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<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>S.M. Awramik</dc:contributor>
  <dc:contributor>K. Morrison</dc:contributor>
  <dc:contributor>D.G. Hadley</dc:contributor>
  <dc:creator>P. Cloud</dc:creator>
  <dc:date>1979</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;We report here the first biologically definable fossils from pre-Saq (pre-Middle Cambrian) rocks of the Arabian Shield. They include the distinctive helically coiled tubular filaments of the oscillatorialean blue-green alga&amp;nbsp;&lt;/span&gt;&lt;i&gt;Obruchevella parva&lt;/i&gt;&lt;span&gt;&amp;nbsp;as well as two size classes of spheroidal unicells of uncertain affinity. Also present is the conical stromatolite&amp;nbsp;&lt;/span&gt;&lt;i&gt;Conophyton&lt;/i&gt;&lt;span&gt;&amp;nbsp;and unidentified stromatolites. All occur in cherty limestones of the Jubaylah Group, northern Saudi Arabia, a nonmarine to locally marine taphrogeosynclinal sequence that fills depressions along the northwest-trending Najd faults.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;&lt;i&gt;Conophyton&lt;/i&gt;&amp;nbsp;has heretofore been found only in strata older than about 680 Ma (except for puzzling records in modern hot springs) while&amp;nbsp;&lt;i&gt;Obruchevella&lt;/i&gt;&amp;nbsp;is so far known only from rocks between about 680 and 470 Ma old. Thus it appears that the Jubaylah Group is close to the Proterozoic-Phanerozoic transition. The simple spheroidal nanno-fossils are not diagnostic as to age. Their relationships within what appears to be early diagenetic chert suggest a classical algal-mat association. The brecciated and microchanneled appearance of much of the fossiliferous rock, its locally dolomitic nature, and the prevalence of cryptalgalaminate favors a very shallow, locally turbulent, and perhaps episodically exposed marine or marginal marine setting.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;The Jubaylah Group lies unconformably beneath the Siq Sandstone (basal member of the Saq Sandstone) of medial Cambrian age, rests nonconformably on crystalline basement, and has yielded a K-Ar whole-rock age (on andesitic basalt) of ∼540 Ma. To judge from the fossils, however, that age may be as much as 100 Ma or more too young.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;&lt;br data-mce-bogus="1"&gt;&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1016/0301-9268(79)90020-2</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Elsevier</dc:publisher>
  <dc:title>Earliest Phanerozoic or latest Proterozoic fossils from the Arabian Shield</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>