Geochemistry, palaeoenvironments and timing of Aptian organic-rich beds of the Paja Formation (Curití, Eastern Cordillera, Colombia)

Abstract

At the Curití 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 Pulchellia, Gerhardtia, Toxancycloceras, Karsteniceras and Prodeshayesites. 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 (d 13 C org between 222.05‰ and 220.47‰) 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 d 13 C org curve are comparable with the Lower Aptian interval C7. Thus, the organic-rich shale interval of the Paja Formation at the Curití section, showing characteristics of oxygendepleted conditions, was deposited after OAE-1a, which is known to occur between isotopic levels C3 and C6.

Regional palaeoenvironmental influence on organic matter sequestration and characteristics of carbon isotope segment C5 in a hemipelagic sequence, Organyà Basin, northeast Spain

“…All samples (n = 109) were analysed for total carbon (TC) and total inorganic carbon (TIC) at Florida International University (FIU) using a LECO CR-412 carbon analyser following the methodology used in the Carbon Analysis Laboratory (Ponton, 2005;Gaona-Narvaez et al, 2013b;, and modified as proposed by Socorro and Maurrasse (2019). Calibration of the instrument was performed by producing a best-fit calibration curve using pure calcite ≥99.0% (C64-500, Fisher Scientific; Sanchez-Hernandez and Maurrasse, 2014).…”

A negative carbon isotope excursion within the Dufrenoyia furcata Zone: proposal for a new episode for chemostratigraphic correlation in the Aptian

“…Based on the planktonic foraminifera biozones used by MENEGATTI et al (1998) from Cismon core reference section in Italy (MENEGATTI et al, 1998;ERBA et al, 1999); 2-Serre Chaitieu section, Vocontian Basin, France (HERRLE et al, 2004), 3-Cassis-La Bédoule section, France (MOULLADE et al, 1998), 4-Prebetic Domain sections, Spain (MORENO-BEDMAR et al, 2012, this study); 5-Djebel Serdj section, Tunisia (HELD et al, 2008), 6-Igaratza section, Basque-Cantabrian Basin, Spain (MILLÁN et al, 2009), 7-Santa Rosa section, Mexico (LI et al, 2008, 8-Permanente Quarry section, USA (ROBINSON et al, 2008), 9-Curití section, Colombia (GAONA-NARVAEZ et al, 2013). (Fig.…”

“…A lack of biostratigraphic data along with the carbon isotope data prevents us from further constraining the age of this negative excursion. In Colombia, the δ 13 C org curve of the Curití section shows a pronounced negative inflection in the lowermost part of the segment C7 that reaches ~2.0‰ (GAONA-NARVAEZ et al, 2013) and is also compatible with the IFNE. All mentioned sections in this chapter are located in Figure 1.…”

Exceptionally preserved ‘skin’ in an Early Cretaceous fish from Colombia

“…These local biogeochemical interactions would favor not only preservation of the general morphology of the skin, but also some of their soft-tissue structures and residues of the original biomolecules by geopolymerization ( Lindgren et al, 2018 ). Another factor that potentially played a key role in the preservation of the ‘skin’ in UR-CP-0001 was the burial environment conditions, dominated by organic-rich shale interval showing characteristics of oxygen depleted conditions at the lower segment of Paja Formation in this region ( Gaona-Narvaez, Florentin & Etayo-Serna, 2013 ). Microcrystalline minerals like clays and shales have extremely large surface area to volume ratios, and are usually charged, both of which favor adsorption and inactivation of degrading enzymes, similar been proposed for the exceptional preservation of Burgess Shale fossils ( Butterfield, 1990 ).…”