Kazimierz Krzemien

Pawel Zieliliski

Landform Analysis, Vol. 4: 65-73 (2003)

Moria Curie-Sklodowska UniversityDivision of Physical Geography and Palaeographyal. Krasnieka 2e, 20-718 Lubline-mail: pzicl@biotop.umcs.lublin.pl

nant direction have much lower velocities thanthose from the secondary direction - which are notnecessarily frequent but strong. Longitudinal dunesappear to originate most often from barchalJs, butthe possibility that thcy develop from parabolic ortransversal dunes cannot be excluded. The occur­rence of various obstructions, mainly vegetation,and small supply of eolian sand are also importantfor thcir development.

Complcx studies of eolian forms in the west­ern part of the Lublin Upland have revealed animportant structural differentiation of the distinc­tive longitudinal duncs and an attempt was madeto explain this phenomenon. The aim of this paperis to determinc the origin of longitudinal dunes,i.e. to show the dependence of dune· formingprocesses on cnvironmental conditions, and toclassify the longitudinal forms.

Key "'f}rd.~: longiludinal dunes, dale Ple;stocene. the lub\in Upland

Abstrtu-t: The development of longitudinal dunes depends on three overlapping factors: the strengtb anddireClion of winds, the amount of supplied sand. and the occurrence of vegetation which can fix therising forms. Il is assumed that 10ngilUdinal dunes in Polish territory were mainly formed from (he armsof parabolic dunes. as a resuh of the deflation of the central pans of these duncs. However, it is possiblelhat some longitudinal dunes in Poland could also have developed as primary fonos.The detailed studies of longitudinal dunes in the wcstern part of the lublin Upland have revealed animpOrtanl slruetural differenliation resulting from various development conditions of each particularform. Three models of developmenl of longitudinal dunes arc derived from these investigations:

t) They are formed by undireetiQnal winds deflaling the central parts of parabolic dunes, when sandsupply is small, and vegelalion fixes the rising forms.

2) They develop after a changc of wind dircctiOn by 90·, in consequcnce of transformation ofa single lransversal dune or a sct of parabolic dunes formed in fronl of or on an obstruction.

3) Thcy arc primary forms originating RI obslrucl;ons. when eolian malerial is transported by bi­direelional winds from a narrow (up to 90·) sector.

In many papers dealing with the formationconditions of inland dunes in Poland, the origin oflongitudinal duncs has never been the principalconcern. Thcy have mainly been considered to becreated by the deflation of the central parts ofparabolic dunes (Galon, 1958; Wojtanowicz,1969). 11 was also suggested that longitudinaldunes wcre primary foons which could developinto parabolic dunes (Dylikowa, 1969). Observa­tions of longitudinal dunes being formed at present(Hack. 1941; Bagnold, 1954; McKee & Tibbits,1964; Verstappen & Delft, 1968; Brookfield, 1970;Fryberger, 1979; Lancaster, 1980; Tsoar, 1983,1984) reveal that shifting, bi-directional windsfrom a sector of < 130" are the main factor stim­ulating thcir developmcnt; winds from the domi-

Introduction

The depositional conditions of longitudinal dunes basedon investigations in the western part

of the Lublin Upland, SE Poland

LA

structure and dynamics, Prace Geogr. InstytutGeografii UJ, 41-55.

Klimaszewski, M" 1972: Karpaty Wewn~trzne.

In: Geomorfologia Polski. T. 1: Polska Po­Iudniowo. Warszawa: 25-52.

Klimek, K., 1983: Erozja wglC(bna doplyw6wWisly na przedpolu Karpat. Ekologiezne pod­stawy zagospodarowania Wisly i jej dorzecza.T. 7: 97-108.

Klimek, K., 1987: Man's impact on fluvial pro­cesses in the Polish Western Carpathians.Geagr. Ann., 69-A, I: 221-226.

Mosley, M.P., 1987: The classification and cha­racterization of rivers. In: K. Richards (Ed.)River channels, environment and process. Inst.of Brit. Geogr., Special Pub!. Series, Blackwell,Oxford: 295-320.

Nawara, K., 1960: Sklad litologiczny :iwirowBiatki i Czarnego Dunajca, Acta Geol. Pol. 10,3, Warszawa: 455-474.

Osuch, 8., 1968: Problemy wynikajllce z nad­miernej eksploatacji kruszywa rzecznego naprzykladzie rzeki Wisloki, Zesz. Nauk. AGHw Krakowie Nr 219, z. 15: 283-301.

RllCzkowska, Z., 1983: Types of stream channelsin the Chocholowski drainage basin (The Po­lish Western Tatra Mts.), Studia Geomorph.Carparho-BaIc, 16, Krskow: 143-159.

Thome, C.R" 1998: Stream reconnaissance hand­book. Geomorphological investigation andanalysis of river channels, John Wiley & Sons,Chichester: 1-133.

Verbraak P., 1999: Re-naturalisation projects forthe River Meuse: New opportunities for naturewith an integrated water management approach.In: M. Kucharczyk (Ed). Problemy ochronyi renatllralizacji doli!l duzych rzek Ellropy. Lu­blin: 209-213.

Wasson, J.G" Bethcmom, J., Degorce, J.N.,Dupuis B. & Joliveau T., 1993: Approche eeo­systemique du bass in dc la Loire. Elementspour I'elaboration des orientations fondamen­tales de gestion. Lyon, Saint-Etienne: 1-102.

Wyzga, B., 1991: Prcsent-day downcutting of theRaba River channel (Western Carpathians,Poland) and its environmental effects. Catena18: 551-566.

References

Augustowski, 8., 1968: Spostrzezenia nad zmia­nami antropogenicznymi w korycie Ropyw Karpatach w okolicy Biecza. Zesz. Nauk.WSP w Gdansk" 10: 161-168.

Bobrowski, W. & Kociszewska-Musial, G., 1959:Analiza zwir6w Dunajca miff;dzy Tatrami a Pie­ninami na tie morfologii i geologii obszaruzlewni. Kwart. Geol. 3, 2: 391-414.

Chelmicki, W. & Krzemien, K., 1998: Naturalnekoryto rzeki Feshie w masywie Cairngorm Mts.i jego ochrona (Szkocja). In: Bliskie naturzeksztallOwanie nek i potok6w. IMGW, Politech­nika Krakowska, Konferencja aukowo-Tech­niczna, Zakopane: 239-240.

Chelmicki, W. & Krzemieit, K., 1999: Channeltypology for the River Feshie in the CairngormMts, Scotland. Proce Geogr., z. 104, InstytutGeografii UJ: 57-68.

Choeley, RJ. & Kennedy, BA, 1971: Physicalgeography. A systems approach. London, Pren­tice Hall: 1-370.

Dllbrowski, P., 1998: Renaturalizacja - CzarnyDunajec jako elemcnt ochrony bior6znorod­nosci regionu. In: Bliskie naturze ksztalto­wanie rzek i pOlokOw. IMGW, PolitechnikaKrakowska. Konferencja Naukowo-Techniczna,Zakopane: 225-234.

Kamykowska, M., Kaslowski, L. & Krz.emien,K., 1999: River channel mapping instruction.Key to the river bed description. In: K. Krze­mien (Ed.) River channels, pallern, structureand dynamics. Proce Geogr. z. 104, InstytutGcografii UJ: 9-25.

Kaszowski, L. & Krzemien, K., 1979: Channelsubsystems in the Polish Tatra Mts. StudiaGeom. Corp.-Bale. 8, Krak6w: 149-161.

Krzemien, K., 1981: Zmiennosc subsystemukorytowego Czarnego Dunajca. Prace Geogr.,z. 53, Instytut Geografii UJ: 123-137.

Krzemien, K., 1991: Dynamika wysokog6rskiegosystemu fluwialnego na przykladzie Tatr Za­chodnich. Rozpr. Hob. Nr 215. Krak:6w: 1-160.

Krzemien, K., 1999: Structure and dynamics ofthe bigb-mountain channel of the River Plimain the Ortler-Cevedale Massif (South Tirol).In: K. Krzcmieil (Ed.) River channels pattern,

64 , - Landronn . 65

d

300 m,

Explanations of tbe detailedgeologic promes

structures in eoliao sands

D massive

ru <!om,,,,,,, ,.)"",~(b)\:lJ 9"'JlSPOrt direction ofeohan Sands

(n - nwnbcr of measurements)

D tabular

S of sandflow cones

f~,,--I trough

[_-I hori7..ontal stratification~ trough infi-Ils .witht:::=:::I cross-laminatIOn

D wedge stratification

~ low.5lng1e; inclined~ stratIfication

inte{\ayers ofcoarse~ sand~ - massive

or With even cross-lamination

D till with pavement in the top

Iiiiirn podzolic soils

~ humus horizons of paleosols

9

,

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parabolic dune. The structural direction cornpo·nents of the growing complex dune indicate thenonh-westerly dune-fonning winds.

Then, a deflation processes produced a seconderosion surfaee on which the middle eolian serieslater accumulated. Low·angle cross·stratificationand cross·laminated infill of troughs indicate thatdeposition of the middle scries was caused bymigration of ripples along the crest of the earli·er-formed complex dune. Structural directioncomponents of the deposits filling the troughsgive evidence of the dominant WSW wind.

In the last (the modem) stage there was pro­gressive enlargement of the dune crest zone. The

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The depositional conditions of longitudinal dunes based...

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f·ig. 2. Glusko Duic I SilCA - Geo"'orpholul!l~al .k~t~b of the rc...,arch 5ile:I planaliun ~urfac..s ,n the tnl~rflu'·e 8rc-~. 2 ~ slope•. 3 dcnud~tlon pM.,menlS. 4 - dnu...kd mon"n,,;· platC.UA. 5 lCC'ls pl:lt~~u~.

6 - dry ..,."",on.d"nud.non ,alleys. 7 higher I~TTBCes. It - c-olian co,·ers. 9 ~ trough-like I>mall "llleyf. tQ _ dun~s: a - panobohc.b - IonglludJnal. C - tomplu: I1 d...nlllLun landfonns: • - remtlaRI$. t> - 00110"'5; 12 gullies. 11 GroIOII'C ~Iructure: I ~ Upper("retaccou~ basement. 2 1I11~. J _ f1u'";ogl,"".1 or elu.,.l ~nds and 1!:JlIvds. 4 ~ carbon-le lonscs. S - decalcified 1""015".6 loes. ddu\"I•• 7 - s,lty-undy co,"er-s. g cohan CO"Cl Silnds. 9 _ dunt Hnds. 10 - pealS. C St.1" of dUM ~...loplJI(nt:1 - dnecl10n of dunc.fOJTTlIng "",rnls. 2 d~f1all0n--dcposil,on proceSKI. 3 - tocal dlt'«ltOl:l or coltan IlUIt~n.l tnIn5pOl1-.. 4 - dl­r«l1OR or dune movement

tation is supported by an examination of thedeposits in the profile No 3 (Fig. 3B). Sands withthe trough structure typical of a distal slope areprescnt in its lower pan, and they are overlain bysands with the tabular structure typical of trans·pon of material across a slope. These beds wereprobably the front of a small dune sensu Hunter(1977), on which sand accumulated as a result ofthe drift associated with the approach of thesecond dune. The next bed, which is separatedfrom the earlier· formed structure by an erosionsurface, displays tabular structure and structuraldirection components which provide evidence ofthe encroachment of western ann of the second

elongated WNW-ESE and WSW·ENE are subor­dinate (Fig. I).

The structure of longitudinal dunes is de­scribed at the most typical sites: Glusko Duze I.Glusko Duze 11, Solec, Kolonia Elzbieta, GoryOpolskie, Zgoda.

Glusko Duze I. This W·SE-trending duneis situated on the denuded morainic plateau whichconsists of tills ovcrlain by discontinuous nu­vioglacial or c1uvial sands with gravels (Fig. 2).This form consists of onc sandy series which i~

structurally differentiated, i.e. sandflow conestructure occurs on the SW slope, and tabularstructure on the NE slope (Fig. 28).

Sands with sandflow cone structure are typ­ical of a distal slope in a dune frontal zone, wheresediment is mobilised only by gravity. However.sands with tabular structure are typical of a slopeon which material moves not only due to gravit)but also across the slope as a result of its expo­sure to wind (Borowka, 1979, 1980). It is as­sumed that such conditions can also occur on theanns of parabolic dunes or on the slopes of lon­gitudinal dunes (Stankowski, 1963). It is inferred.therefore, that the structural features of the depos­its are probably an effcct of thc migration of aparabolic dune from the Nord-West to the South­East, and the form described is essentially adeflation remnant which was probably formedfrom the eastern arm of tbis dune (Fig. 2e).

Glusko Duze n. This WSW·ENE dune IS

situated in the contact zone of the denudedmorainic plateau and the sandy higher river ler­race (Fig. 3). The dune is composed of threesandy series which arc separated by soils or ero­sion surfaces (Fig. 38): I) a lower series withhigh-anglc cross-stratification, with differentstructures according to its situation in the longi­tudinal section of the dune: sandflow cones.tTOugh or tabular structures; 2) a middle serieswith horizontal or low-angle cross-stratification:3) an uppcr scries, restricted only to the crest panof the dune, with horizontal stratification (in thedune top) or tabular structure (in the upper partsof dune slopes), and with sandflow cone structure(in the eastcrn part of the dune).

The lower sandy series, which accumulatedduring the first stagc of dune development, hasstructures typical of a distal slopc - sandflowcone structure and trough structure, and tabularstructure which is a typical of dune arms (Boraw­ka, 1979, 1980). These features suggest that thisdune originated during a migration of two para­bolic dunes when their arms joincd in the finalstage of their development (Fig. 3C). The west­ern dune probably fonned fi.rst. Such an interpre-

&1 sites presented

& sites studied~Ioesses

o eolian cover sands

1",,:.1 dunes

Geomorphological fealuresof longitudinal dunes

Longitudinal dunes in the western pan of theLublin Upland arc usually symmetrical ridges to500 111 long and up to 6 m high, which run eitherrectilinearly or irregularly and onen have peaksand saddles. They occur mostly as single formsor sets of ridges in the peripheries of dune areas,near the scarps of river terraces and loess patch­es, and in the border parts of interfluve planationsurfaces. They arc also found in the central pansof dune areas where they form two parallel orsub·parallel scts of ridges. The forms of W·SEand W·E orientations predominate, whereas those

Fi\;. J. Situation of the rescan:h sites in relation to distribu­tion of eolian deposits in tbe western part of the LublinUpland1- Glu5ko Oui~ J. 2 Gluslo Dutc 11. J - Solec. 4 KoJonia ElZbieta.5 Gory Opol.•ki~. 6 ~ Lgoda

Field work was conducted in sections perpen­dicular to the long axes of the studied forms. Theresearch methods comprised macroscopic analy­sis of grain size, registration of sedimentary struc­tures according to the classifications published byHunter (1977), Borowka (1979, 1980), Gozdzik(1998) and Izmailow (1998), and measurementsof structural direction components. On the basisof the data set an attempt is made to reconstructthe development stages of the panicular forms.

Pawel ZieJinski

66 '" 67

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Fig. 5. Kulonia Elzbieta SiteA - Geomorpholo~iul ikclCb ofthc rcsca"h S,,~. B - gcolog'e wucturc, C - stagu of dune dc\'dopmcnl. Olher expJ~n~liuns

as in fig. 2

on the denudation pediment whichconsists of tills in places. The structureof both dunes is similar (Fig. 58).They consist of one structurally differ­entiated series; the internal slopes ofthe dune complex arc composed of thesands with sandflow cone structure,and external slopes - of tabular sands.

These features and the structuralsymmetry of these fonns suggest thattheir origin was associated with thedevelopment of a single parabolic dune(Fig. 5C). Therefore, they provide ev·idence of the migration of the parabol­ic dune front in a SE direction, withconstant north-western dune· formingwinds, and they were probably fonnedfrom the anns of this dune. Such a sit­uation may occur when vegetationencroaches on the lower dune parts,i.e. its anns (Hack, 1941; Galon, 1958;Vcrstappen & Del ft, 1968: Wojtano­wicz, 1969).

Cory Opolskie. This WSW-ENEfonn is situated in the north·westernpart of the plateau, in the contact zonewith its slope (Fig. 6). It is directly

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sands with tabular structurc on the north-easternslope.

The structure of the windward part of the dune(sands with low-angle cross·stratification andtabular structure) is very similar to that of theparabolic dune arm (Rotnicki, 1970), while struc­tures in the lee part reflect the migration of theparabolic dune front in the SE direction (Fig. 4C).Thus, this form must be a remnant of the easternann of a dune which was originally a stationaryform as can be concluded from the low-anglecross-stratification in the proximal part of thedune (Stankowski, 1963; Rotnicki, 1970; Nowa­czyk, 1976).

Kolonia Elibieta. Two parallel dune ridgesare elongated NW-SE (Fig. 5). They are situated

o 300 m, ,

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structural features of the uppcr scries, i.e. hori­zontal lamination and even cross· lamination,indicate that its deposition resulted from themovement of ripples and megaripples (Hunter,1977; Pye & Tsoar, 1990; Goidzik, 1998), and itsdirection components provide evidence of WSWwind.

Solec. This NW-SE dune is situated on thedenudcd morainic plateau (Fig. 4). h consists ofonc, structurally differentiatcd series (Fig. 48).The windward part consists of sands with 10w­angle cross-stratification on the south·westernslope, and with tabular structure on the north­eastern slope. Within the leeward part, the high­angle, cross~stratified sands with sandflow conestructures occur on the south-western slope, and

68 69

Pawel Zielinski The depositional conditions of longitudinal dunes based...

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strong winds which remove the central parts ofparabolic dunes, especially when sand supplyis small, and vegetation fixes the rising fonns,i.e. in the manner proposed by Hack (1941),Galon (1958), Vcrstappcn & Dclft (1968), andWojtanowicz (1969). The common conversionof only one parabolic dune ann into a longitu­dinal dune may be explained by the deflationof the second arm after a change of wind di­rection.In the second model (Fig. 8, 11), the longitudi­nal dunes develop after a change of wind di­rection through 90°. They represent conversionsfrom a single parabolic or transversal dune, ora set of parabolic dunes earlier-formed usuallyagainst or on top of an obstruction. This mod­el is somewhat similar to that proposed byTsoar (1984) though there are significant dif­ferences: the change of wind direction occurs

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the possibility of its formationby transformation of a parabol­ic dune. Therefore, it is prob­able that this form was origi+nally formed as a longitudinaldune.

Discussion andconclusions

I. In respect of onglO,longitudinal dunes can be di­vided into primary formswhich developed initially aslongitudinal forms, and sec­ondary forms which representconversions from other dunetypes.

2. In respect of formationtime, longitudinal dunes can bedivided into simple typeswhich were formed during onephase, and complex oneswhich were fonned during re·petitive dune-forming phases.

3. The development of lon­gitudinal dunes is closely de­pendent on the co-operation ofthree factors (Hack, 1941).However, later studies indicatethat these forms can also orig­inate when sand supply is greatand, most importantly, thewinds are bi-directional with­in a narrow sector (Bagnold,1954; Brookfiled, 1970; Fry­berger, 1979; Lancaster, 1980; Tsoar, 1983,1984). To summarize, the formation of longitu.dinal dunes depends on:• the regime of dune-forming winds, i.e. their

velocity and direction changes;• relief and other features of land surface. i.e. the

presence of obstructions, wet ground, and theobstacles which influence wind direction, andthe direction of sediment deposition;the amount and availability of sand in alimen.tation areas or occurrence of non-longitudinaldunes which can be transformed into longitu+dinal types.

4. On the basis of the data presented in tbisstudy three development models of longitudinaldunes in the western pan of the Lublin Upland(Fig. 8) may be assumed:

In the first model (Fig. 8, I), the longitudinaldunes are formed by unidirectional, rather

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by the sandy-silty cover which occurs on the loessdeluvia. These deposits are transected by fossil,trough-like, small valleys. This dune consists oftwo series (Fig. 7B): a lower series with sandflowcone structure, and an upper with tabular struc­ture on the slopes and with cross·wedge stratifi­cation in the crest zone.

The lower series may reflect the movement ofa small parabolic dune (Fig. 7e). Its structuraldirection components suggest that the dune-form­ing west-north-westerlies were. The accumulationof this series could have left a row of deflationremnants which conditioned the development ofthe second series bearing the tabular structure onits slopes and cross-wedge stratification in thecrest zone, i.e. typical of longitudinal dunesoccurring in desert and semi-desert regions (Bag­nold, 1954; McKee & Tibitts, 1964; Tsoar, 1982).These features and the structural direction com­ponents suggest that this dune was formed bytwo-directional shifting winds blowing from theWSW- \V sector. The erosional contact betweenthe two series building this form seems to exclude

~.,,

Fill.. 6. Gory Opolskic SiteA - Geomo'l'bological .ketcb of the resurch ~itc. 8devdopmenl. Other explanations a. ;n Fill. 2

underlain by weathered Creta­ceous rocks which are covered bya thin series of sandy and sandy­silly rhythmites (Fig. 68). Thedune consists of two sand series,separated by an erosion surface;the lower series has a sandflowcone structure, and upper onc ­tabular structure.

The structure of the sandflowcones which occur in the lowerseries is typical of a distal slope,

""and gives evidence of a migratingdune front. Owing to the small

number of exposures, it is difficult l:'..1=::~~~~~~~~~~~!to find if this represents front of [J.a parabolic dune or of a transver- :sal onc. However, on the basis of :structural direction components, it :is concluded that these deposits : 0

o "\10-:were deposited in a SE direction. 'If it was a transversal dune, this Cdirection would evidence of NW "...--;,.---"a'--,~'--,dune-fonning winds. The detenni­nation oftbe wind dircction wouldbe more complicated if the lowerseries displayed a parabolic dunedevelopment. However, Kozarski(1962) considered that dip of bedsin tbe highest (frontal) part ofdistal slope of a parabolic dunefollows wind direction. Accord­ingly, if it is recognized that thestructures building the lower series (i.e. structuresof sandflow cones) occur only in the front part ofa parabolic dune (as was indirectly suggested byBor6wka, 1979, 1980), the orientation of thesestructures may also be indicative of a NW wind­flow during the construction of this series(Fig. 6C).

The tabular structure representing the young­er series was found on both slopes of the longi­tudinal dune. This seems to indicate a shift ofdune-forming winds from the NW to the WSW.The erosion surface which separates the twoseries provides evidence of deflation processeswhich preceded accumulation of the longitudinaldune. Therefore, as a result of a wind shift, thisdune was formed by the conversion of a transver­sal dune or a set of parabolic dunes. Of thesealternatives, the second is supported by themorphological features, i.e. the irregular patternof its crest, which resembles parts of parabolicdunes in some sections.

Zgoda. This WNW-ESE dune is situated onthe scarp of a loess patch (Fig. 7). It is underlain

70 71

Pawel Zielitiski The depositional conditions of longitudinal dunes based...

Humer, R.E., 1977: Basic types of stratificationin small eolian dunes. Sedimen101ugy 24, 3:366-387,

Izmailow, 8., 1998: Slruktury scdymentacyjnepiaskow wydmowych. In: E. Mycielska·Dow.giallo (Ed.) Struktury sedymemacyjne i post­sedymentacyjne w osadach ezwartorzttdowychi ich wartosc interpretaeyjna. UW. Warszawa:153-166,

Kozarski, S., 1962: Wydmy w Pradolinie Notecikoto Czamkowa. Hadal/ia Fizjograficzne nadPolskq Zachodniq, IX, Poznan: 37-60.

Lancaster, N., 1980: The fonnation of seif dunesfrom barchans - supporting evidence for Bag­nold's model fTom the Namib Desert. Zeitsehriftflir Geomorphologie N.F. 24,2: 160-167.

McKee, E.D. & Tibbits, G.c., 1964: Primarystructures of a scif dune and associated depos­its in Libya. J. Sedim. Petrol. 34: 5-17.

Nowaczyk, B., 1976: Geneza i rozwoj wydmsr6dl~dowych w zachodniej cz((sci pradolinywarszawsko-berlinskiej w swietle badan struk·tury, uziarnienia i stralygrafii budujqcych jeosad6w. Prace Komisji Geograficzno-Geolo­giezlle) 16: 108 pp.

Pye, K. & Tsoar, 1-1., 1990: Aeolian sands anddunes. The Academic division of Unwin Hy­man Ltd., London.

Rotnicki, K., 1970: GI6wne problemy wydmsr6dllldowych w Polsce w swictle badan wyd­my w Wl(glewicach. Prace Komisji Geograficz­no-Geologicznej 11, 2, PTPN: 146 pp.

Stankowski, W., 1963: Rzeiba eoliezna Polskip61nocno·zachodniej oa podstawie wybranychobszar6w. Prace Komisji Geograficzno-Geo­logicznej 6, I, PTPN: 146 pp.

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origin of longitudinal (seif) dunes. Zeitschriftfiir Geomorphologie 12, 2: 200-220.

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transportu i sedymentacji piask6w eolicznychoraz ich uwarunkowania i skutki na obszarzcwydm nadmorskich. Prace Komis)i Geograficz­'JO~Geologicznej 20: 126 pp.

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References

a) dunes of complex structure (Fig. 9, I) orig­inale through the addition of successive parabol­ic forms, when the wind direction is stable;

b) longitudinal dunes are primary fonns (Fig.9, 11), and material is deposited in the mannerdescribed by Bagnold (1954, p. 193). In that case,the direction of dune-fonning winds and the modeof sediment accumulation was controlled by landconfigurations.

However, these models have yet to be testedfully and further, more detailed investigations aredesirable.

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c;y :.:.'".' ..,'".' ".'", '"" ,.'

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5

by bi-directional winds from a narrow (up to90°) sector, i.e. in the aerodynamic conditionsdescribed by Bagnold (1954), Fryberger (1979),LancaSler (1980), Tsoar (1983. 1984).

5. Preliminary studies of some forms suggestthat two additional development models of lon­gitudinal dunes may be considered (Fig. 9):

-

t

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~ ~.. .

, "

~ ."; ~ <':'

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IT

1

only once, the longitudinal dune originates inthe place of a previous form, and a smaller vol·umc of sand is added on the lee flank, in thewindflow direction.

• In the third model (Fig. 8, 111), the longitudi­nal dunes are primary forms originating on ob­structions, when eolian material is transported

IJ

Fi~ 8 Developmenl modds of the longitudinal dunes based on the analysis of typical sites in the western pan of the Lublin UplandI' '''''lill! forms. 2 _ dom'DllIt d,,,""oll of dur>c-fonD,na ....W, 3 ~ IlIrfKU IlIbm;Ued .0 ddlatKm." d,reellon~ of Pond transport on dune,.

S _ arellS of Pond dc:posmon

I

."Ig. 9. Developmenl models of the longitudinal dunes based on the preliminary investigations. Other cltplanations as in Fig. K

7210 - Landfonn 73