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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>Luis A. Buatois</dc:contributor>
  <dc:contributor>Guillermo F. Acenolaza</dc:contributor>
  <dc:creator>M. Gabriela Mángano</dc:creator>
  <dc:date>1996</dc:date>
  <dc:description>&lt;p&gt;The Santa Rosita Formation is one the most widely distributed lower Paleozoic units of northwest Argentina. At the Quebrada del Salto Alto section, east of Purmamarca, Jujuy Province, it is represented by four sedimentary facies: thick‐bedded planar cross‐stratified quartzose sandstones (A), thin‐bedded planar cross‐stratified quartzose sandstones and mudstones (B), wave‐rippled sandstones and bioturbated mudstones (C), and black and greenish gray shales (D). Paleocurrent data, sandstone architecture, and sedimentary structures from faciès A and B indicate bipolar/bimodal paleoflows, suggesting the action of tidal currents. The succession is interpreted as that of a tide‐dominated shelf, with only secondary influence of wave processes. Trace fossils are restricted to facies B and C.&lt;/p&gt;&lt;p&gt;The&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Cruziana&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;ichnocoenosis is preserved on the soles of thin‐bedded planar cross‐stratified quartzose sandstones (faciès B). This ichnocoenosis consists of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Conostichus&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;isp.,&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Cruziana omanica, C. semiplicata, C.&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;cf.&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;tortworthi, Cruziana&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;isp.&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Helminthopsis abeli, Monomorphichnus bilinearis, M. multilineatus, Palaeophycus tubularis, Rusophycus carbonarias, R. latus&lt;/i&gt;, and&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;R.&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;isp. The occurrence of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Cruziana semiplicata&lt;/i&gt;, C.&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;omanica, C. cf. tortworthi&lt;/i&gt;, and&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Rusophycus latus&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;supports a Late Cambrian‐Tremadoc age. Slabbing of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Cruziana&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;shows complex interactions between biologic and sedimentologic processes, and suggests a predominance of exhumed traces, washed out and recast by tractive sand deposition. Sandstone soles are densely packed with biogenic structures and exhibit distinctive clusters of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Rusophycus&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;isp. that most likely represent trilobite nesting burrows. The&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Cruziana&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;ichnocoenosis records the resident fauna of a protected, lower intertidal to subtidal interbar setting.&lt;/p&gt;&lt;p&gt;The&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Skolithos&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;ichnocoenosis is represented by high to low density vertical burrows of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Skolithos linearis&lt;/i&gt;, which extend downwards to the quartzose sandstone soles of faciès B and cross the&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Cruziana&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;ichnocoenosis. The&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Skolithos&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;ichnocoenosis represents colonization by suspension‐feeding organisms following a major change in environmental conditions, related to the migration of lower intertidal to subtidal sandwaves.&lt;/p&gt;&lt;p&gt;The&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Planolites&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;ichnocoenosis consists exclusively of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Planolites montanus&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;within mudstones overlying wave‐rippled sandstones (facies C). The&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Planolites&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;ichnocoenosis records opportunistic colonization by inf aunal deposit feeders that mined the organic‐rich fine‐grained sediment during the waning phase of storms that scoured organic detritus from the sea bottom.&lt;/p&gt;&lt;p&gt;The section records, from base to top, a&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Cruziana‐Skolithos&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;ichnofacies zone, a&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Skolithos&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;ichnofacies zone and an unbioturbated zone typified by the thick‐bedded cross‐stratified quartzose sandstone (fades A). This trend reflects progressively higher energy conditions linked to the establishment of a large sand wave complex. The presence of a mixed&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Cruziana‐Skolithos&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;ichnofacies in the lower interval reflects changes in substrate and energy levels, rather than water depth. Accordingly, contrasting ichnocoenoses from interbars&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;(Cruziana)&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and sandwaves&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;(Skolithos)&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;must be considered an example of ichnofacies controlled by local parameters instead of general bathymétrie trends. Conversely, the vertical replacement of the&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Cruziana&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;ichnofacies by the&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Skolithos&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;ichnofacies towards the middle interval of the section reflects the environmental changes associated with the transition between the intertidal and subtidal zones. As overall tidal energy increases from supratidal to subtidal settings, the&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Skolithos&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;ichnofacies tends to occur seaward of the&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Cruziana&lt;/i&gt;ichnofacies in tide‐dominated shallow marine environments. Therefore, onshore‐offshore ichnofacies replacement in tide‐dominated shallow seas is opposite to that in wave‐dominated marine settings.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1080/10420949609386406</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Taylor &amp; Francis</dc:publisher>
  <dc:title>Trace fossils and sedimentary facies from a Late Cambrian‐Early Ordovician tide‐dominated shelf (Santa Rosita Formation, northwest Argentina): Implications for ichnofacies models of shallow marine successions</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>