Paleoproductivity proxies and alkenone precursors in the Western Mediterranean during the Early-Middle Pleistocene transition
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| Natura: | Dataset Open Access |
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PANGAEA
2025
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| author | Marino, Maria Rodrigues, Teresa Quivelli, Ornella Girone, Angela Maiorano, Patrizia Bassinot, Franck |
| author_facet | Marino, Maria Rodrigues, Teresa Quivelli, Ornella Girone, Angela Maiorano, Patrizia Bassinot, Franck |
| collection | Datos científicos de ciencias marinas y ambientales |
| contents | Multidisciplinary analyses (taxonomic analysis of coccolithophore assemblages, stable oxygen isotopes, marine and terrestrial biomarkers) have been carried out on sediments from Ocean Drilling Program Site 975 in the Algero-Balearic basin (38°53.8′ N, 4°30.6′ E), through late marine isotope stage (MIS) 20-19 (from 800 to 756 thousand years ago). The aim of the study was to compare coccolithophore paleoproductivity proxies, such as C37 alkenone concentration (ng/g) and nannofossil accumulation rate (NAR=coccoliths * cm- 2 * kyr-1), and understand their relationship with paleoceanographic condition and paleoenvironmental changes, alkenone-producing precursors and unsaturated C37 alkenone compounds (C37:2, C37:3, C37:4). Measurements of stable oxygen isotope analysis were performed on four to fifteen specimens of Globigerina bulloides (250–315 μm). These analyses were performed on an Isoprime 100 (Elementar) dual-inlet Isotope Ratio Mass Spectrometer (Elementar) at the Laboratoire des Sciences du Climat et de l'Environnement (LSCE, France). The results are expressed as δ18O vs V-PDB (in ‰) through calibration to international NBS standards. Quantitative analyses on coccolithophores were performed at the Dipartimento di Scienze della Terra e Geoambientali, Bari University (Italy), using a polarized light microscope at 1000 X magnification, and abundances were determined by counting at least 500 coccoliths of all sizes. Nannofossil dissolution index (DI) has been calculated as follows: small gephyrocapsids/(small gephyrocapsids + Calcidiscus leptoporus). Marine and terrestrial biomarkers have been processed at the Instituto Português do Mar e da Atmosfera (Portugal). The patterns of C37 alkenone concentration and NAR provided reliable information on past paleoproductivity changes. The Alkanol Preservation Index (API) obtained by the relative proportion of n-hexacosan-1-ol (C26OH) to the sum of C26OH plus n-nonacosane (C29) [API = C26OH/(C26OH + C29)], was used as a proxy of sea bottom ventilation in the basin. Sea surface temperature (SST) was estimated calculating the alkenone Uk'37 index that is based on the di- and tri-unsaturated alkenone ratio [(C37:2)/(C37:2 + C37:3)] and converted into temperature values using the global core top calibration of annual SST [Uk'37 = (0.033*SST) + 0.044], with a methodology uncertainty of ±0.5 ◦C. Tetra-unsaturated compound (C37:4) was considered as an indicator of lower temperature and low salinity waters and linked to polar and subpolar water influx into the Western Mediterranean. |
| format | Dataset Open Access |
| id | pangaea_https___doi_org_10_1594_PANGAEA_982519 |
| institution | PANGAEA |
| language | en |
| publishDate | 2025 |
| publisher | PANGAEA |
| record_format | pangaea |
| spellingShingle | Paleoproductivity proxies and alkenone precursors in the Western Mediterranean during the Early-Middle Pleistocene transition Marino, Maria Rodrigues, Teresa Quivelli, Ornella Girone, Angela Maiorano, Patrizia Bassinot, Franck 161-975; Algero-Balearic basin; alkenone SST; Biomarkers; Coccolithophores; COMPCORE; Composite Core; Joides Resolution; Leg161; marine biomarkers; Ocean Drilling Program; ODP; Oxygen isotopes; terrestrial biomarkers; Western Basin Multidisciplinary analyses (taxonomic analysis of coccolithophore assemblages, stable oxygen isotopes, marine and terrestrial biomarkers) have been carried out on sediments from Ocean Drilling Program Site 975 in the Algero-Balearic basin (38°53.8′ N, 4°30.6′ E), through late marine isotope stage (MIS) 20-19 (from 800 to 756 thousand years ago). The aim of the study was to compare coccolithophore paleoproductivity proxies, such as C37 alkenone concentration (ng/g) and nannofossil accumulation rate (NAR=coccoliths * cm- 2 * kyr-1), and understand their relationship with paleoceanographic condition and paleoenvironmental changes, alkenone-producing precursors and unsaturated C37 alkenone compounds (C37:2, C37:3, C37:4). Measurements of stable oxygen isotope analysis were performed on four to fifteen specimens of Globigerina bulloides (250–315 μm). These analyses were performed on an Isoprime 100 (Elementar) dual-inlet Isotope Ratio Mass Spectrometer (Elementar) at the Laboratoire des Sciences du Climat et de l'Environnement (LSCE, France). The results are expressed as δ18O vs V-PDB (in ‰) through calibration to international NBS standards. Quantitative analyses on coccolithophores were performed at the Dipartimento di Scienze della Terra e Geoambientali, Bari University (Italy), using a polarized light microscope at 1000 X magnification, and abundances were determined by counting at least 500 coccoliths of all sizes. Nannofossil dissolution index (DI) has been calculated as follows: small gephyrocapsids/(small gephyrocapsids + Calcidiscus leptoporus). Marine and terrestrial biomarkers have been processed at the Instituto Português do Mar e da Atmosfera (Portugal). The patterns of C37 alkenone concentration and NAR provided reliable information on past paleoproductivity changes. The Alkanol Preservation Index (API) obtained by the relative proportion of n-hexacosan-1-ol (C26OH) to the sum of C26OH plus n-nonacosane (C29) [API = C26OH/(C26OH + C29)], was used as a proxy of sea bottom ventilation in the basin. Sea surface temperature (SST) was estimated calculating the alkenone Uk'37 index that is based on the di- and tri-unsaturated alkenone ratio [(C37:2)/(C37:2 + C37:3)] and converted into temperature values using the global core top calibration of annual SST [Uk'37 = (0.033*SST) + 0.044], with a methodology uncertainty of ±0.5 ◦C. Tetra-unsaturated compound (C37:4) was considered as an indicator of lower temperature and low salinity waters and linked to polar and subpolar water influx into the Western Mediterranean. |
| title | Paleoproductivity proxies and alkenone precursors in the Western Mediterranean during the Early-Middle Pleistocene transition |
| topic | 161-975; Algero-Balearic basin; alkenone SST; Biomarkers; Coccolithophores; COMPCORE; Composite Core; Joides Resolution; Leg161; marine biomarkers; Ocean Drilling Program; ODP; Oxygen isotopes; terrestrial biomarkers; Western Basin |
| url | https://doi.org/10.1594/PANGAEA.982519 |