1 research outputs found
Geochemistry, palaeoenvironments and timing of Aptian organic-rich beds of the Paja Formation (CuritÃ, Eastern Cordillera, Colombia)
<p>At the Curità Quarry, Eastern Cordillera of Colombia, a 23.35 m section includes a 6.3 m interval of organic-rich marlstones,
calcareous clay-shales and clay-shales devoid of benthic fossils and bioturbation, at the base of the Paja Formation. It overlies
carbonate ramp deposits of the Rosablanca Formation, with the topmost layer containing reworked and phosphatized assemblages
of middle Barremian to lowest Aptian ammonites of the genera <em>Pulchellia</em>, <em>Gerhardtia</em>, <em>Toxancycloceras</em>, <em>Karsteniceras</em> and <em>Prodeshayesites</em>. High-resolution analyses of the section, including total inorganic carbon (TIC, 0.09–50 wt%), total organic carbon (TOC,
up to 8.4%) and stable carbon isotope measurements (δ<sup>13</sup>C<sub>org</sub> between −22.05‰ and −20.47‰) allow the determination of the stratigraphic relationship between the organic-rich level within
the Paja Formation and Oceanic Anoxic Event-1a (OAE-1a). The range of values and the overall pattern of the δ<sup>13</sup>C<sub>org</sub> curve are comparable with the Lower Aptian interval C7. Thus, the organic-rich shale interval of the Paja Formation at the
Curità section, showing characteristics of oxygen-depleted conditions, was deposited after OAE-1a, which is known to occur
between isotopic levels C3 and C6.
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