Impact of restriction of the Atlantic-Mediterranean gateway on the Mediterranean Outflow Water and eastern Atlantic circulation during the Messinian

Messinian foraminiferal stable oxygen and carbon isotopes of the Montemayor-1 core (Guadalquivir Basin, SW Spain) have been investigated. This record is exceptional to study the Mediterranean Outflow Water (MOW) impact on the Atlantic meridional overturning circulation (AMOC) and global climate during the Messinian because the core is near the Guadalhorce Corridor, the last Betic gateway to be closed during the early Messinian. Our results allow dating accurately its closure at 6.18 Ma. Constant benthic d18O values, high difference between benthic and planktonic d18O, and low sedimentation rates before 6.18 Ma indicate the presence of a two-layer water column, with bottom winnowing due to an enhanced Mediterranean outflow current. The enhanced contribution of dense MOW to the North Atlantic Ocean likely fostered the formation of North Atlantic Deep Water (NADW). After 6.18 Ma, benthic d18O values parallel that of the global glacioeustatic curve, the difference between benthic and planktonic d18O is low, and sedimentation rates considerably increased. This indicates a good vertical mixing of the water column, interruption of the MOW, and a dominant glacioeustatic control on the isotopic signatures. According to the role of MOW in the modern Atlantic thermohaline circulation, the reduction of the MOW after the closure of the Guadalhorce Corridor might have resulted in a decreased NADW formation rate between 6.0 and 5.5 Ma weakening the AMOC and promoting northern hemisphere cooling. After the Gibraltar Strait opening, the restoration of the MOW and related salt export from the Mediterranean could have promoted an enhanced NADW formation

Messinian paleoenvironmental evolution in the lower Guadalquivir Basin (SW Spain) based on benthic foraminifera.

Benthic foraminiferal assemblages of a drill core from the lower Guadalquivir Basin (northern Gulf of Cádiz, SW Spain) have been analyzed in order to reconstruct the paleoenvironmental evolution in the vicinity of the Betic seaways during the Messinian. The core consists of marine sediments ranging from the latest Tortonian to the early Pliocene. Changes in the abundance of certain marker species, planktonic/benthic ratio (P/B ratio), paleodepth estimated with a transfer function, content of sand grains and presence of glauconitic layers indicate a complete transgressive-regressive sea-level cycle from the bottom to the top of the section. An abrupt sea-level rise, from inner-middle shelf to middle slope, is recorded at the lowermost part of the core (latest Tortonian-earliest Messinian), followed by a relatively rapid shallowing from middle slope to outer shelf. Magnetobiostratigraphic data show that this sea-level fall postdates the onset of the Messinian salinity crisis (MSC) in the Mediterranean. Finally, the early Pliocene deposits are interpreted as inner-middle shelf. Changes in the benthic foraminiferal assemblages through the core are mainly controlled by the trophic conditions, specifically by the quantity and quality of the organic matter reaching the sea floor. The upper slope and part of the outer shelf assemblages are highly diverse and dominated by shallow infaunal species, indicating a generallymesotrophic environment with moderate oxygenation. These environments have likely been affected by repeated upwelling events, documented by increased abundance of Uvigerina peregrina s.l., an opportunistic species thriving in environmentswith enhanced labile organic matter supply. The assemblages of the transitional interval between upper slope to outer shelf, and of the outer shelf are generally characterized by a relatively low diversity and epifaunal-shallow infaunal taxa, indicating oligotrophic and well-oxygenated conditions. The innermiddle shelf assemblages are characterized by very lowdiversity and dominance of intermediate to deep infaunal taxa, suggesting an eutrophic environmentwith lowoxygen content. These assemblages are dominated by Nonion fabum and Bulimina elongata, two taxa that are able to feed from continental low-quality organicmatter,most likely derived from river run-off. The paleoenviromental evolution on the Atlantic side of Betic and Rifian seaways is similar during the Messinian, with a Messinian continuous sea-level lowering driven by regional tectonic uplift and upwelling-related waters reaching the upper slope. This study will further contribute to understand the role of tectonics on the sea-level changes as well as on the closure of the Atlantic-Mediterranean gateways that led to the MSC, and on the paleoceanography on the Atlantic sides of these corridors

Magnetobiochronology of Lower Pliocene marine sediments from the lower Guadalquivir Basin: insights into the tectonic evolution of the Strait of Gibraltar area

The Gibraltar Arc is a complex tectonic region, and several competing models have been proposed to explain its evolution. We studied the sedimentary fill of the Guadalquivir Basin to identify tectonic processes that were occurring when the reopening of the Strait of Gibraltar led to the reestablishment of Mediterranean outflow. We present a chronostratigraphic framework for the Lower Pliocene sediments from the lower Guadalquivir Basin (SW Spain). The updated chronology is based on magnetobiostratigraphic data from several boreholes. Our results show that the studied interval in the La Matilla core is in the early Pliocene section, providing better constraints on the sedimentary evolution of the basin during that period. Migrating depositional facies led to a younger onset of sandy deposition basinward. At the northwestern passive margin, a 0.7 m.y. period of sedimentary bypass related to a sharp decrease in sedimentation rates and lower sea levels resulted from the tectonic uplift of the forebulge. In contrast, high sedimentation rates with continuous deep-marine sedimentation are recorded at the basin center due to continuous tectonic subsidence and west-southwestward progradation of axial depositional systems. The marginal forebulge uplift, continuous tectonic basinal subsidence, and southward progradation of clinoforms in the early Pliocene can be explained by the pull of a lithospheric slab beneath the Gibraltar Arc as the Strait of Gibraltar opened. These findings are, to our knowledge, the first reported sedimentary expression of slab pull beneath the Betics related to the opening of the Strait of Gibraltar after the Messinian salinity crisis.Peer ReviewedPostprint (author's final draft

Mixed carbonate-siliciclastic contourite drift deposits associated with the entrance of an Atlantic-Mediterranean corridor (late Miocene, southwest Spain)

Carbonate contourite drifts are poorly documented in the onshore record because of the difficulty of implementing diagnostic criteria for their recognition. Accordingly, little is known about the relative position of carbonate drifts with respect to ancient carbonate platforms, seaways and shallow passages within the context of palaeoceanography. This study presents a fossil example of mixed carbonate-siliciclastic drift cropping out in a quarry in Osuna (Sevilla province, southern Spain) at the northern end of the Guadalhorce Corridor, a Miocene strait connecting the Mediterranean Sea and the Atlantic Ocean in the Betic Cordillera. Based on the facies and sedimentary structures, the studied succession is divided into three units: 1) the lower unit, Unit 1, is a 33-m thick succession of large carbonate bodieswithmega cross-stratification pointing to the southeast and secondarily to the northwest interpreted as a contourite drift; 2) the intermediate Unit 2 is a 0.5–2-m thick terrigenous conglomerate body eroding the top of Unit 1; and 3) the uppermost Unit 3 consists of a 6-m thick siliciclasticdominated succession with herringbone cross-stratification and a dominant direction of the structures to the northwest interpreted as tidal deposits. The large-scale sediment bodies with mega cross-beds, the presence of reactivation surfaces with grain-size changes, and the unidirectionality of the structures were diagnostic for the recognition of Unit 1 as drift deposits. The dominant sedimentary structures pointing to the southeast in the drift were generated by Atlantic inflow into the Mediterranean. This challenges the classical “siphon” model for the Atlantic-Mediterranean water-mass circulation pattern for this age. The conglomerates of Unit 2 evidence regional uplift of the southernmargin of the Guadalquivir Basin that promoted a change in the depositional mode from a bottom-current dominated (Unit 1) to a tide-dominated environment (Unit 3) after the closure of the Guadalhorce Corridor in the Messinian.Juan de la Cierva Project (Ministerio de Ciencia, Innovacion y Universidades) JC2019042375-I project SECAMARA PGC2018099391-B-100Junta de Andalucia European Commission RNM-19

Análisis arqueométrico de la cerámica dorada andalusí de la Alcazaba de Onda (Castellón)

In the present article there are exposed the results of the analysis of the bodies and the glazes of 21 ceramic representative fragments of a set found in the excavations of the Alcazaba of Onda and that can be dated in outline between ends the XIth and the first half of the XIIth centur y. We have attended fundamentally to the lustre potter y and to the ceramics with white cover. The principal aim is to determine if it is a question of one or of several productions. For it there has been analyzed the composition and texture of the body, as well as the microstructure and composition of the glaze by means of microscope electronics of sweep (SEM). Also there have been compared with ceramics that we suppose local, such productions as common ceramics of the same archaeological context and fragments found in the califal arqueological site Mas de Pere, where kilns were situated for the manufacture of ceramics. Also we have arranged with clays of the nearby deposit of the Sitjar. The results show that there are different productions of lostre ceramics, both for composition of the bodies and for the glaze. In addition, the composition of the white ceramics is ver y similar to the local clays of Onda, with which it is not possible to reject that it was a question of a local production.Postprint (published version

An enigmatic kilometer-scale concentration of small mytilids (Late Miocene, Guadalquivir Basin, S Spain).

Upper Miocene heterozoan carbonates crop out extensively in a NE-SW-trending belt (42 km long and 1.5-8 km wide) along the so-called El Alcor topographic high, from Carmona to Dos Hermanas (Seville, S Spain). These carbonates formed at the southern active margin of the Guadalquivir Basin, the foreland basin of the Betic Cordillera. They change to marls basinward (NE) and to sands landward (SE and SW). Therefore, carbonate production was constrained to a limited area in an otherwise siliciclastic shelf. The carbonates (up to 40 m thick) overlie a gradually coarsening-upward succession of marls followed by silts and sandstones. The carbonate sequence can be divided into three subunits corresponding, frombottom to top, to lowstand, transgressive, and highstand system tract deposits. The lower subunit, exhibiting extensive trough cross-bedding, is interpreted as a shallow-water bar deposit. The intermediate subunit onlaps underlying sediments and was deposited in deeper, lowturbulence conditions. The upper subunit deposits accumulated in a well-oxygenated outer platform based on benthic foraminiferal assemblages. The presence of hummocky and swaley cross-stratification in these latter deposits suggests that theywere affected by storms. Pervasive fluid-escape structures are also observed throughout the carbonates. The three subunits consist of bioclastic packstones to rudstonesmade up of abundant fragments of smallmytilids. Isotopic data from serpulid polychaete Ditrupa tubes show 13C-depleted values (up to −16.1¿), whereas δ18O yields normal marine values. Additional isotopic data on shells of scallops, oysters, and small mussels, as well as bulk sediment, show diagenetic alterations. Based on actualistic examples of massive concentrations of mussels, the nearly monospecific composition of the El Alcor deposits, together with negative δ13C values of Ditrupa tubes, indicates that cold seeps presumably promoted carbonate formation. However, the absence of typical features of cold-seep deposits, such as authigenic carbonatesmediated by anaerobic bacterial activity and the typical chemosynthetic shelly organisms, makes the large carbonate body of El Alcor an unusual cold-seep deposit

Rare earth elements and Nd isotopes as tracers of modern ocean circulation in the central Mediterranean Sea

Seawater rare earth element (REE) concentrations and Nd isotopic composition (εNd) are increasingly applied as valuable tracers of oceanographic processes such as water mass mixing and lithogenic inputs to seawater. However, their measurements are basically lacking in the Mediterranean Sea water column. This study analyzes 9 seawater stations around the central Mediterranean Sea to clarify the relative importance of external sources, vertical (biogeochemical) processes and lateral water mass transport in controlling REE and εNd distributions. Concentrations of REE do not show nutrient-like profiles with depth, likely indicative of relatively young waters with limited accumulation of remineralized REE. Light REE (LREE) present a non-conservative behavior, which largely peak at surface waters and rapidly decrease with depth. The negative correlation of surface LREE enrichment with offshore distance highlights the influence of continental input from the western Italian coast to the Tyrrhenian surface waters. In contrast to other regions with reported boundary exchange, this process does not modify the εNd values here. On the other side, distributions of dissolved heavy REE (HREE) and εNd display a conservative behavior that can be explained by mixing of western- (MAW and WMDW) and eastern- (LIW and EMDW) originated waters. We test this hypothesis with an Optimum Multi-Parameter Analysis (OMPA) including HREE and εNd parameters. Even though the limited data set, consistent results of water mass fractions are obtained for the four main water masses although with some particularities. While LIW takes on major importance when considering HREE in the model, EMDW fractions are preferentially detected with εNd. This latter finding implies a noticeable deep water flux across the Sicily Strait into the Western Mediterranean that was not clearly evidenced before

Geomorphological record of extreme wave events during Roman times in the Guadalquivir estuary (gulf of cadiz, SW Spain): An archaeological and paleogeographical approach

Analysis of the geological record has made it possible to delimit for theGuadalquivir estuary the traces of extreme wave events (EWEs) during the Roman period in the Iberian Peninsula (218 BCE to 476 CE). The largest event occurred in the 2nd-3rd century CE. It generated clearly visible erosive effects in the coastal barriers, including washover fans and erosional scarps. In the inner estuary, however, the effects were minor: crevasse splays that broke levees and cheniers, as well as a residual sedimentary lag. The significant development of the spits protected the inner estuary from the marine incursion, which only caused a water level rise with low-regime waves. Correlation of the geomorphological and sedimentary marks left by this event with the archaeological and geological evidence of other events recognized elsewhere in the Gulf of Cadiz effectively argues for a tsunami as to the nature of the 2nd-3rd century CE event. Yet this and the other identified EWEs in the Guadalquivir estuary during the pre-Roman and the Roman period all fit a model of paleogeographic evolution dominated by processes of coastal progradation and estuarine infilling. Radiocarbon dating, geomorphological analysis, and historical references fail to warrant the so-called '218-209 BCE' Atlantic tsunami, as hypothesized in the received scientific literature. In pre-Roman and Roman times, human occupation at the mouth of the Guadalquivir River was strongly influenced by various geodynamic processes, the location of the settlements being contingent upon dependable, fast communication with the sea and, above all, upon adequate protection from EWEs, on the leeward side of spits. Progressive progradation of these coastal barriers combined with the gradual infilling of the estuary to make navigation to open sea increasingly difficult and, eventually, to result in the abandonment of settlements