Kevln A. Lindsey, NorthwestCollege and Universty Assocationfor Scence, c/o WestinghouseHanford Geoscience Group, N,4S|NH4'56, P.O. Box 1970, R chland, Washngton 99352 and Oavid R. Gaylord, Departmenlof Geology,Wash ngton State Un versity,Pullman Washington99164-2A12

Lithofaciesand Sedimentologyof the Miocene-PlioceneRingold Formation,Hanford Site, South-CentralWashington

Abstract "unconfined" The Miocene-PlioceneRinsold Formation is one ofthe principal stratigraphicunits vithin the suprabasah aquifer at fie Hanford Site in southcentralWashington. Consequently, undersunding the geologyof the Ringold Fomation is nec€ssary for th€ accuratecharacterization and nodeling of groundwaterflow and contaminanttransport st Hanford. The Ringold For- nation is a conplexly interstralified s€quenceof unconsolidatedto semiconsolidatedclay, silt, sand, and granule to cobble gravel. Evaluation of borehole g€oloeical and geophysicaldata and outcrops on and adjacent to the Hanford Site suggests that the most accuratem€$od for the study of Ringold sedinents is through the use of lithofacies.Six lilhofacies are defin€d using prinarily grain size data and borehol€ geophysicalresponses. These lirhofacies are: l) mud (M), 2) nud and snd (MS), 3) sand(SS), a) sand and granule to pebble gravel (SG),5) sranule to pebble gravet(C), and 6) cobble to boulder gravel (CB). Analysisoflithofacies distributions and associarionsreveal that: l) coarse-grainedlithofacies (CB, G, SG,SS) tend to be concen- trated along conplexly stacked,elongate fluvial chann€l tracts that displat a high degree of vertical interconnectedness,2) fine-$ained lirhofacies(M, MS) tend to occupyrelatively stable positions,and 3) individual lithofsciesidenrified ar ih€ Hanfo.d Site tend to be discontinuouseven over shon lateral distances.Based on the analysisof lithofaci€s distributions and associa, tions mo.€ accurareappraisals of the hydrogeolosy of the Hanford Site are possible.

Introduction Geologic Setting Thousandsof tons of radioactive and other haz- Suprabasaltterrigenous clastic sediments (Figure ardouswastes have been introduced into the late l), including the Ringold Formation,are present Cenozoicsediments on the Hanford Site, Wash- throughout much of the central Columbia Pla- ington,since the late 1940's(PNL, 1986,1987). teau in south-centralWashington (Grollier and The accumulationof thesewastes has necessi Bingham1971, l9?B; Myers et oL 1979;Tallman tated a long-termprogram of groundwatermon- et al. 1979,1981;Fecht et al. 1985).Regionally, itoring and geohydrologiccharacteization of the the Ringold Formation consistsof up to 280 m unconfinedaquifer to assessthe extent of pres- of interstratified unconsolidatedto cemented ent and potentialfuture groundwatercontamina- clay,silt, sand,and granuleto cobble-sizedgravel tion in this area.The Miocene-PlioceneRingold deposited in fluvial and lacustrine settings Formation is the principal stratigraphic unit (Newcomb 1958; Bjornstad 1985; Fecht et al within the suprabasalt "unconfined" aquifer; 1985;DOE 1988).Exposures of the Ringold For- thus,its stratigraphicand sedimentarycomplex- mation are limited because of an extensive ities are important to the characterizationof the Pleistocene-Holocenesedimentary cover and ero- groundwaterflow system,A fundamentalparam- sion by catastrophic, proglacial Pleistocene eter in stiatigraphic and sedimentarystudies are floods.However, informative outcrops exist; 1) on lithofacies(Miall 1977,l97B; Rust 1978). the White Bluffs north and east of the Colum- bia River,2) in ravinesand couleesbetween This paper presentsfindings from a study of and MosesLake, ,and primarily subsurfacelithofacies identified in the 3) near prominent anticlinal ridges including Ringold Formationon and immediatelyadjacent RattlesnakeMountain, the SaddleMountains, to the HanfordSite. The paperreevaluates the Gable Mountain, and the FrenchmanHills (Fig- five-tieredsubdivisions of the Ringold Formation ures 2 and 3). generallyused at the Hanford Site (Myers e, al The Ringold Formation at the Hanford Site 1979;DOE 1988),suggests alternative methods consists dominantly of sand and granule to for characterizing these strata, and presents cobble-sizedgravel with lesser,yet still signifi- sedimentologicalinterpretations, canl amountsof clay, silt, and sand (Nevcomb

Northrest Science,Vol. 64, No. 3, 1990 165 drill core, while Leopoldand Nickman(l98l) o determineda Mioceneage for the oldestRingold o Holocenesurficial strataon the basisof pollensamples collected nearthe baseof the RingoldFormation. Fecht dep06its et al. (I9BS)established a maximum age of 8.5 |! Ma for the Ringold Formationfrom K-Ar whole- q, - unconformity - rock dating of the underlying Miocene basalt (McKee er al. 197?) ard a minimum age of 3.4 o Hanfordformation a1 Ma on the basisof paleomagneticdata and ver- unconformity tebrate evidence. Early'' soil c, unconformity PreviousStudies .L All suprabasaltsediments (including strata now Plio-Pleistoceneunit assignedto the Ringold Formation)on the cen- tral ColumbiaPlateau and in the easternfoothills o) unconformity of the southernWashington Cascades were orig- t inally assignedto the Ellensburg Formation by Smith (1901). Smith's stratigraphy was later Ringold modifiedby Merriamand Buwalda(1917), who 'F assigned the fine-grained terrigenous clastic q, Formation sedimentsexposed on the White Bluffs and near F Pasco, Washington to a unit they called the unconformity RingoldFormation. Culver (193?) later mapped ColumbiaRiver the Ringold Formationacross the centralColum- (1917) BasaltGroup bia Plateau.Both Merriamand Buwalda and Culver (193?)restricted their definition of the Ringold Formation to strata exposedat the surface. Iigue 1. Generalized srratigraphy of the late Cenozoic sediments in the Pasco Basin, southcentral The concurrentestablishment of the Hanford Washington. Site and expansionof nearbyirrigated farmland in the early 1940's resulted in numerous test 1958; Newcombet al. 1972; Myerc et al- 1979; boreholesand production wells that revealeda Tallman et al. 1979,l98l; Bjornstad1984, 1985); sequenceof buied sedimentsoverlying the Co- it is greater than 50 m rhick at most localities lumbia River BasaltGroup. A significantpropor- and reachesa maximum thicknessof260 m near tion of thesestrata were found to be subsurface the centerof the HanfordSite. Exposures ofthe ertensionsof Ringold exposuresfound on the Ringold Formation along the White Bluffs (Fig- White Bluffs (Newcombl95B). As a result, the ure 3) consistof up to 125m of interbeddedclay, Ringold Formation wasredefined to include all silt, sand, and relatively minor granule to cob- sedimentarystrata in the PascoBasin that overlie ble gravel.These exposuresgenerally lie strati- the Basalt Group and that un- graphicallyabove those Ringold strata described derlie Pleistoceneglaciofluvial deposits (New- from the Hanford Site. comb 1958). Ringold Formationstrata originally were con- sideredto be Pleistocene-aged(Merriam and The Ringold Formation as defined at the Buwalda 1917. Newcomb 1958. Grollier and HanfordSite by Newcomb(1958) and Myersel Bingham1971, Newcomb et al. 1972).However, al. (1979\ is divided into the following five subsequentpaleontologic, paleomagnetic, and lithostratigraphicunits. Theseare the: l) gravel- palynologicstudies haye demonstrated a greater dominatedbasal unit. 2) interstratified to mixed age for the Ringold. Gustafson(1973, 1980) and clay,silt, sand,and local gravelof the lower unit 'blue Packerand Johnson (1979) suggesred a Miocene (including the prominent clays' of geologic to Plioceneage basedon paleomagneticand drill logs),3) quartzosegravel of the middle unit, paleontologicdata from Ringoldexposures and 4) interstratified to mixed clay, silt, and sandof

166 Lindseyand Gaylord Figur€ 2. Ceo$aphic selting o{ south-centralVashingron and location of rhe Hanford Site.

the upper unit, and 5) Iocally-derivedbasaltic and accompanyinggeophysical data (primarily gravel of the fanglomerate unit. Only the fan- natural gamma and neutron-neutronlogs) from glomerateunit, upper unit, and upper part of the 147 boreholesthat extendto basaltwere chosen middle unit crop out. Offsite the Ringold For- for study. The majority of the sedimentsamples mation ha6 been subdivided on the basis of availablefrom thoseholes are drill cuttings. In- lithofacies(Grollier and Bingharn1971, 1978). terpretativestratigraphic sections, that are con- Theselithofacies are not the sameas those de- structed from this joint geologic/geophysical finerl in thic.pnn.r database,forrn the basis for identification and descriptionoflithofacies and the constructionof Methods isolith, isopach, and lithofacies maps. Six lithofaciesare defined primarily on the basisof Discussionof the Ringold Formationin this grain size descriptionsfrom geologicdrill logs, paperis largelyrestricted to subsurfaceinvestiga- textural analyses,and to a very limited extent, tions at the Hanford Site (Figures2 and 3); our from boreholegeophysical logs, cores,and out- crops on the Hanford Site are uncommon and crops.These lithofacies are: l) mud (M),2)mud only occur along the flanks of a few anticlinal and sand(MS), 3) sand(SS), 4) sandand granule ridges.Borehole geologic logs, sediment samples, to pebblegravel (SG), 5) granulero pebblegravel

Lithofacies and Sedimentologyof the Ringold Formation 167 SADDLEMOUNTAINS

lOOD&DR

rooB&c0 Pe-sJQ

rd---l20ow-:-. I zxtE t----rIl \J YAIQUA SEPARATIONAREAS A PPRO X IMA TE POSITIONOF c Ross- sEcTto N ca""* ILLUSTFATED . Y4|(€}FIGURE 5. - 69S-6-24

FFTF

RICHLANO

0t23 KILOMETERS MILES o12 34 5

.. APPROXIMATELOCATION OF BOREHOLES CITEDIN TEXT OB ON FIGURES.

Fi$r"3. Lo.arionmap of the HanlordSit" modifi.d from Tallmanct ol.ll97q)'.

168 Lindseyand Gaylord (G), and 6) cobble to boulder gravel (CB). The lithofaciescode is looselybased on the set of codesintroduced by Miall (19?7,1978) and Rust (19?8)for studiesin fluvial sedimentology.How- ever,unlike the lithofaciesidentified by Miall and Rust, Ringold lithofacies are not further sub- divided on the basis of primary sedimentary gtructures.This reflects the small number of in- tact coresavailable for study and the lack of clear correlation between drill cuttings and either coredsamples or outcrops.This reliance on less than optimum subsurfacedata as well as the distancesbetween boreholes (usually many hun- dredsto thousandsof feet). limits but doesnot prohibit identification of the major depositional trends and large-scalearchitectural elements necessaryto reconstruct depositional setting (Miall 1985,I98?).

LithofaciesDescription and Interpretation LithofaciesM: Mud LithofaciesM (Figure 4) consistsof massiveto laminatedgray, brown, olive, and blue clay and silt. Bedsare a few centimetersto tens of meters thick and averageless than l0 m thick. Sandcom- prisesup to l0 percentof this lithofaciesand oc- curs as thin (( 30 cm thick) lenticular interbeds and as intermixed grains.Meters-thick paleosols are commonin core and surfaceexposures. Thin (< l0 cm),laterally extensive ash beds are pres- ent,but uncommon.Mud lithofaciestend to be 4. Thicl laminatedto rhin beddedin d analogousto discontinuousin the subsurface(Figure 5) and figur€ the type assignedto faciesM. GradationsonJacob commonlygrade down into muddy-sand(MS) and staff are 10 cn. sandy-gravel(SG) lithofacies; they are most com- monly overlain by gravel(G) and cobble-boulder LithofaclesMS: Mud and Sand (CB) lithofacies. LithofaciesMS (Figure 6) consistsof massiveto The fine grain size and generallygood sort- interlaminatedgray, brown, olive, and rarelyblue ing indicate that this facies resulted primarily clay and/orsilt, and sand.Bedding thicknesses from suspensiondeposition in standingor slow- rangefrom a ferrcentimeters to lessthan l0 m. moving waters, probably in an overbank and Sand contentsrange from l0 to 80 percenrand possiblyin a backvaterswamp or lacustrineset- average50 percent. Climbing rippled and nor- ting such as describedfor similar lithofaciesby mally graded fine-grainedsands in sets20 to 40 Miall (197?,I9?8). Abundant paleosols indicate cm thick and soft-sedimentdeformation is com- periodicsubaerial exposure. The laminated clay mon in the lithofacies along the White Bluffs. and silt of this lithofacieshave been interpreted Meters-thickpaleosols are common in core and as lacustrine(Bjornstad l9B5). Thin sandbeds surfaceexposures while thin ( < l0 cm) ash beds are consistentwith intermittent tractional trans- are lesscommon. However, as in lithofaciesM, port of ripplesand sheetsands (Miall 1977,l97B), paleosolsand ashesare difficult to identify in probably during flood stage. boreholecuttings. Deposits of lithofaciesMS

Lithofacies and Sedimentologyof the RingoldFormation 169 (hc.B E Mud! M dnd Msl flc.n,r. ".a pebure rro",*cr

6-26-r5c f] sandsltacies ss) E cobbresand bou rd€E (ra.ies cBl I Loc6no. or bor..o'. - sd-ds"noq'&er3 fr*J:,,-1:f"1:i"' li.j {hci6 scr LjlBd$'r Al contld. !r. hloii.d

Figur€ 5. G€olosic cros!'section 6ho insrhe marked lateral lithostratigraphic va ability ofthe Ringold Formation. See Figtrre 3 for location of cross-seclion.

rr- -rsfl '\' r;.,.l j "11r .R; '- if. .r S td,

Figur€ 6. Strata rypical ol those assignedto facies MS. Dashedline separatessand (above)from mud (below).Note rock han-

170 Lindseyand Gaylord tend to be discontinuous,generally grade down LithofaciesSS: Sand into sand(S) and sandy-gravel(SG) lithofacies, LithofaciesSS (Figure7) consistsof sandthat are gradationallyoverlain by lithofacies M, and is gray,olive, and lesscommonly, tan frequentlyare truncated and overlainby deposits and brown, fine to of the gravel (G) and cobble and boulder (CB) coarse-grained,moderately to poorly lithofacies. sorted,subangular to subrounded,and uncon- solidatedto weaklycemented. Up to 20 percent The mixed textural character of lithofacies of this lithofacies may be composedof mud, MS impliesrhat it resultedfrom episodicinput granules,and pebbles,most commonlyas len- of coarse-graineddetritus transportedinto stand- ticular interbeds. Sand lithofacies in core and ingor slowmoving walers by intermittenttrac- outcrop display massive bedding, plane to tion and possiblyflood currents in an overbank horizontal stratification, and planar and trough to lacustrineserting. Miall (1977,1978) and cross-stratificationin 5 cm to I m thick tabular Galloway(1981) ascribe an overbanksetting to sets. Total thicknessesof lithofacies SS are similar fluvially-derived strata. The relatively generally( l0 m. Depositsof the sandlithofacies high concentrationof sand in this lithofaciesas commonlygrade upwards into lithofaciesM, MS, comparedto that in lithofaciesM suggestsa more and SG, and grade downwardsinto lirhofacies proximal location to stream channeling. Pedo- SG,G, and CB. LithofaciesSS also sharplytrun- genesisis consislentwith a floodplaininterpre- cateslithofacies M and MS and is, in turn, trun- tation(Miall 1977,l97B). However, the presence catedby lithofaciesSG, G, and CB. Sanddetritus of soft-sedimentdeformation indicates oeriodic is composeddominantly of quartz,feldspar, and rapidaccumulation of sedimentin deliaicand mica grains,and with lesserganitic, basaltic,and lacustrine settinss. gneissiclithic fragments,

-:'....

:' : :{,j;r.|,ro

Figure 7. Cross'beddedsand analogousto the stata comp sing facies SS.

Lithofaciesand Sedimentologyof the RingoldFormation 171 The coarse-grainsizes, and primary sedimen- trough and planar cross-strata,clast imbrication, tary structuresare consistentwith migration and rneters-widechannel scours, and bar-shapedlen- aggradation of ripples, sand-waves,and plane ticular bodies.Deposirs of the sand and gravel beds(Miall 1977,l97B). The discontinuousnalure lithofaciescommonly are gradationallyoverlain of sand lithofacies suggesta channel-likechar- by lithofacies M and MS, are sharply to grada- acter for thesedeposits. Deposition of lithofacies tionally overlain by lithofacies SS, and grada- SSis inferred to havebeen confined to trunk and tionally overlie and are sharply truncated by tributary channels, probably during normal lithofacies G and CB. Gravels are composed stream flow and during the waning stages of dominantlyof quartzitic,basaltic. granitic. floodswhen these sediments were deposited atop gneissic,and porphyriric volcanic clasts;sands coarser-grained,gravel-dominated lithofacies, generally are quanzo-feldspathic.

LithofaciesSG: Sand and Gravel Depositsof the SGlithofacies are interpreted as mixed in-channel sediments.Deoosition of LithofaciesSG (Figure 8) consistsdominantly of cross-stralified,slratified. and imbri,"atedgravel- gravel that is light to dark gray, poorly sorted, dominatedand sand-dominatedlenses and beds unconsolidatedto poorly cemented,matrrx- anct reflectaggradation of transverseand longitudinal clast-Bupportedand granule- to pebble-sized. gravelbars and dunes(Miall 1977,1978). The in- Sandand mud makeup lessthan 50 percentof terstratificationof sandand gravel,as well as the lithofaciesSG and occursas matix and in lenses incorporationof sand as matrix and lensesis and bedsup to I rn thick. Limited outcropsof common to braid plain systemsthat expeience apparentlyanalogous SG strata (Figure 8) occur widely fluctuating currents (Rust and Koster, in I to 20 m thick beds that exhibit larse-scale 1984).Periodically strong stream curients are

Figure 8. Interbedded crudely stratified granule to pebble grsvel and cros.stratifi€d sand analogousto the srrata compri3ing faci€s SG. Nor€ roct hanner fo. scale. t72 Lindseyand Gaylord impliedby concentrationsof pebble-sizedgravel Depositsof lithofacies G are interpreted as within this lithofacies. in-channel sediments. Deposition of cross- stratified, stratified, and imbricated gravel- LithofaciesG: Granule to Pebble Gravel. dominatedbeds reflect aggradation of tiansverse and longitudinal gravel bars and in-channel LithofaciesG (Figure 9) consistsdominantly of dunes(Miall 1977, 1978;Rust 1978).The inter- clast-and mat x-supportedgranule and pebble stratification of sand and gravel as well as the gravelthat is light to dark gray, poorly sorted incorporationof sandand mud asmatrix material and unconsolidatedto poorly cemented.Sand, and lensesis commonto braid plain systemsthat mud, and cobble-sizedgravel comprise less than experiencewidely fluctuating cudents (Rust and 20 percentof the lithofacies.Sand and mud oc- Koster l9B4). However, the concentration of cur as both intermixed matrix and as (50 cm granulesand pebblesin this lithofaciesatresr to thick lenses;cobbles are present as floating either consistentlystronger currents,or a more grains. Limited outcrops of analogous strata limited and gravel-dominatedsource than is in- (Pigure9) display I to l0 m thick interyals that ferred for the SC lithofacies. exhibitlarge-scale trough and planar cross-strata, clast imbrication, meters-widechannel scours, LitholaciesCB: Cobble and Boulder and bar-shapedlenricular bodies. Upper and lower bounding surfaces of lithofacies G are LithofaciesCB (Figure 9) consistsof lensesand sharp to gradational. Gravelsare composedof beds of cobblesand boulders that are light to quartzitic, basaltic, granitic, gneissic,and por- dark gray, massiveto crudely stratified, matrix phyritic volcanic clasts; sands generally are to clast-supported,poorly sorted, and uncon- quartzo-feldspathic. solidatedto poorly cemented.The cobbleand

'.1 x &*

:, a, -.:*1, .td:'-

Figure 9. Crudely stratifi€d granule to p€bble gravel of th€ typ€ typical of strata conprising faciesC intersrratifiedwith cobbl€ and boulder gravel typical of facies CB. Gradationson Jacob staff are 10 cm.

Lithofacies and Sedimentologyof the Ringold Formation 173 bouldercontent exceeds 20 percent,Sand, mud, commonlydisplay fining and coarseningupwards and granuleto pebble-sizedgravel can comprise sequercesthat are lessthan 30 m thick (Figure up to 80 percent of the lithofacies and may oc- 9). The fining-upwardssequences identified in cur as both matrix and as less than I m thick our work are generally an order of magnitude interstratified lensesand beds. Strata assigned thinner and much lesscontiluous than those to lithofaciesCB form sequences0,5 to 5 m thick. describedby Websterand Crosby(1982). Lithofacies CB overlies sharply truncated sur- Mappingthe total thicknessof coarse-grained facesand is overlain gradationallyby lithofacies lithofaciesSS, SG, G, and CB in the Ringold For- SG and G and rarely by lithofacies M and MS. mation indicates that theselithofacies are con- Depositsof lithofaciesCB are interpreted as centratedin elongatetrends (Figure ll). These in-channeland outwashsediments deposited dur- coarse-grainedlithofacies trends probably reflect ing major floods. Matrix-supportedcobble- and rnultiple stackingof channeltracts that resulted boulder-dominatedlithofacies deposits commonly from one or all of the following factors: l) focus- reflect masstlansport and deposition as debris ing of stream flow betweenGable Mounrain in flow deposits(Bull 1972;Miall 1977,l9?8). Clast- the north and Yakima Ridge and Rattlesnake supported cobble and boulder gravel probably Mountain in the south, 2) lateral resrriction of reflect tractional transport during aggradation stream floiv by highly cohesivemud-dominated of longitudinalbars (Miall 1977, 1978; Rust overbankareas, and 3) structuralcontrols. A high 1978). degree of vertical interconnectednessof such coarse-grainedlithofacies is a commonresult of LithofaciesAssociations, Sedimentary suchchannel stacking (Bridge and Leeder 1979). Architecture,and Environmentsof The fine-grainedoverbank lithofacies associa- Deposition tion is composedof lithofaciesM, MS, and subor- dinateSS. Deposits of this associationcommon- The architectural anangement of lithofacies in ly occurin highly dissectedlocal sequences up Ringold Formation on the Hanford Site is the to 50 m thick (Figure 5) and as relatively thin a complexly interstratified sequenceof fluvial lensesand tongues,The fine-grainedcharacter depositscomposed of two principal lithofacies and pedogenic alteration of lithofacies vithin associations:coarse-grained channel deposits this association support an overbank and/or fine-grained overbank and/or backswamp- and backswamp-lacustrineinterpretation, lacustrine deposirs.These sediments were de- posited by both the ancestral Columbia and The concentrationof fine-grainedlirhofacies Salmon-ClearwaterRiver systemsas they crossed M and MS in relatively thick, bur localized se- rhe Pasco Basin (Fecht er al 1985). Fluvial quences(Figure 5) indicates that areasof fine- depositson the Hanford Site are stratigraphically grained overbank deposition were stable for complexand were subjectedlo numerousepi relatively long periods of time. Possiblecauses sodesof fluvial incision and pedogenesis.The in- for such persistent deposition include: l) re- tercalation and gradation between lithofacies striction of depositionalenvironments to struc- seenin cross-sectionsand stratigraphicsections tural lows and 2) the rapid accumulation of (Figures 5 and l0) are not easily reconciled by cohesiveoverbank muds. Thin lensesof litho- any existing lithofacies models (e.g., Rust and facies M and MS that intertongue with the Koster 1984,Walker and Cant 1984,Collinson coarser-grainedlithofacies are common locally 1986). and are interpreted to reflect areas influenced by channel processes. Depositsof the coarse-grainedchannel litho- faciesassociation are composedoflithofacies SS, Discussion SG, G, CB, and subordinateM and MS litho- facies, The abundanceof coarse-grainedlitho- Stratigraphictrends comrnon to the Ringold For- faciesand the relativescarcity of mud-dominated mation are not easilyintegaated into the general- lithofaciesin this associationsuggest that deposi- ly usedRingold stratigraphicmodel (Myers et al. tion occurredprimarily in a bedload-dominated 1979,DOE 1988)because of the high degreeof stream system (see Schumm 1976, Galloway lateral and vertical variability of the cornponent l98l). Depositsof this lithofaciesassociation Iithofacies of this unit. For example. where

174 Lindsey and Gaylord 299-W15-14(top 670 ft)

699-40-128(top 515 ft)

E E ,= {, I E iffi 6 :tiii"".$

r--r--r- i'"8

I--T--r--r =v,o9 N

Figure 10. Fining-upwardsfluvial sequencestypical of those seenthroughout th€ Ringold Formation. See Figure I2 for kel to slmbols. multiple mud-dominatedintervals are separated grade into and intertonguewith coarse-grained by thick, coarse-grainedlithofacies (Figure l2), strata containing numerous fine-grainedinter- it is difficult, if not impossible,to determinethe beds(Figure 5). In caseswhere fine-grained strata stratigraphic position of the lower mud- are absent(Figure l3), it often is not possibleto dominatedunit. This problemis compounded differentiatebetween the gravelsofthe basaland further where strata typically assignedto the middle units of the Ringold Formatior. mud-dominatedlower unir of Myers er aL (1979) Ir is generallyaccepted that syndepositional

Lithofacies and Sedimentologyof the Ringold Formation 175 Wahluke Wildlite Refuge

N Miles o2 d--*---i Kilometers . Locationol boreholesused in preparationof map. CountourInlerval is 10%

Figure ll. Map ilustrating the distributionofcoarse facies (SS, SG, G, and CB) in the Ringold Fornation southofCable Mo ntain. Contours indicate p€rc€nt of coarse facies. subsidenceof the Pasco Basin influenced the Bjornstad 1985;Fechr et al. 1985; DOE 1988). position of fluvial depositionalsystems during For example,strata generallythicken into struc- accumulationof the Ringold Formation(Tallman tural lowswhere subsidence and associatedsedi- et ol- 1979, l98l; Reidel and Fecht l98l; mentation are interDreted to have been more f76 Lindsey and Gaylord N ir.rB r-T--r-l

EXPI.AMNC{

! MSGCBGrainsize scale, indicat6 E dominantgrain size in interval. .g M- Clayand Sitt (Mud) S - Sand o G - Granulesand pebbles CB - Cobbl6 and Boulders Lithologic Symbols lEIl clav t = [ mud ll-ll silt I ll:,=l,"no ffi oranuleand pebbte ffi cobbteand boutder Other Symbols GE R Top of RingoldFormation _____-s.19861986 Water Tabte 7, )- Top of basalt

Commentsto right of section refer to color and petrology

Figure 12. Ceologicsection of borehole69-6-2A. This sectionshows a casewhere seyeralnud-doninated faciesare separated by thick graYelrystrara.

Lithofacies and Sedimentologyof the Ringold Formation t'77 l,oB

!t o E

Figxre 13. Ceologicsection of borehole 699'2-E14.This section d€nonstratesa casewhere mud-doninated siraia largely are abs€nt. See figure 12 for key to synbols. pronounced(Tallman et a/ 1979,l98l; Reidel tion. However,there are caseswhere coarse- and Fecht l98l). Stratigraphicreconsfuctions gained faciesthicken onto structuralhighs (Fig- completedas part of this work also indicate the ure 5) or sedimentationoccurred transversero importanceof structural controls on sedimenta- a structural feature.Where this occurssediment

178 Lindseyand Gaylord disribution alsowas controlled by the migration the Ringold Formation on the Hanford Site re- of depositionalenyironments wirhin rhe fluvial veals a complexly stacked sequenceof fluvial sysrem, depositscomposed of two principallithofacies associations:coarse-grained channel deposits and Conclusions fine-grainedoverbank and/or backswamp-lacus- trine deposits.Coarse-grained channel deposits Analysis of existing subsurface geologic and are concentratedalong relatively elongate tracts geophysicaldata reveals that the five{iered reflecting multiple-stacking of bedload-dominated RingoldFormation stratigraphy as currendy used strearn channel tracts. Overbank and/or back- at theHanford Site may lead to erroneousinter- swamp-lacustrinedeposits are concentratedin a pretationsof the distribution, architectural ar- few localizedareas that escapedextensive stream rangement.and ultimately,geohydrologic proper- channel incision for sedimentologicand struc- ties ofthe Ringold Formation. In particular, the tural reasons. markedlenticularity and variability of Ringold strata, the relative lack of continuous marker horizons,and the gradationaland ambiguousna- Acknowledgements ture of unit contactsall hinder strict application This researchwas supportedby a grant to the of the generally accepted Ringold formation NorthwestCollege and UniversityAssociation for lithostratigraphicmodel (Myers et al 1979,DOE Science(NORCUS) (University of Washington) 1988)to the Ringold Formation on the Site. An for K. A. Lindseyby WestinghouseHanford Com- alternate method for the characterization of panyiWHC). NORCUSoperates under Contract Ringold Formation strata has been suggested. DE-4M06-76-RL02225and WHC under Contract Six broad categoriesof lithofacies were de- DE-4C06-87RL10930with the U.S. Deoartmenr fined primarily on the basisof grain sizedescrip- of Energy.Additional support was provided to tions from geologicdrill logs, textural analyses, D. R. Gaylord by Battelle and to a limited extent,on boreholegeophysical Laboratoryunder ContractB-N9l9l-A-6 ryith the logs,cores, and outcrops, These are: 1) nud (M), U.S. Departmentof Energy.We wish to rhank 2)mud and sand(MS),3) sand (SS),4) sand and BruceBjornstad, Karl Fecht,Eileen Poeter, Mike granuleto pebblegravel (SG), 5) granule to peb- Hagood, Steve Reidel, Ann Tallman, Tyler ble gravel (C), and 6) cobble to boulder gravel Gilmore, George Last, and Wally Walters for (CB). These lithofacies aid in porrraying the their useful discussionsregarding Site geology variability of sedimentarypackages or elements, and lithofacies. Review of this manuscripr by interpretationof depositionaland erosionalsys- BruceBjornstad, Steve Reidel, Jim Consort,Mike tems, and evaluation of hydrologic properties. Hagood,Virginia Rohay,and Bob Petersonaid- The architectural arangement of lithofacies in ed greatly in its preparation.

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Lithofacies and Sedimentologyof the Ringold Formation 179 Grollier, M. J., and J. W. Bingham. l9?1. Geologicmap and Newcomb,R. C. 1958.Ringold Fomation of Pleistocen€age sectionsof parrsof Grant,Adams, and Franklin Coun- in the type of localiry,rhe Whire Bluffs, Washinglon. ties, Washinston. U.S. Geological Survey Aner. J. Sci. 25632a.340. Miscellaneo'.rsCeologic Investisariors S€ri€s Map Newcomb,R. C.,J. R. Strand,and F. J. Franl. I9?2. Geolog'7 1.589,6 sheets,l:62500. and $oundvater charact€nstics of the Hanford Reser- l9?8. Geologyof parts of Grants,Adarns, and vation of the Alomic En€rgy Comrnission, Franklin Counti€s, €ast-c€ntral Washington. Vashington. U.S. Geological Survey Professional Washingon DivisionofGeology and Earth R€sources Papet717.7A p. Bulletin71.91 p. PNL. 1986.Environmental nonitoring at Hanfo.d for 1986. Gustafson,E. P. 1973. The vert€brate fauna of the late Battelle, Pacific Northwest Laboratory Repon Pliocen€ RiDgold Forrnation, south.c€nt.al PNL6l20. Richland. Vashington. Universityof WashinFon, Seaule.Ph.D. -. 198?.Environnental moniloring at Hanfordfor Di€sertation.164 p. 198?.Batt€Ile, Pacific No.thwest Laboratory Report -. t985. Soricids(Mannalia, Iroectirora)from the PNL6l45. Richland. Bl.rfftop Local Fauna,Blancon Ringold Formation of Packei, D. R., and J. M. Johnson. 1979.A preliminary in- central Washington,and &€ corr€lation of Ringold v€stigationof th€ nagaetostratigraphyofthe Ringold Fornation faunas. J. V€rt. Paleont. 5:88.92. Fornation. Rockrel Hanford 0perations Report Leopold,E. B., and R. Nickmann.1981. A lareMioceDe pol€n RH0.BVI,C-46. 48 D. and spore flora from the Hanford Reservation, eutern Reidel, S. P., and K. R. F€cht. 198I. Vanapun and Saddle Washington. Golder Associares,Kirkland. 23 p. Mounrains Basaltsof the Cold Creek SynclineArea. McKee, E. H., D. A. Swanson,and T. L. V.ight. 1977.Dura- .Iz C. W. Myers and S. M. Price (eds.),Subsurface tion and volumeofColumbia Riv€r Basaltvolcanisn: Geologyof the Cold Creel Syncline.Rockwell Han- Washington, Oregon, and ldaho. Geol. Soc. Aner. ford Ope.arionsReporr RH0-BWI-ST-14. 45 p. (Abst.)9:4:4634&. Rust, B. R. l9?8. A classificationofalluyial chann€lsrsrens. Merriam, J. C., and J. P. Buwalda. 1917.Age of rhe strata 1n A. D. Miall (ed.),Fluvial S€dimentology.Can. Soc. referred to the f,llensburg formation in th€ White Pet. Geolo. M€mior 5. Pp. 187-198. Bluffs ofthe Colunbia River. Univ. Calit Bull. Geol. Rust, B. R., and f,. H. Koster. 1984.Coars€ a uvial deposits. Sci. I0:255-2f,6. /n R. C. walker (ed.),Facies Models, 2nd ed. ceo- Miall, A. D. 1977.A.evierv ofrhe braided river d€positional scienc€Canada Reprint Series l. Pp. 53-70. enrironmeot.Earrh Sci. Rev. l3:162. Schunn, S.A. 1976.The Fluvial Systen. Wiley.Int€.science, 1978. Lithofacies types and r€rrical profile New York. nodels in braided river deposirs:A sulnnary, /n A. Smnh, G. O. 1901.Ceolosy and rvaterresources of a porrior D. Miall (ed.),Fluvial Sedinenrology.Can. Soc. Pet. of Yakina County, Washington. U.S. Ceological Geolo. Memoir 5. Pp. 597-604. Survey Water-Supply Paper 55. 68 p. 1985. Architectural-elementanalysis: A new Tallnan, A. M., K. R. Fecht,M. C. Marratt, and C. V. Last. n€thod of faci€sanallsis applied to fluvial deposits. 1979.Geology of the SeparationsAr€as, Hanford Site, Earth Sci. Rev. 22:261-308. south-centralWashington. Rockwell Hanford 0pera. 1987. Recenr developmentsin the study of tionE R€po RH0-ST-23. 132 p. fluvial faciesrnodels,/n F. G. f,thridge, R. M. Flores, Talnan, A. M.,J. T. Lilie, and K. R. Fecht.1981. Supralaralt and M. D. Harvey (eds.),Recent Developmentsin Eedimentsofthe Cold Creek Synclin€Area.1r C. W. Fluvial SediBentologl. Societyof Econonic Paleon- Myers and S. M. Price (eds.),Subsurface Geology of tologists and Min€ralogist€ Sp€cial Publication 39. Pp. the Cold Creel Syncline.Rockwell Hanford Opera- I-9. tions Report RHO-BWI-ST.l4. 28 p. Myers, C. W., S. M. Price, J. A. Caggiano,M. P. Cochran, Walker, R. G., and D. J. Cant. 1984.Sandy fluvial systens. V. H. Cziner, N. J. Davidson,R. C. Edwards,K. R. 1z R. G. valker (ed.),Facies Models, 2nd ed. Geo- Fecht, G. E. Holnes, M. G. Jones,J. R. Kunk, R. D. science Canada,Reprint Series l. Pp. ?l-90. Landon, R. K. Ledgemood, J. T. Lillie, P. E. Long, Vebster, G. D., and J. W. Crosby. 1982. Stratisraphic in- T. H. Miichel, E. H. Price,S. P. Reidel,and Talnsn, vestigationof the SkagidHanfordNuclear Project.In A. M. 1979.Geolosic studi€s ofthe Colunbia Plateau: Skagit/Hanford Nuclear Project Pr€liminary Safety A slatusreporl. RockwellHanfo.d OperationsR€port AnalysisRepo . Pug€t SoundPower and Light Com- RH0-BWI-ST-4. pany. s:app€ndix 2R:35.

Receioed,29 July 1989 Acceptedfor publication 20 December l9B9

180 Lindsey and Gaylord