R O C Z N I K P O L S K I E G O T O W A R Z Y S T W A G E O L O G I C Z N E G O A N N A L E S D E L A S O C I f i T E G E O L O G I Q U E D E P O L O G N E
T o m (V o lu m e ) X X X I — 1961 Z e s z y t ( F a s c i c u le ) 1 K r a k ó w 1961
MARIAN KSIĄŻKIEWICZ
ON SOME SEDIMENTARY STRUCTURES OF THE CARPATHIAN FLYSCH
(PI. I — V and 2 Fig.)
A b s t r a c t : Oriented tubes of bathysiphons, crescent casts caused by pebbles, wood fragm ents o r sandstone fragm ents, lam inated flute casts, flow-casted flute casts and contem porary flute m arks are described.
INTRODUCTION
D uring last few years R a d o m s k i (1958), D ż u ł y ń s k i atnd Ś ł ą c z k a (1959), and B i r k e n m a j e r (1958) have described m any sedim entary stru ctu re s developed on th e surfaces "Of flysch sandstones.
T h eir observations greatly increased the know ledge of these stru ctu re s d u e to G i r o s s h e i m (1946), W a siso e v i c h (1951), K u e n e n (1957) and others. To th ese descriptions I wish to add a few observations p e rta in ing to some stru c tu re s of th e lower surfaces.
1. ORIENTATION OF BATHYSIPHONS
O riented organic rem n an ts have been noted from deposits of various type. Aligned graptolites w ere reported by R u e d e m a n n (1894), orien
tatio n of pelecypods in deposits of flysch type was noted b y K u e n e n and S a n d e r s (1956), and N a t l a n d (1957) observed aligned sm all foram inifera in deposits probably laid down by tu rb id ity currents.
C r o w e l l (1955) described plants debris aligned in th e c u rre n t direc
tion.
In th e C arpathian flysch, beside p lan t detritus, organic rem n an ts a re v ery scarse, and so far no observations indicating a n alignem ent of fossils h av e been made. T herefore it is w orth w hile to note, th a t in some cases aligned B athysiphon tubes m ay be observed. B a th y sip h o n s1 a re not in freq u en t in C arpathian sedim ents; th e y quite often occur on th e soles of sandstones. U sually th ey are stuck to the sole in an unoriented m anner,
1 Very much the same flattened tubes, w ith a longitudinal furrow, have been described under the name of Jereminella from deposits of Senonian age and regarded to be tubes of worms.
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although it seems, th a t as th ey a re as a ru le fragm ented, th ey m ust have been detached from th e bottom on w hich they lived, and redeposited.
The oriented bathysiphons occur near Tabaszowa, on th e w estern side of th e Rożnow lake, in th in sandstones form ing intercalations in the d ark shales covering th e Low er Istebna sandstones. From th e sam e area, only from th e other side of th e lake, bathysiphons w ere reported by B i e d a (1949) from th e Low er Eocene Ciężkowice sandstone.
In th is series th e soles of the thin-bedded sandstones are often covered w ith small, on th e w hole poorly developed organic hieroglyphs, belong
ing to Spiroraphe and. „Helminthoida” appendiculata H e e r . If th e sandstones a re ripple-current-bedded, tubes of B athysiphon are lying disorderly on the sole. If th ere is graded bedding, as a ru le n o t conspi
cuous in these beds, because of th e uniform grain size (the top is, how ever, alw ays lam inated), th e fragm ents of tubes are aligned (PI. I, fig. 1).
Bathysiphon has one end of th e tube pointed (cf. B i e d a 1949, A v n i - m e l e c h 1952). If th e tubes of B athysiphon are aligned, th e ir pointed ends are directed in one direction. Most of th e fragm ents a re stuck to tiny, irreg u la r ridges: th ese are elongated, parallel to each other, feebly linguoid, and can be regarded as sm all im perfect flu te'casts, filling little furrow s eroded by th e sam e cu rren t which carried th e fragm ented tubes.
These w ere trapped in th e furrow s, a t th e same tim e u n d er th e influence of th e cu rren t tu rn in g th e ir pointed ends dow neurrónt. An a ltern ativ e possibility is th a t th e furrow s w ere form ed on th e lee-side of th e obstacle form ed by th e tubes if th e y stuck in th e m uddy bottom before the c u r
re n t arrived, o r th ey w ere driven into th e soft m ud by the c u rren t, t h u s . becoming a n obstacle for it. The c u rre n t flowing around th e obstacle, concentrated on its lee-side and eroded below m ore strongly. In th is case th e tin y ridges would be th e filling of „cu rren t m ark s” of T w e n- h o f e 1 (1932, p. 667, fig. 89) which are form ed on th e sea-shore below sm all obstacles. In th e discussed case the tu b e fragm ents form ed th e obstacle; subsequently the tubes w ere overturned and trapped in the furrow s. In both altern ativ es the pointed ends indicate cu rren t direc
tion. In th e sam e w ay according to D a p p l e s and R o m i n g e r (1945) are aligned qu artz grains, as in this position th e resistance to flow is th e smallest.
The length of th e oriented tu b es is up to 4 cm. If th e tubes are longer, th e ir arrangem ent is chaotic. Probably long tubes w ere not far transported, w hilst broken tubes w ere transported fa rth e r away and aligned.
In several instances, particu larly in th e Inoceram ian beds, th e b a th y siphons occur on th e low er surfaces exhibiting w ell developed flu te casts. In th is instance th e tubes are n o t placed on casts b u t accum ulated betw een them ; th e y are n o t aligned, often lying at rig h t angle to th e casts. It m ay be thought th a t if th e cu rren t w as strong enough to erode norm al furrow s, th e vortex eroding furrow s th rew aw ay th e tubes and deposited them in m ore quiet places betw een the furrow s.
In some cases w hen a lineation on th e low er surface is ‘m arked by delicate lines, one m ay observe th a t sm aller fragm ents of bathysiphons are parallel to th e lineation, w hile larg er fragm ents a re lying obliquely.
Som etim es small, elongated ridges m ay be observed in th e prolonga
tion of th e tubes. Possibly th e y a re form ed by dragging or by im pact of th e tubes w ith th e sea-floor.
2. CRESCENT CASTS
Fossil structures corresponding w ith recent erosional furrow s cut around some obstacles on the shore w ere first described by F i e g e (1937, Pl. VIII, fig. 3, 1942, p. 308, fig. 15). L ater they were found in de
posits of various type. D z u l y n s k i and S l ^ c z k a (1959), and R a - d o m s k i (1958) found sm all crescentic hieroglyphs in the C arpathian flysch caused by sm all chips of shales. In a num ber of instances I found fairly large crescent casts provoked by fragm ents of wood, quartz pebbles and sandstone lumps.
Pl. II, fig. 2 rep resen ts a crescentic hieroglyph on the lower surface of a sandstone, (14 cm. thick, from th e Podhale flysch). The cast is asym m etrical, one side being b e tte r developed th a n the other, a feature also freq u en t in th e shore cu rren t m arks. The cast has the form of a bent sem i-cylindrical ridge. Sim ilarly as at m any flu te casts, the m ain cast is accompanied by a sm all collateral cast. The length of the cast is 13 cm, its w idth 8 cm, in its c e n te r th e re is a piece of carbonized wood 8 cm.
long and 3 cm. wide. The direction pointed o u t by th e cast, n early exactly eastw ard, corresponds w ith th e directions of flu te casts and cu rren t bed
ding as found by R a d o m s k i (1958) in th e area.
Pl. I. fig. 2 represents crescent m arks form ed around q u artz pebbles.
The arm s of th e casts tend to join each o th e r on the lee-side. It seems th a t in coarser types of the C arpathian flysch the crescent casts around pebbles are as much freq u en t as th e crescent casts caused by shale fragm ents in fine-grained beds. Usually, however, th e pebble falls out and the crescent cast rem ains w ith no obvious cause.
On P la te II, fig. 1 an exceptionally large crescent cast is shown. It occurs on the sole of a flaggy sandstone belonging to the complex of th e M agura sandstone. Its w idth a t the base is 8 cm, the length 25 cm, both arm s are w ell developed and n early of th e same size. They do not unite w ith each o th er and gradually die out. A sm all flute cast appears among them . On the arm s of the cast th ere are sm all ridges screwed tow ard th e center; to be sure, th ey w ere form ed by th e filling of sm all secondary furrow s eroded by horizontally moving vortices, created in th e cu rren t w hen it was flowing around th e obstacle. A formless lum p of a sandstone,
8 cm. long was th e obstacle. The sandstone is yellowish, micaceous, d iffer
ent from th e sandstone on the sole of which it occurs, and also from o th er sandstones of th e M agura complex. On th e whole, rew orked sandsto
nes a re rare in th e C arpathian flysch, and redeposited pebbles (i. e. peibibles of th e sandstones of nearly th e same o r the same age as the beds in which th e y occur) so far have n o t been described, although redeposited fragm ents of shales are q u ite num erous. In all probability tu rb id ity cu rren ts moving along the clayey bottom , rem ove th e soft clay, and w hen th e y reach m ore hardened clay resp. shale, erode it. Occasionally th e y m ay, on rem oving th e shale, reach deeper and erode the sandy layer, m ore or less conso
lidated.
3. LAMINATED FLUTE CASTS
T e n H a i a f (1959) under the nam e „terraced flu te casts” described flu te casts the surface of which is covered w ith sm all parallel steps. The
se steps are a reflection of th e differences in hardness of th e underlying lam inated bed. Sim ilar stru ctu res a re also m entioned b y K u e n e n (1957).
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The hieroglyphs of this tyipe occur in the C arpathian flysch ap p aren tly very infrequently, probably because th e flu te casts are usually cu t into non-lam inated shales. T he m ost distinct terraced flute casts w ere observed by th e p resent w rite r in th e A lbian flysch (internal flysch) in the valley of th e Jalom itioara in the R oum anian C arpathians d uring an excursion in th e com pany of D r D. P a t r u l i u s and L . R. C o n t e s c u .
On th e o th e r hand, a t Kamesznica (Żywiec area) in th e m ain q u arry th ere w ere exposed th e casts, resem bling th e terraced casts, b u t probably of a d iffe re n t origin. T hey occur on th e lower surface of a m edium -bedded sandstone, belonging to th e Krosno beds of the P re-M agura scale.
These a re large casts (PI. Ill, fig. 1). corresponding in shape w ith th e hieroglyphs of th e neighbouring beds. They are cut into a m udstone w ith very indistinct, if any, lam ination. The sandstone, on th e o th e r hand, is la
m inated th ro u g h o u t its whole thickness. Lam ination inside th e cast is h ard ly visible, w hilst on the1 surface is w ell m arked, in th e same w ay as in th e sandstone, in which it is visible on w eathering. T herefore iit m ay be surm ised th a t th e lam ination of the casts is in tern al, and th a t it is not a reflection of th e lam ination of th e underlying layer, as th e case is w ith th e terraced flu te casts.
Lam ination, according to all w riters, is form ed at sm all velocities. In flysch sandstones it is very often visible in th e topm ost p a rt of th e bed.
There a re cases, how ever, th a t th e whole bed is lam inated. This usually pertains to beds of sm all thickness:, such beds usually have no flute casts which w ere form ed w hen the cu rren t was relativ ely fast, and had a cor
responding turbulence, although according to L a m o n t (1957) turbulence m ay be active a t low velocities. In th e discussed case, th e large furrow s m ust have been eroded in th e early stage of th e current, and probably w ere filled w ith lam inated sand some tim e after. T here a re know n th e cases th a t casts a re filled w ith current-bedded sand ( K u e n e n 1953, fig. 11, p. 25), and K u e n e n and P r e n t i c e (1957) note th a t a h o ri
zontal lam ination m ay occur in flu te casts. In the described case it is not possible to say w hether th e filling took place from the same cu rren t th a t eroded th e furrow s, or th e fu rro w s w ere filled by another cu rren t flowing along th e furrow ed bottom a t a later date.
4. FLUTE CASTS DEFORMED BY SUBSIDENCE
F lu te casts, sim ilarly as o th er stru ctu res of lower surfaces, are in the C arpathian flysch usually not deform ed. In some instances they exhibit deform ations posterior to th e tim e of th e ir form ation. D ż u ł y ń s k i and R a d o m s k i (1955) called a tte n tio n to the possibility th a t sole casts m ay undergo compaction, and K e l l i n g and W a l t o n (1957) noted th a t sole stru ctu re s m ay be load-casted.
A peculiar case of flute casts deform ation m ay be observed a t Struga (near Tęgoborze, Nowy Sącz area) on th e w estern side of the Rożnów lake.
H ere fairly thick sandstone beds, occurring sparingly in a shaly series, show well developed flute casts. T he sole of one bed (which is overturned) is covered w ith flu te casts of various dim ensions (PL III, fig. 2). The sm al
ler and lower flu te casts are norm ally developed, on the contrary th e large casts have irre g u la r shapes and are truncated to one fla t common surface, 3 to 4 cm. above th e sole of th e bed. The truncated surface is g ran u lar and
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rough, w hile th e surface of th e sole and of th e not tru n cated casts, as w ell as th e surface of th e no t tru n cated p arts of larger hieroglyphs is smooth.
The tru n cated caists a re enlarged a t a distance from th e ir h ead s as if th e y w ere swollen sidewards. The sides below th e tru n c a te d surface a re b e n t outw ard, and at places at th e edge of th e truncating surface th e re a re sm all overhangs and inclined ridges.
I t follows from this description th a t all th e casts th a t reached a cer
ta in depth, w ere truncated. This m ay be explained as follows:
T he sandy bed was laid dow n on a soft clay; th e deeper p a rt of the clay was already hardened. A fter a certain time, b u t before th e com plete con
solidation, th e sandy bed subsided as a whole owing to th e com paction of th e underlying soft clay. D uring th e subsidence the sole of th e sandstone reached th e hard layer of clay. This layer wa-s so consolidated th a t it did n o t yield and bend under th e load of th e sandy bed, b u t conversely, th e larg er and deeper casts of th e sole adapted th e ir surfaces to th e surface of h ard clay. U nder th e load of th e sandy bed these casts spread laterally and became enlarged sidewards, because the surplus of th e ir mass in th e confined space could only laterally be accomodated, in th e direction w he
re th e clay was not yet en tirely consolidated (Fig. 1).
As a m a tte r of fact th e re exist same featu res indicating th a t below a certain d ep th clays w ere consolidated. T e n H a a f (1959) noted th a t load casts reach a certain lim iting height, and explained this by th e as
sum ption th a t the deposited sand was sagged only to th e d ep th a t which it reached th e hardened clay.
The described ty p e of deform ation is probably lim ited to thick-bedded sandstones as in the deiscribed case, and is probably ra th e r rare. In th e li
te ra tu re I have not found sim ilar cases. Possibly th e „hieroglyphs” of W i a l o w (1955, fig. 3) from th e Lower Paleozoic flysch of Turkestan, w ith flat surfaces, are th e casts of ripple-m arks on th e low er surface,, flattened by a wholesale subsidence of th e bed, lim ited by the u n d er
lying hard clays.
5. FLOW-CASTED FLUTE CASTS
Describing th e stru ctu re s of th e lower surfaces of th e C arpathian sand
stones I underlined th a t some bum ps of th e sole show a m arked asym m etry and are b en t in one direction (1954, p. 420, 446)]. T herefore I thought, th a t F u c h s ’ explanation of some hieroglyphs as form ed by th e flowing of freshly deposited isand could be rig h t. Sim ilar views w ere held by Soviet w orkers ( W a s s o e v i c h 1951) at th a t tim e, w hilst in th e A nglo-saxon litera tu re a g re a te r role was ascribed to vertical m ovem ents d u e to yielding of hydroplastic clay below th e burden of sand. Soon, however, P r e n t i- c e (1956) delim ited th e stru ctu res caused by a la teral flow from th e stru c tu re s formed by load-casting, a distinction already know n in th e C arpath
ian flysch.
Flow -casts m ay be form ed in th e m om ent of sand deposition, o r a t a slightly later time. In th e first case th e m echanism of tran sp o rt and deposition muist have been d ifferen t ( P r e n t i c e 1956) th a n in th e
1 In the same paper (p. 418) the presence of flow hieroglyphs on the upper sur
face was noted. Such structures w ere described from the Alpine flysch by K r a u s . (1935).
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instance when th e c u rre n t eroded and form ed flute-m arks. This is the reason w hy flu te casts and flow -casts do not occur usually tog eth er on one and th e same sole. This also probably is th e reason w hy flow-casts occur m uch m ore fre q u en tly in v ery thick beds, and flu te casts are m ore num erous in m edium - and thin-bedded (although not v ery thin-bedded) sandstones.
F lu te casts or groove casts deform ed by a lateral flow of sedim ent seem to be much less freq u en t th a n flow-castls 1. The flow m ust have been subsequent to th e deposition and form ation of casts, b u t certainly before the consolidation of th e deposit. A few observations on deform ed cu rren t stru ctu re s are given below.
PI. IV, fig. 1 presents a groove cast deform ed by a lateral m ovem ent.
A strong unilateral overhang (Fig. 2) points out th a t the deform ation is not caused only by compaction. Ju st above th e deform ed p a rt th e bed is not in tern ally contorted; th is clearly indicates th a t the deform ation was not caused by a slum p m ovem ent of the whole bed. The flow m ovem ent was then lim ited to the sole, and to all appearance the groove cast itself was not translocated b u t th e underlying clay dragged by th e horizontal mo
vem ent of th e adjoining p a rt of th e sole was horizontally pushed into th e sand above th e cast.
Sm all im pact casts ( R a d o m s k i 1958, D z u i y n s k i and S 1 3 c z- k a 1959) are associated w ith the groove cast and indicate th e cu rren t direction. The flow deform ation is nearly a t rig h t angle to th e direction of th e current.
PI. IV, fig. 2 shows a much larger flow cast on th e lower surface of th e M agura sandstone. H ere th e deform ation is also lim ited to th e lowest p art of th e bed; upw ard no traces of flow o r slum p stru c tu re can be detec
ted w ithin th e sandstone. H ere th e cu rren t hieroglyphs are deform ed by flow or creep w hich form ed flow casts in th e form of o v ertu rn ed folds w ith axes p arallel to th e direction of the c u rre n t hieroglyphs. In this ca'se an influence of the cu rren t drag m ust be excluded, and it should be p resu med th a t th e slope induced the flow ( P r e n t i c e 1956). The flow is again nearly at rig h t angle to the cu rren t direction.
In th e year 1956 during the Conference on S edim entation of the Geo
logical Society of Poland, afte r the lecture of B u k o w y (1957, p. 153) I called atten tio n to th e fact th a t from th e facts presented by th a t author th e inference should be draw n th a t th e direction of flow (in th e m eaning now used a fte r P r e n t i c e ) and the direction of cu rren t hieroglyphes (flutes) m ay differ, aind th a t in th e M agura beds I observed in some cases in th e sam e bed th e direction of flow a t rig h t angle to th e cu rren t direction.
Sim ilar featu res w ere in great d etail described by B i r k e n m a j e r (1958) who found in th e series exam ined by him th a t th e direction of flu te casts differs from th e orientation of flow casts. B irkenm ajer concluded th a t th e cu rren ts could become independent from th e slope under influ
ence of various factaris. It should be noted in this respect th a t G r o s s - 1 To this cathegory belong according to B i r k e n m a j e r (1959, p. 60) „deltoidal”
hieroglyphs. He regards them as groove casts converted by a lateral flow into „flow- -load casts”. Previously (1958, p. 125—126) he regarded them as a variety of flow casts, influenced by the presence of a erosional furrow. The present w riter regards these hieroglyphs as a variety of flute casts (feather-like type, 1958, PI. IV, fig. 1).
T e n H a a f (1959) regards these structures, called „frondescent m arks” by him, also as a variety of flute casts.
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h e i m and K o r o t k o v a (1954, also G r o s s h e i m 1959) found in th e Caucasus flysch th a t in individual beds the cu rren t direction m arked by flu te casts, had at first been parallel to th e basin axis, b u t in th e upper p a rt of th e bed the cu rren t directions m arked by cu rren t bedding are variable and less m arkedly longitudinal. The Caucasian authors believe th a t th e cu rre n t had been strong at first, b u t subsequently it changed intensity and direction. T e n H a a f (1959) also gave an exam ple of direc
tional differences at the base (flute casts) and in th e top (ripple-m arks) of a bed. Sim ilar facts w ere reported by P r e n t i c e (1960). This w riter thinks th a t erosional stru ctu re s such as flu te m arks, drag m arks etc. are form ed when th e cu rren t has the g reatest velocity and flow s in the direc
tion im parted to it in th e initial phase, w hile the upper p a rt of th e bed was deposited by the slown down current, which had to adapt itself to th e 'Configuration of the sea-bottom . According to Prentice this could happen w hen th e current changed its course from transversal to longitu
dinal (with reg ard to the axis of th e basin).
The observed differences betw een flu te casts and flow stru ctu re s ( K s i ą ż k i e w i c z in B u k o w y 1957, B i r k e n m a j e r 1958) and th e difference betw een th e initial and u ltim ate direction in the same cur
re n t (G r o s s h e i m and K o r o t k o v a 1954, T e n H a a f 1959, P r e n t i c e 1960, (also some cases observed in th e Carpathians, e. g. the H au- terivian-B arrem ian Gnodischt beds south of Cracow) indicate th a t the cu rren ts did n o t always follow th e m axim al inclination of the bottom b u t in some instances th ey flowed obliquely to th e m axim al slope. This view is corroborated by fairly num erous instances th a t in one and the sa
m e area neighbouring beds exhibit d ifferen t flu te ca&ts directions ( K s i ą ż k i e w i c z 1958, D ż u ł y ń s k i a nd § ł ą c z k a 1959)
It seems th a t these facts m ay be referred to th e hypothesis of th e late
ra l filling of flysch basins ( K s i ą ż k i e w i c z 1956, p. 387). The tu rb i
d ity currents, flowing dow n th e slopes from cordilleras and reaching th e central p art of the basin, had to follow th e resu ltan t from th e direction given to them on th e subm arine slope of the' cordillera (i. e. approxim a
te ly at rig h t angle to th e axis of th e basin) and the longitudinal inclina
tion of floor. It is possible th a t for th is reason th e oblique direction of cur
re n t structures w ith regard to th e faicies boundaries and tectonic lines is so freq u en tly observed. Oblique directions are a t any ra te m ore frequenit in th e C arpathians ( K s i ą ż k i e w i c z 1958, 1960) th a n longitudinal, although ait first W a s s o e v i c h (1951, p. 70) presum ed th a t th e cur
ren ts w ere directed along th e trough, basing on the analogy w ith th e Caucasus. L ast data from th e Caucasus seem to give a m ore com plex pictu re of cu rren t directions. In th e Polish p a rt of th e C arpathians recent
1 B i r k e n m a j e r (1958, Polish tex t p. 136, also English tex t p. 146) referring to my paper published in 1954, says th at I regarded the data resulting from the m ea
surem ent of groove and flute casts as sufficient for determ ination of the slope of the ba&in-floor and for the location of the source of detrital m aterial. It should, be said th a t this problem is not even m entioned in my paper. In another paper, published in 1956 (perhaps this paper B irkenm ajer had in mind) the location of the sources of the C arpathian flysch was reconstructed on the 'base of a fad es analysis (p. 383—385) and not on transport directions, at th at tim e very little known. In this paper I presu
med th a t the laterally flowing currents turned w ith the inclination of the axial re gion of the trough, but this inclination was reconstructed not only on the ground of the flute casts orientation, but prim arily again on the ground of the faeies distri
bution. ] ;.
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research (K s/i ą ż k i e w i c z 1958, D ż u ł y ń s k i and S ł ą c z k a 1959, K s i ą ż k i e w i c z 1960) shows th a t oblique and tran sv e rsal directions are q u ite frequent. O blique directions w ere reported from New Zeeland by W e b b y (1959), oblique and transversal directions in the Alps are re ported by C n o w e l 1 (1955) and H s u (1960).
It is possible th a t a cu rren t on th e sea-floor m ay flow not in th e direc
tion of the m axim al slope, and even, if achieves a considerable velocity, it m ay be independent from th e angle and -direction of th e slope (B i r- k e n m a j e r 1958, p. 136), bu t it is doubtful w hether in the com parati
vely narrow flysch basins th is independence could be of g reater im portan
ce. A tu rb id ity cu rren t, even locally deflected, will in any case seek the direction of m axim al slope for it moves p rim arily u n d er th e influence of gravity. The Coriolis force, if it really affects th e tu rb id ity c u rre n ts which seems to be debatable ( t e n H a a f 1959), m ay be p erh ap s effective on a large, flat sea-floor, b u t its effect in th e narrow flysch troughs is d u bious. The facts know n from th e C arpathians do not confirm its influence.
Both principal flysch troughs in all probability w ere filled from eith er si
des (K s i ą ż k i e w i c z 1960). In th e n o rth e rn trough th e currents d e
scending to th e central p a rt w ere deflected eastw ard, no m a tte r w hether they flowed from th e n o rth e rn or th e southern coast. I t they w ere under th e influence of th e Coriolis force, th e 'currents flowing from th e n orth should have been tu rn ed w estw ard (to th e right), and th e cu rren ts flowing from th e south should have been deflected eastw ard (to the right). Con
currently, in th e so u th ern trough th e cu rren ts flowing from th e southern border w ere deflected w estw ard (to th e 'left) and the c u rren ts coming from th e n o rth tu rn ed also w estw ard (to th e right). These facts im ply th a t the morphology of th e troughs and not th e Coriolis force controlled the tren d of th e currents.
It should be pointed out, th a t the direction as read from flow casts does n o t necessarily indicate th e actual slope of the sea-floor in th e m o
m ent w hen th e tu rb id ity c u rren ts w ere flowing over it. Sand beds w ere laid down on a clayey layer, which u n d er the load of th e bed, especially of a thick bed (flow casts occur m ainly in thick beds), undergoes compac
tion. In m any instances th e compaction could be differential, depending on th e thickness of th e underlying clay and o th e r its properties. In th is way a secondary unevenness could be formed, in som e cases sloping a t rig h t angle to th e original slope and cu rren t direction.
6. ON THE ORIGIN OF FLUTE MARKS
Since G r o s s h e i m (1946) and R i c h (1950) published th e ir p a
pers on flu te casts, these structures have become an im portant in stru m en t of paleogeographical and paleosedimentological research. Erosional form s, corresponding to flute casts w ere obtained experim entally (R ii c k 1 i n 1938), bu t very little observation has been m ade on recent form ation of these m arks. Erosional furrow s cut in hard rocks w ere described by M a x s o n and C a m p b e l l (1935), while W a s s o e v i c h (1951, p. 51) observed th e ir form ation on soft riv er deposits. To his com m ents two pho
tographs are added, presenting erosional furrow s not q u ite exactly, as th e au th o r him self states, corresponding w ith flu te m arks. More sim ilar fu r
rows w ere obtained by him experim entally.
— 45 —
It seems, however, th a t contem porary flu te m arks are not very rare, and although from th e sea-floor th ey are y e t unknown, in rivers th ey are fairly often form ed.
In th e C arpathian stream -beds I observed several tim es asym m etrical hollows, w ith slightly overhanging and steep upstream wall, probably cor
responding to anti-dunes. They m ay be observed shortly a f te r overfloods.
In sm aller stream s on m any occasions I could observe the furrow s ntore or less sim ilar to flu te m arks. They are usually form ed during short show
ers w hen a stream is swollen for a few hours or so. In th e silty stream - -bed or on th e floodplain aligned furrows, som etim es strongly resem bling flu te m arks converted into casts in fossil beds, are formed.
It is w orth w hile to n ote th a t th e furrow s are not entirely filled. In som e cases larg er grains or pebbles are trapped in th em (PI. V) b u t a lth
ough turbid w a te r flowed above th em for some tim e, no m aterial was deposited in th e furrows. Thus the problem arizes, lately often discussed, w h eth er th e cu rren t can erode flu te m arks and not fill them im m ediately.
The problem was risen by C r o w e l l (1958) who in some instances observed in flute casts grain aggregates which could be coprolithes. Accord
ing to him th e y had got into th e fu rro w at a stage a fte r erosion, and be
fore th e furrow was filled. A sim ilar observation was m ade by th e present w rite r (1954, p. 419): „Not all cu rren t hieroglyphs a re connected w ith the origin of th e sandy bed, on the surface of which they occur.... sometimes th e y have on th e ir surface biogenic hieroglyphs, which m eans th a t after th e ir form ation b u t before th e filling by sand, some organism s still crept o n th e m ” (transl. from the Polish text). Incidentally, traces of creeping organism s across em pty furrow s in stream -beds m ay occasionally be obser
ved. C u m m i n s (1958) found th a t in some instances flu te casts w ere cut b y currents flowing from another direction th an th e cu rren ts th a t filled them .
A lthough, no doubt, th e conditions in riv ers are different from th e con
ditions under which tu rb id ity cu rren ts eroded and deposited, th e presence of unfilled furrow s indicates th a t a cu rren t can erode th e m ark b u t does
n o t necessarily fill it.
In m ountain stream s one m ay observe th a t unfilled flu te m arks usual
ly are form ed ait a certain distance below the knickpoint of th e slope. Pos
sibly in th is zone th e cu rren t has still a velocity (apparently not very great) and tu rb u le n ce necessary for fluting, w h ile th e tail of th e cu rren t is still sw ift enough to carry its load fa rth e r away. It m ay be presum ed th a t above and below th e furrow s w ere in stan tly filled. P erh ap s sim ilar condition^ m ay be visualized in th e basins filled w ith turibidite deposits w here also th e flu te m arks in some zones could be le ft unfilled for a cer
ta in time.
The shape of erosional furrow s in stream s is v ery m uch th e sam e as th e shape w hich m ay be reconstructed for flu te casts. The variability of shapes is also th e same. F our types of R i i c k l i n (1938) m ay easily be found, e. g. th e hoof-like (PI. V, fig. 2 n ea r th e front), and also sm all ac
cessory flu te casts accom panying larg er ones (PI. V, fig. 2). It seems, how ever, th a t in riv ers on one surface one encounters a greater variabi
lity of shapes as compared w ith flysch deposits, w here usually one ty p e o f flu te casts prevails on a sole. The spacing of furrow s is in riv er deposits also not so reg u lar as in th e case of tu rb id ite deposits in which as u n d er
lined by W o o d and S m i t h (1959) th e spacing is very uniform . In ri
vers th e furrow s are not so parallel. This would confirm th e view of K u e n e n (1957, p. 241) th a t th e flute casts in th e beds deposited by tu r bidity currents are m ore straig h t and m ore parallel. My observations, however, p erta in to sm all stream s, w h ere th e influence of near river banks and th e unevenness of th e bottom are certainly an additional factor in fluencing the spacing of vortices in th e river current. It is possible th a t in large rivers erosional furrow s are of a m ore uniform type and m ore uniform ly spaced.
Department of Geology
Jagellonian University of Cracow February 1961
EXPLANATION OF PLATES I — V
Plate I
Fig. 1. Oriented tubes of Bathysiphon. Istebna beds, Senonian. Tabaszowa on the Rożnów lake.
Fig. 2. Crescent casts caused by pebbles. Inoceramian intercalation w ithin the Istebna beds. Senonian. Czchów on the Dunajec
Plate II
Fig. 1. Crescent cast caused by lumps of sandstones. Magura sandstone. Eocene.
Polany near Grybów.
Fig. 2. Crescent cast caused by a piece of wood. Podhale flysch, Eocene. Krempachy.
Plate III
Fig. 1. Lam inated flute casts. Krosno beds. Upper Eocene. Kamesznica near Żywiec.
Fig. 2. Flute casts flattened by the subsidence of the sandy bed. Beds are inverted.
Submagura beds, Eocene. Struga on the Rożnów lake.
Plate IV
Fig. 1. Groove cast, deformed by flow. Lower Senonian flysch. Pieniny.
Fig. 2. Flow cast. M agura sandstone, Eocene. Zawoja.
Plate V
Fig. 1 —,2. Erosional furrow s (flute marks) in the Jalom itioara river near Fieni, Roumanian Carpathians.
