This article was downloaded by: [Retallack, Gregory J.] On: 2 November 2009 Access details: Access Details: [subscription number 916429953] Publisher Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Alcheringa: An Australasian Journal of Palaeontology Publication details, including instructions for authors and subscription information: http://www.informaworld.com/smpp/title~content=t770322720 Cambrian-Ordovician non-marine fossils from South Australia Gregory J. Retallack a a Department of Geological Sciences, University of Oregon, Eugene, OR, USA Online Publication Date: 01 December 2009 To cite this Article Retallack, Gregory J.(2009)'Cambrian-Ordovician non-marine fossils from South Australia',Alcheringa: An Australasian Journal of Palaeontology,33:4,355 — 391 To link to this Article: DOI: 10.1080/03115510903271066 URL: http://dx.doi.org/10.1080/03115510903271066 PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Cambrian–Ordovician non-marine fossils from South Australia GREGORY J. RETALLACK RETALLACK, G.J., December 2009. Cambrian–Ordovician non-marine fossils from South Australia. Alcheringa 33, 355–391. ISSN 0311-5518. Newly discovered trace and body fossils from the Grindstone Range Sandstone of South Australia reveal evidence of megascopic life on land during the Cambrian–Ordovician. Arthropod trackways (Diplichnites gouldi) are interpreted here to have formed on land. The most persuasive evidence for this view is that footprints vary in clarity along the length of the trackway as it traversed moist then dry silt, then biological soil crust. Compatible, though not diagnostic of walking on land is trackway symmetry, without one side buoyed up by current. The footprints bulge outward and are partially filled with miniature talus cones. Footprints also are alternate as in walking, rather than opposite as in sculling. Arthropod resting traces (Selenichnites sp. indet.) have 11 lateral furrows, and footprints are bundled into sets of 8–11, most like euthycarcinoids. No arthropod dwelling burrows were found in associated palaeosols, so the track maker was more likely amphibious than fully terrestrial. Associated trace fossils include a new ichnotaxon of burrow, Myrowichnus arenaceus gen. et sp. nov. Thallose impressions (Farghera robusta gen. et sp. nov.) have the radiating dichotomous form of lichens, algae and liverworts. All these trace and body fossils were found in weakly developed palaeosols. Other palaeosols in the same formation are evidence of terrestrial ecosystems of modest biomass, weathering, carbon sequestration and stability in dry tropical regions. Gregory J. Retallack [[email protected]], Department of Geological Sciences, University of Oregon, Eugene, OR 97403-1271, USA. Received 2.10.2008; revised 9.2.2009; accepted 5.3.2009. Key words: Ordovician, South Australia, euthycarcinoid, track, trace fossil, lichen. ANCIENT terrestrial ecosystems can now land, and burrows may reveal the limits of be studied using palaeosols, even in non- the soil water-table. Although biological marine rocks as old as Ordovician and affinities of this new assemblage are un- Cambrian (Retallack 2000, 2001, 2008). certain, they provide macroscopic images Downloaded By: [Retallack, Gregory J.] At: 18:34 2 November 2009 Insights from palaeosols into such ecosys- of a terrestrial ecosystem prior to Late tem parameters as soil respiration and Ordovician millipede-liverwort communities chemical weathering do not provide (Retallack 2001). details of the organisms involved, because The main purpose of this work is a Cambrian and Ordovician palaeosols are formal description of a newly discovered sparsely fossiliferous, like geologically assemblage of trace and body fossils from younger palaeosols (Retallack 1998). This the Grindstone Range Sandstone of South article reports newly discovered assemblages Australia. Sedimentary palaeoenviron- of Cambrian–Ordovician non-marine trace ments, palaeoclimate and palaeosols of this and body fossils in palaeosols. The plant- new biota have been described elsewhere like fossils are problematic but were more (Stock 1974, Moore 1990, Retallack 2008, likely lichens or algae than plants. Track- 2009). Palaeobiological and palaeoecologi- ways may reveal arthropod excursions onto cal interpretations of such poorly preserved and largely unprecedented fossils are a ISSN 0311-5518 (print)/ISSN 1752-0754 (online) Ó 2009 Association of Australasian Palaeontologists challenge but are attempted here following DOI: 10.1080/03115510903271066 systematic description. 356 GREGORY J. RETALLACK ALCHERINGA (Ride et al. 1999) for trace fossils and Materials and methods fossils of uncertain fungal-animal affiliation Exposures of the Grindstone Range (Retallack 1994), and palaeobotanical pro- Sandstone were examined in Ten Mile visions of the International Code of Bota- (N31.253648 E138.977938) and Balcoracana nical Nomenclature (McNeill et al. 2006) creeks (S31.172468 E138.929638) in the for morphogenera of problematic plant-like eastern Flinders Ranges, South Australia impressions. Toponomic nomenclature of (Figs 1, 2). Stratigraphic sections were mea- trace fossils follows Martinsson (1970). All sured using the method of eyeheights. specimens (numbers prefixed P-) are held An environmental SEM was used (Univer- in the collections of the South Australian sity of Oregon’s FEI Quanta) to obtain Museum, Adelaide. Specimens were col- high-resolution images without conductive lected from two palaeosols and intervening coating. flaggy sandstone of the Grindstone Range Trace fossils and body fossils are named Sandstone in Ten Mile and Balcoracana here with legal provisions of the Interna- creeks, Wirrealpa Station, South Australia tional Code of Zoological Nomenclature (Fig. 1). Measurements of cross-sectional Downloaded By: [Retallack, Gregory J.] At: 18:34 2 November 2009 Fig. 1. Geological map and Early Ordovician fossil localities in the Grindstone Range Sandstone in Ten Mile and Balcoracana creeks, South Australia. ALCHERINGA CAMBRIAN–ORDOVICIAN FOSSILS 357 Downloaded By: [Retallack, Gregory J.] At: 18:34 2 November 2009 Fig. 2. Overall stratigraphic section (A) and fossiliferous intervals in (B) Ten Mile and (C) Balcoracana creeks, South Australia. Degree of development, thickness and stratigraphic position of individual palaeosols is indicated (dark bars). Some palaeosols have calcareous nodules (Bk horizon) whose depth (open circles) is a proxy for former mean annual precipitation (Retallack 2008). dimensions were made in the field on small homestead, in the central Flinders Ranges pieces in which the other side of the fossil of South Australia (Fig. 1). The age of the could be seen. Grindstone Range Sandstone is not older than late Cambrian (Paibian), because conformably underlying marine strata in- Geological setting clude age-diagnostic trilobites, such as The Grindstone Range Sandstone has Onaraspis rubra and Leiopyge laevigata its type area southwest of Wirrealpa (Jago et al. 2006). The Grindstone Range 358 GREGORY J. RETALLACK ALCHERINGA Sandstone is also no younger than Late with comparable palaeosols in the Officer Ordovician (Hirnantian, 446.3 + 2.2 Ma), Basin of South Australia and northern which is the oldest U–Pb isochron age of Perth Basin of Western Australia also local granites and Delamerian deformation suggests a geological age slightly younger in the northern Flinders Ranges, much than the Cambrian–Ordovician boundary younger than Delamerian deformation (Retallack 2009). The age of this deep-calcic further south in South Australia (Elburg palaeosol in the Officer Basin is constrained et al. 2003). by underlying volcanics dated by K–Ar The geological age of the Grindstone at 484 + 4 Ma (Table Hill Volcanics of Range Sandstone is poorly constrained Stevens & Apak 1999) and 483.6 + 20 Ma biostratigraphically and radiometrically, and 493.7 + 20 Ma (Kulyong Volcanics but two lithological correlation techniques of Major & Teluk 1967, corrected using favour an age of Early Ordovician (Trema- the decay constants of Dalrymple 1979). docian) suggested by Daily & Forbes (1969), The deep-calcic palaeosol in the Officer rather than late Cambrian (Jago et al. 2006). Basin also underlies the Indulkana Shale, First, linear extrapolation of tie points in which has been correlated with the Horn the Ten Mile Creek section (Fig. 2A) dates Valley Siltstone of the Amadeus Basin the fossiliferous level of the Grindstone and its Castlemainian trilobite (Lycophron Range Sandstone as 483 Ma (+2.8 Ma freemani) assemblage (Laurie 2006), from standard error of correlation and equivalent to Llanvirnian of Avalonia dating),