Journal of the Geological Society, London, Vol. 145, 1988, pp. 339-350, 5 figs. Printed in Northern Ireland Trace fossils in coal-bearing sequences J. E. POLLARD Department of Geology, University of Manchester, Manchester M13 9PL, UK Abstract: Inthe past decade trace fossils have been recorded extensively from coal-bearing sedi- ments, differingwidely in facies, age and location.Westphalian or Stephanian‘coal-measures’ in Britain,Europe and EasternCanada contain an ichnofaunaproduced by invertebrates and/or vertebrates in upper delta plain sediments. This contrasts with the marine-related lower delta plain ichnofaunas known from Pennsylvanian rocks of the United States and Permian Gondwana ‘coal- measures’ of South Africa. Deltaic complexes of Middle Jurassic age in the North Sea basin and UpperCretaceous age in NorthAmerica contain marine trace fossils and dinosaurfootprints in coastal coal-bearing facies. Thesecase histories illustrate the importance of trace fossils both in facies analysis of coal-bearing sequences and in recording the presence of animals rarely known as body fossils in such clastic sediments. The recognition and use of trace fossils in the sedimen- to the diverse studies presented at the Egham Symposium tological and palaeontological analyses of coal-bearing and appearing in its publications. (Scott 19870, 19876). sediments is a major advance of the past decade. Although distinctive burrows, tracks and trails have been known from Silesian coal measures Euramerica Westphalian rocks since the mid 19th century, for example of fromLancashire (Binney 1852) and the Maritime Provinces, Canada (Dawson 1868), little notice was taken of Westphalian coal measuresof Britain them until the 1950s and 1960s. Over this period German Atthe previous British symposium on ‘Coal and workers established that trace fossil associations in the Ruhr Coal-BearingStrata’, Calver (196th) reviewed the trace CoalMeasures paralleled fauna1 and sedimentary cycles fossils then recognized in the Coal Measures of Britain. He (Jessen 1949; Jessen et al. 1952; Seilacher 1963, 1964). concluded that they demonstratedthe presence of the From this beginning we may recognize the two-fold Planolites ophthalmoides assemblage inmarine bands and development of moderntrace fossil studies, firstly in the P. montanus assemblage in non-marine strata as known conjunction with sedimentological or facies analysis of from theRuhr (Seilacher 1964), but totalling only four coal-bearing sedimentsand secondly, in recording the ichnogenera. More recent work in the Lancashire, presence,behaviour patternsand environmental distribu- Yorkshire and East Midlands coalfields (Eagar et al. 1985; tions of the animals producing the traces. Guion 1985; Pollard 1986) established the presence of more Detailed stratigraphical and sedimentological analysis of than fifteen ichnogenera, in five or morerecurring Silesian deltaicsequences of both Britianand North associations; these associations may be correlated with America in the past decadedemonstrated a close sediment type and specific sedimentary environments (Fig. relationship between trace fossil assemblages, sediments and 1). These diverse ichnofossils form part of a series which environmental models (Hakes 1977; Archer & Maples 1984; first appeared in interchannel strata of late Namurian sheet Eagar et al. 1985). Comparable results are being obtained by deltas of the Pennine area (Eagar et al. 1985, figs 5 and 8) workers on Gondwanacoal-bearing facies andNorth and they constitute a distinct lower delta-plain ichnofauna of American Cretaceous sequences (see below). Recent major largely Westphalian Aage. Figure 1 relatesthese trace publications on ichnology of marginal marineand fossils to specific subaqueous delta plain environments. The continental environments (Miller et al. 1984), on the use of traces reflect the variety of producersand differing biogenic structures in interpretingdepositional environ- behavioural responses to sedimentation conditions in the ments (Curran 1985) and on trace fossils in cores respective environments. (Chamberlain 1978; Ekdale et al. 1984) all contain Muddy sediments of marinea band contain both coal-bearing sediment case-studies. The relative abundance Ophthalmidium [‘Planolites’] ophthalmoides (Calver 1968b; of good quality corematerial produced during coalfield Rippon 1984) and newly recognized Lingula burrows, exploration can reveal a wealth of trace fossil information to Lingulichnus, in the regressive phase of the vanderbecki the trained observer. MarineBand in Lancashire (Fig. 2a). The ichnofauna of Palaeontologistsinterested in the ethological aspect of laminated muddy sediments of the interdistributary bay, or trace fossils have produced new information on diversity and floodbasin lake in higher Westphalian sediments, is the P. environmental distribution of both arthropods and tetrapods montanus association, (Fig. 2b) including Cochlichnus, by the detailed analysis of their trackways. Such ‘Gyrochorte’ carbonaria, Arenicolites, bivalve resting traces information is complementary tothe very limited data (Pelecypodichnus), and rare arthropod resting or crawling available from body fossils of these animals in clastic traces (Selenichnus and Acripes) (Rippon 1984; Guion 1985; coal-bearing sequences. Eagar et al. 1985; Pollard 1986; Romano & Whyte 1987). This paper reviews briefly some of these discoveries and The greatest diversity of traces is recorded from crevasse developments of the past decade particularly in relationship splay sheet sands (Fig. 1) wheretraces frequently show a 339 Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/145/2/339/4889504/gsjgs.145.2.0339.pdf by guest on 02 October 2021 340 J. E.POLLARD Trace fossil associations T I I Lithology and I sedimentaryenvironment I I T I I I I I 7 I l Crevasse splay I I -1- mdallt l m ..l fig. 1. Diversity, associations and facies relationships of trace fossils in Westphalian Coal measures of Britain. 1, Ophthalmidium association; 2, Planolites montanus association; 3, Arenicolites carbonarius association; 4, Pelecypodichnus association; 5, spreiten burrows; 6a, aquatic arthropod traces; 6b, terrestrial arthropod traces; 7, vertebrate tracks. Key to lithologies, see Fig. 4. behavioural response to sedimentation. Burrows of suspen- 1983, 1985; Hardy 1970a; Eagar et al. 1985) (association sion feeders, Arenicolites carbonarius and Polykladichnus 6a). The sinuoussurface trail or burrow Cochlichnus has are usually initiated from the topof the crevasse splays (Fig. recently been the subject of behavioural and mathematical 2c, e). Resting burrows Pelecypodichnus, preserved on the analysis (Elliot 1985). It was probably formed by nematode base of the crevassesplay sands frequently show current worms duringlocomotion or feeding,sometimes on response orientation or are associated with vertical escape decaying bivalves (Hardy 1970b). shaftsindicating behavioural response to seasonal flood The diverseichnofauna of the WestphalianCoal sedimentation (Hardy & Broadhurst 1978; Broadhurst et al. Measures of Britainillustrates clearly both the facies 1980) (Fig.2d). In channel fill sequencesbioturbation is significance and behaviouralaspects of trace fossils. limited to finer sediments although Arenicolites, Pelecypod- However it is remarkably different from contemporaneous ichnus and Planolites arerecorded (Guion 1985; Fielding ichnofaunas of coal-bearingsediments of the Canadian 1986; H. Williams pers.comm. 1986), perhaps associated Maritime Provinces. (Fig. 3). with starvation of active channel fill. Rare horizontal U-shapedor spreiten burrows (association 5) have been recordedfrom channel floor deposits or leveesediments Westphalian sequencesof eastern Canada (Hardy 1970b; Eagar et al. 1985) (Fig. 2f). The classic 'Joggins Section' of coal-bearing strata of the Trackways of terrestrialarthropods Diplichnites, Cumberland Basin of Nova Scotia has long been famous for Paleohelcura (association6b) tetrapodor footprints its fossils, especially vertebrates and upright trees. However (association 7)are not known from CoalMeasures of it also contains a variety of arthropodand vertebrate Britain below the Keele Beds (Westphalian D or trackways figured by Dawson (1868, 1873), suggestive of a Stephanian)but diversebehaviour patterns of aquatic or diversetrace-producing freshwater and terrestrial fauna. semi-aquatic belinurids (limulids) including burrows, resting Thevertebrate footprints show a predominance of traces and locomotion trackways are known (Chisholm amphibians,microsaurs (but also rhachitomes),and rarer Fig. 2. Burrows from British Westphalian sediments (a-e are cut vertical sections or core section). (Scale bars are 10 mm long.) (a) Lingulichnus sp. Vertical burrows with variable diameter and thick mud-lined walls inlaminated siltstone. uanderbecki Marine Band, Westphalian A/B, Lancs. MGSF 100 (Manchester Geology Department Special FossilCollection) (b) Planolites rnontanus (Richter). Sand-filled irregular horizontal burrows in laminated siltstone. Westphalian A, Lancashire. MGSF 101. (c) Arenicolites carbonarius (Binney). Mud-filled, small U-shaped burrows without spreiten. Westphalian A, Elland, Yorkshire. Manchester Museum L6211. (a) Pelecypodichnus and bivalve escape shaft. Cross section (V-shaped) of bivalve resting burrows which are repeated vertically by upward escape. Westphalian A, Up Holland, Lancashire. MGSF 102. (e) Polykladichnus sp. Small upward Y-branching burrows in ripple cross-laminated fine standstone.