trace fossils from a permian shoreface-foreshore environment, eastern australia

Trace Fossils from a Permian Shoreface-Foreshore Environment, Eastern AustraliaAuthor(s): Bruce McCarthySource: Journal of Paleontology, Vol. 53, No. 2 (Mar., 1979), pp. 345-366Published by: SEPM Society for Sedimentary GeologyStable URL: http://www.jstor.org/stable/1303876 .

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JOURNAL OF PALEONTOLOGY, V. 53, NO. 2, P. 345-366, 1 PL., 11 TEXT-FIGS., MARCH 1979

TRACE FOSSILS FROM A PERMIAN SHOREFACE-FORESHORE ENVIRONMENT, EASTERN AUSTRALIA

BRUCE McCARTHY Department of Geology, University of New England, Armidale, N.S.W. 2351 Australia

ABSTRACT-Evidence from sedimentary structures, rock types, body fossil and trace fossil associations is used to define three depositional environments (foreshore, open shoreface and protected shoreface) in the Wasp Head Formation, Sydney Basin, Australia. Common trace fossils include Skolithos, Diplocraterion, Rhizocorallium, Cylindrichnus and Rosselia; less abundant forms are Catenichnus n. ichnogen., Psammichnites, Keckia and Thalassinoides. Trace fossils found in protected shoreface sediments are most diverse, and indicate that variables other than depth of water are locally significant for the development of different associations of trace fossils and different styles of bioturbation. A new ichnospecies, Rosselia rotatus, and a new ichnogenus, Catenichnus (C. contentus n. ichnosp.) are described herein. Body fossils are selectively preserved in bands in typical foreshore sediments; in open shoreface sediments, some were preserved in their life position.

INTRODUCTION

OF the countless marine invertebrates that have existed, most perished leaving no direct evidence of their former presence. In sands which were deposited in nearshore environments, erosion and diagenetic processes generally precluded preservation of skeletal parts of the inhabitants. However, trace fossils provide some insight into the sorts of soft-bodied and shelly organisms which inhabited these nearshore environments and provide a valu- able tool for paleoenvironmental analysis.

In the Wasp Head Formation (Text-fig. 1), different types of preservation suggest that fossil shells were much more widely distributed than they now appear, and that most were destroyed during diagenesis by chemical processes (McCarthy, 1977). The Wasp Head Formation is an Early Permian unit which unconformably overlies folded Ordovician basement rocks on the southern margin of the Sydney Basin. It thins towards the north (Gos- tin & Herbert, 1973) and is conformably overlain by tidal flat and shallow subtidal sediments of the Pebbley Beach Formation. From an analysis of the bed characteristics and sediment types, Gostin & Herbert (1973) conclud- ed that the lower part of the Wasp Head For- mation was deposited in a littoral to sublittoral environment and that the upper part was laid down in deeper water as the sea transgressed the Permian land surface. In support of this, the trace fossils are typical of shallow marine environments and are much more common in Copyright ? 1979, The Society of Economic Paleontologists and Mineralogists 3

the upper part of the unit than in the lower part. Characteristic ichnogenera include Sko- lithos, Diplocraterion, Rhizocorallium, Cylin- drichnus, Rosselia and Catenichnus (n. ichnogen.), but the associations which occur in different beds in the upper part of the formation are quite distinctive. These differences in the trace fossil associations enable the depositional environment to be more readily recognized, and provide evidence of minor-fluc- tuations of environmental conditions between lithologically similar units.

This work is part of a detailed study of trace fossils in the 'marine Permian units of the southern Sydney Basin.

THE SEDIMENT

The Wasp Head Formation is composed mainly of sandstone with much lesser thick- nesses of conglomerate and siltstone (Text-fig. 2). Sedimentary breccia occurs in four lobes in the basal parts of the unit and was probably emplaced as solifluction debris which flowed over the beach sands into shallow water (Conybeare & Crook, 1968, p. 96, pls. 8, 10b). Thin bands of pebbles are common throughout the sandstones (Conybeare & Crook, 1968, p. 130, pl. 24) and isolated clusters of pebble to cobble grade material indicate ice rafting (Gostin & Herbert, 1973). Gostin & Herbert (1973) described the rock types and subdivided the formation into numbered beds according to their stratigraphic position within particular measured sections (for example, bed 4.3 is the

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TEXT-FIG. 1-Locality map and outcrop map of the Wasp Head Formation, southern Sydney Ba- sin.

third bed from the base of section 4); this study embraces sections 2-5 (Gostin & Herbert, 1973, figs. 6, 7).

From the base of the formation to the top of bed 4.3 the rock types are sedimentary breccia, conglomerate, sandy conglomerate and pebbly sandstone. Sandy conglomerate and pebbly sandstone are most common as low-angle cross bedded units with shallow, pebble- lined scours. Conybeare & Crook (1968, p. 130) interpreted these as littoral sands which were probably deposited as offshore shoals in very shallow water.

Bed 4.4 comprises interbedded conglomerate, siltstone and fine to very fine sandstone. Gostin & Herbert (1973) reported a distinct change in the composition of the sandstones and conglomerates above bed 4.3 compared with those lower in the section. Lithic sandstone and chert pebble conglomerate occur low in the section, whereas quartz-rich feldspath-

olithic sandstone and conglomerate with vol- canic and granitic clasts occurs high in the section. Also, there is a decrease in grain size higher in the unit and a change from siderite cement in the upper parts of bed 4.3 and in bed 4.6, to calcite cement in the sediments above bed 4.6. This last change is significant, because the contrast in the type of cement further implies a different environment of deposition for the sediments in the upper part of the Wasp Head Formation compared with those in the lower part. Hallam (1967) used the relative abundance of early diagenetic siderite and calcite in concretions as a sensitive index of environmental change by relating increasing proportions of siderite and decreasing proportions of calcite to the progressive ad- vance of a river delta over marine sediments. Similarly, increasing proportions of calcite and upward fining of the sediment in the Wasp Head formation may be directly related to increasing distance from the shoreline, associated with a marine transgression. Fossiliferous bands of iron-enriched sediment were probably formed by postdepositional segregation of siderite from the beach sands to levels where shells (mainly molluscs) had been concentrated by storm induced currents. Shells which were contained in the sediment outside these bands were dissolved prior to lithification of the sediment and are now apparent only as rare, in- distinct, composite molds (McCarthy, 1977).

FOSSIL SHELLS

Fossil shell types in the Wasp Head For- mation include shallow burrowing pelecypods (Australomya, Megadesmus, Pyramus, Schizo- dus) and epifaunal brachiopods (Martiniopsis, Trigonotreta, Pseudosyrinx), pelecypods (Eu- rydesma) and univalved molluscs (Keenia, Mourlonia, Warthia). Runnegar (1969) and Dickins, Gostin & Runnegar (1969) have listed and described the shelly fossils from five localities in the Wasp Head Formation. Fossil shells occur in two distinct modes of preservation: 1) a molluscan assemblage containing Eurydesma, Australomya, Megadesmus, Py- ramus, Schizodus, Warthia and Mourlonia as

TEXT-FIG. 2-Stratigraphic column of Wasp Head Formation, distribution and relative abundance of trace fossils, and interpreted depositional environments. Numbers to the right of the column are bed numbers of Gostin & Herbert (1973).

346



PERMIAN TRACE FOSSILS

Environment of Deposition

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TEXT-FIG. 3-a, c, Keckia sp. B, bedding plane sections of burrows with well developed backfill structures, UNE L1665, Wasp Head Formation; b, e, Psammichnites sp. B, oblique and longitudinal vertical sections of backfilled burrows; e, inclined exit burrow, backfill structures are curved in center of the burrow and are more angular towards the lateral extremities as shown at about the midpoint of the length of the tube, from UNE L1665, Wasp Head Formation; d, Keckia sp. A, eroded bedding plane

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the dominant forms, and found in iron-enriched bands in the foreshore sediments of bed 4.6; and 2) a pelecypod-brachiopod association containing Eurydesma, Martiniopsis, Trigon- otreta, Pseudosyrinx and bryozoans as the main components, some of which occur in life position, and found higher in the unit in siltier sediments which were probably deposited in a quieter offshore environment.

Most infaunal pelecypods die when they are unable to burrow again after being washed out of the sediment by strong currents (Schafer, 1972, p. 158). In the molluscan assemblage found in the iron bands (McCarthy, 1977), most of the pelecypod shells are preserved as complete, disarticulated valves, but some are articulated and oriented at various angles to bedding. The presence of small fragile shells, particularly those of juvenile Pyramus and Schizodus, and the general absence of broken valves indicate that the shells were transport- ed only a short distance after they were disinterred and that they suffered only a little postdepositional reworking. Some of the articulated valves (Pyramus, Schizodus, Megades- mus) are closed and one Pyramus has the lig- ament preserved (Runnegar, 1968, pl. 20, figs. 7-9), suggesting that the animals may have been alive when they were deposited, or died very shortly before. Rapid burial would have facilitated preservation of unbroken and articulated valves.

Except for Eurydesma, the pelecypods of the molluscan assemblage were probably all infaunal suspension feeders, but shallow and deep burrowing forms can be distinguished. Megadesmus and Pyramus were forms which are closely related to Australomya and show progressively greater adaptation for deeper burrowing (Runnegar, 1974). Megadesmus had weak or nonretractable siphons (Runne- gar, 1965) and, like most shallow burrowers, is seldom preserved in life position because it was readily exhumed by currents. It is likely

that the shallow burrowing forms inhabited sediments further offshore than the deeper burrowing forms which could better withstand the rigors of more turbulent nearshore environments. Consequently, the molluscan assemblage is considered a mixed unit containing shells derived from nearshore and offshore environments which were disinterred and concentrated during periods of strong current activity. The univalved molluscs (Warthia and Mourlonia are most abundant) may have grazed on surface algae, or lived on weed or kelp, from where they were dislodged by currents and subsequently accumulated with the pelecypods.

In contrast, in the silty sandstone higher in the unit, some of the epifaunal forms like Mar- tiniopsis and Eurydesma are preserved in life orientation. Martiniopsis probably had no pedicle attachment, but is thickened in the umbonal region; this served as an anchor and kept the anterior margin of the shell above the sediment surface, as has been suggested for some other Permian spiriferid brachiopods (Clarke, 1972). Eurydesma was a suspension feeding pelecypod that lived with the plane of the commissure vertical and was anchored in the sediment by the weight of its thickened umbones (Runnegar, 1970). Although some of these large, robust shells remain essentially undisturbed, it is impossible to know how many less robust individuals were selectively removed by intermittent strong currents which deposited shell gravels and pebble bands above and below the fossiliferous silty layers. Bryozoans are also common at these levels. In contrast to the molluscan assemblage which is essentially a mixed death assemblage of individuals, the pelecypod-brachiopod association is representative of at least part of a life association of epifaunal suspension feeders which inhabited fine sands and silts of quieter, offshore environments below normal wave base.

section of a small burrow that has been actively backfilled with alternating curved laminations of light colored sand and darker silt, UNE L1665, Wasp Head Formation; f, bedding interface trails, eroded bedding plane section of straight, shallow grooves, UNE L1665, Wasp Head Formation; g, Thalassi- noides paradoxicus, horizontal section of mud-filled tunnels in sand, UNE L1661d, Wasp Head For- mation; h, Planolites montanus, burrows concentrated in silt funnel of Rosselia rotatus, UNE L1661a, Wasp Head Formation; i, Skolithos verticalis, vertical section, UNE L865.

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TRACE FOSSILS

Trace fossils in marine environments reflect the behavioral responses of animals to variables such as salinity, temperature, amount of dissolved oxygen in the water, nature of the substrate (including grain size, organic content, compaction and sedimentation rate) and current strength (Rhoads, 1975). In general terms, these variables are related to depth of water, and Seilacher (1967) proposed that several recurring trace fossil facies could be related to water depth according to the relative availability of food at different energy levels. Crimes (1970, 1973) and Frey (1975) point out, however, that the distribution and abundance of trace-making organisms is controlled by dy- namic environmental factors which are not necessarily directly related to bathymetry. The general gradation of trace fossil assemblages in relation to some of these factors in increasing depth of water is given by Rhoads (1975, fig. 9.1) following the scheme initially proposed by Seilacher (1964, 1967). In nearshore environments, conditions are generally more highly variable than in deeper water and are subject to more rapid and more regular change. Consequently, animals which inhabit these shallow water zones must be tolerant of a wider range of conditions than deeper water counterparts and must be able to relocate readily following onset of unfavorable conditions.

In the Wasp Head Formation, three trace fossil associations can be distinguished and these have been named after the dominant forms present as 1) Skolithos association, 2) Diplocraterion association and 3) Rosselia- Cylindrichnus association.

1) Skolithos association.-Skolithos is monodominant in sediments such as those of bed 4.3 that are typical of high energy foreshore environments. The burrows are very sparse, vague, unlined forms that probably served as temporary dwellings for itinerant annelids that were able to relocate readily when necessary.

2) Diplocraterion association.-The characteristic association in the uppermost part of the Wasp Head Formation contains abundant Diplocraterion, Skolithos and ?Cylindrich- nus, and less abundant large Rhizocorallium, Catenichnus (new ichnogenus described herein) and Psammichnites. This association represents a community dominated by suspension feeding organisms which inhabited fine sandstones and silty sandstones in middle to lower shoreface open marine environments. Some of the beds are intensively bioturbated and at these levels complete, individual traces are difficult to distinguish. Lenses of cross stratified sandstone occur as small isolated pockets or as elongate features which may persist along strike for up to about 50 m. The surface on which these lenses have developed was irregular and this suggests that strong currents were operative immediately before the well stratified sands were deposited. Channels and scours were eroded by currents during periods of storm activity when the wave base was ef- fectively lowered, and the sand was redepos- ited in these depressions under relatively high energy conditions, or as low sand bars. The well stratified lenses contain few trace fossils.

Rhizocorallium jenense and shallow grooves parallel to bedding are the only trace fossils preserved in sediments above the intensively bioturbated sandstones characterized by the Diplocraterion association. R. jenense is most abundant where a shelly fauna of epifaunal suspension feeding organisms (including Eu- rydesma, spiriferoid brachiopods and bryozoans) becomes more common.

3) Rosselia-Cylindrichnus association.-In contrast to the general persistence of Diplocra- terion, Cylindrichnus and, to a lesser extent, Rhizocorallium in bed 5.2, the trace fossils which are found in beds 4.4 and 4.5 are more diverse. Different beds may be dominated by any of Planolites, Thalassinoides, Diplocra- terion, or Cylindrichnus, but the most consistently abundant trace fossils are Rosselia and Cylindrichnus which reflect a deposit feeding

TEXT-FIG. 4-a, d, i, j, Rosselia rotatus which are more or less funnel-shaped, all in vertical section, UNE L1161a and L1665, Wasp Head Formation; b, c, g, h, intermediate patterns of development of funnel shaped R. rotatus n. ichnosp. b, c, horizontal sections, g, h, oblique horizontal sections, UNE L1661a and L1665, Wasp Head Formation; e, f, R. rotatus holotype UNE F14797 from UNE L1661c, in vertical and horizontal sawn sections showing intensive back-filled structures. All same scale.

351



BRUCE McCARTHY

a b c

e d TEXT-FIG. 5-There is a gradational sequence be-

tween burrows with concentric wall structure, more complex meandering burrows with backfill structures, and funnel-shaped burrows with backfill structures. a, b, Cylindrichnus concentricus; c, intermediate form; d, concentric structure in funnel of R. socialis; e, pattern of rotational movement in the funnel of R. rotatus.

mode of life for their producers (Chamberlain, 1971; Fiirsich, 1974b).

Cylindrichnus and Rosselia occur with Psammichnites, Planolites, backfilled trails and escape burrows in laminated and massive siltstones and fine sandstones in beds 4.4 and 4.5. Planolites is most common where sediments are siltiest and richest in organic material and, in some instances, has worked the sediment fills of Rosselia funnels (Text-fig. 3h). Cylindrichnus may be subvertical or inclined; subvertical forms generally have concentric wall structures, whereas the inclined forms may possess structures which look like short stacks of retrusive spreite. The same sorts of variation have been described and figured for Cylindrichnus from the Jurassic of England and Normandy by Fiirsich (1974b). However, Cylindrichnus that occur with large Rosselia exhibit a greater degree of variation,

and a number of apparently intermediate forms between Cylindrichnus and Rosselia can be recognized (Text-fig. 4b, g, h). This gradational sequence suggests that some of the forms recognized as Cylindrichnus may be erosional remnants of Rosselia. The pattern of movement indicated by other specimens (e.g., Text-fig. 4h), indicates that these forms may be incipient Rosselia in which the burrow was vacated before it was fully developed (Text-fig. 5). Consequently, it is difficult to determine the relative abundance of Rosselia and Cylindrichnus. The best preserved Ros- selia indicate that they were formed by back- filling a tube which moved in a rotational pattern about an approximately central axis. In the lower parts of the Rosselia funnel, thin concentric lining about the tube indicates that at this level there was little movement of the tube, and suggests that most of the feeding activity of the animal which produced Rosse- lia was carried out at the sediment surface, as indicated by Chamberlain (1971, text-fig. 8c- g). In some cases Cylindrichnus reflect similar behavior to that which produced Rosselia; Cylindrichnus which are either juvenile stages of development of Rosselia or erosional remnants, obviously do not indicate an infaunal deposit feeding mode of life for the producer.

Thalassinoides occurs at only one level in bed 4.4 where it is extremely abundant. The network comprises mainly horizontal elements. Thalassinoides has been recorded from protected, low energy environments in shallow marine sediments from the Jurassic of France (Ager & Wallace, 1970) and Yorkshire (Far- row, 1966). The predominance of horizontal elements may be the result of erosion having removed many of the vertical elements of the network (Fiirsich, 1973). More significantly, restricted depth of suitable substrate might control the pattern of the network, or the pre-

TEXT-FIG. 6-a-e, Diplocraterion parallelum. a-c, horizontal sections of tubes with protrusive spreite, and concentric lining (c); d, vertical section normal to the plane of the tube with retrusive spreite; a- d from UNE L1661b, Wasp Head Formation; e, vertical section in the plane of the tube of similar specimen from the Pebbley Beach Formation (UNE L1662). a-c same scale, d-e same scale. f, g Rhizocorallium jenense, sections of partly eroded tubes in bedding plane, same scale, UNE L1661c, Wasp Head Formation; h, Psammichnites sp., bedding plane section of burrow with vague backfill structures, movement is in direction of arrow, UNE L1665, Wasp Head Formation; i, j, escape structures, i, narrow type obvious only because the animal destroyed sedimentary laminae; j, broad structure with concave laminae, vertical sections, same scale, UNE L1661a, Wasp Head Formation.

352



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2cm TEXT-FIG. 7-Clusters of various sized ice-rafted

clasts sank into intensively bioturbated, thixo- tropic sediment immediately following deposition on the surface. The sunken clusters formed depressions on the surface which were infilled with laminated sand.

dominance of either vertical or horizontal elements in Thalassinoides networks may be related to different environmental settings (Farrow, 1971; Fiirsich, 1973, 1974c); in modern examples, Farrow (1971) noted that horizontal networks are characteristic of areas with thin sediment cover and strong currents.

Escape burrows (Text-fig. 6i, j) occur where thinly laminated sediments are overlain by coarser, graded sediments. The burrowing has destroyed or deformed bedding and indicates upward movement in response to sudden burial by sediment (Schafer, 1972).

Bioturbation and rate of sedimentation.- Three different bioturbation-sedimentation relationships occur in sediments dominated by the Rosselia-Cylindrichnus association. These are: 1) parallel and low-angle cross stratified fine sandstones which contain only a few Ros- selia and Cylindrichnus with short spreite. These traces occur in beds of about 0.4-0.7 m thick which have erosional upper contacts, and laminae of dark carbonaceous material or heavy minerals (probably iron minerals). These sediments were deposited relatively rapidly and were occupied by organisms which constructed burrows (including large Rosselia funnels) during periods when thin beds of dark silt were slowly laid down. When conditions of stronger current activity again prevailed most of the dark silt was eroded and the environment became unsuitable for the Rosselia and Cylindrichnus inhabitants. The funnels

remained in the sand at the erosional surfaces as the only testimony to the former occupation of these sediments by infaunal surface deposit feeding animals. Conditions suitable for the development of this relationship may have prevailed in very shallow water environments near the shoreline of a protected bay or lagoon; 2) parallel stratified sands in beds 0.1-0.15 m thick are either completely bioturbated throughout, or only in the uppermost 5-8 cm. This suggests that burrowing organisms did not penetrate deeper than about 5-8 cm. Con- sequently, beds deposited rapidly in units up to about 8 cm thick were thoroughly worked by burrowing organisms during intervening periods of nondeposition or slow deposition. These sediments were probably deposited under conditions of lower energy in deeper water than the stratified sands with sparser trace fossils; 3) fine sands which have a mottled texture occur in beds up to about 1 m thick; some spreite structures are discernible and are probably parts of Cylindrichnus. Individual traces are generally not recognizable. Similar bioturbation patterns are figured by Fiirsich (1974c, fig. 27a, c). This sort of preservation indicates that sedimentation proceeded at a relatively slow rate and that it was essentially continu- ous (Howard, 1975). Bedding planes separat- ing these mottled siltstones indicate depositional breaks without significant erosion. Rhoads (1967, 1975) suggests that such intensively bioturbated horizons are a function of the turnover rate of the population and rate of sedimentation, and less controlled by the den- sity of burrowing organisms than by their mo- bility. Sediment consistency of these mottled beds was low, as indicated by clusters 6f ice- rafted clasts which have sunk into the sediment (Text-fig. 7). Rhoads & Young (1970) suggested that unstable bottoms with a high proportion of water are dominated by infaunal, deposit feeding organisms. In the depositional environment of these beds, current activity was low and sediment was deposited slowly and continuously.

SYNTHESIS OF PALEOENVIRONMENTS

On the basis of sediment types, body fossils and trace fossils, three broadly distinctive depositional environments can be recognized in the Wasp Head Formation (Text-figs. 2, 8). These are marine foreshore, open shoreface and protected shoreface environments.

354




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Protected Foreshore- Shoreface ' - Offshore - shoreface

TEXT-FIG. 8-Inferred relationships of the three main trace fossil associations in the Wasp Head For- mation. a-c, Rosselia-Cylindrichnus association. a, Rosselia funnels at bedding surfaces are generally eroded, complete funnels occur with Planolites in thin dark mudstones; b, Thalassinoides is abundant at one level; c, some beds are mottled, Cylindrichnus is the most common trace; d, Skolithos association, burrows are sparsely distributed in cross stratified foreshore sands; e, f, Diplocraterion association. e, intensive bioturbation in sands containing no shells; f, epifaunal molluscs and brachiopods occur with less common burrows further offshore. The column gives the stratigraphic succession of the main trace fossil associations from the base to the top of the Wasp Head Formation.

Foreshore.-This environment is characterized by almost total absence of trace fossils, except for sparse, vague Skolithos, and body fossils which have been selectively preserved in iron-enriched bands following catastrophic disinterment and subsequent burial on the beach. The sediments are clean, low-angle, cross stratified sandstones and pebbly sandstones with a variable proportion of wood

fragments which normally accumulate in shallow troughs. Siderite cement occurs at some levels.

Open shoreface.-Burrows of infaunal suspension feeders, and body fossils of epifaunal suspension feeders comprise the characteristic association of organisms which inhabited

deeper water sediments below wave base. Di-

plocraterion, Catenichnus, Skolithos, ?Cylin-

drichnus and Rhizocorallium are the burrows of infaunal inhabitants, and large pelecypods (Eurydesma), spiriferoid brachiopods (Marti- niopsis, Trigonotreta and Pseudosyrinx), and bryozoans are the preserved sessile, epifaunal inhabitants. The sediments are generally finer, thicker bedded, and have fewer sedimentary structures than those of the foreshore. Calcite is the main cement.

Protected shoreface.-The most diverse range of sediments and trace fossils occurs in this environment and body fossils are absent. Sediments range from thinly laminated siltstones and sandstones to conglomerate with individual clasts up to about 1.7 m diameter. Rosselia and Cylindrichnus are the most significant trace fossils, although at particular levels, other forms such as Thalassinoides,

355



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TEXT-FIG. 9--Catenichnus n. ichnogen. compared to other vertical, U-shaped burrows (in vertical and horizontal section). a, Catenichnus in longitudinal section and transverse section with retrusive spreite; b, Diplocraterion with parallel arms linked by protrusive spreite which may or may not comprise obvious concave laminae; c, Corophioides with parallel arms and bidirection- al spreite; d, Arenicolites without spreite.

Psammichnites, Planolites and backfilled burrows become common. Evidence from both sediments and trace fossils suggests that this environment was subject to frequent changes in prevailing conditions. The relationship between the style of bioturbation and sedimentary features indicates a progressive change from very shallow water to quieter, deeper water environments; the intensity of bioturbation was probably highest in the deeper environments. The protected shoreface environment fluctuated between one in which current activity was strong, and one where currents were weak enough to permit deposition of laminated siltstones. This is best explained by the development of an offshore bar or shoals which gave some protection from waves on its landward side, but still provided access to open marine conditions. Rapid sedimentation of material derived from the shoals probably occurred during periods of storm activity. The conglomerates may have been derived from talus at the base of nearby headlands, or from deposits of short-headed streams which drained the glaciated inland.

SYSTEMATIC PALEONTOLOGY

Extensive use had been made of the Treatise on Invertebrate Paleontology, Supplement to Part W (Hantzschel, 1975), and this should be consulted for further comments and discussion of ichnogenera and reference lists. Specimen numbers refer to material housed in the De- partment of Geology, University of New En- gland, and are prefixed UNE F. Locality numbers are prefixed UNE L.

Ichnogenus DIPLOCRATERION Torell, 1870

Remarks.-The diagnosis given by Knox (1973, p. 134), based on redescription of the original material by Westergard (1931, p. 3- 4), is followed. Fiirsich (1974b) reviewed the vertical, U-shaped burrows with spreite and included Corophioides Smith in the synonymy of Diplocraterion Torell. Reasons for main- taining Corophioides Smith and Diplocrater- ion Torell as separate ichnogenera are given by Knox (1973).

DIPLOCRATERION PARALLELUM Torell, 1870 Text-figs. 6a-e, 9b

Diagnosis. -Vertical, spreite-bearing, U- shaped burrows with straight or slightly curved, parallel or subparallel arms formed by successive deepening of an originally shallow burrow.

Description.-In bedding plane section, paired openings of the sand-filled tube are linked by a dumbell-shaped structure of slightly darker sediment. This structure is the protrusive spreite which formed during initial stages of tube construction. The tubes are vertical, U-shaped, and some possess a thin lining of black, clayey material. Arms are circular or slightly elliptical in transverse section. Diam- eter of the arms is 6-8 mm, average distance between the arms is about 15 mm, and the depth of the burrow is variable. The burrows have no preferred orientation on bedding surfaces, and are sparsely distributed. In vertical section, some specimens had retrusive spreite; protrusive spreite was difficult to discern.

Remarks.-D. parallelum is abundant in overlying tidal flat and shallow subtidal siltstones and sandstones of the Pebbley Beach Formation, and like the forms described above from the Wasp Head Formation, very few specimens have conspicuous protrusive spreite (Text-fig. 9b). Most specimens possess a "sep-

356




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TEXT-FIG. 10-Catenichnus contentus n. ichnosp. a, c, longitudinal transverse sections of burrows with partly retrusive (a), and partly protrusive (c) spreite, from Snapper Point Formation, UNE L874; b, d, bedding plane sections of tubes with and without spreite, from Pebbley Beach Formation, UNE L1669.

tum" of structureless sediment of slightly different contrast between the arms of the tube. The septum is incipient protrusive spreite. The characteristic laminations are absent because during construction of the burrow, there were no stages of intermittent stability when the tube is maintained at a particular level, as is the case for spreite constructed in response to changing levels of the sediment surface.

D. parallelum from the Wasp Head For- mation are closest in size and shape to the forms named D. yoyo by Goldring (1962) although Goldring suggested that the burrows were constructed in a single episode and not as a gradual deepening sequence. D. parallelum and D. lyelli figured by Westergard (1931, pls. 1-4) have smaller diameter tubes and some specimens have funnel-shaped openings at the surface. D. parallelum, described by Pickerill, Roulston & Noble (1977), are approximately the same size, but only basal sections of retrusive spreite are figured. Draper (1977, fig. 6H) reported smaller D. parallelum from Ordovician rocks of north central Aus- tralia. D. parallelum described by Fiirsich (1974c) are much larger in tube diameter, width and depth of the burrow, and all of the

figured specimens have well developed restru- sive spreite. Lessertisseur (1955, fig. 40) figured two D. parallelum, one of which he called Corophioides luniformis, and another with well developed retrusive spreite which could have destroyed the initial protrusive forms.

Ichnogenus CATENICHNUS n. ichnogen.

Type ichnospecies.-Catenichnus contentus n. ichnosp.

Diagnosis.-Large vertical, symmetrical, curved burrows without parallel arms, and with or without spreite; tubes may be lined or unlined, and were formed by a single exca- vation episode, not by gradual enlargement of an initial depression. Burrows are circular or oval in cross section, and openings may be ex- panded. Depth:width ratio is less than 1:4, width of the tube 15-25 cm.

Remarks.-Catenichnus is always strongly divergent at the openings of the tube and this feature distinguishes it from U-shaped burrows like Diplocraterion, Arenicolites and Corophioides (Text-fig. 9). The tube diameter of Catenichnus is much greater than in these other burrows, and spreite reflects a response

357

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BRUCE McCARTHY

to erosion and sedimentation only. In Diplo- craterion and Corophioides protrusive spreite formed during initial construction of the tube, and in Arenicolites spreite is absent or may be present as floor deposits (Fiirsich, 1974c).

CATENICHNUS CONTENTUS n. ichnosp. P1. 1, figs. 4-6, Text-figs. 9a, 10a-d

Etymology.-Latin catenarius-of a chain; contentus-stretched, strained, tense, or tight. The names refer to the similarity in shape of the burrow to the catena shape of a moderately taut chain suspended between two points.

Holotype.-UNE F14794, paratypes UNE F14795 and F14796 collected from beds 14.13-14.18 (Gostin & Herbert, 1973) of the Snapper Point Formation, Willinga Point, UNE L874, Kioloa 1:31680 sheet, GR 3398 6174.

Description.-Specimens in the Wasp Head Formation are sparse, poorly preserved forms which were observed only in eroded bedding plane section as shallow, concave grooves up to about 20 cm wide and showing no preferred orientation. At the type locality, the burrows are numerous and may be crowded in patches on a single bedding plane. The burrows are vertical, symmetrical, curved tubes which are lined with dark, clayey material and generally possess spreite. Retrusive spreite is most common, although some specimens also have the protrusive type. The tube meets the surface at an angle of about 25?-35?, tube diameter is 15-25 mm, and the width of the tube between apertures is 20-25 cm. Depth:width ratio is

about 1:5. Burrow walls are thin and smooth, and the sediment infilling the tubes is the same as the surrounding sediment. In bedding plane section, the tubes may appear as elongate pits with preferred orientation in two directions at about 90? to each other (orientation was measured in the vertical plane of the tubes on single bedding planes). In vertical transverse section, the tubes are usually elliptical or round, and spreite is well defined by thin, dark laminae.

Remarks.-Undescribed trace fossils from an Ordovician, shoreface-barrier island sandstone (Carlo Sandstone) figured by Draper (1977, p. 103, figs. 6F(?), L) can probably be assigned to Catenichnus on the basis of similar shape in vertical section. Modern crustaceans like Nephrops norvegicus (lobster) may con- struct burrows similar to Catenichnus, but the shape of the modern forms is generally much less consistently regular, and many have more than two openings at the sediment surface (Rice & Chapman, 1971). Elders (1975) figured burrows formed by N. norvegicus which have an enlarged opening at one end of the tube; these forms are similar to Catenichnus except for the pronounced apertural enlargement. Catenichnus probably functioned as a dwelling burrow inhabited by an organism which fed from suspended material in water currents actively pumped through the tube. Catenich- nus occurs elsewhere in the southern Sydney Basin in greater abundance in shallow subtidal sediments of the Pebbley Beach Formation and in clean, quartzose, barrier-shoreface sandstones of the Snapper Point Formation.

EXPLANATION OF PLATE 1

FIG. 1-Planolites sp. Horizontal oblique view of burrows mainly parallel to bedding, X0.5, UNE L1661c, Wasp Head Formation.

2-3-Rosselia rotatus n. ichnosp. 2, horizontal section of funnel infilled with dark material, and eccentric tube, x0.6, UNE L1665, Wasp Head Formation; 3, vertical section of funnel-shaped burrow and remnant sand-filled tube, x0.5, UNE L1665, Wasp Head Formation, bed. 4.5.

4-6-Catenichnus contentus n. ichnogen., n. sp. 4, vertical section of burrow with retrusive spreite, x0.3; 5, horizontal oblique view of sand filled tube, partly eroded, arrow directed to other aperture, x0.3; 6, vertical transverse section of burrow with retrusive spreite, circular tube at top slightly left of center, x0.8, holotype UNE F14794. All specimens from UNE L874, Snapper Point Formation.

7-Planolites montanus Richter, 1937. Bedding surface with abundant burrows, x0.5, UNE L1661a, Wasp Head Formation.

8-Cylindrichnus concentricus Howard, 1966. Vertical section of sediment with abundant forms, some with spreite structures, x0.15, UNE L1661a, Wasp Head Formation.

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Ichnogenus SKOLITHOS Haldeman, 1840 SKOLITHOS VERTICALIS (Hall, 1843)

Text-fig. 3i

Diagnosis.-Burrows cylindrical to pris- matic (where they are in contact), straight to curved, vertical to inclined. Diameter 1-4 mm, burrow wall smooth, rarely corrugated (Alpert, 1974).

Description. -Vertical, cylindrical, slightly curved to straight, linear burrows. Diameter is about 4 mm, and greatest length observed about 10 cm. Walls are smooth, and either very thin or poorly defined. Vertical burrows are very sparsely distributed in cross stratified sands, and inclined burrows are more abundant in silty sands.

Remarks. The lack of contrast between the host rock and the burrow infill, and poorly defined walls in some specimens, makes rec- ognition of these forms difficult. Vertical burrows are restricted to low-angle cross bedded, and parallel bedded sandstones. In silty sandstones (bed 5.2), tubes are commonly inclined; relative abundance to other burrows of suspension feeding organisms (e.g., Diplocrater- ion) is difficult to determine. Alpert (1974) suggested that Skolithos may have been the dwelling burrow of an annelid or phoronid.

Ichnogenus RHIZOCORALLIUM Zenker, 1836 RHIZOCORALLIUM JENENSE Zenker, 1836

Text-fig. 6f, g

Diagnosis.-Generally straight, short U- shaped spreite-bearing burrows, commonly oriented oblique to bedding, and may be vertically retrusive (after Fiirsich, 1974a).

Description.-Burrows are horizontal and U-shaped, and arms of the tube are generally parallel or may converge slightly near the apertures. The burrows are relatively consistent in size, about 15-18 cm long, distance between the centers of the tubes about 8 cm, and tube diameter about 2-3 cm. There is no preferred orientation on individual bedding planes. The burrows are preserved in epirelief; neither tubes nor apertures are preserved. Spreite is preserved as closely spaced, low, discontin- uous ridges between the arms of the tube.

Remarks. -Fursich (1974a) discussed the morphology of Rhizocorallium and the ethol- ogy of likely producers, and interpreted R. jenense as the burrow of an infaunal suspension feeding organism. Sellwood (1970) de-

scribed smaller, vertically retrusive Rhizocor- allium from the lower Jurassic of Britain, and attributed these to organisms similar to modern callianassid crustaceans. These organisms adopt deposit-feeding habits during construction of the burrow, and a suspension-feeding mode of life when the burrows are completed (Sellwood, 1970). None of the R. jenense from other localities in the Sydney Basin exhibit vertically retrusive structures, and most are of similar size to those described herein. R. jenense is most abundant in overlying sediments deposited in protected shallow subtidal environments.

Ichnogenus THALASSINOIDES

Ehrenberg, 1944 Remarks.-For comments on Thalassi-

noides and related ichnogenera see Kennedy (1967), Fiirsich (1973), Bromley & Frey (1974) and Hantzschel (1975).

THALASSINOIDES PARADOXICUS

(Woodward, 1830) Text-fig. 3g

Diagnosis. -Irregular, very extensive horizontal burrow network occurring at several levels and connected by vertical shafts. Di- ameter of tunnels is highly variable; short, blind tunnels very common (after Kennedy, 1967, p. 142).

Description.-Dense network of small, branching burrows, most commonly about 4- 6 mm diameter, some tunnels up to 15 mm diameter. The network is largely horizontal and is probably confined to a single level in the sediment. Bifurcations are generally Y- shaped, without noticeable enlargement at the junctions; many of the branches terminate after a short distance as blind tunnels. Many of the tunnels seem to be unconnected to others, but this is probably an aspect of preservation; the tunnels are not always strictly horizontal, and oblique parts of the network are covered on horizontal bedding surfaces. Walls are smooth and unlined. The network was constructed in fine sand and subsequently infilled with dark silt and sand.

Remarks. T. paradoxicus is the most irregularly branching of the forms recognized by Kennedy (1967), and one of the smaller types, despite having some components with greater diameter. This form occurs in a thin sandy limestone associated with tidal flat sediments

360




in the overlying Pebbley Beach Formation. A variety of modern crustaceans produce burrows similar to Thalassinoides (Bromley & Frey, 1974), but most workers attribute these burrows to callianassid or thalassinidean shrimp.

Ichnogenus CYLINDRICHNUS Howard, 1966 CYLINDRICHNUS CONCENTRICUS

Howard, 1966 P1. 1, fig. 8

Diagnosis.-Vertical or inclined, straight or weakly curved, unbranched tubes with an ex- terior wall of multiple concentric layers.

Description.-Simple cylindrical or slightly ovate tubes 4-6 mm diameter and inclined at various angles to bedding. Simplest forms have a concentric wall structure in which the tube is central, but others may be slightly excentric because wall structures are biased towards one side of the tube. Concentric laminae are very fine, and comprise alternating dark material and lighter colored fine sand or silt.

Remarks.-These burrows comprise one end of a spectrum of burrows which culmi- nates at the other end in large Rosselia funnels. Specimens described as 'Asterosoma form "Cylindrichnus concentricus"' by Frey (1970), and 'Asterosoma form Cylindrichnus' by Frey & Howard (1970) are similar to the cylindrical forms with true concentric wall structure from the Wasp Head Formation, and are about the same size. Some of the burrows are part of a sequence which grades into rod-shaped burrows and Rosselia (Frey & Howard, 1970, p. 162), others grade into Asterosoma (Frey, 1970). For further comments see remarks on Rosselia rotatus and Text-fig. 5.

Ichnogenus ROSSELIA Dahmer, 1937 ROSSELIA ROTATUS n. ichnosp. P1. 1, figs. 2, 3, Text-fig. 4a-j

Etymology.-Latin rotatus-rotation. Holotype.-UNE F14797a, b, c from the

top of bed 4.4.12 (Gostin & Herbert, 1973) in the Wasp Head Formation at UNE L1661.

Diagnosis.-Vertical or inclined, straight or curved cylindrical tube which is enlarged to a funnel shape in upper parts; the funnel comprises finer grained sediment with intensively developed, crescentric backfill structures formed by rotary movements of the tube within the funnel.

Description.-Straight or curved funnel-

shaped burrows with a simple cylindrical tube central to the burrow in the lower parts, and may be excentric in the funnel. Concentric lay- ering occurs in the lower parts of the burrow below the funnel. Crescentic backfill structures in the funnel are alternating, closely spaced dark clay and silt laminae. In transverse section the funnels are circular or elliptical and attain greatest diameter at bedding surface. Maximum diameter of the funnels about 6.5 cm, maximum length of burrows about 12 cm, maximum diameter of tube about 0.8 cm. The type specimen has vertical, narrow ridges or striations which extend towards the apex of the funnel. In thin section, small dark fecal pellets are most abundant in clay laminae of the backfill structures, but may be scattered through the coarser laminae as well.

Remarks.-R. rotatus differs from R. socialis, which is the type ichnospecies, in having well developed backfill structures, and lacking the concentric laminae that are used to diag- nose R. socialis (Text-fig. 5d). Chamberlain (1971, text-fig. 8c-g) figured R. socialis from Pennsylvanian-Mississippian rocks of Okla- homa and proposed that Rosselia was inter- gradational with Asterosoma Otto, a burrow with similar morphology but oriented more closely to horizontal. Frey (1970) and Frey & Howard (1970) described Late Cretaceous funnel-shaped burrows as Asterosoma form "helicoid funnel." The forms figured by Frey (1970, fig. 3b) and Frey & Howard (1970, fig. 8h) show rather intensive development of structures similar to the backfill structures seen in R. rotatus, but in all other ways the burrows are entirely different. The Cretaceous forms have a well defined wall of closely ap- pressed whorls arranged in a low helicoid, and may pass upward as well as downward into cylindrical stems (Frey, 1970). No such wall structure or stem on the upper side of the burrow exists in R. rotatus, and these features have not been reported for R. socialis. In the Wasp Head Formation, R. rotatus is found with burrows similar to Cylindrichnus concentricus, some of which have short spreite (Text-fig. 5). These burrows may be sections through R. rotatus at a low level below the funnel, or they may be burrows which were occupied for only a relatively short period of time. Other burrows (e.g., Text-fig. 4b, c, g, h) similarly represent different phases in de-

361



BRUCE McCARTHY

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a

e TEXT-FIG. 11-Structures in Psammichnites. a,

Psammichnites sp. which lacks the low median ridge in the burrow floor; b, Psammichnites gigas from the Pebbley Beach Formation with the median ridge; c, d, longitudinal, vertical, oblique (c), and horizontal (d) sections with features common to both Psammichnites sp. and P. gigas; e, horizontal section low in the burrow with median ridge.

velopment of funnel shaped structures. In other parts of the southern Sydney Basin, R. rotatus and R. socialis are mutually exclusive, but may be closely related stratigraphically. In R. socialis from other localities, the tube is most commonly central to the funnel and backfill structures are absent.

Ichnogenus PLANOLITES Nicholson, 1873

Remarks.-Frey (1970) included branching burrows in description of forms from Creta- ceous rocks of Kansas. Following Alpert (1975) and Hantzschel (1975), branching forms are excluded from Planolites Nicholson herein.

PLANOLITES MONTANUS Richter, 1937 P1. 1, fig. 7, Text-fig. 3h

Diagnosis.-Horizontal to oblique, unbranched, cylindrical burrows, 1-5 mm diameter, with irregularly meandering or un- dulating pattern.

Description.-Horizontal and subhorizon- tal, cylindrical or slightly flattened burrows, diameter about 2 mm. Steeply inclined burrows are uncommon. Burrows are straight or curved, and infilled with cleaner sediment than that surrounding them. Walls of the burrows are smooth or slightly irregular. None of

the burrows branch, although some specimens partly overlap, or follow earlier formed specimens for short distances before diverging. Many burrows intersect.

Remarks.-P. montanus is extremely abundant in some silty and very fine sandy beds and may partly destroy other traces; many silt- filled Rosselia funnels have been intensively bioturbated by the P. montanus producer (Text-fig. 3h). The burrow was probably formed by an infaunal, sediment eating, worm- like animal, so that the burrow fill represents material that has been ingested and packed behind the animal as waste (Nicholson, 1873; Alpert, 1975).

PLANOLITES sp. P1. 1, fig. 1

Description.-Small, short, straight or slightly curved, cylindrical burrows up to about 2.5 mm diameter; they do not intersect, but may parallel earlier formed burrows, giv- ing the appearance of branching from a central axis.

Remarks.-Of the forms described by Al- pert (1975), Planolites sp. most closely resem- bles P. beverleyensis. However, Planolites sp. is smaller and does not exhibit the random cir- cling and burrow-crossing behavior, or meandering and looping reported by Alpert (1975, p. 514). This form occurs with P. montanus, Rosselia rotatus and Psammichnites sp. but is not abundant.

Ichnogenus PSAMMICHNITES Torell, 1870 PSAMMICHNITES sp.

Text-figs. 3b, e, 6h, 11

Description.-Linear, meandering, internal burrow preserved in full relief, with maximum width about 15 mm, height about 10 mm. In transverse section, the burrows are lenticular, lateral extremities are angular, and the burrows are more strongly curved in the convex upper parts than in the concave lower parts (Text-fig. 11). The burrows are oriented approximately parallel to bedding; an inclined, curved exit burrow indicates that the animal which produced the burrow was working the sediment at a depth of 10-12 cm when it began to move towards the sediment surface. The burrows do not appear to intersect, but may come in close lateral contact. Backfill structures occur as closely spaced, distinct or indis- tinct, transverse striations in vertical and hor-

362




izontal median sections. These structures are more strongly curved in the basal parts of the burrow than they are in the upper parts, and become more angular towards the lateral extremities; they are concave in the direction of movement. The backfill structures are also more angular in the convex upper parts of the burrows in horizontal section. The burrows are well defined, but have no constructed walls.

Remarks.-Slightly larger forms (P. gigas) found in overlying intertidal and shallow subtidal sandstones (Pebbley Beach Formation) have a vague, low median ridge in the floor of the burrow, and are otherwise the same as the forms described above (Text-fig. 11). The median ridge was not apparent in outcrop specimens, but could be seen in sectioned, collected specimens. Hantzschel (1975, p. W98) included Psammichnites in the broadly defined group of trails and burrows called Scol- icia de Quatrefages. Scolicia comprises a wide range of morphological forms thought to have been formed by burrowing univalved molluscs (Hantzschel, 1975). Glaessner (1969) described lower Cambrian burrows similar to Psam- michnites and suggested that these forms may have been produced by a primitive mollusc without a shell. General features of the burrows imply that they were formed as the mollusc selectively sorted the sediment for food, and packed material which was not ingested behind to produce the characteristic backfill structures (Frey & Howard, 1972).

Ichnogenus KECKIA Glocker, 1841 KECKIA sp. A Text-fig. 3d

Description.-Horizontal or slightly oblique burrows with transverse, crescentic, alternating annulations of clean, light colored sand, and darker silt. The burrow has poorly defined walls, and may be straight or curved. Width of the burrow is 7-12 mm. Transverse annulations vary in degree of curvature.

Remarks.-K. annulata Glocker (in Hantz- schel, 1938, figs. 4, 5) have better defined walls and more regularly shaped transverse annulations than the forms described above. Hantzschel (1975) suggested that the infilling sediment is probably material that has been ingested and packed behind the animal in the tunnel. By contrast, Frey & Howard (1972) maintain that well developed meniscus back-

fill structures are more likely to form from an animal passing sediment externally around it- self rather than from passing sediment through its digestive tract. Keckia sp. A is similar to the chevron trails figured by Frey & Howard (1970, fig. 8a) from Cretaceous rocks of Utah.

KECKIA sp. B

Text-fig. 3a, c

Description.-Curved or straight, horizontal or slightly oblique, bilaterally symmetrical burrows about 4.5 cm wide. Backfilled structures are strongly concave in the direction of movement and are delineated by thin laminae of darker clay. There is a high proportion of small, dark grains within the burrows which are probably fecal pellets; some of these pellets are aligned subparallel in the clay laminae. Walls of the burrow are made up of contin- uations of the clay laminae to lateral margins and, where lateral parts of successive laminae overlap, a fine concentric structure may be produced. Walls are generally smooth, but may be locally irregular.

Remarks.-Keckia sp. B is found at only one level in the Wasp Head Formation where Thalassinoides paradoxicus is otherwise monodominant. Keckia sp. B was formed at a later time than T. paradoxicus, and T. paradoxicus were destroyed where they were in- tersected by Keckia. T. paradoxicus was probably formed at shallow depths below the sediment surface, and presuming that there was no subsequent period of significant erosion, it is likely that Keckia also formed as a totally infaunal burrow rather than as a surface trail. The burrow illustrated as Text-fig. 3a is approximately parallel to bedding, but dips below bedding in the direction of movement. Keckia sp. B is much larger, and generally straighter, with more strongly curved backfill structures than Keckia sp. A.

BEDDING INTERFACE TRAILS

Text-fig. 3f

Description.-Straight or gently curved horizontal trails, 3-6 mm wide, and up to about 4 mm deep, although depth along length of the trails is variable. This variability in depth may be a preservational aspect, or it may indicate that the animals that produced the trails moved slightly inclined to bedding for some of the time. Some of the trails intersect. Those trails that have not been eroded

363



BRUCE McCARTHY

are infilled with sediment similar to that in which the trails were formed. There is no in- dication of structure on the walls, or of any internal structure.

Remarks.-It is most likely that these trails were formed along sediment interfaces by an animal working solely within the sediment; the burrows collapsed as the animal moved on, and were preserved in the manner described by Seilacher (1964) and Osgood (1970) as the primary cast of a burrow along an interface. The varying depth of the trails along their length suggests that there was an overlying body of sediment at the time the burrows were formed; it is unlikely that erosion removed parts of some burrows and left nearby burrows intact at a similar level.

ESCAPE BURROWS

Text-fig. 6i, j

Description. -Vertical, cylindrical burrows which are either rounded or tapered in the basal parts. Some burrows have internal structure of concave upward laminations and others are internally structureless. In the latter case, the burrows are evident only where they trans- gress other sedimentary structures. In some instances, sedimentary laminae on the margins of the burrows have been downwarped. Depth of the burrows is variable up to about 6.5 cm; diameter ranges from 1.2 cm in a deep burrow, to about 8 cm in a broad shallow burrow.

Remarks.-The contrast between deep, narrow burrows, and broad, shallow burrows reflects the different types of organism which produced the different forms. Small pelecypods may have produced the deeper forms during upwards escape by pulling or pushing movements of the foot, like that figured in Schafer (1972, p. 373, fig. 221). The broader, shallow forms may have been produced by an organism similar to modern echinoids.

ACKNOWLEDGMENTS

I wish to thank Bruce Runnegar, R. E. Gould, B. C. McKelvey and T. G. Russell of the Department of Geology, University of New England, for their assistance, useful sug- gestions and discussion of various problems. The work was carried out during the tenure of a Commonwealth Postgraduate Award.

REFERENCES

Ager, D. V. and P. Wallace. 1970. The distribution and significance of trace fossils in the uppermost Jurassic rocks of the Boulonnais, North- ern France. In T. P. Crimes and J. C. Harper (eds.), Trace fossils. Geol. J. Spec. Issue No. 3, p. 1-18.

Alpert, S. P. 1974. Systematic review of the genus Skolithos. J. Paleontol. 48:661-669.

.1975. Planolites and Skolithos from the Up- per Precambrian-Lower Cambrian, White-Inyo Mountains, California. J. Paleontol. 49:509-521.

Bromley, R. G. and R. W. Frey. 1974. Redescrip- tion of the trace fossil Gyrolithes and taxonomic evaluation of Thalassinoides, Ophiomorpha, and Spongeliomorpha. Bull. Geol. Soc. Den. 23:311- 335.

Chamberlain, C. K. 1971. Morphology and ethol- ogy of trace fossils from the Ouachita Mountains, southeast Oklahoma. J. Paleontol. 45:212-246.

Clarke, M. J. 1972. The growth position and post- mortem asymmetrical distortion of some Tas- manian neospiriferids. Tech. Rep. Dept. Mines Tasmania 15:139-143.

Conybeare, C. E. B. and K. A. W. Crook. 1968. Manual of sedimentary structures. Aust. Bur. Miner. Resour., Geol. Geophys., Bull. 102, 327 p.

Crimes, T. P. 1970. The significance of trace fossils in sedimentology, stratigraphy and palaeo- ecology with examples from lower Palaeozoic strata. In T. P. Crimes and J. C. Harper (eds.), Trace fossils. Geol. J. Spec. Issue 3, p. 101-126.

.1973. From limestones to distal turbidites: A facies and trace fossil analysis in the Zumaya flysch (Paleocene-Eocene), North Spain. Sedi- mentology 20:105-131.

Dickins, J. M., V. A. Gostin and B. Runnegar. 1969. The age of the Permian sequence in the southern part of the Sydney Basin, p. 211-225. In K. S. W. Campbell (ed.), Stratigraphy and Palaeontology: Essays in Honour of Dorothy Hill. Aust. Natl. Univ. Press, Canberra.

Draper, J. J. 1977. Environment of deposition of the Carlo Sandstone, Georgina Basin, Queens- land and Northern Territory. Aust. Bur. Miner. Resour., Geol. Geophys., Bull. 2:97-110.

Elders, C. A. 1975. Experimental approaches in neoichnology, p. 513-536. In R. W. Frey (ed.), The Study of Trace Fossils, Springer-Verlag, New York.

Farrow, G. E. 1966. Bathymetric zonation of Ju- rassic trace fossils from the coast of Yorkshire, England. Palaeogeogr., Palaeoclimatol., Palaeo- ecol. 2:103-151.

. 1971. Back-reef and lagoonal environments of Aldabra Atoll distinguished by their crusta- cean burrows. Zool. Soc. Lond., Symp. 28, p. 45 5-500.

Frey, R. W. 1970. Trace fossils of Fort Hays Limestone Member, Niobrara Chalk (Upper Cre-

364




taceous), west-central Kansas. Univ. Kans. Pa- leontol. Contrib., Art. 53, 41 p.

.1975. The realm of ichnology, its strengths and limitations, p. 13-38. In R. W. Frey (ed.), The Study of Trace Fossils, Springer-Verlag, New York.

and J. D.Howard. 1970. Comparison of Up- per Cretaceous ichnofaunas from siliceous sandstones and chalk, western Interior Region, U.S.A. In T. P. Crimes and J. C. Harper (eds.), Trace fossils. Geol. J. Spec. Issue 3, p. 141-166.

and - . 1972. Georgia coastal region, Sa- pelo Island, U.S.A.: sedimentology and biology. VI. Radiographic study of sedimentary structures made by beach and offshore animals in aquaria. Senckenbergiana Marit. 4:169-182.

Fiirsich, F. T. 1973. A revision of the trace fossils Spongeliomorpha, Ophiomorpha and Thalassion- oides. N. Jahrb. Geol. Palaontol. Mh., H. 12:719-735.

1974a. Ichnogenus Rhizocorallium. Palaon- tol. Z. 48:16-28.

.1974b. On Diplocraterion Torell 1870 and the significance of morphological features in vertical, spreiten-bearing, U-shaped trace fossils. J. Paleontol. 48:952-962.

.1974c. Corallian (Upper Jurassic) trace fossils from England and Normandy. Stuttg. Beitr. Naturkd., Ser. B, Nr. 13:1-52.

Glaessner, M. F. 1969. Trace fossils from the Pre- cambrian and basal Cambrian. Lethaia 2:369- 393.

Goldring, R. 1962. The trace fossils of the Baggy Beds (Upper Devonian) of North Devon, En- gland. Palaontol. Z. 36:232-251.

Gostin, V. A. and C. Herbert. 1973. Stratigraphy of the Upper Carboniferous and Lower Permian sequence, southern Sydney Basin. J. Geol. Soc. Aust. 20:49-70.

Hallam, A. 1967. Siderite- and calcite-bearing concretionary nodules in the Lias of Yorkshire. Geol. Mag. 104:222-227.

Hantzschel, W. 1938. Quer-gliederung bei Litto- rina-Fahrten, ein Beitrag zur Deutung von Keck- ia annulata Glocker. Senckenbergiana 20:297- 304.

1975. Trace fossils and problematica. In C. Teichert (ed.), Treatise on Invertebrate Paleon- tology, Part W, Supplement 1 (Trace Fossils), Univ. Kans. Press and Geol. Soc. Am., Law- rence, Kansas, 269 p.

.1975. The sedimentological significance of trace fossils, p. 131-146. In R. W. Frey (ed.), The Study of Trace Fossils, Springer-Verlag, New York.

Kennedy, W. J. 1967. Burrows and surface traces from the Lower Chalk of southern England. Br. Mus. (Nat. Hist.) Bull. Geol. 15:125-167.

Knox, R. W. O'B. 1973. Ichnogenus Coro- phioides. Lethaia 6:133-146.

Lessertisseur, J. 1955. Traces fossiles d'activate

animale et leur signification paleobiologique. Soc. Geol. France, Mem. n. ser. 74:1-150.

McCarthy, B. 1977. Selective preservation of mollusc shells in a Permian beach environment, Syd- ney Basin, Australia. N. Jahrb. Geol. Palaontol. Mh., H. 8:466-474.

Nicholson, H. A. 1873. Contributions to the study of the Errant Annelides of the Older Palaeozoic Rocks. R. Soc. Lond., Proc. 21:309-310.

Osgood, R. G. 1970. Trace fossils of the Cincinnati Area. Palaeontol. Am. 6(41):281-444.

Pickerill, R. K., B. V. Roulston and J. P. A. No- ble. 1977. Trace fossils from the Silurian Cha- leurs Group of southeastern Gaspe Peninsula, Quebec. Can. J. Earth Sci. 14:239-249.

Rhoads, D. C. 1967. Biogenic reworking of intertidal and subtidal sediments in Barnstable Har- bor and Buzzards Bay, Massachusetts. J. Geol. 75:461-476.

. 1975. The paleoecological and environmental significance of trace fossils, p. 147-160. In R. W. Frey (ed.), The Study of Trace Fossils, Springer-Verlag, N.Y.

and D. K. Young. 1970. The influence of deposit-feeding benthos on bottom sediment stability and community trophic structure. J. Mar. Res. 28:150-178.

Rice, A. L. and C. J. Chapman. 1971. Observa- tions on the burrows and burrowing behaviour of two mud-dwelling decapod crustaceans, Ne- phrops norvegicus and Goneplax rhomboides. Mar. Biol. 10:330-342.

Runnegar, B. 1965. The bivalves Megadesmus Sowerby and Astartila Dana from the Permian of Eastern Australia. J. Geol. Soc. Aust. 12:227- 252.

. 1968. Preserved ligaments in Australian Permian bivalves. Palaeontology 11:94-103.

.1969. Permian fossils from the southern ex- tremity of the Sydney Basin, p. 276-298. In K. S. W. Campbell (ed.), Stratigraphy and Palaeon- tology: Essays in Honour of Dorothy Hill, Aust. Natl. Univ. Press, Canberra.

.1970. Eurydesma and Glendella gen. nov. (Bivalvia) in the Permian of Eastern Australia. Aust. Bur. Min. Resour., Geol. Geophys., Bull. 116:83-116.

. 1974. Evolutionary history of the bivalve subclass Anomalodesmata. J. Paleontol. 48:904- 939.

Schafer, W. 1972. Ecology and Paleoecology of Marine Environments. G. Y. Craig (ed.), trans- lated by I. Oertel, Oliver & Boyd, Edinburgh, 568 p.

Seilacher, A. 1964. Biogenic sedimentary structures, p. 296-316. In J. Imbrie and N. Newell (eds.), Approaches to Paleoecology, Wiley, New York.

.1967. Bathymetry of trace fossils. Mar. Geol. 5:413-428.

Sellwood, B. W. 1970. The relation of trace fossils

365



BRUCE McCARTHY

to small scale sedimentary cycles in the British Lias. In T. P. Crimes and J. C. Harper (eds.), Trace Fossils. Geol. J. Spec. Issue No. 3, p. 489- 504.

Westergard, A. H. 1931. Diplocraterion, Mono- craterion and Scolithus from the Lower Cam-

brian of Sweden. Sver. geol. Unders., Ser. C. Avh. och Upps. No. 372 (Arsbok 25 No. 5), p. 25.

MANUSCRIPT RECEIVED MARCH 5, 1976 REVISED MANUSCRIPT RECEIVED FEBRUARY 28, 1978

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trace fossils from a permian shoreface-foreshore environment, eastern australia

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