Neogene palynostratigraphic zonation of the Marañon Basin, Western Amazonia, Peru

Abstract

The palynology (150 species of pollen grains, 43 species of spores, eight species of dinoflagellate cysts, five genera of algae, two genera of fungal spores, foraminiferal linings, and copepod eggs) of the Neogene succession in the Marañon Basin, north Peru, was thoroughly investigated for the first time from six industrial wells (Arabela-1X, Maynas-1, Tucunare-1X, Tigrillo-30X, Nahuapa-24X, and La Frontera-1). Six palynozones spanning the Early Miocene to the Early Pliocene were defined. The zones in stratigraphically ascending order are as follows: the Mar-A Corsinipollenites oculusnoctis Zone (Aquitanian to early Burdigalian: 23.03–17.71 Ma), delimited by the appearance of Acaciapollenites myriosporites, Retitricolporites wijmstrae and/or Corsinipollenites oculusnoctis and/or the disappearance of Cicatricosisporites dorogensis at the base; the Mar-B Malvacipolloides (Echitricolporites) maristellae Zone (Burdigalian: 17.71–16.1 Ma), from Malvacipolloides maristellae at the base to the disappearance of Retitricolporites wijmstrae at the top; the Mar-C Mauritiidites crassibaculatus Zone (latest Burdigalian to Late Langhian: 16.1–14.2/13.9 Ma), from the appearance of Grimsdalea magnaclavata at the base to the disappearance of Retitriporites dubiosus and/or the appearance of Crassoretitriletes vanraadshooveni and/or Psilastephanoporites tesseroporus; the Mar-D Crassoretitriletes vanraadshooveni Zone (Late Serravallian: 14.2–11.62 Ma), from the appearance of Crassoretitriletes vanraadshooveni and/or Psilastephanoporites tesseroporus to the disappearances of Mauritiidites crassibaculatus, Bombacacidites nacimientoensis, and Cyathidites congoensis; and the Mar-E Psilastephanoporites tesseroporus Zone (Early Tortonian to Late Messinian: 11.62–5.48 Ma) from the disappearance of Corsinipollenites oculusnoctis and/or Cyathidites congoensis to the disappearance of Psilastephanoporites tesseroporus and/or Siltaria santaisabelensis. These zones were corroborated by means of events ordination demonstrated using graphic correlation. The Mar-F Ctenolophonidites suigeneris Zone (latest Messinian to Zanclean) is described only in the Frontera-1 well from the disappearance of Psilastephanoporites tesseroporus to the last record of Ctenolophonidites suigeneris and/or Siltaria hammenii. This study suggests that Pliocene sedimentation is also recorded in the Western Amazonia of Peru, and provides new palynological information compared with the Mio–Pliocene Solimões, Acre, and eastern Amazonas basins.