<?xml version='1.0' encoding='utf-8'?>
<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>J. Dale Nations</dc:contributor>
  <dc:contributor>Jeffrey G. Eaton</dc:contributor>
  <dc:creator>William P. Elder</dc:creator>
  <dc:date>1991</dc:date>
  <dc:description>&lt;p&gt;Lithology, carbonate and organic carbon geochemistry, and molluscan macrofauna were investigated in fine-grained clay-dominated strata spanning the Cenomanian-Turonian Stage boundary in the southern Colorado Plateau region. Analyses of these data show basinal and onshore to offshore changes in sedimentologic and molluscan assemblage trends through the upper Cenomanian&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Sciponoceras gracile&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Neocardioceras juddii&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and lower Turonian&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Watinoceras coloradoense&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;Biozones.&lt;/p&gt;&lt;p&gt;Diverse infaunal/epifaunal bivalve assemblages are best developed in the&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Sciponoceras gracile&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;Biozone and at the more clay-rich nearshore sections. Gastropod and infaunal bivalve abundance and diversity decrease in an offshore and up-section direction as carbonate and organic carbon percentages generally increase.&lt;/p&gt;&lt;p&gt;The&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Neocardioceras juddii&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;Biozone precedes the stage boundary and is characterized in Utah and Arizona by pulsed increases in organic carbon and detrital-feeding gastropods, and by a shift in infaunal bivalve dominance toward species adapted for soft-substrate conditions. These data suggest that pulses of increased organic detrital resources and decreased substrate firmness were associated with the stage boundary extinctions.&lt;/p&gt;&lt;p&gt;The stage boundary is marked by a change to depauperate epifaunal assemblages at western sections. At all sections, the base of the&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Watinoceras coloradoense&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;Biozone is reflected by an abrupt increase in carbonate and decrease in organic carbon percentages as well as by the immigration of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;Mytiloides&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;bivalves. Periods of progressive recovery through this biozone were associated with carbonate-rich depositional periods.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1130/SPE260-p113</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Geological Society of America</dc:publisher>
  <dc:title>Molluscan paleoecology and sedimentation patterns of the Cenomanian-Turonian extinction interval in the southern Colorado Plateau region</dc:title>
  <dc:type>chapter</dc:type>
</oai_dc:dc>