A N N A L E S D E L A SO CIETE GEO LOG IQUE DE PO LO G N E
Tom (Volume) XXXVII — 1967 Zeszyt (Fascicule) 4 K raków 1967
F R A N K SIM P SO N
O NIEKTÓRYCH RÓŻNICACH W MORFOLOGII
P A L A E O D I C T Y O N
HEER
(Tabl. X X X V , X X X V I)
Som e morphological variants of Palaeodictyon H eer
(PI. X X X V , X X X V I )
STRESZCZENIE
Fragm enty siatki Palaeodictyon znajdują się często na m ałych w y niosłościach powierzchni spągowej piaskowców fliszowych, odsłoniętych w potoku Białej Wody, w pobliżu Szczawnicy (Pieniny). Te w yniosłości odpowiadają pierwotnym zagłębieniom, które znaczą obszary najgłębiej żłobiącego prądu. Stosunek m iędzy morfologicznymi różnicami siatek i pierwotnym i nierównościami spągu bywa taki, iż w iększe i bardziej sym etryczne sieci można z zasady znaleźć na szczytach nierówności spą
gu, a natomiast m niejsze sieci, wykazujące stosunkowo w ysoki stopień zróżnicowania, odbiegające od sześciokątnej postaci, znajdujemy zwykle w zagłębieniach. Siatki Palaeodictyon zostały utworzone przez zwierzęta żerujące w poziomie odpowiadającym mniej więcej obecnej granicy m ię
dzy łupkiem a piaskowcem. Nastąpiło to po wyżłobieniu przez prąd śla
dów na zerodowanej powierzchni dna morskiego, a po w ypełnieniu tych
że śladów przez piasek przyniesiony prądem.
K a te d r a Geologii
U n iw e r s y te tu Jagiellońskiego K r a k ó w
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A b s t r a c t : F ra g m en ts o f P alaeodictyon n etw ork s, p reserv ed on th e lo w e r su r fa c e s of sa n d sto n e la y er s in a C retaceou s fly s c h s e q u e n c e e x p o se d in th e B ia ła W oda str e a m -se c tio n , near S z cza w n ica (P ien in y ), fr e q u e n tly c o in c id e w ith s m a ll- - s c a le e le v a tio n s of th e so le s, w h ic h m ark th e areas of d e e p e st cu rren t-scou rin g . T h e r ela tio n sh ip b e tw e e n v a r ia tio n s in n e tw o r k m orp h olog y and p rim a ry irr e g u la r itie s of th e sa n d sto n e so le s is such th a t th e la rg er and m o re sy m m e tr ic a l m esh e s a re co m m o n ly fou n d on th e crests of p o s itiv e fea tu r e s of th e soles, w h ile sm a ller m e sh e s sh o w in g r e la tiv e ly h ig h degrees of d ep artu re fro m 'the com m o n ly occurring h e x a g o n a l form ten d to occur in h o llo w s b e tw e e n th e e le v a tio n s. It is con clu d ed th a t th e P alaeodictyon n e tw o r k s w e r e g en era ted b y a se d im e n t-e a tin g organism in a p la n e corresp o n d in g ro u g h ly to th e p r e s e n t shale/sands'tone in te r fa ce , a fter th e fo rm atio n of cu rren t m a rk in g s in th e e rosio n al upp er su r fa c e of th e bottom m u d s, and at a tim e la te r th an th e f illin g of th e se la tte r fea tu r e s d u rin g th e d ep o sitio n of th e sa n d y p art of th e su c c ee d in g bed.
A flysch sequence, comprising alternating sandstone and shale units of lower Senonian age, is exposed in the stream Biała Woda, Szczawnica, in the eastern part of the P ieniny region of southern Poland. Lithological profiles o f the beds exposed in this stream are given in a detailed study made by B i r k e n m a j e r (1963, Plate XXIII, Figs. 2— 5, explanation pp. 377— 378). The low er surfaces of the flysch sandstones are chara
cterized by the frequent preservation of numerous „trace fossils” (S. S i m - p s o n, 1957, p. 477) as positive structures forming interfering patterns w ith the current-produced sole markings, which latter give rise to widespread unevenness of the shale/sandstone interfaces. The purpose of this note is to account for the morphological variation frequently observed in one group of trace fossils, Palaeodictyon H e e r (fide H a n t z - s c h e 1, 1965, p. 65), in terms of the disposition of the different con
figurations w ith respect to sm alliscale, primary irregularities in the low er surfaces of sandstone layers.
Palaeodictyon is most commonly seen on the low er surfaces of sand
stone layers as retiform patterns of ridges, frequently w ith hexagonal or nearly hexagonal interstices, and is known to occur in beds ranging in age from Silurian to Tertiary. S e i 1 a c h e r (1954) attributed the for
mation of the netw orks of Palaeodictyon to burrowing at the mud/sand interface, but later ( S e i l a c h e r , 1962) supported an origin „predeposi- tional” w ith respect to the sandstone part of the bed, at the base of w hich they are found. According to this latter view, stated in general term s by K u e n e n (1957, p. 234) and S e i l a c h e r (1962, p. 232), the follow ing sequence of events is envisaged: 1.) Formation of the Palaeodictyon n e t
work in sea-bottom m uds as a system of interconnected tunnels, filled w ith faecal material; 2) Erosion of the muds to the level of the Palaeo
dictyon network by a sand-laden turbidity current, w hich in rem oving the faecal infilling m odifies the delicate network only slightly, if at all, and deposits sand w ithin excavated areas of th e tunnei-system so that these w ill be later preserved as positive structures on th e sandstone sole.
In support of a predepositional origin, „partly eroded” networks are mentioned by t e n H a a f (1959, p. 53), and S e i l a c h e r includes a photograph of Palaeodictyon ( S e i l a c h e r , 1962, P late 2 : 3, explan
ation on p. 229) w hich he considers to show fluting of the m eshes and also eroded areas elongated parallel to the current direction as deduced from sole markings. S e i l a c h e r (1962, Plate 2 : 4 ) also records an occurrence of Palaeodictyon as „flattened tube fillin gs” in shale. D ż u- ł y ń s k i and S a n d e r s interpret a sandstone sole figured by them (D ż u ł y ń s k i and S a n d e r s , 1962, Plate IA) as recording the partial obliteration of Palaeodictyon netw orks by current-form ed grooves and prod marks, and accordingly consider the organic markings to be of pre
depositional age w ith respect to the sandstone layer. However, it is here emphasised that the com m only seen cross-cutting relationships existing between sets of structures respectively of organic and inorganic origins, occurring as m ixed assemblages on sandstone soles, at the best offer no more than a choice betw een two conflicting and equally probable inter
pretations of the order of formation. The processes envisaged by S e i l a c h e r (1962) are nevertheless of great importance in the preservation of a great number of sole trails, for unequivocal evidence of predepositional burrowing activity is provided by certain „painted” trace fossils (for example, S e i l a c h e r , 11962, Plate 2 :2), by scour-m odified traces w hich are connected to, or associated with, similar but relatively unmodified
forms ( t e n H a a f, 1959, Fig. 40, p. 55) on the same bedding surface, and by occurrences on the soles of sandstones of paired, meandering trails dis
playing a coarse-grained infilling ( K s i ą ż k i e w i c z , 1960, p. 739, and Plate II, Fig. 8). V i a 1 o v (1964, p. 665), on the basis of taxonom ic analysis of a large number of specimens of Palaeodictyon from sandstone soles, considers the networks to be formed at the sedim ent/water interface as a series of grooves in th e bottom muds, arranged in ithe form of connecting series of channels, w ith each separate system surrounding an „elevated central part”, hexagonal in outline. This view fails to take into account erosion of the bottom muds, prior to, or during the deposition of the sandy material.
In a sedimentological study of Upper Llandoverian turbidites in North Wales, W o o d and S jn i t h (1959, p. 167) describe relatively large-sized m eshes of Palaeodictyon networks, occurring both on the soles of grey- wacke units as positive structures, and in the uppermost parts of the underlying mudstones in the form of rounded tubes exhibiting a distinct branching ( W o o d and S m i t h , 1959, Fig. 3, p. 167). In either mode of occurrence, the tube-like components are filled w ith sandy material, w hich in composition and grain-size does not differ from that seen at the base of the overlying greywacke unit. The authors conclude that the structure was formed as a result of burrowing activity at the sand/mud interface, and is thus postdepositional in relation to the grey
wacke layer. Similar conclusions concerning the tim e-relations betw een depositional episodes and burrowing activity w ere reached by K s i ą ż k i e w i c z (1960, p. 738), in his study of the branched, meandering trace fossil Protopalaeodictyon K s i ą ż k i e w i c z . A postdepositional origin is favoured by N o w a k (1959, p. 118) as a result of considerations of occurrences in which Palaeodictyon is seen as a negative sole feature.
On the soles of flysch sandstones exposed in Biała Woda, inorganic hieroglyphs, seen as closely spaced, sm all-scale irregularities, are m ainly those attributable to the infilling of marks made on a mud surface by the short-lived contact of current-borne objects. Prod and groove moulds are common, the latter most frequently occurring as fine, short ridges, which together w ith low, narrow flute moulds, form a prominent lineation on low er bedding surfaces. In addition, there are long, continuous groove moulds, seen as ridge-like elevations of the sole, less than one centim etre in width, and them selves marked by sets of longitudinal striations showing abrupt termination, overlapping, tw isting and other features suggestive of incision by crenulated tools undergoing rotation during transport. As pointed out by M. K s i ą ż k i e w i c z (personal communi
cation, 1966), such grooves may have been cut by current-transported fragm ents of Inoceramus shells common in these beds. Other tools likely to have contributed to the formation of the assemblage of current-formed sole markings are isolated mineral grains of coarse-sand size, found on the sandstone soles, and plant fragm ents evidenced by finely comminuted carbonaceous debris concentrated on internal parting surfaces. It is emphasized that the entrainment of particles of bottom sedim ent is evi
denced by interfacial structures occurring over the entire surface of soles displaying Palaeodictyon (Plate XXX V, Fig. 1). Furthermore, the sandstones are fine-grained and composed of horizontal lam inae occurring to the very base of each layer.
In the Biała Woda specimens, Palaeodictyon varies in morphology from sym m etrical patterns of ridges arranged in perfect hexagons,
through a variety of rounded forms, to networks consisting of compressed, elongate meshes, roughly elliptical in shape. These different retiform ridge-configurations are frequently joined together so that the larger and more regular hexagons are seen on elevations of the sole corres
ponding to areas of deepest erosion of the bottom muds (Plate X XXV, Figs. 1— 3; Plate XXXVI, Figs. 1— 3), w hile asym metrical m eshes of small size tend to occur in depressions (Plate XXXV, Figs. 3, 4). Where m eshes of varying size are joined together in the same network, changes in size and shape of m eshes of similar relief are not as a rule accompanied by changes in the thickness of the constituent ridges (Plate XXX V, Fig. 3).
The ridges making up a given network m ay vary considerably in m icro-relief and in degree of separation from the sandstone sole. In some cases, portions of the network situated on the central parts of relatively flat, positive features of the sole comprise ridges so low in elevation as to be barely discernible (Plate XXXVI, Fig. 4). These indistinct areas of the network frequently terminate in incomplete hexagons (Plate X XXVI, Fig. 4), and presumably mark regions of the sole w here the network enters the sandstone layer. Other parts, situated on the edges of positive areas of the sole and in relatively flat hollows, are seen as system s made up of tube-like components of high relief, w hich may be detached from the base of the sandstone layer. Where the network is in high relief, it m ay follow irregularities of the sole so closely as to give the appearance of encrusting the structures of inorganic origin (Plate XXXV, Figs. 1, 2, 4).
Only the acceptance of a postdepositional origin of Palaeodictyon w ith respect to the sandstone layers beneath w hich it occurs can provide a satisfactory explanation for the sand-filled system s of branching tubes in mudstones, described by W o o d and S m i t h (1959), and the obser
vation in the Biała Woda specimens of Palaeodictyon networks w hich follow closely the relief of current-formed sole markings. Distortion of the network, accompanying changes in the relief of the sole, marks modification in the structure of the burrow of a sedim ent-eating organism, made to accomodate relatively sharp irregularities in the mud/sand interface. The Palaeodiclyon-forrmng animal may have burrowed in sand or follow ed the mud/sand interface in preference to burrowing in mud, because of the relatively strong cohesion of the latter, w hich property had evidently caused sporadic resistance to scouring during the earlier formation of primary current markings. Local differences in consistency of muds at the mud/sand interface m ay be reflected in Palaeodictyon networks comprising m eshes of variable size and shape, in the absence of interfacial irregularities.
It is generally accepted that trace-fossil „species” occupy a special place in taxonomy, in so far as they are not taken to im ply specific designations for the animals active in their formation. Though the possibility of subdividing Palaeodictyon and similar forms into a number of genera and species on the basis of network m orphology has been presented (see, for example, W i a ł o w and G o l e w , 1966; an extensive bibliography is given by these authors), the present author feels that the usefulness of such a rigorous taxonomic treatment has yet to be demon
strated. The existence of individual networks showing considerable morphological variation suggests that new species should not be based upon specimens displaying only a small numbers of meshes.
The author acknowledges his gratitude to Prof. dr M. K s i ą ż k i e w i c z and Prof. dr. St. D ż u ł у ń s к i for helpful discussion and for reading the manuscript, to Prof. dr. F. B i e d a for his comments on the manuscript, and to dr. St. G ą s i o r o w s k i for guidance in the field during several instructive days in t h e P ieniny region.
D e p a r tm e n t of Geology Jagellonian U n iv e r s ity K r a k ó w
W Y K A Z L IT E R A T U R Y RE FER EN C ES
B i r k e n m a j e r К . (1963), S tr a ty g r a fia i p a le o g eo g r a fia serii czo rszty ń sk iej p ie n iń sk ieg o p a s a s k a łk o w e g o (S tratigrap h y and p a la eo g eo g ra p h y o f th e C zorsztyn S eries, P ie n in y K lip p en B elt, C arpathians, in P oland). Studia geol. poi., 9: 380 pp.
D ż u ł y ń s k i St., S a n d e r s J. E. (1962), C urrent m a rk in g s on fir m m ud b ottom s.
Trans. Conn. Acad. A r ts Sc., 42: 57—96.
H a a f E. ten (1959), G raded b ed s of th e N orth ern A p en n in es. Ph. D. th e sis, Sta'te U n iv . of G ron ingen, G ron ingen, 102 pp.
H a n t z s c h e l W. (1965), V e stig ia In verteb ratoru m et P r o b le m a tic s. F o ssiliu m C atalogus I: A n im a lia , E d itor F. W estph al, P108, 142 pp.
K s i ą ż k i e w i c z M. (1960), O n iek tó ry ch p r o b le m a ty k a c h z fliszu K arp at P olsk ich : Część I. (On so m e p rob lem a tic organie traces from th e fly s c h of t h e P o lish C arpathians: P art I) K w a r t, geol., 4: 735— 747.
К u e n e n Ph. H. (1957), S o le m ark in gs of graded g r a y w a c k e beds. J. Geol., 65:
231— 258.
N o w a k W. (19i59), P alaeodic tyu m w K arp atach fliszo w y c h (P a la eo d ictyu m in th e C arpathian fly sch ). K w a r t, geol., 3: 103— 125.
S e i l a c h e r A. (1954), D ie g e o lo g isc h e B e d e u tu n g fo ss ile r L eb en ssp u ren . Z. deutsch.
geol. Ges., 105: 214— 227.
S e i l a c h e r A. (1962), P a le o n to lo g ic a l stu d ies on tu r b id ite s e d im e n ta tio n and erosion. J. Geol., 70: 227— 234.
S i m p s o n S. (1967), On th e ’trace fo ss il Chondrites. Quart. J. geol. Soc. Lond., 112: 475— 499.
V i a l o v O. S. (1964), N e tw o r k stru ctu res sim ila r to th o se m a d e b y ta d p oles. J. s ed i
m ent. Petrol., 34: 664— 666.
W i a ł o w О. S., G о 1 e w В. T. (1966), K ry ty c zn y przegląd n o w y ch albo m a ło z n a n y c h form P a le o d ic ty o n id a e (R evue critiq u e d es form es n o u v e lle s ou p eu co n n u es d e P a leo d icty o n id a e; Критический обзор новых или м алоизвестны х сведений о находках P a le o d ic ty o n id a e) Rocz. Pol. Tow. Geol., 36: 181— 198.
W o o d A. , S m i t h A. J. (1959), T h e se d im e n ta tio n and se d im e n ta ry h isto r y of th e A b e r y s tw y th G rits (U pper L la n d o verian ). Quart. J. geol. Soc. Lond., 114: 163— 195.
O B J A Ś N IE N IA T A B L IC E X P L A N A T IO N OF P L A T E S
W k a ż d y m p rzypadku strza łk a w s k a z u je k ie ru n e k prądu w y z n a c z o n e g o na p o d sta w ie ze sp o łó w h ie r o g lifó w p rąd ow ych . S k a la w c e n ty m en tra ch . M iejsco w ość:
B ia ła W oda, S zczaw n ica. W iek: d oln y senon.
In each case, arrow in d ica te s current d irectio n d eterm in ed fro m a ssem b la g e s of in te r fa cia l m ark ings. S c a le in cen tim etres. L o c a lity . B ia ła W oda, S zcza w n ica . A g e: L o w e r S en on ia n .
4 R o c z n i k P T G t. X X X V I I z. 4
Fig. 1. S p ąg drob n oziarn istego p ia sk o w c a u k a zu ją cy b lisk o osad zon e ja m k i w ir o w e i śla d y p rzed m io tó w z sia tk o w y m i n aroślam i Palaeodictyon. „C y lin d r ite s ” r ó w n ie ż p o std e p o z y cy jn a fo rm a w p osta ci ro zg a łęzio n y ch i p r z e ry w a n y c h lin ijn y c h h ie ro g lifó w
Fig. 1. S o le of fin e -g r a in e d san d ston e, sh o w in g c lo s e ly sp a c e d f lu t e m o u ld s and m ould s of tool m ark in g s w ith retiform o vergro w th s of Palaeodictyon H e e r.
„C ylindrites” a lso a p ostd ep o sitio n a l form , p resen t as b ra n ch in g and in te r m itte n t lin e a r r e lie fs
Fig. 2. W y cin ek z fig . 1. Palaeodictyon z sie c ia m i o sto su n k o w o d u żych rozm iarach r o z w in ię ty m i na o d lew a ch ja m ek w ir o w y c h
Fig. 2. D e ta il from Fig. 1. Palaeodictyon m esh e s of r e la tiv e ly la rg e size develop ed on flu te m ou ld s
Fig. 3. W y cin ek z fig. 1. Sia'tka Palaeodictyon p rzy le g a ją ca do p o w ierzch n i spągu.
O czka sie c i o n ie w ie lk ic h rozm iarach (u góry i w c zęści środ k o w ej) w za
g łę b ie n ia c h sp ągu
F ig . 3. D e ta il from Fig. 1. Palaeodictyon n etw o rk fo llo w in g irreg u la rities in lo w e r su r fa c e of bed. S m a ll m esh-sizes; (top, centre) in n e g a tiv e areas
Fig. 4. W y cin ek z fig. 1. S ia d y ro z m y w a n ia i p rzed m io tó w „ in k r u sto w a n e ” sia tk a m i Palaeodictyon. M ałe, p o dłużne sie c i w za g łęb ien ia ch stru k tu r sp ągu
Fig. 4. D e ta il from Fig. 1. M oulds o f scour and tool m a r k in g s „ e n c r u ste d ” by Palaeodictyon n etw o rk s. M esh es on n e g a tiv e so le stru ctu res sm a ll, elo n g a te
T a b lic a — P la te X X X V
T a b lica — P la te X X X V I
Fig. 1. Palaeodictyon, śla d y ro zm yw an ia i przed m io tó w na spągu piaskow ca. P ra w a stro n a i środek: ślad p rzed m iotu otoczony sia tk ą Palaeodictyon. L in ia in te r - se k c y jn a p r z e cin a ją cy c h się śla d ó w p o z o sta w io n y ch p rzez zw ie rz ę żeru jące, które w ch o d ziło lu b w y c h o d ziło z p iask u
Fig. 1, Palaeodictyon and m ould s o f scour and tool m ark in gs on sa n d sto n e sole.
R ight, centre: m ou ld of to o l m a rk surrounded b y Palaeodictyon n etw ork ; lin e o f in te r se c tio n of organic and in o rga n ic stru ctu res is lo cu s of p oin ts w h e r e a n im a l p a ssed from m ud in to sand, and v ic e v e r sa
Fig. 2. S p ąg p ia sk o w ca z Palaeodictyon w y stę p u ją cy m w p o sta ci narośli na śla d a ch ro zm y w a n ia
Fig. 12. S a n d sto n e s o le w ith Palaeodictyon as „ o v erg ro w th ” upon m o u ld s of lo w scour strudture
Fig. 3. S p ąg p ia sk o w c a p r z e d sta w ia ją c y „in k r u sta c ję ” Palaeodictyon na śla d a ch r o z m y w a n ia i ro zd zielo n y ch sto su n k o w o p ła sk im i p o w ie r z ch n ia m i
Fig. 3. S a n d sto n e s o le w ith P alaeodictyon „ en cru stin g ” both th e m o u ld s of scours and th e r e la tiv e ly fla t areas b e tw e e n
Fig. 4. S p ąg p iask ow ca . L e w y róg: c a łk o w ic ie w y k sz ta łc o n e sia tk i P alaeodictyon na w y n io s ło śc i n a w ią z u ją c e do n ie w y r a ź n y c h sz eśc io b o k ó w zak oń czon ych p rzer-
n y m i oczkam i sie c i
Fig. 4. S a n d sto n e sole. Top, left: c o m p le te r id g e -s y s te m s of r e la tiv e ly h ig h r e lie f jo in ed to sy ste m s of lo w e r r e lie f w h ic h end in in c o m p le te m esh e s
F. Simpson
F. Simpson
