determined statistically tor a large number of Devonian outcrops in Britain and North America, but application of the model has demonstrated that it can be used appropriately in many other areas. The lag deposits are overlain by trough cross-bedding. which is in turn overlain by small scale trough cross-lamination. Horizontal lamination can occur at several places within this sequence (Fig. 2). depending on the river stage at the time when the depthlvelocity criteria for plane bed were met. After the channel migrated away laterally, the tacies sequence continued with vertical accretion deposits introduced at flood stage. The diagram (Fig. 2) shows root traces, dessication cracks and caliche-like . Using the data presented by Allen (1 970. Table 9). it can be seen that the vertical and lateral accretion deposits in the meandering model are on average Figure 3 2nd abundance 01 )iorrronlal slialrlrcal~onh roughly equal in thickness. Coarse, sandyporlron ola Devonran Irn!ng- ccnlre (hammer1 Upperrnosr par1 rs very fine Allen's model serves excellently as a upwardsequence(Appalach!ans, Western sandstone wrth ripple cross-lamination (R): norm with which to compare other Maryland), with Stratrgraphic top to left Note above here (under leaves) are the vertical- fining-upward sequences (see low angle cross-strar,lication in lower pad. accretion deposits particularly Allen. 1964). In its construction. Allen apparently used a -- - - Flgure 4 Meander Imps can be abandoned by chute or neck cut-off.Oldchannelshownsolid, new channels dashed. Chute cur-of1involves reoccupatron ol an oldswale andgradual WTE CUT-OFF 1 abandonment olthe mafn channel The stratigraphrc sequence wilt conslst 01 some trough cross-beddeddeposifs 01 the active river (ACT) anda thlck sequence of ripple cross-laminated line sands representnrg gradual abandonment (AB) Aner cut-all, the sequence is completed by vedical-accretron WF (V.A.)deposifs. By contrast, aner neck cut-OM, the meanderlooprs suddenlyabandonedand sealed of1 by deposlfron 01 sand plugs (st~pple)Alter the actrve deposrts, the rrpple cross-lammated lrne sands reoresentfno low I flow durrng abandonment (AB) are veryfhin. and the bulk 01 the seouence consrstsol I

with the actrve lateral-accret~onsequence Figure 5 (FKl 2) Ldryeiool syslemin tluvialoverbank deposrts part 01 the U Devonran (Catskrll) Clastrc wedge olfhe Appalach~ansPhoto horn Rlver Road, West Vrrgmra (near Hancock, Md) wide variety of fining-upward sequences. Comparlson of sequences such as those in Figure 4 with Allen's norm immediately shows that the trough cross-bedding is very reduced in thickness, that one of the sequences contains anabnormalthlcknessofripple trough cross-lamination, and that both contain unusual thicknesses of vertical accretion deposils. The comparison with Allen's model suggests the interpretations shown in Figure 4; without the model. we would not be so conscious that the sequences in Figure 4 differed significantly from the sequence developed by lateral accretion in an active channel.

e) Sand Body Geometry andflood-Plain Aggradalion. One of the essential components of a meandering model is the fact that meander loopsare cut off. abandoned, and ultimately filled with fines -silt and clay Through ttme, these Flgure 6 grades up into verlrcal-accrelron s~llstones clay plugs may become abundant A complele hnmg-upward sequence from !he about at the level 01 lhe small lree Coarse enough lo confine the meander belt. membel aboul I0 rn Ihlck hammer (arrowedl u Devon,an(Calsh~ll)clasl,c wedge Western because the plugs are relatively hard to Maryland Base resls upon red mudslones for scale B IS the base slratlgraphrc lop erode, Once confined, the entire with rooliels The ~n-channelcoarse member to fell meander belt may become raisedabove the general level of the flood plain by vert~calaccretion (Fig. 8A) This situation can perslst until one catastrophic break results in the sudden switch of the entlre river to a lower part of the ("avuls~on", Fig8A)Thusthe sand body geometry of a highly sinuous meandering stream will be essentrally elongate ("shoestring"). bounded below and on both sides by flood-basin flnes. The shoestring will also stand a good chance of being covered by overbank flnes from the active river in its new position. Thus the high srnuosity meandering model predictsthat, given continulng supply and basin subsidence, a series of sand lenticles interbedded with shales should be developed. The internal structure of the sand lenticles themselves should conform roughly to the pattern shown in Figure 7 Figure 1. The vertical scale in Figure 8A A cuirlpfete lining-upwardsequence fromlhe is considerably exaggerated, and upper par1 of lhe Ballery Poml Formairon individual shoestrings will probably be (L. Devonian) a1 Penou,Ile (near Gaspel. many times wider than they are thick. Ouebec. Base (81 resls on massive red mudstones (the venrcal-accreliondeposds of Ihe underlvino. - seouencei. The coarse member is cross-bedded(above figure1 and Dasses uo [nro thick verl~cal-accrelronred srltstones A new lmmg-upwardsequence begrns on (he lefl of lhephofo Geoscience Canada. Volume 3. Number 2. May. 1976 105

Flgum 8 accrelron srlls~one~andmudslones Verlcal can occur dur~ngll& stage for example on A. Block bragram 01 Wood-plarn aggraaalon scale 8s ngnlv exagwraled Com~arewi~h 8. lne veaelaled rslana bul aews~rsare rarelv with verysinuousrivers. ~hoeslriibsandsare block diagram olabrardedsandysyslemwilh ~iagramimodifr~?d lrom those i preserved, and are wrrwnded by vertical low sinuosily channels Verlicalaccretim Allen (1 965).

Sndy Br.i&d nuvial Systems becoming more common downstream to trough cross-bedding when In contrast to meandering rivers, sandy as the slope and coarseness of load preserved (Fig. 9). In shallower braided systems have received decrease. channels, and on bartops when they are relatively little study. The best known submerged at flood stage, the bedtorms rivers include the Durance and Ardbche b) Braided Channels and Sand now known as sandwaves are common (Doeglas. 1962), Brahmaputra Accumulalions. The channels tend to be (see Harms ef al,. 1975, p. 24.47-49). (Coleman. 1969). Plane (Smith. 1970). very variable in depth and width, and do Sandwavestend to be straight crested. Tana (Collinson. 1970) and South not conform to the simple pattern shown and have a very long wavelength (many Saskatchewan (Cant. 1975). The by meandering rivers. The channel floor metres) compared with their height (20- morphological elements of these rivers commonly has a lag deposit, and above 50 cm); they give rise to planar tabular (Fig. 9) are complex, and include (in the lag. sand is transported through the sets of cross bedding when preserved increasing scale) individual . System as bedload. Bedforms in the (Fig. 9 beneath letter 8). small "unit" bars, bar complexes (or deeper channels (5 m or deeper) tend to In contrast to meandering systems, sandflats),and mature vegetated be sinuous crested dunes that give rise point bars are very uncommon in islands. The river itself flows over and between these sand accumulations in a constantly branching and rejoining braided pattern. The finer material (sill and clay) tends to be transported through the system without accumulation: vertical accretion deposits are rarely preserved, and deposition in flood basins is not such an important process as it is in meandering systems. a) Braiding vs Meandering - Conlrols. The fundamental processes that control whether a river has a braided or meandering pattern are not completely understood, but we do know that bratding is favoured by rapid discharge Flgun 9 Ilood-stagesandwaves. Large sandllals may Block diagram showtng elemenls ofa brarded develop by growth born an emergent nucleus fluctuations, of a greater absolute river (based upon the Soulh SaskalchewanJ. on a major cross-channelbar (see Ftg. 10). magnitude than in meandering rivers. Stippled areas exposed, aM olher features The vertical lining-upwardsequence Braided rivers also tend to have higher underwater. Bar A is being driven lalerally resulting frompreservalron ollhis syslem Slopes. a coarser load, and more easily toward the lar and is forming aslough in would include if-channeldepools overlam erodable banks. In combination. these whrch mud is being deposded SandflalB is a bybar-lop' deposils. See Figure 2 and rexr features would suggest that braiding is complex area, wflh dissection features and lor deta~ls. more characteristic of the upstream reachesof a river, with meandering ,- (smith. 1970). Unit barscan be longitudinal (elongated parallel to flow) or transverse: in the South I; Saskatchewan transverse bars can extend across the entire width of channels and have been termed cross- channel bars by Cant (1975: Fig. 10 of th~sarticle). In the Platte. Tana and Brahmaputra, many of the transverse bars are lhnguoid (tongue) shaped, and there is a wide spectrum of intermediate shapes. The term diagonal bar has been given to those which have a foreset trending at an angle tothe main direction of fhe channel. The cross-channel bars shown in Figure 10 Figure 9 are forms of transverse bars. In Cruss channelbar wrlh s~veralnucleiilNl dtp m driection nlaiiowb Nucleus N.is m rls the South Saskatchewan, many cross- Soulh Saskalchewan R,near Ouliook. Sask, r,riliesl ,ind srmprcsl slalr an0 N lids grown channel bars have a "nuc1eus"that is flow lo iell Nucleus N, has the weli. wings downslream but has also aggraded emergent at low stages (Figs. 9, 10: developed "w!ngs"o, "horos'lhal have consrderably on the upslrearn slde Pnolo Cant. 1975). The nucleus grows by grown downslream. Foresel avalanche laces courtesy olDouglas J. Cant lengthening downstream as sand is swept around in two "horns" or "wings" (Fig. 101, and it also grows in the upstream direction as dunes and sand wavesare driven up from the channel floor. Asthe nucleus grows, possibly with other bars coalescing onto it, the original unit bar expands into a large sandflat (Cant. 1975: Fig. 1 1 ). The South Saskatchewan sandflats are complex. and their original shape has been obscured by dissection and redeposition dur~ngchangingriverstage (Flg. 9: sandflat B is theentireexposed area in the r~ghthand corner of the diagram). They are one to two km long in theSouth Saskatchewan, three km in the Tana (Collinson. 1970) and up to 10 km in the Brahmaputra (Coleman, 1969). In the South Saskatchewan, they remain constant for at least five to six years, and because of their size, they would seem Figure 11 the most likely parts of the braided Cuirlpound sandllar in Sourh Saskalchewan system to be preserved in the R a1 Outlook. Sash llow lo left.inforeground stratigraphic record. nucleus N has exlensive "wings"growing In the South Saskatchewan, one other downslream Upslrearn horn nucleus large type of bar is commonly developed. The Sandwaves canlust be seen lhrough the bar is elongated parallel to the channel waler As they are driven onlo the nucleus, 11 trend, but flow is diagonally across the wlllaggrade andgrow rn !he upslream bar, resulting in a foreset slope dipping direclron: Pholo courtesy of Douglas J. Can1 almost perpendicularly tothe channel trend (bar A, Fig. 9).They form in areasof flow expansion (not shown on Fig. 9). and commonly isolate a quiet slough between thebar and an adjacent bankor vegetated island. The slough is an area Geosc~enceCanada. Volume 3. Number 2. May. 1976 107

of mud deposition at low stage, or may The Brahmaputra spills into its flood 1976. Fig. 7). The bar-top' deposits be a passage for sandwaves at high basins every year, but the clays settling consisted mainly of small sets of planar- stage. from the flood waters are deposited tabular cross-bedding (D),and the thin From our understanding of the South slowly, with thicknessof two cm or less record of vertical accretion included Saskatchewan (Cant. Ph.D, thesis in per annum. However, vegetation is cross-laminated siltstones interbedded prep.), we propose a possible abundant in these flood basins, and with mudstones(F), and some enigmatic stratification sequence that mght deposits one to four m in thickness are low-angle cross-stratified characterize the preserved deposits of forming (Coleman. 1969. p. 232-3). (G). this type of river. Above the lag, trough These various sub-environments of the Upon developing this summary cross-bedding would represent the braided sandy system are sketched in sequence, our first reaction was to passage of sinuous-crested dunes in Figure 9, but there is certainly more compare it to theexisling fluvial the deeper channels (Fig. 9). Aiter complexity in the deposits than is (meandering) norm (Fig. 2). Although , the style ol deposition indicated in the diagram. both sequences showed channelled could change if a cross-channel bar bases, lollowed by fining-upward d) Ancienl Sandy Braided Fluvial were developed. It would first deposit a sequences, there appeared to be set of planar tabular cross-bedding. Deposits. Very few ancient sandy sufficient differences that the norm systems have been positively identified possibly at a high angle to wwld no1 act reliably as a basis for as braided (or low sinuosity) rivers. The the underlying dunes (Fig. 9), and interpretation (Walker, 1976). Inother best studies include those of Moody- overlying planar tabular sets could words, the meandering model seemed characterize smaller bedforms being Sluarl(1966; Devonian of Spitsbergen). inappropriate for the Battery Point Kelling (1968; Measures, South driven up onto the nucleus. These Sandstone. deposits can be termed "in-channel" Wales) and Cant and Walker (1976; Comparison with the norm Devonian of Quebec Appalachians). I (Figs. 2.9). to contrast them with the "bar nevertheless highlighted the major will briefly comment on the Cant and top" deposits (Figs. 2.9). Once differences, and this gave us added Walker (1976) study of the Battery Point essentially emergent, the bar suffers understanding of the Battery Point. Sandstones because I am familiar with it. modification during flood stage. Typical Similar comparisons of other systems In the field area near Gas*. Quebec. bar top bed forms include ripples, with the two sequences in Figure 2 we found a 110 m sequence that could sandwaves, and small sinuous-crested should also give added understanding. be divided into at least 10 generally dunes, giving rise to the features shown For example, the vertical-accretion fining-upward sequences. Within the as "bar top" in Figure 9. The bar top' deposits in the Battery Point are verythin section, we were also able to define (vvlth asterisk) implies that deposition compared with the meandering norm, eight distinct facies, characterized by and modification are not restricted tothe both in absolute terms, and in proportion their various scales and combination of exposed bar tops, but may alsotake tothe amount of in-channel sandstone. sedimentary structures. The sequence place in shallow dissection channels. The in-channel sandstones do not offacies was"distilled"(Walker. 1976) in The terminology of in-channel and bar contain parallel lamination, but planar- order to look for a general facies top' was first used for ancient rocks tabular sets of cross-bedding are (Cant and Walker. 1976: Flg 2 of this sequence that could act as a general common, and show high paleocurrent basis for interpretation. I did not discuss article): it is Important that the same divergences from the main channel the distillation process in my terms be used for anclent and recent trend. All of these points of comparison introduction to this series of articles on sediments where possible. aided in making our "braided" facies models (Walker, c) Vertical Accrel~onDeposits. In t976), but interpretation (Cant and Walker, 1976, interested readers should study the contrast to meandering streams, the p. 115-8). method described by Mia11 (1973), vertical accretion deposits of braided Harms el a/, (1975. p. 68-73) and Cant streams are less commonly deposited e) Sand Body Geomelry andflood-f'lain and only rarely preserved. At low stage. and Walker (1976. p. 11 1-114). The end Aggradation. One major point of contrast result of the Battery Pointdistillation was the river may only occupy one or two of with the meandering system is that the sequence shown here in Figure2. It the available channels on the flood plain braided rivers tend to have easily 1s no1 a model -it is only a summary of a (Fig. 80). It adjusts to flood stage by re- erodible banks, and noclay plugs. The local example that could, inthefuture, be using the empty or abandoned area occupied by the may re-distilled with local examples from channels, and only during major therefore be very wide, and coalescing other areas to produce a general facies does the rlver spill from its mainchannel bars and sandflats will result ina laterally model (Walker, 1976). In the Battery system onto the surrounding flood plain. continuous and extensive sand sheet, Polnt summary sequence, we identified In the South Saskatchewan between the unconfined by shales (Fig. 88).Vertical a channel-floor lag overlain by poorly Gardiner and Saskatoon, the flood accretion deposits (if formed) will tend to defined trough cross-bedding (Facies A, plain is very narrow and the braided be quickly eroded because of the Fig. 2). The in-channel deposits portlon is essentially confined between comparatively rapid lateral migration of consisted of well-defined trough cross- Ple~stocenebluffs. Consequently. the channels. Consequently, any shales bedding (0) and large sets of planar- narrow flood plain and the vegetated preserved in the section will tend to be tabular cross-bedding (C) that islands can relatively easily be patchy, laterally discontinuous, and commonly showed a large paleocurrent submerged and receive vertical relatively ineffective barriers to vertical divergence from the trough cross- accretion deoosits. hydrocarbon migration. This will not be bedding (Figs. 2.9: Cant and Walker. the case for meandering systems. Sandy fluvial Facies Models This paper is a basic source of Allen. J. R. L.. 1970. Studies in fluviatile The meandering model effectively does information on bed forms, stratification sedimentation: a comparison offining- all of the things a facies model should. It and flow regimes in rivers. Some of the upward cyclothems, with special is a well-established norm, and serves more recent ideas can also be found in reference to coarse-member as a guide for future observations. It has chapters 2.3 and 4 of Harms el a/., 1975 composition and interpretation: Jour. been used as a basis for hydrodynamic (below). Sediment. Petrol.. v. 40, p. 298-323. interpretation (Allen, 1970; Coner, 19711, McGowan. J. H, and L. E. Garner, 1970, Good technical discussion of the and has served many oil companies asa Physiographicfeatures and stratification internal structures of the coarse predictor in new situations. The braided types of coarse-grained point bars: member, and their hydrodynamic "model", in as much as one exists, does modern and ancient examples: interpretalmn. none of these things very well. Sedirnentdogy, v. 14. p. 77-1 11 Comparisons of new braided Bernard. H. A,, C. F. Major. Jr.. examples with the existing meandering This isone of the most recent integrated B. S. Parrott, and R. J. LeBlanc, Sr., 1970. norm will be instructive, but will not add descriptions of meandering systems. Recent Sediments of Southeast Texas: to the braided "norm". What is needed is and the comparison of ancient and Bur. Econ. Geol. Texas, Guidebook a well-established braided norm, so that modern sediments is particularly useful. No. 11 new examples can be placed within a Smith. N. D., 1970. The braided stream The first partoftheguidebookcontainsa spectrum of fluvial types. The : comparison very brief description but abundant establishment of this norm will require of the Platte River with some Silurian illustrations of the Brazos River. much more detailed field description. clastic rocks, north-central accompanied by careful analysis and Appalachians: Geol. Soc. Amer. Bull.. Cant. 0. J., 1975. Sandy braided stream distillation. v. 81, p. 2993-301 4. deposits in the South Saskatchewan River: Geol. Soc. Amer.. Abst. with Good description of downcurrent Programs. v. 7. no. 6. p. 731 Adcnowled~ment changes in bar type, on aregional scale. The descriptions of the South and comparison with ancient rocks. Abstract outlining morphological Saskatchewan river are based upon elements in the South Saskatchewan, an almost complete Ph.D. thesis by Cant. D. J. and R. G. Walker, 1976, and their relationships. Douglas Cant, at McMaster University. Development of a braided-fluvial facies model for the Devonian Battery Point Coleman, J. M.. 1969. Brahmaputra I am indebted to him lor use of this River: channel processes and material, and for supplying the air Sandstone, Ouebec: Can. Jour. Earih Sci.. v. 13, p. 102-1 19. sedimentation: Sedimentary Geol.. v. 3. photos. p. 129-239. Distillation of a local summary facies Basic References on Sandy Fluvlal sequence from an ancient sandstone. Excellent description of the Sedlmentatlon emphasizing facies descriptions. Brahmaputra system. The best, most Reineck, H. E. and l 0. Singh, 1973, analytical methods, and comparisons detailed (but longest) description of a Depositional Sedimentary with a meandering norm. bra~dedriver yet published. Environments: New York. Springer- Collinson, J. D.. 1970. Bedforms of the Verlag. 439 p. Other References Clted In Text Tana River. Norway: Geograf. Ann., The basic, up-to-date summary of all Allen, J. R. L.. 1964, Studies in fluviatile v. 52A. p. 31 -56. fluvial types of sedimentation can be sedimentation: six cyclothems from the Good description of bedlorms and their found in the section on Fluvial Lower Old Red Sandstone, Anglo-Welsh interaction with changing river stage. environment. p. 225.263 This is a good. Basin: , v. 3, p. 163-198. Cotter, E., 1971, Paleoflow well-illustrated review for readers Contrasts the features of six lining- characteristics of a late Cretaceous unfamiliar with fluvial sedimentation,and upward sequences, and interprets their river in from analysis of is recommended over Allen. 1965 origin in terms of river type, behaviour, sedimentary structures in the Ferron (below), which istoo longand a littleout- and sub-environment. An interesting Sandstone: Jour. Sediment. Petrol.. v. 41. of-date. and well illustrated detailed comparison. p. 129-138. Harms. J. C. and R. K. Fahnestock, 1965, Allen. J. R. L.. 1965. A review of theorigin An example of the typeof hydrodynamic Stratification, bed forms and flow and characteristics of Recent alluvial predictions that can be made lrom pnenomena (wltn an example lrom tne sediments: Sedimentology, v. 5. ancient fluvial sediments. R oGranoe), m G V M~ddleton.ed . p. 89-191. Primary sedimentary structures and Doeglas. D. J., 1962, The structure of their hydrodynamic interpretation: Soc. An excellent review, with abundant sedimentary deposits of braided rivers: Econ. Paleontol. Mineral.. Spec. Publ. 12, citations, of fluvial systems. Because of Sedimentology, v. 1 .p. 167-190. p. 84-1 15. its length, I recommend readers begin A pioneering paper on fluvial with Reineck and Singh (quoted above) Stratification in braided systems: before working through Allen. contains excellent descriptions and illustrationsthat are still useful. Geoscience Canada. Volume 3. Number 2. May. 1976

Harms, J. C.. D. 8. MacKenzie, and Canadan Examples Appalachian Ama D. G. McCubbin. 1963. Stratification in There is an astonishing absence in the Belt, E. S.. 1968, Carboniferous modern sands of the Red River. Canadian literature of detailed continental sedimentation, Atlantic Louisiana: Jour. Geol.. v. 71, p. 566-580. interpretations of ancient sandy fluvial Provinces. Canada, in G. DeV. Klein. ed., One of the first full descriptions of the depositional environments. A quick Late Paleozoic and Mesozoic review of the total contents of the internal structuresof point bars, and still continental sedimentation, northeastern one of the best. Canadian Journal of Earlh Sciences and Nwth America: Geol. Soc. Amer., Spec. Bullelin of Canadian Pelroleurn Geology Paper t 06. p. 127-1 76. Harms. J. C., J. B. Southard. gave no references at all. There are D. R. Spearing and R. G. Walker. 1975. obviously great thicknesses of terrestrial Discusses four facies - fanglomerate. Depositional environments as deposits in the clastic wedges of the fluvial, lacustrine and mixed interpreted from primary sedimentary Cordilleran. Arctic Island, and fluvial/lacustrine. Many formations structures and stratification sequences: Appalachian foldbelts, but if detailed discussed and citations given. Soc. Econ. Paleontol. Mineral..Short interpretations of the sandy fluvial Cant, D. J. and R. G. Walker. (see above). Course 2 (Dallas. 1975). 161 p. svstems exist. thev are in oovernment . ,~ -~ ~ Summary d modern ideas on bedforms reports. There are, of course, many MS received. February 27,1976 and stratificatiqin Chapters 2 and 3. examples described as fluvial, with \ Jackson. R. G., 11.. ~npress. Largescale some petrographic and paleocurrent ripples of the lower Wabash River: information. However, none containsthe Sedimentology. necessary data on sedimentary structures and their sequence, The paper emphasizes bedjorms, their integrated with paleoflow data in such a hydrodynamic conditions of stability. way that they contribute to sandy fluvial and the resulting stratification. facies models. Kelling, G., 1968, Patterns of sedimentation in Rhondda Beds of South Wales: Amer. Assoc. Petrol. Geol.. Bull.. v. 52, p. 2369-2386. Emphasizes fining-upward sequences and paleocurrent variations in late Pennsylvanian (Coal Measure) braided stream deposits. Miall. A. D., 1973. Markovchain analysis applied to an ancient alluvial plain succession: Sedimentology. v. 20, p. 347-364. Discussion of analytical methods of Special Paper 13, now available sequence analysis, applied to Devonian rocks in Arctic Canada. THE CRETACEOUS SYSTEM Moody-Stuart,M.. 1966, High and low IN THE WESTERN INTERIOR OF sinuosity stream deposits with examples from the Devonian of Spitsbergen:Jour. NORTH AMERICA Sediment. Petrol., v. 36, p. 11 02-1 11 7. edited by W.G.E. Caldwell. Description of rocks in Spitsbergen, with a general discussion of low and high sinuosity models. Sundborg, A. 1956. The river Klaralven: a study of : Geog. Ann.. v. 38. p. 127-316. Proceedings of an international colloquium held at the University of Walker. R. G., 1976. Facies models - 1 Saskatchewan, Saskatoon. Contains 27 papers by Canadian, American and General Introduction: Geosci. Can.. v. 3. European authors. P. 21 -24.

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