ORDOVICIAN TRACE FOSSILS FROM THE UPPER TIOURIRINE FORMATION OF MOROCCO: PRELIMINARY RESULTS J.C. Gutiérrez-Marco1, A.V. Dronov2, D. Knaust3, S. Lorenzo Álvarez4 1Instituto de Geociencias CSIC-UCM, Severo Ochoa 7, 28040 Madrid, Spain. [email protected] 2Geological Institute RAS, Pyzhevsky per. 7, Moscow 119017, Russia. [email protected] 3Equinor ASA, Svanholmen 8, Stavanger, Norway. [email protected] 4Universidad de Castilla-La Mancha, 13400 Almadén, Spain. [email protected] Key words: Trace fossils, Ordovician, Katian, Anti-Atlas, Morocco. Contact author: J.C. Gutiérrez-Marco, [email protected] In contrast to the high abundance of Ordovician invertebrate fossils in Morocco, which promotes a good part of the fossil trade worldwide (Gutiérrez-Marco and García-Bellido, 2018), there are only few references to the record of trace fossils in the thick siliciclastic units that compose the Ordovician sequence in the large region of the Moroc- can Anti-Atlas, situated to the north of the Tindouf Basin and the West African Craton. The classic regional synthesis of Destombes (in Destombes et al., 1985) only mentioned the sporadic occurrence of Skolithos (identified as “Tigil- lites”) in diverse Middle and Upper Ordovician formations, as well as of Daedalus (determined as “Vexillum”) in the Guezzart Formation (upper Darriwilian) of the First Bani Group. The updated synthesis of Álvaro et al. (in press) neither paid attention to the trace fossils, and the more recent palaeontological literature dealing with the renowned Ordovician biotas of Fezouata and Tafilalt, just lists few ichnogenera without description or illustration. The only detailed ichnological contributions are from Gibb et al. (2010), dealing with Lower Ordovician Rusophycus carleyi (James) from the eastern Anti-Atlas, and from Azizi et al. (2017), who describe Skolithos linearis Haldeman from the Cambrian-Ordovician boundary of the central Anti-Atlas. The purpose of our investigation is to provide a first evaluation of the ichnofauna from the Upper Tiouririne Formation of the Ktaoua Group, which is a trace-fossil rich unit in comparison with other units of the Anti-Atlas, and which is of Katian 2–3 age (for lithostratigraphy see Destombes et al., 1985 and Álvaro et al., in press). The only trace fossils cited from that formation are “Tigillites” (= Skolithos), mentioned by Destombes (in Destombes et al., 1985, p. 200) for a single section in the western Anti-Atlas, and large but undetermined ‘cord-like’ trace fossils, which appear rather widespread in the eastern Anti-Atlas (Van Roy 2006, p. 336; MacGabhann 2012, figs. 3.06a, 3.11a-b). The trace-fossil list from our work suggests a higher ichnodiversity and may contribute to the general knowledge of a large area of northern Africa and the Middle East, where Ordovician data are still scarce (see Seilacher 2007 and references therein). The studied material comes from two sections located northeast of the town of Merzane that, together with the localities mentioned by Van Roy (2006) and MacGabhann (2012: M001 and M003), are located between 11.5 and 17.7 km east-southeast of the city of Erfoud (= Arfouf). The Upper Tiouririne Formation mainly consists of ca. 50–140 m of medium- to coarse-grained, grey-brown sandstones, interbedded with sandy mudstones and some microconglomeratic horizons mainly of intraformational origin. It has been sedimentologically studied (a. o.) by Álvaro et al. (2007), Colmenar and Álvaro (2015) and Med- dour (2016), and its most striking features are the record of slightly mineralised and soft-bodied fossils, including paropsonemid eldonioids, aglaspidid arthropods and problematic taxa (Van Roy 2006, MacGabhann 2012), which are exceptionally preserved in several of the massive sandstone beds (Tafilalt Biota). This ‘Ediacara-type’ preservation is linked to episodes of very rapid, possibly storm-influenced burial, of organisms with biopolymeric tissues preserved in special microbially bound substrates (MacGabhann et al., 2019). Commonly associated with the extraordinary fossils of the Tafilalt Biota, and occurring in the same or adjacent strata, are prominent trace fossils of the Upper Tiouririne Formation, consisting of winding horizontal burrows that are composed of inclined, densely aligned knobby sediment aggregates, which appear along the upper bedding plane as characteristic beaded strings (Fig. 1A–G). These large burrows can be assigned to Neoeione moniliformis (Tate) and probably originated by the probing activity of a deposit-feeding animal. N. moniliformis was originally described from the Carboniferous of the UK (Boyd and McIlroy, 2018), and the occurrence from the Ordovician of Morocco is one of the oldest records of this ichnotaxon. The trace-fossil association is diverse and pending detailed investigation. The following ichnotaxa could be identified: Arenicolites isp.; Arthraria antiquata Billings (Fig. 2C), Arthrophycus brongniartii (Harlan), Asteriacites cf. lumbricalis von Schlotheim (Fig. 2A), Asterichnus lawrencensis Bandel, Cheiichnus isp., Cruziana problematica (Schindewolf), Cruziana isp. (Fig. 2B), Curvolithus simplex Buatois et al., Diplocraterion parallelum Torell, Gyro- 13th International Symposium on the Ordovician System 55 Fig. 1. Neoeione moniliformis (Tate) from the Upper Tiouririne Formation (Katian, eastern Moroc- can Anti-Atlas). A–C, G – photographs of some long specimens preserved in full relief and as convex epichnia. D–E – a wide trace in top (D) and lateral (E) views; F – longitudinal section between three consecutive knobs showing massive sand infill. Scale bars, 50 mm (A–C, G) and 10 mm (D–F). Fig. 2. Trace fossils from the Upper Tiouririne Formation (Katian, east- ern Moroccan Anti-Atlas). A – Asteriacites cf. lumbricalis von Schlotheim; B – Cruziana isp.; C – Arthraria antiquata Billings (upper left) and Cruziana isp.; D – Protovirgularia dichotoma M’Coy; E – Teichichnus rectus Seilacher, a burrow fragment in oblique-lateral view; F – Heughia gregaria Smith; G – Rusophycus carleyi (James); H – Nereites cf. irregularis (Schaf- häutl) in hyporelief preservation; I-J – Gyrochorte comosa Heer in epi- (I) and hyporelief (J) preservation; K – Taenidium barretti (Bradshaw); L – Nereites cf. irregularis (Schafhäutl) in epirelief preservation; M – Nere- ites pugnus Emmons; N – Nereites macleayii (Murchison). Scale bars, 10 mm (A, B, F, G, K–N) and 5 mm (C–E, H–J). 56 Contributions of International Symposium chorte comosa Heer (Fig. 2I-J), Heughia gregaria Smith (Fig. 2F), Nereites cf. irregularis (Schafhäutl) (Fig. 2H, L), N. macleayii (Murchison) (Fig. 2N), N. pugnus Emmons (Fig. 2M), Oravaichnium hrabei Plička and Uhrová, Proto- virgularia dichotoma M’Coy (Fig. 2D), P. rugosa (Miller and Dyer), ?Ptychoplasma conica Pieńkowski and Uchman, Taenidium barretti (Bradshaw) (Fig. 2K), T. serpentinum Heer, Teichichnus rectus Seilacher (Fig. 2E), Rusophycus carleyi (James) (Fig. 2G) and Rusophycus isp. This trace-fossil association is characteristic for a shallow-marine, probably shoreface environment, and the relatively high ichnodiversity is indicative of favourable living conditions for the benthic organisms. Acknowledgments This work has been supported by project CGL2017-87631-P of the Spanish Ministry of Science, Innovation and Universities (to JCG-M) and Russian Foundation for Basic Research (Grant no. 19-05-00748, to AVD). It is also a contribution to the IGCP 653 project (IUGS-UNESCO). REFERENCES Álvaro, J.J., Vennin, E., Villas, E., Destombes, J., Vizcaïno, D., 2007. Pre–Hirnantian (latest Ordovician) benthic com- munity assemblages: controls and replacements in a siliciclastic-dominated platform of the eastern Anti-Atlas, Morocco. Palaeogeogr., Palaeoclimatol., Palaeoecol., 245, 20–36. Álvaro, J.J., Benharref, M., Destombes, J., Gutiérrez-Marco, J.C., Hunter, A.W., Lefebvre, B., Van Roy, P., Zamora, S., In press. Ordovician stratigraphy and benthic community replacements in the eastern Anti-Atlas, Morocco. In: Hunter, A.W., Álvaro, J.J., Lefebvre, B., van Roy, P., Zamora, S. (Eds), The Great Ordovician Biodiversification Event: Insights from the Tafilalt Biota, Morocco. Geol. 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