First skeletal microfauna from the Cambrian Series 3 of the Jordan Rift Valley (Middle East) OLAF ELICKI ELICKI, O., 2011:12:23. First skeletal microfauna from the Cambrian Series 3 of the Jordan Rift Valley (Middle East). Memoirs of the Association of Australasian Palaeontologists 42, 153-173. ISSN 0810-8889. For the first time, a Cambrian microfauna is reported from the Jordan Rift Valley. The fauna comes from low-latitude carbonates of the Numayri Member (Burj Formation, Jordan) and to a lesser degree the equivalent Nimra Member (Timna Formation, Israel). Co-occuring with trilobite, brachiopod and hyolith macrofossils, the microfauna is represented mostly by disarticulated poriferid (mostly hexactinellids) and echinoderm remains (eocrinoids and edrioasteroids). Among the hexactinellids, Rigbyella sp., many isolated triactins and tetractins, as well as a few pentactins and rare hexactins occur. Additional poriferid spicules come from heteractinids (Eiffelia araniformis [Missarzhevsky, 1981]) and polyactinellids (?Praephobetractinia). Chancelloriids (Archiasterella cf. hirundo Bengtson, 1990, Allonnia sp., Chancelloria sp., ?Ginospina sp.) are a rather rare faunal element. Micromolluscs are represented mainly by an indeterminable helcionellid. The probable octocoral spicule Microcoryne cephalata (Bengtson, 1990), torellellid and hyolithellid hyolithelminths, and a bradoriid arthropod occur as very few or single specimens. The same is the case with a probable siphogonuchitid. The occurrence of a cornulitid related microfossil may extend the stratigraphic range of this fossil group significantly. The rather low-diversity microfauna is overwhelmingly dominated by sessile epibenthic biota. The preferred feeding habit seems to have been suspension feeding and minor deposit feeding. The microfauna from the Jordan Rift Valley is typical for low-latitude carbonate environments of Cambrian Series 3 age that corresponds to the traditional late early to middle Cambrian. Some taxa indicate a closer relation to the equatorial Gondwanan Iran and Australia. Some connection to the European shelf of Perigondwana may also have existed. O. Elicki ([email protected]), Freiberg University, Geological Institute, Bernhard-von- Cotta Street 2, 09599 Freiberg, Germany. Received 9 August 2011. Keywords: Small shelly fossils, poriferids, echinoderms, Cambrian, Jordan, Israel, Dead Sea. CAMBRIAN successions are spectacularly Much of the previous palaeontological work exposed in the Jordan Rift Valley. Outcrops along concentrated on the stratigraphic position and the eastern (Jordanian) shoreline of the Dead Sea correlation of the Dead Sea Cambrian succession. and a little south in the northern Wadi Araba yield As such, there was often focus on macrofossils. fossiliferous deposits of shallow and marginal Micropalaeontological sampling has been lagging marine origin (Burj Formation). In the south- behind in this region. This paper documents the western Wadi Araba (Israel) equivalent Cambrian first skeletal microfauna of Cambrian age from sediments also occur locally (Timna Formation). this region. Cambrian trilobites have been known from the In the course of several joint research projects region for about a century (Dienemann 1915; between the Freiberg working group and King 1923; Richter & Richter 1941). More recent colleagues from Yarmouk University (Irbid) work on trilobites and substantial investigation and the Natural Resources Authority (Amman) on other fossil groups including brachiopods, has resulted in bulk collections of carbonate, hyoliths and trace fossils have been completed siliciclastic and mixed lithological successions (Parnes 1971; Cooper 1976; Bandel 1986; along measured stratigraphic sections from Seilacher 1990a, b; Rushton & Powell 1998). Jordanian Cambrian surface outcrops. These have A summary of the history of palaeontological, undergone palaeontological and sedimentological petrographical, palaeogeographical and facies analyses (Elicki & Shinaq 2000; Elicki et al. investigations in this region is provided by Elicki 2002; Elicki 2007a; Shinaq & Elicki 2007; Geyer (2007a) and Shinaq & Elicki (2007). & Elicki submitted; Hofmann et al. submitted). 154 AAP Memoir 42 (2011) Powell 1989; Teimeh et al. 1990; Bandel & Shinaq 2003). The oldest Cambrian sedimentary rocks (part of Umm Gaddah Formation and Salib Formation, about 200 m thick; Fig. 2) are continental, fluvial to alluvial siliciclastics (Powell 1989; Amireh et al. 1994; Makhlouf 2003; Amireh et al. 2008). The overlying Burj Formation represents a marine maximum stage transgression (Amireh et al. 1994; Rushton & Powell 1998; Schneider et al. 2007). The start of transgression is indicated by some trace-fossil content in the lower Burj Formation (Tayan Member: Elicki 2007a), pointing to an early Cambrian age of these siliciclastics. The conformably succeeding Numayri Member (limestones, dolostones, minor siliciclastics) includes a variety of marginal- marine environments including open and restricted marine areas, shoals, lagoons, sabkhas (Shinaq & Bandel 1992; Rushton & Powell 1998; Elicki et al. 2002; Shinaq & Elicki 2007). The Numayri Member yields various macrofossils including trilobites, brachiopods and hyolithids, but also trace fossils (Richter & Richter 1941; Parnes 1971; Cooper 1976; Seilacher 1990a; Rushton & Powell 1998). The upper portion of the Burj Formation is represented by the siliciclastic Figure 1. Geographical map of the Jordan Rift Valley. Hanneh Member containing a rich marine Working areas are indicated (for detailed location of ichnofauna (Seilacher 1990a, b; Mángano et al. the sampled sections see Elicki 2007a). 2007; Hofmann et al. 2008; Elicki et al. 2010, Hofmann et al. submitted) and some trilobites The systematic and detailed field work led to the (Elicki & Geyer, submitted). The package is discovery of sections largely unaffected by the conformably overlain by the siliciclastic Umm heavy diagenetic overprint typical of the region, Ishrin Formation which contains trilobites and facilitated detailed micropalaeontological and trace fossils only at its base, but generally investigation of skeletonised body-microfossils. indicates regression and return of continental For the first time, this paper focuses on description conditions (Makhlouf & Abed 1991; Hofmann and documentation of Cambrian microfossils et al. submitted). from this palaeogeographic region. The thickness of the Burj Formation in the The palaeontological specimens figured in this Dead Sea region varies from about 190 m in the paper, are housed at the Geological Institute of north (Wadi Zerqa Ma’in) to approximately 120 Freiberg University, Germany (archive numbers m in the (southern) Safi region (Powell 1989), FG 595 and FG 619). thinning to zero in the basement area of southern Wadi Araba. GEOLOGICAL AND STRATIGRAPHIC Evidence for the stratigraphic position of BACKGROUND the Cambrian succession comes from trilobites. The field area is situated along the eastern These have been found in the marine carbonates shoulder of the Jordan Rift Valley in the Dead Sea (Numayri Member) over the last hundred area, and the northeastern Wadi Araba south of years (Dienemann 1915; King 1923; Richter & the Dead Sea (Jordan). The Timna region (Israel), Richter 1941) and were recently summarised from where some microfauna was kindly provided and reviewed by Rushton & Powell (1998). for investigation by Professor Michael Bassett New discoveries of abundant, well preserved (Cardiff), represents the only locality investigated specimens by the Freiberg working group from from southwestern Wadi Araba (Fig. 1). the carbonate Numayri Member and the Hanneh The Cambrian sediments nonconformably Member siliciciclastics, enabled a critical review overlie Precambrian basement rocks of the of the Cambrian trilobite fauna and confirmed a Arabo-Nubian Shield (Aqaba Complex) or, stratigraphic position within the traditional Early– locally, Neoproterozoic volcanoclastics and Middle Cambrian boundary interval, probably conglomerates (Araba Complex; Bender 1974; equivalent to parts of Series 3, stage 5 (Rushton AAP Memoir 42 (2011) 155 Figure 2. Generalised composite stratigraphic column of the Cambrian in the Dead Sea area (left; Salib Formation and Umm Ishrin Formation are only partially illustrated). Lithostratigraphic range of the Numayri Member in the investigated sections at the right (Numayri Member without fill pattern; Tayan Member and Hanneh Member with cross fill pattern and only partially illustrated). Lithostratigraphic position of the described microfaunas are indicated by bars. & Powell 1998; Geyer & Landing 2004; Geyer ml acid) has been used, a method which utilises & Elicki submitted). the absorption of water by crystals of calcium acetate (Nötzold 1965). Sieving procedure was MATERIALS AND METHODS executed using sieves of mesh size 0.3 mm and 0.1 The fossiliferous carbonates were investigated mm. Microscopic work has been achieved using by thin-section analysis and also preparated by a ZEISS SV-11 polarisation light-microscope. laboratory chemical work. Best results have SEM investigation was undertaken at the been attained by careful chemical solution of Geological Institute of Freiberg University with the carbonate rocks using formic acid (about the field emission scanning electron microscope 15%) and in some cases acetic acid (about 15%). JEOL JSM-7001 F. For related compositional In some cases, concentrated acetic acid with identification of the microbiota, an energy added anhydrous copper