Late Cryogenian-Ediacaran history of the Arabian-Nubian Shield: A review of depositional, plutonic, structural, and tectonic events in the closing stages of the northern East African Orogen

Two groups of Precambrian macrofossils are reexamined. Members of the first group are usually determined as Nemiana simplex Palij, 1976 and regarded as remains of animal organisms; members of the second are often determined as Beltanelloides sorichevae Sokolov, 1965 and assigned to green algae or cyanobacteria. The co-occurrence of the two groups in burials of the White Sea outcrops, the similarity in morphology, and the presence of transitional forms suggest that they could have been variants of preservation of the same extinct species. As a result of critical analysis of published data and examination of available type specimens, the species Beltanelliformis brunsae Menner, 1974, Beltanelloides podolicus A. Istchenko, 1988, Hagenetta aarensis Hahn et Pflug, 1988, Medusinites paliji Gureev, 1987, and Namamedusium wendti Zessin, 2008 are assigned to the same species. Beltanelliformis brunsae is regarded as the senior synonym. Taphonomic and comparative morphological data and the SEM study of phosphatized remains of Beltanelliformis agree with the hypothesis developed by M. Steiner of the microbial nature of these fossils. It is proposed that round colonies of B. brunsae grew in the area of extremely shallow water in Late Vendian marine basins. Beltanelliformis minutae McIlroy et al., 2005 is the second species of the same genus; it was more tolerant of changes in salinity and shows a wider stratigraphic range, while the species Nemiana bakeevi Becker, 1992 and Beltanelloides amorphus Menasova, 2003 are considered to have nothing in common with the groups and genus discussed.

Revision of the problematic Vendian macrofossil Beltanelliformis (=Beltanelloides, Nemiana)

The Ediacaran Araba Complex in Jordan is defined and described for the first time
in lexicon style, with an emphasis on the sedimentary, volcanic and volcaniclastic
units outcropping adjacent to Wadi Araba, and from seismic and deep exploration
well data. The Araba Complex ranges in age from ca. 605 to 550 Ma and comprises
a major cycle of sedimentary, volcanic and volcaniclastic, and igneous rocks
emplaced in an overall extensional tectonic regime that followed intrusion and
amalgamation of the granitoid and metamorphic Aqaba Complex, a part of the
Gondwanan Arabian-Nubian Shield (ANS; ca. 900 to 610 Ma).
The Araba Complex is bounded by two major erosional unconformities, the
newly defined Ediacaran Araba Unconformity (ca. 605 Ma) at its base, underlain
by the Aqaba Complex, and the post-extensional, regional lower Cambrian Ram
Unconformity (ca. 530 Ma) that is marked by the widespread deposition of thick
alluvial and marginal-marine siliciclastics (Ram Group).

/pdf/ediacaran-araba-complex-of-jordan-1ipvvy1mx8.pdf

Ediacaran Araba Complex of Jordan

The Ediacaran Jibalah Group comprises volcano-sedimentary successions that filled small fault-bound basins along the NW–SE-trending Najd fault system in the eastern ArabianNubian Shield. Like several other Jibalah basins, the Antaq basin contains exquisitely preserved sedimentary structures and felsic tuffs, and hence is an excellent candidate for calibrating late Ediacaran Earth history. Shallow-marine strata from the upper Jibalah Group (Muraykhah Formation) contain a diversity of load structures and intimately related textured organic (microbial) surfaces, along with a fragment of a structure closely resembling an Ediacaran frond fossil and a possible specimen of Aspidella. Interspersed carbonate beds through the Muraykhah Formation record a positive d 13 C shift from 6t o 0&. U-Pb zircon geochronology indicates a maximum depositional age of ~570 Ma for the upper Jibalah Group, consistent with previous age estimates. Although this age overlaps with that of the upper Huqf Supergroup in nearby Oman, these sequences were deposited in contrasting tectonic settings on opposite sides of the final suture of the East African Orogen.

A middle–late Ediacaran volcano‐sedimentary record from the eastern Arabian‐Nubian shield

\n The Ediacaran–Cambrian Middle East Geologic Time Scale is extensively revised in the 2014 version (Enclosure). It suggests the top of the Abu Mahara Group glacial diamictites in Oman represent the termination of the late Cryogenian Marinoan Glaciation at 635 Ma. The overlying Ediacaran Nafun Group of Oman is shown between 635 and 547 Ma based on geochronologic data, and divided into: (1) the Lower Nafun Supersequence (635–582 Ma) consisting of the Hadash Formation (cap carbonate), the Masirah Bay Formation (clastics) and the Khufai Formation (carbonates); and (2) the Upper Nafun Supersequence (582–547 Ma) consisting of the Shuram Formation (clastics and carbonates) and the Buah Formation (carbonates). The Nafun Group lies below the Ediacaran– lower Cambrian Ara Group (evaporites and carbonates), which contains the Ediacaran/Cambrian Boundary currently dated at 541 Ma.\n The Sub-Shuram Unconformity, which corresponds to the global Shuram δ13C Negative Excursion, separates the Nafun supersequences. Its age was estimated by assuming the thicknesses of the Nafun formations are proportional to time in the Masirah-1 Well, where the Nafun Group attains its greatest-known thickness of 2,308 m in Oman. This assumption coincidently estimated the unconformity at 582 Ma, the same age as the Ediacaran Gaskiers (Varanger or Varingian) Glaciation. The new calibration was used to correlate the Nafun formations to the rock-time units of the Jibalah Group in several isolated basins along the Najd Fault System in the Arabian Shield, using recently published geochronologic data and δ13C measurements, as follows.\n The younger part of the Lower Nafun Supersequence (635–582 Ma) is here correlated to the Lower Jibalah Supersequence (605 ± 5 to 582 Ma), represented by the Umm al-Aisah Formation in the Jifn Basin, located along the Halaban-Zarghat Fault Zone of the Najd Fault System. The Umm al-Aisah Formation consists of volcanics and clastics that give way to the Umm al-Aisah Limestone. The Upper Nafun Supersequence (582–547 Ma) is here correlated to the Upper Jibalah Supersequence, which unconformably overlies the Umm al-Aisah Limestone, with its basal unit being the Gaskiers-coeval Jifn Polymictic Conglomerate (≥ 200 m thick). In the Bir Sija Basin, located along the Rika Fault Zone of the Najd Fault System, the likely Gaskiers-coeval polymictic conglomerate (150 m thick) is overlain by a 20 m-thick limestone unit, the Bir Sija Limestone, possibly a cap carbonate. The Upper Jibalah Supersequence continues with clastics overlain by the Muraykhah Formation (carbonates) or mixed clastics-carbonates of its equivalent formations. In several outcrops the Upper Jibalah Supersequence is overlain by the lower Cambrian Siq Sandstone Formation (≤ 525 ± 5 Ma) implying the Sub-Siq Unconformity represents a hiatus between 547 and 525 ± 5 Ma. The Jifn Formation in the Jifn Basin, however, may represent continuous deposition between 582 Ma and 525 ± 5 Ma.

/pdf/proposed-correlation-of-oman-s-abu-mahara-supergroup-and-47pas109l1.pdf

Proposed correlation of Oman’s Abu Mahara Supergroup and Saudi Arabia’s Jibalah Group

Reconnaissance for an Ediacaran fauna, Kingdom of Saudi Arabia

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Reconnaissance for an Ediacaran fauna, Kingdom of Saudi Arabia