TRACE FOSSILS FROM THE KUFRA BASIN, LIBYA

BRIAN R. TURNER AND MICHAEL J. BENTON Department of Geology, The University, Newcastle upon Tyne, NE1 7RU, England

Ass~~~cr-ThePaleozoic succession in the southeastern part of the Kufra Basin, Libya, comprises a sequence of sedimentary facies up to 250 m thick, representing fluvial, tidal, subtidal, shoreface and marine shelf depositional environments. Body fossils are rare, and precise age and stratigraphic relations uncertain. However, many of the formations contain trace fossils. The oldest association of Cruzianu, Arthrophycus and Monocraterion comes from the Cambro- at Jebel Archenu which unconformably overlies basement. This is the first recorded presence of Cru- ziana and Arthrophym from the Cambro-Ordovician in the Kufra Basin. Elsewhere, the Cambro- Ordovician contains fine, deep, shoreface sands characterized by the occasional presence of Cylin- drichnus followed by coarser, shallower, shoreface sands with abundant Phycodes. Arthrophym and Cruziana are common in the Lower Tadrart Formation (youngest record of true Arthrophycus) and the upper part of the Acacus Formation. The presence of abundant Cruziana at this level throughout the area provides a useful local stratigraphic marker. Skolithos is abundant at the base of the Upper Devonian Binem Formation and Zoophycos at the top where it forms a thin, but extensive marker bed known as the Zoophycos . The Dalma Formation has a more diverse ichnofauna including Bifungites (youngest record?), Neo- nereites and Scoyenia preserved mainly in the upper part of a major transgressive sequence rep- resenting a transitional environment between the shoreface zone and nearshore shelf.

INTRODUCTION STRATIGRAPHY THEKum BASIN in southeast Libya (Figure The trace fossils come from two main sec- 1) occupies an area of about 400,000 km2 and tions measured at Jebel Asba and Jebel is filled by a sequence of Paleozoic and Meso- Archenu (Figures 2, 3). No previous descrip- zoic up to 2,600 m thick, separated tion of the stratigraphy of the area has been by an . Although outcrops of published; the only reference to it is con- Paleozoic sediments are confined to the tained in confidential oil company reports. southwest, north and southeast corners of the The succession at Jebel Asba extends from basin the stratigraphy is remarkably consis- the Cambro-Ordovician through the Silurian tent throughout despite variations in thick- and Devonian to the Carboniferous. The base ness of up to 600 m (Turner, 1980). The pres- of the succession is not exposed and litho- ent study focusses attention on the Paleozoic stratigraphic subdivisions and age relations succession in the southeast centered on Jebel are based mainly on comparisons with other Asba and Jebel Archenu (Figure 1) where the Paleozoic basins which generally retain the succession is discontinuously exposed along same terminology throughout Libya. The only the southern limb of a large syncline dipping exception in Kufra is the Carboniferous at between 5 and 10" north. Owing to the lack Dalma Formation which is named for expo- of exposure, subsurface data and biostrati- sures in the northern part of the basin at Jebel graphic control, correlation between the two Dalma Kebir. Two major problems are 1) areas is uncertain. Body fossils are generally that the Carboniferous is confined to an area lacking but trace fossils are present, partic- north of Jebel Asba where the base is not ularly at Jebel Asba where they occur exposed; hence its relationship to the rest of throughout the succession. Little previous the succession is uncertain and 2) that fault- study ofthe trace fossils has been undertaken. ing has disrupted stratigraphic relations at the The main purpose of this paper is to northern end of Jebel Asba where hitherto describe the trace fossils and assess their unrecognized Cambro-Ordovician sedi- stratigraphic and environmental significance ments occur along a major fault plane trend- with particular reference to the relationship ing northwest-southeast (Figure 1). Addi- between distribution and litho- tional photogeological reconnaissance facies. suggests that these Cambro-Ordovician sed- Copyr~ghtG 1983, The Society of Econom~c 447 0022-3360/83/00574447$03 00 Paleontologists and Mineralogists and The Paleontolog~calSociety 448 BRIAN R. TCTRNER .41VD MICHAEL J. BENTON

TI Uniform sand cover Intrusive rocks,mainly granitic(Post-Carboniferous) Upper Nubian Sandstone (Upper ) Dalma Formation (Carboniferous) Binem Formation (Middle-Upper Devonian) Tadrart Formation

Formations(Si1urian) Cambro-Ordovician,includes HassaounaandMemouniat rzdMetamorphic Basement --- Major fault Measured section

FIGURE1-Generalized geological map of the southeastern part of the Kufra Basin and location of study area. iments may extend farther to the northeast borehole penetrating Silurian shales in cen- towards Jebel Rukn as depicted on the geo- tral Jebel Asba. These graptolites, chitinozoa logical map (Figure 1). Body fossils are rare and pelecypods have been identified (Turner, and have only been recorded from a shallow 1980). An extensive search of the shales on TRACE FOSSILS 449

FIGURE2-Generalized stratigraphy, facies analysis and trace fossil distribution in the Paleozoic succes- sion at Jebel Asba. the outcrop failed to reveal any further body exposed, but only accessible at one locality fossils. Trace fossils in comparison are com- because of the precipitous cliff face. The strata mon and occur repeatedly at intervals rest unconformably on the Precambrian throughout the succession (Figure 2). basement. The contact is defined by a thin, The strata at Jebel Archenu are well discontinuous pebble conglomerate. The 450 BRZA,\- R. TLTRATERAATD ztfZCH.lEL J BENTO!V

bedded coarse

LOW angle and horizontally lammated

sandstones w~thalternating

Cross-bedded coarse pebbly feldspath~csandstones

Locally cross-bedded coarse pebbly sandstones Interbedded wlth manor s~ltstones, Subtldal channels s~lty-shales and shales and shoals

FIGURE3-Generalized stratigraphy, facies analysis and trace fossil distnbution in the Paleozoic suc sion at Jebel Archenu. TRACE FOSSILS 45 1

pebbles are composed mainly of subrounded indicative of a non-barred, macrotidal, tide- to subangular up to 7 cm in diam- dominated, sandy coastline comparable with eter and display a crude imbrication. The contemporary macrotidal coastlines, such as succession of strata is assigned to the Cam- the North Sea coast of Germany. The only bro-Ordovician solely on the basis of its posi- exception to this general trend occurs at Jebel tion above Precambrian basement. There is Asba where burrowed shoreface sediments no confirmatory biostratigraphic evidence characteristic of a high energy, wave-domi- and the generalized succession and lithofacies nated coastline such as the present day Ore- patterns do not correlate with the Jebel Asba gon coastline occur beneath a high energy, section, 80 km to the north. However, it has tide-dominated sequence probably in been suggested that an erosion surface about response to changes in offshore slope and 160 m above the base of the succession is the shoreline configuration. The dominance of contact between the Hassouna and Mem- strong tidal currents implies that the Kufra ouniat formations recognized at Jebel Asba Basin was connected with an open ocean (Turner, 1977). Body fossils are absent and (Tethys), probably through the Quattara trace fossils uncommon; most of them being embayment in the northeast. The general lack confined to the middle of the succession of fine silts and muds is attributed to the low except for Monocraterion. According to concentration of suspended in the unpublished oil company reports (Turner, fluvial input to the basin, the effectiveness of 1977) Monocraterion occurs just above the wave and tidal processes in the nearshore area base (Figure 3) and appears to be character- and the tidal flushing mechanism generated istic of the Cambro-Ordovician in other parts in response to basin hydrography (Turner, of the basin. The similar thickness of strata 1980). at Jebel Asba and Jebel Archenu is attributed to the fact that the Cambro-Ordovician in TRACE FOSSIL DESCRIPTIONS this area is very thick (400 m) compared to Ichnogenus ARTHROPHYCUSHall, 1852 the rest of the strata. ARTHROPHYCUSALLEGHANIENSIS (Harlan, 1831) SEDIMENTOLOGY Figure 4A Detailed facies analysis and environmental Description. -Some slabs from the Tadrart interpretations of the succession at Jebel Asba Formation are packed with curving, crossing, and Jebel Archenu have been given elsewhere branching horizontal to subhorizontal bur- (Turner, 1980). Only a brief description of rows which are 1-2 cm wide, and circular to the sedimentology is presented here. The elliptical in cross section. The burrows widen stratigraphy, facies descriptions and environ- and become partly bilobate before branching mental interpretations, and trace fossil dis- and then run on in bunches. The burrows are tribution are summarized in Figures 2 and 3. crossed regularly by transverse ridges (3 to 4 The sedimentary facies represent fluvial, tidal, per cm). subtidal, shoreface and marine shelf depo- Remarks.-Arthrophycus has been de- sitional environments. The repetition of sim- scribed from the Lower Silurian of New York ilar facies implies a recurrence of similar State (e.g., Hall, 1852, p. 4-6, Pis. l,2; Hantz- depositional processes and environments schel, 1975, fig. 25.4), Lower Ordovician of which is attributed to interaction of a marine Jordan (Selley, 1970, p. 485 ("Harlania")), coastline and a braided alluvial plain. When and the Cambro-Ordovician of Spain (Bald- the fluvial system was active due to source win, 1977, p. 26, P1. 2a), in association with area tectonism or shifts in the depositional Cruziana. Libyan Cambro-Ordovician and system the environments prograded seaward; Silurian material is also associated with Cru- when it was inactive transgression and ziana, and appears similar in form and rela- drowning of the coastline occurred. This tions to these described occurrences. Our sequence of regressive and transgressive Lower Devonian material resembles these in events caused a repeated northwest (regres- size and form, but shows more frequent and sion) and southeast (transgression)shift of the regular branching and does not occur with facies tracts. The more common nearshore Cruziana. Later forms compared with shallow water marine environments are Arthrophycus from the Cretaceous and Ter- 452 BRIAN R. TURNER AND MICHAEL J. BENTON TRACE FOSSILS 453 tiary of the United States (Frey and Howard, and Mississipian Montana material com- 1970, p. 147, 152) and Europe (Ksiazkiewicz, monly displays arrow-shaped ends. 1970, p. 284) are not typical of the genus (Hantzschel, 1975, p. W38-W39), and the Bifungites has been interpreted as a cast of Lower Devonian Tadrart material described the top part of a U-shaped burrow by Sei- here is, then the youngest representative of lacher (1955) and Dubois and Lessertisseur the genus yet described. (1964), and as the base of a U-shaped burrow Arthrophycus is a feeding burrow formed by Osgood (1970), Rodriguez and Gutschick by arthropods or worms and seems to be typ- (1970) and Gutschick and Lamborne (1975). ical of Seilacher's Cruziana Facies. The latter interpretation seems best sup- Occurrence.-Tadrart Formation (Lower ported by good material. Osgood (1970, p. Devonian), Jebel Asba; Acacus Formation 323-325) synonymized Bijiungites with (Silurian), Jebel Asba; Cambro-Ordovician, Corophioides biclavata (Miller, 1875) on the Jebel Archenu. basis of a range of Cincinnatian (Upper Ordo- vician) specimens that show all gradations Ichnogenus BIFUNGITESDesio, 1940 from typical dumbbells to complete flat-bot- BIFUNGITESFEZZANENSIS Desio, 1940 tomed U-shaped burrows with spreite. How- Figure 4B ever, since dumbbell forms are relatively Description.-One specimen, preserved as common in the fossil record but not always a convex hyporelief, shows the typical dumb- associated with good comparative U-shaped bell shape characteristic of Bijiungites. The burrow material, it is best not to synonymize bulbous ends are 6 X 9 mm in area, and 5 Bijiungites with Corophioides. Furthermore, mm thick, and the central tie is 2.1 cm long most of these have now been synonymized and 4 X 2 mm in diameter. with Rhizocorallium. Also, some Bijiungites Remarks. -Bijiungites has already been may belong to Diplocraterion-like forms, or reported from the Devonian of Libya and even to U-shaped burrows without spreite other Sahara localities (Desio, 1940; Dubois (e.g., Arenicolites). and Lessertisseur, 1964). Other records Bijiungites occurs commonly in "shallow include: Lower of Pakistan (Sei- nearshore marine and brackish water envi- lacher, 1955, p. 382-385, fig. 5 (1 5)), Ordo- ronments" in the Upper Devonian and Lower vician of Ohio (Osgood, 1970, p. 323-325, of Montana (Rodriguez and P1. 65, fig. 6; P1. 66, fig. 5; P1. 70, fig. 5; P1. Gutschick, 1970; Gutschick and Lamborne, 7 1, fig. 4), Lower Silurian of New York State 1975), in the Cruziana Facies in the Lower (Hall, 1852, p. 20, 25, P1. 6, fig. 2; P1. 10, fig. Cambrian of Pakistan (Seilacher, 1955) and 6), Lower Devonian of New York State (Mil- in the tidal and offshore zones in the Devo- ler, 1979, p. 125, P1. 21), and Upper Devo- nian ofNew York State (Miller, 1979). Bijiun- nian and Lower Mississipian of Montana gites is interpreted as part of a dwelling bur- (Rodriguez and Gutschick, 1970, p. 4 18-4 19, row produced by an annelid or arthropod. P1. 5; Gutschick and Lamborne, 1975). Thus Occurrence.-Dalma Formation (Carbon- the Carboniferous Libyan material matches iferous), Jebel Asba. in age the youngest Bijiungitesfrom Montana. The Libyan Bijiungites differs from the Mon- Ichnogenus CRUZIANAdYOrbigny, 1842 tana material in that the bar is relatively cf. CRUZIANAsp. broader and shorter and the Upper Devonian Figure 4C

FIGURE4-A, Arthrophycus alleghaniensis (Harlan) on sole of sandstone bed, Lower Devonian Tadrart Formation. B, Bufungites fezzanensis Desio, on sole of sandstone bed, Carboniferous Dalma For- mation. C, Cruziana sp., on sole of sandstone bed, Silurian Acacus Formation. D, cf. Diplichnites on sole of mudstone bed, Silurian Tannezouft Formation. E, Cylindrichnus sp., on top of partly eroded sandstone bed, Cambro-Ordovician Hassaouna Formation. F, Neonereites biseralis Seilacher, upper surface of siltstone bed, Carboniferous Dalma Formation. G, Phycodes aK palmatum (Hall) on top of partly eroded sandstone bed, Cambro-Ordovician Memouniat Formation. H, Planolites sp., on sole of siltstone bed, Silurian Tannezouft Formation. BRIAN R. TURNER AND MICHAEL J. BENTON

Description.-The figured slab is packed CYLINDRICHNUSsp. with crossing bilobed trails preserved as con- Figure 4E vex hyporeliefs, 1.5-2.0 cm wide and up to Description.-In several of the lithofacies 2 cm deep. The central ridge is well marked, investigated there occur vertical to subvert- and transverse scratches are visible. The traces ical tubes, circular or slightly flattened in cross are up to 10 cm long, but generally shorter section, and about 1 cm in diameter. There (4-6 cm), and they show some alignment, is a hard outer wall and a central funnel filled possibly in response to bottom currents. The with soft sediment, which is clearly distin- resting traces, Cruziana, grade into Ruso- guished by weathering. The tubes extend to phycus-like forms. a depth of between 5 and 10 cm and are not Remarks. -No attempt is made to ascribe crowded. In some cases, they bifurcate and the present material to a species of Cruziana appear to grade into Phycodes (q.v.). because of the worn nature of the surface. Remarks. -Cylindrichnus is distinguished Cruziana is typical of the distal shelf Cru- from Skolithos by the central core, the con- ziana Facies of Seilacher (1967), and it occurs ical, weakly curved form, and the variation here with Arthrophycus as in some other in orientation from nearly horizontal to ver- Lower Paleozoic examples (see above). The tical (Hantzschel, 1975, p. W57). Our mate- present specimens were probably produced rial conforms with these features, although by trilobites. the conical, curved shape is not seen clearly. Occurrence.-Acacus Formation (Silu- Some of the material could be integrated rian), Jebel Asba; Cambro-Ordovician, Jebel Monocraterion, but it shows no sign of the Archenu. characteristic funnel at the top. Frey and Howard (1970) consider Cylin- Ichnogenus DIPLICHNITESDawson, 1873 drichnus from the Cretaceous of Utah as a DIPLICHNITESsp. permanent burrow of a filter-feeding organ- Figure 4D ism living in slightly turbulent nearshore Description.-The figured specimen shows waters. It generally occurs in fine-grained sand a 12 cm stretch of trail consisting of two par- with surface trails and burrows. The Libyan allel series of small grooves 5-6 mm apart. material is found within fine- to medium- The grooves are chevron-shaped, 1-1.5 mm grained shoreface sands and coarse, pebbly wide, and about 1 mm apart. The trail is subtidal sand bodies, both environments sug- interrupted by an ovoid impression, and gesting a high energy, nearshore turbulent another shorter trail on the same slab ter- regime. minates in a similar mark. Cylindrichnus has previously been reported Remarks. -This trail is interpreted as pro- from the and Cretaceous of duced by the distal elements of the legs of an the United States (Hantzschel, 1975, p. W57). arthropod. The ovoid impression may be The Libyan material is the earliest occurrence resting marks and may show the outline of of Cylindrichnus recorded to date. the producer. Our material resembles some Occurrence. -Hassaouna Formation trails ascribed to Diplichnites (e.g., Cambro- (Cambro-Ordovician), Jebel Asba. Ordovician of Spain, Baldwin, 1979, p. 22, P1. 2d) and the "?trail in the form of two Ichnogenus NEONEREITESSeilacher, 1960 parallel rows" from the Upper Precambrian NEONEREITESBISERIALIS Seilacher, 1960 of the USSR (Fedonkin, 1977, p. 190, P1. 2a). Figure 4F Some forms of Beaconichnus from the Devo- nian of Antarctica appear similar (e.g., Description.-The figured slab shows sev- Hantzschel, 1975, figs. 27. lb, c) but they are eral irregularly meandering horizontal bur- much larger than our specimen (rows 2-30 rows consisting of two rows of alternate flat- cm apart). tened subspherical beads, or lobes, preserved Occurrence. -Tannezouft Formation as convex hyporeliefs. The trace is 1.O-1.5 (Silurian), Jebel Asba. cm wide, and each bead is 0.4-0.8 cm in diameter. The beads occur clearly in places, Ichnogenus CYLINDRICHNUSToots in but blend into a smoother burrow morphol- Howard, 1966 ogy elsewhere. TRACE FOSSILS 455

Remarks.-Although larger than Seilach- Ichnogenus PLANOLITESNicholson, 1873 er's type material (beads 0.3-0.4 cm PLANOLITESMONTAWS Richter, 1937 in diameter). our svecimens correspond to Figures 4H, 5A the characters of ~ionereitesbiserialis. Ne- Description. -Irregular horizontal bur- reites may also be represented by flattened rows, 2-5 mm in diameter circular to sub- lobed burrows but they generally meander circular in section. The burrows appear to more regularly, and the lobes are well defined branch in one specimen (Figure 4H), but this and regular. The figure of the "Neonereites is a misleading appearance caused by cross- view" of Scalarituba from the Pennsylvanian ing. In another specimen (Figure 5A), two of the Ouachita geosyncline, as interpreted circular 3-5 mm burrows run close together, by Chamberlain (1978a, p. 32, fig. 4 (28); and meet at one end. This is not a bilobed 1978b,. - p. 135, fig. 51), is very like our mate- trace because the two burrows are seDarate nal. for their whole length and their spacing var- Neonereites occurs in a range of ichnofacies ies. There are no signs of backfill structures from mid-shelf Skolithos to deep-sea Ne- and the burrow fill is rather different from reites Zones (Chamberlain, 1978a; Seilacher, the matrix. 1978). Remarks.-The lack of backfill structures Occurrence. -Dalma Formation (Carbon- and the differentiation of the burrow fill from iferous), Jebel Asba. the matrix, suggest that these specimens are Planolites rather than Palaeophycus (as Ichnogenus PHYCODESRichter, 1850 defined by Alpert, 1975, p. 5 12). Planolites PHYCODES aff. P. PALMATUM (Hall, 18 52) is a well-known facies-crossing form and is Figure 4G of little use for environmental interpretation. Description. -Subhorizontal burrows, 1 cm Occurrence. -Tannezouft Formation (Si- in diameter branching upwards in tight bun- lurian), Jebel Asba; Memouniat Formation dles to a total width of about 4 cm. (Cambro-Ordovician), Jebel Asba. Remarks.-As suggested by Seilacher (1955, p. 383-386), Hall's Buthotrephis pal- Ichnogenus SCOYENIAWhite, 1929 mata is probably a species of Phycodes. Our SCOYENIAGRACILIS White, 1929 specimens resemble those figured by Hall Figure 5B (1852, PI. 6, fig. I), Seilacher (1955, e.g., PI. 25, fig. 1) and Crimes et al. (1979, p. 104, fig. Description. -Circular horizontal to sub- 5i) as P. palmatum. The Libyan specimens horizontal burrows 4-8 mm in diameter, run- differ from P. circinnatum Richter, 1850 ning straight for up to 20 cm, or curving. No (Hantzschel, 1975, figs. 59, 2b, d) which has branching but frequent crossing, and may far more and narrower branches, P,flabellum pack entire bedding plane surfaces. The sur- Miller and Dyer, 1878 (Osgood, 1970, e.g., face of the burrow is longitudinally striated PI. 70, fig. 6) which consists of broad fans of (striae: 0.2 mm wide). tightly packed small arms, and P. pedum Sei- Remarks.-These burrows might be con- lacher, 1955 (p. 386-388, fig. 4) which is a fused with Fucusopsis (see Hantzschel, 1975, curved burrow system with regular laterally p. W64), but the striations are too regular and and upwards directed branches. well marked. Scoyenia is typical of Seilach- Phycodes occurs in the Cruziana Facies of er's Scoyenia Facies which is characteristic the Lower Cambrian of Pakistan (Seilacher, of nonmarine clastics (e.g., red beds 1955), Cambro-Ordovician of Spain (Bald- of North America and Europe). Bromley and win, 1977), Upper Ordovician of Ohio Asgaard (1979) report S. gracilis from sand- (Osgood, 1970), Lower Silurian of New York stone units of continental red bed sequences State (Hall, 1852), and in intertidal beds of in the of East Greenland. They sug- the Lower Cambrian of Spain (Crimes et al., gest that it was formed under very shallow 1977). water, or in subaerially exposed sediment, Occurrence.-Phycodes crowds beds in the often in association with mud-cracks. Memouniat Formation (Cambro-Ordovi- Occurrence.-Dalma Formation (Carbon- cian), Jebel Asba. iferous), Jebel Asba. 456 BRIAN R. TURNER AND MICHAEL J. BENTON

FIGURE5-A, Planolites sp., on top of sandstone bed. Cambro-Ordovician Memouniat Formation. B, Scoyenia gracilis White, on sole of sandstone bed, Carboniferous Dalma Formation. C, Skolithos linearis Haldeman, field photograph of sandstone bed, Upper Devonian Binem Formation. D, Zoophycos sp., on top of sandstone bed, Upper Devonian Binem Formation. E, Annulated Trail, on sole of sandstone bed, Carboniferous Dalma Formation. TRACE FOSSILS

Ichnogenus SKOLITHOSHaldeman, 1840 a convex hyporelief. Crossed by regular SKOLITHOSLINEARIS Haldeman, 1840 banded transverse annulations, 2.5 per cm. Figure 5C Cross sections show it is a trail or the cast of Description.-Packed vertical burrows, up a washed out burrow. to 30 cm deep, 1.O-1.5 cm wide, and circular Remarks.-This specimen resembles the to subcircular in cross section. The burrows genus Plagiogmus Roedel, 1929 in some re- taper downwards and do not branch. spects. Plagiogmus is a Cambrian burrow Remarks.-Our material corresponds to S. form, 1-2 cm wide, with irregular transverse linearis as defined by Haldeman (1840), marks that reflect its strong internal backfill Howell (1943), Osgood (1970, p. 325-327), structures (Glaessner, 1969). However, our and Hantzschel(1975, p. W 106-W log), and specimen differs in the regularity of the annu- reach the maximum recorded depth of 30 cm. lations, and in fact it is not preserved as a Skolithos occurs in tidal and shoreface typical burrow. Since we have only one spec- zones (Chamberlain, 1978b, p. 142-1 43), and imen, we do not name it. it is interpreted as a rapidly formed living Occurrence.-Dalma Formation (Carbon- burrow probably produced by many different iferous), northern Jebel Asba. animals (Crimes et al., 1977, p. 120). Occurrence.-Binem Formation (Devo- DISCUSSION nian), Jebel Asba. The trace fossils described are mainly shal- low water forms that fall within Seilacher's Ichnogenus ZOOPHYCOS (1967) Skolithos, Cruziana and Zoophycos Massalonga, 18 5 5 facies. They occur at intervals throughout the ZOOPHYCOSsp. succession but tend to be less common in the Figure 5D Cambro-Ordovician at Jebel Archenu which Description.-Apparently a planar circular unconformably overlies Precambrian base- form of Zoophycos showing irregular spreite ment. However, the reported presence of ridges (minor lamellae) curving out from the Monocraterion in the lower part of the central tunnel, which is not clear in this spec- succession (A.G.I.P. report, in Turner, 1980) imen. The ridges are about 3 mm wide and and Cruziana and Arthrophycus in the mid- the diameter of the whole structure is about dle of the succession is comparable to the 40 cm. There are no clearly developed major trace fossil distribution in the lower Cam- lamellae (terminology as defined by Simpson, brian of Spain (Crimes et al., 1977). The pau- 1970; Hantzschel, 1975, p. W 120-W 122). city of trace fossils in this section is largely Remarks.-The nomenclature of the Zoo- attributed to the predominance of coarse- phycos group is in a confused state and no grained, thick bedded subtidal sands. The attempt is made to ascribe our specimen to most abundant trace fossils occur in the more a species. thinly bedded sands, silts and shales in the Zoophycos is typical of Seilacher's suppos- middle of the succession where Cruziana and edly intermediate shelf Zoophycos Facies. Arthrophycus are recorded for the first time More complex forms may occur in the deep from the Cambro-Ordovician in the Kufra water Nereites facies, and a detailed environ- Basin. Thus, a strong facies control on trace mental study by Osgood and Szmuc (1972) fossil abundance and distribution is implied showed that Zoophycos is also found in shal- and this same pattern is repeated throughout low water sediments deposited above wave the Paleozoic succession of Jebel Asba. In base. Thus, no clear environmental evidence view of this it is difficult to assign an early is given by the Libyan Zoophycos. Cambrian age to the succession with any cer- Occurrence.-2oophycos occurs in the tainty. Binem Formation (Upper Devonian), Jebel The upper part of the Cambro-Ordovician Asba. as seen at Jebel Asba shows a vertical increase in trace fossil abundance but low diversity ANNULATEDTRAIL within a sequence of shoreface sands. The Figure 5E finer grained deeper shoreface sands are char- Description.-A 5 cm length of 1.5 cm wide acterized by the occasional presence of Cylin- trail on a mudcracked surface, preserved as drichnus followed abruptly by coarser grained BRL4N R. TC'RNER AATI).bfICE-IAEL J. RENTON shallower shoreface sands with abundant local stratigraphic marker referred to as the Phycodes which show a distinct vertical vari- Zoophycos sandstone (Turner, 1980). The ation in relative abundance and orientation. presence of Zoophycos at the same strati- In the lower part they are very abundant and graphic level in other parts of the basin sug- mainly oblique and horizontal in orientation, gests that it may be of more regional signifi- in the middle they are less abundant and cance (cf. Crimes, 198 1). almost exclusively horizontal to subhorizon- It occurs at the top of the most intensely tal, and at the top, where they are again very burrowed and bioturbated facies in the abundant, they are vertically orientated. Bed- succession. Most of the primary sedimentary ding surfaces at the top of the facies show structures have been obliterated and the only large symmetrical megaripples covered with other identifiable traces are vertical ~kolithoi Scoyenia traces. However, there is a rapid burrows at the base which may indicate an decrease in trace fossil abundance on succes- intertidal as opposed to a shallow subtidal sive rippled bedding surfaces within less than environment (Rhoads, 1967) depending on 1 m of sediment. In view of the uniform lith- energy levels. Although the fining-upward ological character of the shoreface sands and sequences in this facies resemble modern tidal their thinness (3 m), changes in orientation flat deposits there is no preserved sedimen- are largely a response to changes in energy tological evidence diagnostic of such an envi- level within the shoreface environment. The ronment. If intertidal flats did exist they must oblique and horizontal Phycodes in the lower have been predominantly sandy in character part of the facies probably record higher and protected from the full force of the sea energy conditions, as indicated by the scoured to allow for the extensive development of base and overlying pebble conglomerate up Skolithos. This may have been a barrier or a to 50 cm thick (Turner, 1980). The horizontal sheltered embayment comparable to the to subhorizontal Phycodes suggests a lower present day Wash (Turner, 1980). The change energy environment concomitant with the from Skolithos to Zoophycos and the lateral overall vertical decrease in scale of the persistence of Zoophycos may be a function crossbeds; the animal responsible for the bur- of increasing water depth and lower oxygen rows ultimately trying to escape (vertical bur- levels (cf. Frey and Seilacher, 1980) related rows) as water depths increased in response to transgression and progressive deepening of to basinwide transgression and deposition of the basin thought to have occurred at this the overlying Silurian shelf shales. time (Turner, 1980). Unfortunately the con- There is no marked vertical stratigraphic tact with the Carboniferous is not exposed variation in abundance and diversity of trace and locally the Devonian is unconformably fossils in the Paleozoic succession at Jebel overlain by Cretaceous Nubian sandstone. Asba; most of them are associated with the A slight increase in trace fossil abundance more thinly bedded shallow water tidal and at the top of the Carboniferous reflects the subtidal sands and silts. One of the most pro- repeated presence of tidally influenced lific trace fossil horizons occurs at the top of sequences of sandstone, siltstone and silty- the Silurian where thinly bedded, rippled, shale, forming part of a major transgression subtidal sands yield Arthrophycus and Cru- phase of sedimentation. ziana. The presence of abundant Cruziana The shelf deposits contain comparatively at this level throughout the area proved use- few trace fossils despite the fact that they con- ful as a local stratigraphic marker for corre- sist of thinly bedded sands,'silts and shales. lating and identifying sections and and iso- The succession becomes more sandy towards lated exposures. Arthrophycus is more widely the top in passing from an offshore shelf to distributed, but is particularly abundant in a nearshore shelf environment, accompanied the finer grained sands filling tidal channels by an overall increase in trace fossil abun- in the lower Devonian Tadrart Formation. dance. Most traces occur as walking and sur- Its presence here is the youngest represen- face crawling traces on sandstone bedding tative of the genus yet described. surfaces, and there is little evidence of bur- Zoophycos, which is confined to the upper- rowing and bioturbation. This, together with most 5-1 0 m of the Devonian forms a useful the paucity of body fossils suggests that the TRACE FOSSILS depositional environment may have been brian trace fossils from Spain, p. 9 1-1 38. In, T. rather euxinic and not conducive to the P. Crimes and J. C. Harper (eds.), Trace Fossils extensive development of benthic life. 2. Geological Journal Spec. Issue 9. DESIO,A. 1940. Vestigia problematica paleo- ACKNOWLEDGMENTS zoiche delle Libia. Annali del Museo Libico di Storia Naturale, 2:47-92. The work on which this paper is based was DUBOIS,P. and J. LESSERTISSEUR.1964. Note sur carried out whilst one of us (B.R.T.) was co- Bijiungites,trace problematique du Devonien du ordinator of the Kufra Basin Project, financed Sahara. Bulletin de la SociCtC GCologique de by the National Oil Corporation of Libya. France (7), 6:626-63 1. Thanks are due to Farag Said and Ahmed FEDONKIN,M. A. 1977. Precambrian-Cambrian Asbali of the National Oil Corporation and ichnocoenoses of the east European platform, p. 183-194. In, T. P. Crimes and J. C. Harper William Kanes of the University of South (eds.), Trace Fossils 2. Geological Journal Spec. Carolina, without whose help the work could Issue 9. not have been completed. We are grateful to FREY,R. W. and J. D. HOWARD.1970. Com- Chris Kendall and Richard Vos for their parison of Upper Cretaceous ichnofacies from encouragement during the course of the work. siliceous sandstones and chalk, western Interior The manuscript benefited considerably from Region, U.S.A., p. 141-166. In, T. P. Crimes the helpful reviews by R. W. Frey and R. G. and J. C. Harper (eds.), Trace Fossils. Geological Journal Spec. Issue 3. Osgood, Jr. We are particularly indebted to GLAESSNER,M. F. 1969. Trace fossils from the T. P. Crimes for his comments on the final Precambrian and basal Cambrian. Lethaia, 2: version of the manuscript. Finally our thanks 369-393. to Christine Cochrane for drafting and Eliz- GUTSCHICK,R. C. and R. LAMBRONE.1-975. abeth Walton for typing. Bijiungites, trace fossils from Devonian-Missis- sipian rocks of Pennsylvania and Montana, REFERENCES U.S.A. Palaeogeography, Palaeoclimatology and Palaeoecology, 18: 193-2 12. ALPERT,S. P. 1975. Planolites and Skolithos from HALDEMAN,S. T. 1840. Supplement to Number the Upper Precambrian-Lower Cambrian White One of "A Monograph of the Limniades, or Inyo Mountains, California. Journal of Paleon- freshwater univalve shells of North America" tology, 49:508-521. ..,p3. - 1977. Trace fossils and the basal Cam- HALL,J. 1852. Palaeontology of New York. 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Zoophycos as an indicator of water depth. Bul- SELLEY,R. C. 1970. Ichnology of Paleozoic sand- letin of American Paleontology, 62(27 l): 1-22. stones in the southern desert of Jordan: a study RHOADS,D. C. 1967. Biogenic reworking of of trace fossils in their sedimentological context, intertidal and subtidal sediments in Barnstable p. 477488. In, T. P. Crimes and J. C. Harper Harbor and Buzzards Bay, Massachusetts. Jour- (eds.), Trace Fossils. Geological Journal Spec. nal of Geology, 75:461-476. Issue 3. RODRIGUEZ,J. and R. C. GUTSCHICK.1970. Late SIMPSON,S. 1970. Notes on Zoophycos and Spi- Devonian-Early Mississipian ichnofossils from rophyton, p. 505-514. In, T. P. Crimes and J. western Montana and northern Utah, p. 407- C. Harper (eds.), Trace Fossils. Geological Jour- 438. In, T. P. Crimes and J. C. Harper (eds.), nal Spec. Issue 3. Trace Fossils. Geological Journal Spec. Issue 3. TURNER,B. R. 1977. Kufra Basin Study. National SEILACHER,A. 1955. Spuren und Fazies im Oil Corp. Tech. Report, Tripoli, 25 p. Unterkambrian. In, 0. H. Schindewolf and A. -. 1980. Palaeozoic sedimentology of the Seilacher, Beitrage zur Kenntnis des Cam- southeastern part of the Kufra Basin, Libya: a briums in der Salt Range (Pakistan). Akad. Wiss. model for oil exploration, p. 35 1-374. In, Salem Lit. Mainz. Math.-Nat. Kl., Abhandl., 10: 11- and Busrewil (eds.), Geology of Libya. Vol. 2, 143. Academic Press, London. -. 1967. Bathymetry of trace fossils. Marine Geology, 5:413428. -. 1978. Use of trace fossil assemblages for recognizing depositional environments. In, P. B. Basan (ed.), Trace Fossil Concepts. S.E.P.M. Short Course 5: 167-18 1. http://www.jstor.org

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You have printed the following article: Paleozoic Trace Fossils from the Kufra Basin, Libya Brian R. Turner; Michael J. Benton Journal of Paleontology, Vol. 57, No. 3. (May, 1983), pp. 447-460. Stable URL: http://links.jstor.org/sici?sici=0022-3360%28198305%2957%3A3%3C447%3APTFFTK%3E2.0.CO%3B2-T

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Planolites and Skolithos from the Upper Precambrian-Lower Cambrian, White-Inyo Mountains, California Stephen P. Alpert Journal of Paleontology, Vol. 49, No. 3. (May, 1975), pp. 508-521. Stable URL: http://links.jstor.org/sici?sici=0022-3360%28197505%2949%3A3%3C508%3APASFTU%3E2.0.CO%3B2-C