Journal of the Geological Society. London, Vol. 149, 1992, pp. 631-646, 3 figs, 1 table. Printed in Northern Ireland Changes in the trace fossil biota across the Proterozoic-Phanerozoic boundary T. P. CRIMES Department of Earth Sciences, University of Liverpool, L49 3BX, UK Abstract: Tracefossils became relatively diverse in shallow-water clastic seas in the late Proterozoic (Vendian), with a further significant increase in abundance, diversity and complexity in the Tommotian and Atdabanian. Little change followed in the remainder of the Lower Palaeozoic. Traces typical of deeper- water facies evolved in shallow water during the Vendian and early Cambrian, and may have slowly migrated into the deep ocean during the remainder of the Lower Palaeozoic. There are a limited number of short-ranging ichnogenera which may be useful for correlation but the first appearance of ichnogenera may be a more satisfactory method. Three trace fossil zones covering the ranges Redkino and Kotlin, Rovno and Tommotian-lower Atdabanian are recognized and may be useful for world-wide correlation. ‘Explosive evolution’ was how Seilacher (1956) described the Platformare partly time-equivalent to the trilobite-bearing changes in thetrace fossil biotaacross the Proterozoic- Talsy Horizon in the East European Platform. Phanerozoic boundary. He compared the dearth andsimplicity The Rovno Horizon has yielded a relatively diverse ich- of trace fossils in upper Precambrian strata with the abundance nofauna,including Gyrolithes,Phycodes, Teichichnus and and complexityof those from the Cambrian. These rapid Treptichnus. It appears, therefore, that part of the ‘explosive changes have led to suggestions that tracefossils may be useful evolution’took place duringthe Vendian (sensulato). De- forcorrelation at theboundary level (Crimes 1975,1987; velopment of more advanced forms such as trilobite furrows Alpert 1977; Narbonne et al. 1987). (Cruziana) and complexspreite (Diplocraterion, Rhizocoral- The evolution of behaviouraldiversity was investigated in- lium,Zoophycos) occurredlater, in theearly Cambrian dependently by Crimes (1974) and Seilacher (1974) who both (Tommotian and Atdabanian). concluded that, while there was a rapid increase in trace fossil The purpose of this paperis briefly to review the evolution abundanceand diversity in shallow-waterCambrian seas, and diversification of trace fossils acrossthe Proterozoic- significant colonization of the deep oceans did not take place Phanerozoic boundary and into the Lower Palaeozoic. until the Ordovician and then blossomed in the Cretaceous. In the absence of formal acceptanceof a type section for the Seilacher (1977,1978, 1986) suggested that the evolutionary Precambrian-Cambrian boundary,the Russian subdivisions changes in trace fossils, particularly those from the deep sea, will be used, since at present they are most widely known. The involved optimization of feeding behaviour, increase in com- base of the Cambrian will therefore informally be taken as the plexity and reduction in size. It has, however, been recognized base of the Tommotian. The tracefossil zones were, however, recently that some trace fossils which are typical of deep seas erected,as far as possible, independently of body fossil throughout much of the Phanerozoic, actually evolved and correlations and on a world-wide basis (Crimes 1987). Selec- reached a high level of complexity,and optimizationof feeding tion of a type section outside the USSR may therefore result in behaviour, in Tommotian to Toyonian andeven ‘late Precam- a different position for the Precambrian-Cambrian boundary brian’ shallow-water (Crimes & Anderson 1985; Crimes 1987, within the Russian sequence, but should notsignificantly affect 1991; Hofmann & Patel 1989) andperhaps upper-slope the utility of trace fossils in future correlations. sequences (Narbonne& Aitken 1990). The timingof these early evolutionary changes is important, both in relation to the de- Late Proterozoic and Early Phanerozoic trace fossils velopment of the metazoa and in the use of the rapid diversifi- cation of trace fossils in correlations at this level. Thelast 20 yearshave seen numerousinvestigations of Recent investigations have led to a reappraisal of corre- sequences of late Proterozoic and/or early Cambrian age in lations of some of the trace fossil-bearing upper Precambrian many parts of the world, principally: and Tommotian to Toyonian strata across the USSR and into Canada(Young 1972; Fritz 1980; Fritz & Crimes eastern Europe. The traditionalview was that the Rovno Hori- 1985; Crimes & Anderson 1985; Nowlan et zon of the Baltic Shield and the Nemakit-Daldyn Horizon of al. 1985; Narbonne & Hofmann 1987; Nar- Siberia were the lowest units of the Cambrian (Savitsky 1959, bonne et al. 1987; Hofmann & Patel 1989; 1975). Later work by Shishkin (1974) showed an assemblage of Narbonne & Aitken 1990) fossils in the top 11 m of the Nemakit-Daldyn Horizon which USA(Alpert 1976; Mount et al. 1983; Gibson also suggested an early Cambrian (Tommotian) age. In con- 1989) trast,Sokolov & Fedonkin (1984) equatedthe Rovno and Argentina (Acefiolaza & Durand 1973; Acefiolaza Nemakit-Daldyn horizons and assigned them to the Vendian, 1978; Acefiolaza & Toselli 1981; Regalia & generally regarded as Precambrian,and thisview is apparently Herrera 1981; Poire et al. 1984) becomingaccepted inthe USSR. However,Moczydiowska Greenland (Cowie & Spencer 1970; Pickerill et al. 1982) (1991) considered the acritarch evidence to demonstrate that Scandinavia(Banks 1970; Bergstrom 1981) the Nemakit-Daldyn may belong to the Cambrian, and that United Kingdom (Crimes 1970a, b; Brasier et al. 1978; Brasier depositsreferred tothe Tommotian Stage in the Siberian & Hewitt 1979; Cope 1977, 1982) 637 Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/149/4/637/4892388/gsjgs.149.4.0637.pdf by guest on 03 October 2021 638 T. P. CRIMES Spain (Crimes et al. 1977; Brasier et al. 1979; Legg and simple butwinding and meanderingtraces such asHelmin- 1980; Perejon 1982; Fedonkin et al. 1983; thoida and Helminthopsis are interesting in that such habits are Liiian 1984; Liiian & Palacios 1987) uncommonin post-Cambrian shallow-water deposits. They Poland (OrIowski et al. 1970; Paczeina 1985a, b, appear to provide further examples of the evolution of deep- 1986, 1989; Orlowski 1989) water habits in early shallow-water seas. USSR (Fedonkin 1976, 1977, 1978, 1979, 1980a, b, Only a limited number of traces appear in the Kotlin Hori- 1981,1988; Palij 1976; Palij et al. 1983; zon but they include the screw-like burrow Harlaniella which Keller & Rozanov 1979; Urbanek & may be restrictedto that horizon. In contrast, the Rovno Hori- Rozanov 1983; Sokolov & Fedonkin 1984; zon has four traces so far only recorded from that level and Sokolov & Ivanovskii 1985) also includes the appearance of more complex, Palaeozoic- Namibia (Germs 1972; Crimes & Germs 1982) type traces including Phycodes, Teichichnus and Treptichnus. India (Seilacher 1955; Bhargava & Srikantia 1982, Almostall Vendian traces have been recordedfrom 1985; Kumar et al. 1983; Raina et al. 1983; shallow-water sequences andthey show a wide variety of types, Shah & Sudan 1983; Singh & Rai 1983; Bhar- including simple burrows (e.g. Planolites), winding and mean- gava etal. 1984; Bhargava & Bassi1988; deringtraces (e.g. Gordia,Nereites, Helminthoida), circling Kumar et al. 1984; Brasier 1989) traces (e.g. Circulichnis, Gyrolithes), spirals (Planispiralichnus, China (Jiang Zhiwen et al. 1982; Yang Zunyi et al. Protospiralichnus), branching burrow systems (e.g. Phycodes, 1982; Luo Huilin et al. 1984; Crimes & Jiang Treptichnus), simple spreite burrows (e.g. Teichichnus), resting Zhiwen 1986; Luo Huilin & Zhang Shi-shan traces (e.g. Asterichnus, Bergaueria, Intrites, Lockeia) and 1986) arthropod scratch marks (Monomorphichnus). The main Phan- Australia(Glaessner 1969; Webby 1969,1970, 1982, erozoictrace fossil lineages therefore evolved inlate Pro- 1984; Daily 1972, 1973; Jenkins et al. 1983; terozoic shelf seas. Recently. however, Narbonne & Aitken Walter et al. 1984, 1989) (1990) havedescribed a limited ichnofauna of Aulichnites, Helminthoida,Helminthoidichnites, Helminthopsis, Lockeia, Correlations between these world-wide sections are at best Palaeophycus, Planolites and Torrowangea from the late Pre- difficult. Nevertheless, it is becoming evident that, within the cambrian Blueflower Formation of NW Canada, which they Vendian, the Redkino, Kotlin and Rovno horizons and their interpret as being depositedbelow storm wavebase on the slope suggested correlatives have distinctive ichnofaunas. butpassing upwards into shallow-water dolomites. There The lowest occurrences of tracefossils in these horizons are may, therefore, have been some colonization of intermediate shown below, with asterisks indicating traces which may be water depths as early as the late Precambrian. restricted to that particular horizon. In drawing up such lists, Trace fossils from the overlying Tommotian to pre-trilobite only the most obvioussynonymies have been omitted and some Atdabanian strata include: more complex forms of trilobite forms are included which may not even be trace fossils. traces (Cruziana, Dimorphichnus, Diplichnites, Rusophycus), Redkino Asterichnus,Aulichnites, Bergaueria, Bilinichnus, spreitetraces (Diplocraterion,Rhizocorallium), winding and Buchholzbrunnichnus*, Bunyerichnus*, Cochlichnus, meanderingtraces (Belorhaphe, Cosmorhaphe, Taphrhelmin- G ordia, Helminthoida,Gordia, Helminthoidichnites,