Francisco J. Rodríguez-Tovar’s research while affiliated with University of Granada and other places

Recent advances in characterization of turbidite-fans have been achieved through various methodologies, including flume-tank experiments, numerical modeling, seismic analysis, and integrated core and outcrop studies. Ichnology has proven valuable for understanding turbidite systems by providing insights into paleoenvironmental conditions such as oxygen levels, nutrient availability, hydrodynamic energy, and sedimentation rates. Since the 1960s, the Nereites ichnofacies has been linked to flysch deposits, characterized by features such as graphoglyptids, shallow-tier ichnotaxa, complex grazing trails, and diverse, but low density, trace fossils. The aim of this study is to combine ichnological and sedimentological data to improve recognition of subenvironments in turbidite systems. Analysis of five sections in a late Miocene, muddy turbidite system in the Tabernas Basin (SE Spain) shows that: 1) the distal fan lobes are characterized by a high diversity and abundance of predepositional trace fossils linked to the Paleodictyon ichnosubfacies, indicating stable and oligotrophic conditions, and 2) the proximal fan lobes by a low diversity and abundance of postdepositional trace fossils with abundant Ophiomorpha rudis ichnosubfacies in areas close to the feeder channel.

A series of Pliocene ichnofabrics is described from the Cuevas Formation, Almería-Níjar Basin of south-eastern Spain, where a thick, cross-stratified, mixed bioclastic-siliciclastic succession is exposed along a laterally continuous section. It records the dynamic conditions of ancient subaqueous dunes during their deposition and the activities of organisms colonizing them. The ichnofabrics are dominated by Bichordites, traces likely made by burrowing sea urchins adapted to live in shifting sand. Ichnofabrics range from those showing weak bioturbation with little else but Bichordites (representing high-energy, continuously migrating dunes) to ichnofabrics featuring a high degree of bioturbation containing a low to moderately diverse ichnofauna (representing more physically stable environments where organisms could gather food in less agitated waters). Strong burrowers like the Bichordites producers could have acted as ecosystem engineers. Piscichnus producers may have preyed on benthic sand-dune organisms. The non-uniform distribution of ichnotaxa in these Pliocene sand dunes, alongside previous studies, suggests that these ancient bioturbating communities may have been similar to those in modern seas.

The evolution of gateways determines variations in palaeo-environmental (ecological and depositional) conditions affecting trace maker communities, hence biogenic structures. With respect to palaeo-gateways, bottom currents and associated deposits (i.e., contourites) may be approached through trace fossil studies. Ichnological analysis -individual ichnotaxa and changes in ichnofacies- of Late Miocene contourites and associated facies from the Rifian Corridor palaeo-gateway (Morocco) reveals a major impact of food supply, flow velocity, seafloor heterogeneity, and hydrodynamic energy. The fact that Eocene to middle Miocene deep-marine deposits -mainly contourites- from the nearby Indian palaeo-gateway (Cyprus) show ichnofacies replacement is evidence of increased bottom-current flow velocity associated with sea level variations. Moreover, ichnofabric changes reflect pelagic, gravitational, and bottom-current processes that simultaneously influence sedimentation. Changes in the trace fossil composition of both areas , and in the shape of burrows, reflect intermittent bottom current processes that governed contourite deposition. Neoichnological studies complement and validate the trace fossil record of high-energy deep-sea environments that can occur in palaeo-gateways. Modern traces ( lebensspuren ) observed on the seafloor show variable features (e.g., diversity, density, morphology) depending on the type of disturbance that high-energy conditions exert on the trace-making benthic fauna. Parameters such as substrate consistency, nutrient availability/distribution, and the duration and intensity of energetic events play a major role in determining lebensspuren features. We conclude that an integrative palaeo- and neoichnological approach is a powerful tool when used to improve our knowledge of benthic ecosystems in high-energy deep-sea environments such as gateways.

A deep-sea sediment record from the Western Alboran Basin spanning the last 37 kyr has been analysed using a multiproxy approach, integrating sediment colour, magnetic susceptibility, elemental ratios, benthic foraminiferal assemblages and bioturbation, gaining new insights into Alboran Basin deep-sea environments and palaeoceanographic conditions since the Last Glacial Maximum. The combination of a diverse set of proxies made it possible to recognise the diagenetic signals and reconstruct new low-frequency events in the deep basin, recording the significant fluctuations in deep water oxygenation occurred during the studied period. From the studied data, short-term periodic low-oxygen events are recognised during Heinrich Stadials 2 and 3 (HS2 and HS3) and Greenland Interstadial GI8, showing important responses of the deep sea environments to climate climate change. Furthermore, the presence of a not previously well-defined Organic Rich Layer 2 (ORL 2) can be defined from the observations as a sequence of events transitioning between low oxygen (associated with humid conditions and Heinrich Events) and oxygenated conditions, and not as a singular low oxygenation event. In addition, the Organic Rich Layer 1 (ORL1), associated with the most recent low oxygen event has been also recognised in the record, with low oxygen conditions starting as early as 16 kyr before the present (BP) during the HS1 and spanning to 8 kyr BP with important fluctuations in environmental conditions and oxygenation. Several climate events that have been previously recognised in the Northern Hemisphere and the Mediterranean Basin can be linked to the observed changes in oxygen conditions during ORL1 deposition, for instance reoxygenation that occurred during the pre-ORL1, between the demise of Heinrich Event 1.1 (HE1.1) and the end of HS1 and the inception of the Bølling-Allerød (BA); the start of ORL1 deposition during BA with the onset of low oxygen conditions. Interestingly, the BA is punctuated by short duration reoxygenation events that can be recognised in the record and correlated to cold events observed in the North Atlantic records. In addition, there is a partial discontinuous reoxygenation during the Younger Dryas (YD), observed also in the Eastern Mediterranean and in other Mediterranean sites which was followed by the return to lower-oxygen conditions after the YD, coinciding with the start of S1 deposition. Finally, the final reoxygenation event occurs at around 8 kyr BP along with the demise of the ORL1.