Research Paper
Ocean bottom-water oxygenation across the Late Miocene–Early Pliocene biogenic bloom
MARIA ELENA GASTALDELLO
Departamento de Ciencias de la Tierra, Universidad de Zaragoza, Spain
Dipartimento di Geoscienze, Università degli Studi di Padova, Via G. Gradenigo n.6 – 35131, Padova, Italy; mariaelena.gastaldello@phd.unipd.it.
Corresponding author
CLAUDIA AGNINI
Dipartimento di Geoscienze, Università degli Studi di Padova, Via G. Gradenigo n.6 – 35131, Padova, Italy; claudia.agnini@unipd.it.
LAIA ALEGRET
Departamento de Ciencias de la Tierra, Universidad de Zaragoza, Spain; Instituto de Investigación en Ciencias Ambientales de Aragón, Universidad de Zaragoza, Spain; laia@unizar.es.
ABSTRACT
The Late Miocene–Early Pliocene biogenic bloom (ca. 9.0–3.5 millions of years ago, My) represents a period of globally heightened marine biological productivity. Palaeoenvironmental studies across this interval show alternating phases of low-oxygen eutrophic and well-oxygenated oligotrophic conditions. Here, we focus on the bottom water oxygenation changes during the biogenic bloom to assess the validity of the enhanced Benthic Foraminifera Oxygen Index (EBFOI). The index was calculated for three ocean drilling sites: Ocean Drilling Program Site 1085 (southeast Atlantic), and International Ocean Discovery Program sites U1506 (southwest Pacific) and U1488 (equatorial Pacific). The quantitative study of benthic foraminiferal assemblages from Site 1488 allowed us to infer the palaeoenvironmental evolution across the biogenic bloom. At this site, we document a shift from stable oxygen concentrations and seasonal input of phytodetritus (8.7–4.3 My) to short-term fluctuations between low oxygen eutrophic conditions and well-oxygenated oligotrophic conditions (4.3–3.0 My). The EBFOI calculated at sites 1085 and U1506 was cross-referenced with the published palaeoenvironmental conditions. While the EBFOI proves to be a valuable tool to infer palaeoenvironmental changes at the seafloor, it has limitations, as evidenced by comparisons with palaeoenvironmental interpretations of Site U1488, where it does not consistently align with inferred oxygen conditions.
Key words: Late Miocene, Early Pliocene, biogenic bloom, benthic foraminifera, Oxygenation index
How to cite: Gastaldello, M. E., Agnini, C., & Alegret, L. (2024). Ocean bottom-water oxygenation across the Late Miocene–Early Pliocene biogenic bloom. Spanish Journal of Palaeontology, 39 (1)1-14.
Received 10 October 2023, Accepted 8 January 2024, Published online 19 January 2024
https://doi.org/10.7203/sjp.28131
