000135886 001__ 135886
000135886 005__ 20240627102630.0
000135886 037__ $$aTESIS-2024-283
000135886 041__ $$aeng
000135886 1001_ $$aGastaldello, María Elena
000135886 24500 $$aThe Late Miocene-Early Pliocene Biogenic Bloom: Duration, Causes and Paleoceanographic Implications
000135886 260__ $$aZaragoza$$bUniversidad de Zaragoza, Prensas de la Universidad$$c2024
000135886 300__ $$a351
000135886 4900_ $$aTesis de la Universidad de Zaragoza$$v2024-275$$x2254-7606
000135886 500__ $$aPresentado: 30 04 2024
000135886 502__ $$aTesis-Univ. Zaragoza, , 2024$$bZaragoza, Universidad de Zaragoza$$c2024
000135886 506__ $$aby-nc$$bCreative Commons$$c3.0$$uhttp://creativecommons.org/licenses/by-nc/3.0/es
000135886 520__ $$aThe Late Miocene-Early Pliocene Biogenic Bloom (ca. 9.0 3.5 Ma) is a paleoceanographic phenomenon marked by increased marine biological productivity documented in numerous locations, from the Atlantic, to the Pacific and Indian oceans. In deep-sea sediments, the Biogenic Bloom is characterised by a marked increase in biogenic CaCO3 (mainly from calcareous nannofossils and planktonic foraminifera) and SiO2 accumulation rates (mainly from radiolarians and diatoms). Supporting evidence includes the presence of diatom assemblages indicative of elevated productivity, the abundance of suboxic and dysoxic benthic foraminifera, and changes in sediment geochemistry (e.g. reduced Mn/Sc ratio), which point to low dissolved oxygen levels at intermediate water depths. This phenomenon has remained a mystery in the geological record, as the several-million-years high productivity conditions documented for the Biogenic Bloom necessitate a profound alteration in the global nutrient cycling of the oceans to be explained. Despite its widespread occurrence, fundamental questions regarding the temporal and spatial extent, as well as the driving mechanisms behind this phenomenon remain unanswered. In this context, this Ph.D. thesis aims to comprehensively document the Biogenic Bloom through an integrated quantitative approach. We produced comparable datasets from diverse areas worldwide, from the Pacific (IODP Site U1506 and U1488) to the Atlantic (ODP Site 1085) oceans. The first fundamental step of the project consists of developing a highly resolved calcareous nannofossil biostratigraphic classification for all study sites, aiming to establish reliable chronological frameworks. The age models were employed to calculate the linear sedimentation and derive the carbonate mass accumulation rates, a proxy used to identify the Biogenic Bloom on a global scale. The second phase of the project involves an in-depth benthic foraminiferal investigation. Taxonomic and quantitative studies of the benthic foraminiferal assemblages, as well as morphogroup and statistical analyses were carried out for each study site to infer the environmental conditions in the deep-sea in terms of nutrient availability, trophic conditions, and oxygen concentrations during the Biogenic Bloom. These results allow for a thoughtful discussion on the local, regional and global mechanisms and processes that may have triggered the different expressions of the Biogenic Bloom. One of the main advances of this Ph.D. thesis is certainly the discussion on the timing of the Biogenic Bloom, and the conclusion that the onset was synchronous at ca. 8.0 Ma, and the ending appears to be diachronous, with the Biogenic Bloom lasting longer in the Atlantic Ocean, until around 3.0 Ma, compared with the Pacific Ocean (until ca. 4.5 4.0 Ma). The main result obtained through the analysis of benthic foraminiferal assemblages indicates that this prolonged phase of high productivity did not persist consistently for millions of years, but it was marked by high variability and different phases, most likely related to local-to-regional processes. Furthermore, all study sites document an increase in seasonal phytoplankton blooms in surface waters and the consequent thriving of phytodetritus-exploiting taxa (PET) at the seafloor. The PET dominance phase represents a global feature during the Biogenic Bloom, which was most likely related to the local or regional paleoenvironmental and paleoceanographic evolution at each particular site, rather than a synchronous response.<br />
000135886 520__ $$a<br />
000135886 521__ $$97077$$aPrograma de Doctorado en Geología
000135886 540__ $$9info:eu-repo/semantics/embargoedAccess
000135886 6531_ $$apaleontología
000135886 6531_ $$apaleoclimatología
000135886 691__ $$a13 14
000135886 692__ $$aTomar medidas urgentes para combatir el cambio climático y sus efectos. Conservar y utilizar de forma sostenible los océanos, mares y recursos marinos para lograr el desarrollo sostenible.
000135886 700__ $$aAgnini, Claudia $$edir.
000135886 700__ $$aAlegret Badiola, María Laia $$edir.
000135886 7102_ $$aUniversidad de Zaragoza$$b
000135886 830__ $$9489
000135886 8560_ $$fcdeurop@unizar.es
000135886 8564_ $$s39792621$$uhttps://zaguan.unizar.es/record/135886/files/TESIS-2024-283.pdf$$zinfo:eu-repo/date/embargoEnd/2025-04-30
000135886 909CO $$ooai:zaguan.unizar.es:135886$$pdriver
000135886 909co $$ptesis
000135886 9102_ $$aCiencias$$b
000135886 980__ $$aTESIS