The biotic crisis across the Oceanic Anoxic Event 2: Palaeoenvironmental inferences based on foraminifera and geochemical proxies from the South Iberian Paleomargin

Reolid, Matias ; Sánchez-Quiñónez, Carlos A. ; Alegret, Laia (Universidad de Zaragoza) ; Molina, Eustoquio (Universidad de Zaragoza)

Resumen: Open marine sediments deposited during the CenomanianeTuronian transition are well exposed in the Spanish Ba~nos de la Hedionda section (Betic Cordillera, South Iberian Palaeomargin). Analysis of foraminiferal assemblages and geochemical proxies allow inferences on the impact of the Oceanic Anoxic Event 2 (OAE2) in this area of the western Tethys. Three main intervals have been identified corresponding to different lithological units and biozones. (1) The top of the Capas Blancas Member (Rotalipora cushmani Biozone) represents the pre-extinction phase with diverse foraminiferal assemblages and well developed water-column tiering, well-oxygenated, oligotrophic deep-waters and oxygenated to poorly oxygenated, mesotrophic surface-waters. Foraminiferal opportunist species point to a minor event with dysoxic conditions preceding the OAE2. (2) The black radiolaritic shales (Whiteinella archaeocretacea Biozone) consist of a foraminiferal-barren interval, except for the lowermost centimetres where planktic surface-dweller opportunists are common. Redox sensitive elements (Cr/Al, V/Al, U/Th, MoEF, Moaut, UEF and Uaut) and increased TOC values reflect oxygen depleted conditions related to the OAE2. The increase in P/Ti values at the base of this stratigraphic interval indicates an abrupt increase in productivity. High concentrations of radiolarians are congruent with high surface productivity probably related to changes in oceanic circulation and enhanced upwelling currents, as well as subsequent shallowing of the oxygenminimum zone. The increase in MoEF and Moaut towards the top of the black radiolaritic shales indicates temporal euxinic conditions. (3) A slow, bottom-up recovery of foraminiferal assemblages is inferred at the base of the Boqueron Member (Helvetoglobotruncana helvetica Biozone), with seafloor recolonization by benthic foraminifera being recorded previous to the water column colonization by planktic forms, mainly by intermediate-dwellers typical of mesotrophic waters. The subsequent proliferation of surfacedweller opportunists and deep-dweller opportunists adapted to mesotrophic to eutrophic conditions, and the decrease in planktic foraminiferal diversity, may indicate the persistence of poorly oxygenated conditions in the water column towards the lower-middle part of the H. helvetica Biozone.

Idioma: Inglés

DOI: 10.1016/j.cretres.2015.10.11

Año: 2016

Publicado en: Cretaceous Research 60 (2016), 1-27
ISSN: 0195-6671

Factor impacto JCR: 2.015 (2016)

Categ. JCR: PALEONTOLOGY rank: 9 / 53 = 0.17 (2016) - Q1 - T1
Categ. JCR: GEOLOGY rank: 12 / 47 = 0.255 (2016) - Q2 - T1

Factor impacto SCIMAGO: 0.883 - Paleontology (Q1)

Financiación: info:eu-repo/grantAgreement/ES/DGA/E05
Financiación: info:eu-repo/grantAgreement/ES/MICINN/RYC-2009-04316
Financiación: info:eu-repo/grantAgreement/ES/MINECO/CGL2011-229121
Financiación: info:eu-repo/grantAgreement/ES/MINECO/CGL2011-23077
Financiación: info:eu-repo/grantAgreement/ES/MINECO/CGL2012-33281
Financiación: info:eu-repo/grantAgreement/ES/MINECO-FEDER/CGL2014-58794-P

Tipo y forma: Artículo (PostPrint)

Área (Departamento): Área Paleontología (Dpto. Ciencias de la Tierra)