Microscopic biomorphic structures in Upper Cretaceous marine sedimentary pyrite

  • Alberto Blanco Laboratorio de Paleobiología, Facultad de Ciencias Biológicas, Universidad Autónoma de Nuevo León, Av. Pedro de Alba y Manuel L. Barragán s/n, C.P. 66452, Ciudad Universitaria, San Nicolás de los Garza, Nuevo León, México.
  • Susana Abigail Ángeles-Trigueros Área Académica de Ciencias de la Tierra y Materiales, Universidad Autónoma del Estado de Hidalgo, Carretera Pachuca-Tulancingo, km 4.5, C.P. 42184, Mineral de la Reforma, Hidalgo, México.
  • Juan Hernández-Ávila Área Académica de Ciencias de la Tierra y Materiales, Universidad Autónoma del Estado de Hidalgo, Carretera Pachuca-Tulancingo, km 4.5, C.P. 42184, Mineral de la Reforma, Hidalgo, México.
  • Luis E. Silva-Martínez Laboratorio de Paleobiología, Facultad de Ciencias Biológicas, Universidad Autónoma de Nuevo León, Av. Pedro de Alba y Manuel L. Barragán s/n, C.P. 66452, Ciudad Universitaria, San Nicolás de los Garza, Nuevo León, México.
  • Francisco Javier Zavala-Díaz de la Serna Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Nuevo Campus Universitario, Circuito Universitario, C.P. 31125, Chihuahua, Chihuahua, México.
  • Silvia Patricia Ambrocio-Cruz Escuela Superior de Tlahuelilpan, Universidad Autónoma del Estado de Hidalgo, ExHacienda de San Servando s/n, Colonia Centro, C.P. 42780, Tlahuelilpan, Hidalgo, México.
  • Carlos Castañeda-Posadas Facultad de Ciencias Biológicas, Benemérita Universidad Autónoma de Puebla, Ciudad Universitaria, Blvd. Valsequillo y Av. San Claudio, Edificio BIO-1, Col. Jardines de San Manuel, C.P. 72570, Puebla, Puebla, México.
Keywords: biomorphs, iron sulfides, diagenesis, Upper Cretaceous

Abstract

The purpose of this work is to provide a description of biomorphic structures found in sedimentary pyrite present in the organic-rich marine limestone of the Agua Nueva Formation (Upper Cenomanian, Upper Cretaceous), central Mexico, using scanning electron microscope images. Six types of biomorphic structures were found and interpreted as coccoids (type 1), stomatocysts (types 2 and 3), pollen (types 4 and 5) and tubular structures corresponding to bacterial sheaths (type 6). Energy-dispersive X-ray spectroscopy analysis revealed iron and sulfur within the analyzed structures, indicating that they were replaced by pyrite. Furthermore, the high content of elemental carbon in the biostructures, in contrast to the surrounding pyrite in which this element is absent, suggests that the biostructures are of biotic origin. The coccoids and tubular elements were interpreted as autochthonous bacterial fossils or remains of bacterial activity associated with pyrite formation. In contrast, the stomatocysts and pollen represent allochthonous elements imported from continental areas.
Published
2016-12-14
Section
Articles