Análisis integrado del impacto de la variabilidad ambiental en las condiciones del fondo marino en el Mediterráneo durante el último Ciclo Glacial

Resum

The Last Glacial Cycle is one of the most interesting periods for environmental studies, presenting some of the most complete records of climatic and environmental changes that can be analogous to the current anthropogenic climate change. In addition, the Mediterranean area presents a highly interesting setting for palaeoceanographic, paleoclimatic and palaeoenvironmental studies, situated and impacted by both the north, middle and equatorial latitudes climate systems and presenting al the oceanographic characteristics of a big ocean with much faster reaction times. The layers rich in organic carbon, such as the sapropels in the Eastern Mediterranean Sea and their counterparts in the Western Mediterranean, the Organic Rich Layers (ORL), represent one of the most interesting phenomena within the recent geological record of the Mediterranean Sea Basin. These events have occurred over the past 3 million years as a consequence of the restriction of the waters of deep parts of the Mediterranean basins in response to climatic changes. This doctoral thesis presents a comprehensive analysis of these layers during the Last Glacial Cycle, with a particular focus on the ORLs, which have received less attention in past works, with the objective of deciphering the environmental changes and oceanographic and climatological triggers of these events in the Mediterranean. Additionally, a comparative examination between events in the West and East Mediterranean Sea basins is conducted, elucidating the temporal evolution of both basins and differences in the external factors leading to the deposition of these layers. In the present thesis, a multiproxy approach is employed to assess the stated objectives, integrating inorganic geochemistry and palaeontological proxies, in particular, the ichnological features observed on core surfaces. Novel ichnological analysis tools have been developed through image analysis, which have been applied in conjunction with traditional ichnological and geochemical analysis techniques on three cores from the Alboran Sea and one core from the Ionian Sea, near the Gulf of Sirte. Through the different projects completed during this thesis, some particular and general conclusions have been obtained. It has been observed that the relationship between ORLs and sapropels is intricate, and they generally respond asynchronously to climatic events, with no clear correlation between the bottom water conditions in the eastern and western events found, indicating a differential response to climatological variations over the Last Glacial Cycle. Sapropel depositions are more influenced by the African Monsoon cycles, while ORLs exhibit a more coherent response to the warm-cold cycles of the Last Glacial Period. Further, differences between the different ORLs and sapropels have been found, indicating variable conditions and important differences between the events that produced their deposition, with at least 3 main typologies of ORLs described. The utility of a multiproxy analysis, encompassing geochemical and paleontological data, in deep-sea core studies has been confirmed. Furthermore, the value of continuous ichnological analysis has been underscored in comparison with other indicators and in complementing other data in the analysis of marine sediment cores.