Guillermo Francés

• Dr
• University of Vigo

En este trabajo se han estudiado muestras extraídas en campos de gas de la ría de Vigo con el fin de analizar el efecto de la presencia de gas biogénico sobre las asociaciones de foraminíferos bentónicos y sobre la distribución vertical de carbonato cálcico en los primeros centímetros del registro sedimentario. Así mismo se pretende obtener nuevos...

Marine macrobenthic tracemaker communities are controlled by limiting parameters (e.g., oxygen, organic matter availability and hydrodynamic energy, among others) which are determined by ocean/atm dynamics affecting the sea bottom. Over the last few years, detailed ichnological studies have provided information about trace fossils content of contou...

The Western Mediterranean Deep Water (WMDW), on its way out toward the Atlantic Ocean, has favored the formation of contourite drifts in the Alboran Sea (SW Mediterranean) since the opening of the Strait of Gibraltar. Resolving the nature of these deposits is crucial for reconstructing the WMDW variability at a millennial scale, deciphering its bot...

Heinrich events (HEs) are climatic changes, occurring during the Pleistocene, related to massive discharge of freshwater from the Laurentide Ice Sheet, through the Hudson Strait, recognized in the sedimentary record through distinctive layers of ice-rafted detritus (IRD), the so-called Heinrich layers (HLs). Environmental changes during HEs influen...

Although bioturbation is commonly recognized in contourites, only a few studies have analyzed the ichnological content of these deposits in detail. These studies have mainly focused on meso-scale bigradational sequence (a coarsening upward followed by a fining-upward sequence resulting from variations in current velocity). Here we present data from...

In order to establish the chronology of deep-sea sediments from high-resolution 210Pb-dating, the determination of 210Pb and 226Ra activity concentrations needs to be improved. Gamma spectrometry allows determining simultaneously both radionuclides. However, spectrum background is still an issue to obtain high sensitivity. Four deep-sea sediment co...

Evaluation of biogeochemical processes in Anthropocene deep-sea sediments require accurate dating techniques. Here we show the results of an approach using high resolution low level background gamma spectrometry with two simultaneous hyper-pure germanium (HPGe) detectors. The quantitative role of the deepest zones (>3000 m depth) of the Irminger Ba...

The Galicia Interior Basin (GIB; NW Iberian Peninsula) is located near a critical transition between the subtropical (temperate) and subpolar (cold) gyres of the North Atlantic. It therefore witnesses oceanographic changes driven by global climatic events. This study reports on the recent (latest Pleistocene) sedimentary, palaeoceanographic and pal...

This work presents a detailed study of CONTOURIBER and Integrated Ocean Drilling Program 339 sediment data targeting sand-rich contourites in the Eastern Gulf of Cadiz. All of the collected sediments are interpreted as contourites (deposited or reworked by bottom currents) on the basis of oceanographic setting, seismic and morphometric features and...

Proyecto basado en el análisis y contraste de ecosistemas diversos marcados por las diferentes condiciones biogeografías y ambientales como son los ecosistemas costeros y marinos Atlánticos y Mediterráneos a través de una metodología enmarcada en el aprendizaje activo.

A new data set of 88 marine surface sediment samples and related oceanic environmental variables (temperature, salinity, chlorophyll a, oxygen, etc.) was studied to quantify the relationship between assemblages of coccolithophore species and modern environmental conditions in the western Mediterranean Sea and the Atlantic Ocean, west of the Strait...

A new dataset of 88 marine surface sediment samples and related oceanic environmental variables (temperature, salinity, chlorophyll a, oxygen, etc.) was studied to quantify the relationship between assemblages of coccolithophore species and modern environmental conditions in the Western Mediterranean Sea and the Atlantic Ocean, west of the Strait o...

Coccolithophore productivity and surface water dynamics for the last 25 kyr in the Alboran Sea (Western Mediterranean) are described in a study of high-resolution sedimentary records from two cores, HER-GC-T1 and CEUTA10PC08, whose locations are currently characterized by different hydrographic conditions. Fossil coccolithophore assemblages and oxy...

Non-destructive techniques of core analysis, especially of marine cores, are being broadly employed for sedimentary, paleoceanographic and paleoclimate research. In particular, Computed Tomography scanning (CT–scanning) allows acquisition of 3D and 2D images, according to desired planes, and thus the identification of sedimentary structures, large...

Coccolithophore productivity and surface water dynamics for the last 25 kyr in the Alboran Sea (Western Mediterranean) are described in a study of high-resolution sedimentary records from two cores, HER-GC-T1 and CEUTA10PC08, whose locations are currently characterized by different hydrographic conditions. Fossil coccolithophore assemblages and oxy...

Acidification of the oceans is one of the consequences of ongoing increasing atmospheric CO2 concentrations. The effects on organisms that build their shells of calcium carbonate are not sufficiently studied and might be detrimental. Simulating ocean acidification scenarios in the laboratory is a reasonable way to study their response to decreased...

Coccolithophore records along with oxygen isotopes and sea surface temperature (SST) profiles from two different cores located in the Alboran Sea (Western Mediterranean) are used to describe variations in primary productivity and surface water dynamics during the last 25 kyr in the study area. By combining these proxies with other from different na...

Geological guide of the Atlantic Islands of Galicia National Park (Spain), in which the materials as well as the geological and geomorphological processes in the territory of the archipelagos covered by the National Park are described. The most representative geological itineraries of each island are also included. See preview in: https://www.igme....

High-resolution reconstruction of productivity using Coccolithophores in two sites of the Alboran Sea (Western Mediterranean) during the last 25 kyr. B. Ausín 1 (b_ausin@usal.es); J-A. Flores 1 (flores@usal.es); F-J. Sierro 1 (sierro@usal.es); I. Cacho 2 (icacho@ub.edu); G. Francés 3 (gfrances@uvigo.es)

Controls of sediment dynamics at the Galician continental slope (NW Iberia) during the past 30 ka were reconstructed from three new gravity cores (GeoB11035-1, 130206–1, 13071–1) based on sedimentological (e.g. sortable silt, IRD), micropalaeontological (e.g. coccoliths), geochemical (AMS 14C, XRF) and geophysical (e.g. magnetic susceptibility) dia...

An extensive terrace comprising sandy sheeted drifts characterises the proximal sector (close to the Straits of Gibraltar) of the Contourite Depositional System (CDS) of the Gulf of Cadiz and the western continental margin of Portugal. A novel morphosedimentary study over this terrace has been executed based on new multibeam echosounder data, seism...

Compositional, mineralogical and grain size data from 13 superficial samples recovered between 490 and 1144 m water depth in three Contourite Depositional Systems (CDSs): the Gulf of Cadiz, Ortegal Spur and El Cachucho are presented. First surficial centimeter was analysed in different contourite features: depositional (drifts), erosive (moats) and...

Computed tomography (CT scan) is a non-destructive technique of sedimentary analysis rarely used in oceanic cores. This technique allows a simple way to obtain radio-density measurements of high quality, very high resolution and detail. Its application allows obtaining an accurate image of the sedimentary changes recorded and the correlation betwee...

Controls of sediment dynamics at the Galician continental slope (NW Iberia) during the past 30 ka were reconstructed from three new gravity cores (GeoB11035-1, 130206-1, 13071-1) based on sedimentological (e.g. sortable silt, IRD), micropalaeontological (e.g. coccoliths), geochemical (AMS 14C, XRF) and geophysical (e.g. magnetic susceptibility) dia...

A multidisciplinary study of the elemental geochemistry and mineralogical characteristics of the marine sur-ficial sediment in the Northern Rias (NW Iberian Peninsula) has been carried out. The linkages between the marine sediment composition and their potential sources were examined. The influence of the river-borne sediments is only detected in t...

The no-destructive techniques of core analyses are being more employed due to the quality and quantity of data that can be obtained without the re-quirement of the use of samples. These samples are then available to other kind of analyses. The Computerized Tomography (CT) is a technique few ex-tended in sedimentology. The CT is relevant because it...

Seasonal variability of diatom abundances was measured in the water column, sediment traps and in the underlying sediment from the Pontevedra rı´a. Seasonal variations of the diatom species in the water column were indicative of ocean influence, river influx and water column stratification. Additionally, analysis of diatom distribution and other bi...

This contribution aims to illustrate the Ortegal Cape Contourite Depositional System (OCCDS), a new example of contourites located on the northern Galicia margin generated by the Mediterranean Outflow Water (MOW) influence. This work is based on several datasets collected during two multidisciplinary cruises, including: single echosounder and swath...

This study evaluates the postmortem processes acting during the transition from live to dead assemblages in the Ría de Vigo, Spain. The thanatocoenosis component of benthic foraminifera has been studied along the muddy central axis of the ría and compared with previously published data on living taxa. There are some general differences between live...

The gravity core GeoB-11035 (2045 m depth, 505 cm) was recovered 65 km from the occidental Galicia coast over the continental slope. In this core the planktonic foraminifera assemblages was analyzed to carry out a reconstruction of the surface paleoceanographic conditions and to investigate in the climate changes which induced the observed climatic...

Ladeira beach forms a barrier-lagoon system known as the Ramallosa Complex, located at the southwestern extremity of the Ria de Vigo (NW Spain). In the north of this beach has done a test drilling of 26 m long that go through sedimentary materials. The basis of this test drilling is Upper Pleistocene age and most of the recovered materials are Holo...

The Holocene palaeoclimatic history of the Galician continental shelf has been investigated through the analyses of diatom remains, other siliceous compounds, biogenic silica (BSi) and metals content in a multiproxy approach to a gravity core recovered from the Galicia Mud Patch, NW Iberian Peninsula, covering the last 5000 years. Downcore changes...

Modern diatom distribution patterns in the surface sediment of the Ferrol Ría and their relationship to the hydrography and diatom patterns in the water column were studied to determine the hydrographic influence on the record of these biogenic components. Diatom abundance in the water column was assessed for different oceanographic periods and com...

This study reconstructs climatic variability over the last 4700 yr in the NW Iberian Peninsula on the basis of lithological, sedimentological, biogeochemical, micropaleontological (diatoms and biosiliceous compounds) and AMS 14C analyses conducted in a gravity core retrieved from the Galician continental shelf. The core was recovered at the Galicia...

The spatial and vertical distributions of live benthic foraminifera from the muddy central axis of the Ría de Vigo were examined under downwelling and upwelling conditions. The spatial distribution of the main benthic foraminiferal species is controlled by salinity variations (San Simón Assemblage), food availability (Outer Ría Assemblage) and oxyg...

Gravity core GeoB-11035 (2045 mbsl, 505 cm length) was retrieved 65 km offshore the Galician occidental coast at the lower continental slope. Preliminary analysis of the planktonic foraminifera assemblage and the terrigenous material in the sand fraction have led to identify successive climate events off the NW Iberian Margin. The core stratigraphy...

The Tagus Prodelta (W Portugal) and the Muros Ría (NW Spain) are areas of high deposition rates registering high-resolution palaeoclimatic records for western Iberia. We compare the climatic conditions of the two areas over the last two millennia based on proxies of temperature (sea surface temperatures and oxygen isotopes), continental input (grai...

Opal concentrations in dry bulk sediment were measured in 43 sampling stations in the Ría de Vigo at 0–1, 1–2, 4–5, 10–11 and 14–15cm sediment depths. The amount of opal was correlated with the biogenic silicon flux to the sediment obtained by means of a box model. The biosiliceous flux to the sediment (annual mean) is in good agreement with the co...

Live benthic foraminifera in the superficial sediments from the muddy central axis of the Ría de Vigo were examined under two contrasting hydrographic conditions: downwelling and upwelling. During downwelling conditions the abundance of benthic foraminifera does not show large differences between sites with different organic carbon contents. The ar...

Holocene climate fluctuations in the temperate region of the Northeast Atlantic have been established by comparing marine and terrestrial proxies. This work is based on suction-cores collected in the Cies Islands lagoon (NW Spain) and vibro-cores from the adjacent continental shelf. The lower Holocene marine record (9400-7000 yr BP) consists on san...

A combined study of coccolithophore assemblages and biomarkers in gravity core VIR-18 (380 cm long) located in the Ria de Vigo (42°14.07 N, 8°47.37W) at a water depth of 45 m situated in the Ria de Vigo (SW Spain) has allowed us to reconstruct the paleoenvironmental conditions for the last 3000 years. The quantitative distribution of coccolithophor...

Biogenic silica (BSi) content was determined in both superficial marine sediments from the Ría de Vigo and gravity core samples (core CGPL00-1) from the adjacent continental shelf. Samples were processed following the alkaline leaching procedure. The standard deviation for opal-rich samples is very low (±0.2), whereas for opal-poor samples (<1.3 wt...

A combined study of coccolith assemblages and biomarkers in a gravity core collected from the Ría de Vigo (NW Spain) allowed us to reconstruct the paleoenvironmental conditions for the last 3000 years. The quantitative distribution of coccolithophore species points to three different intervals within the core, dated by AMS radiocarbon measurements....

A multiproxy study of the sedimentary record carried out on gravity core CGPL00-1 retrieved from the outer Galician continental shelf (NW of Spain) has allowed us to establish the main climate fluctuations affecting the region during the Upper Holocene. Grain size, TOC, C/N ratio, biogenic opal and planktonic foraminifera are the main analysed para...

The distribution of live benthic foraminifera (0.0�63 �mm) in box core samples from coarse sediments of the Ría de Vigo (NW Iberian margin) is mainly related to food availability and bottom current range. Live benthic foraminifera are dominated by small forms (63–125 �microns). Faunal densities and diversity values suggest that very coarse substrat...

Benthic foraminifera assemblages from the outer sector of the ría de Muros have been analyzed in order to obtain a detailed reconstruction of Holocene environmental evolution. The studied core (EUGC-3B: 42' 45.10'N; 9' 02.23'W, at 38 m.b.s.l. and 410 cm length) consists of muddy sand from the core bottom (8200 cal yr BP) to 200 cm (2700 cal yr BP)...

Carbon and oxygen stable isotopes and ICP-OES elemental ratio concentrations (Mg/Ca, Sr/Ca, Ba/Ca) from core EUGC-3B (42 45.10'N; 9 02.23'W, at 38 m.b.s.l. and 410 cm length) were measured over monospecific benthic foraminiferal samples (Nonion fabum) ranging over the last 4500 yr BP. From the oldest analysed sample (289 cm) to the core top, stable...

Coastal deposits are not prominent in the Ria de Vigo, high cliffs dominate the coast line, but several well-preserved sedimentary areas are observed. Beach and aeolian sand dunes are preserved in protected bays along margins between low cliffs, as Playa America, Patos and Samil. Several rivers form prominent estuaries such as the Verdugo-Oitaven,...

High-resolution quantitative diatom abundances and assemblages have been reconstructed from cores retrieved from the Northwest Norwegian Margin, and from the Ria de Muros, in Northwestern Spain. The Norwegian core is subject to oceanic processes and lies near the boundary of the Norwegian current (63°45'44"N; 05°15'18.5"E), whereas the Muros core i...

Sedimentological and micropaleontological analyses of the vibro core ZV-27 (403 cm length, 42 8.67' N, 8 55.73' W and 73 m depth) bring new insights on the reconstruction of Holocene eustatic and climatic changes in the Galician continental shelf (NW of Spain). The lowest 185 cm contain a grain-supported conglomerate with rounded quartzite pebbles...

We use quantitative analyses of the planktic foraminiferal assemblages and stable isotope analyses of the Sorbas section in the western Mediterranean to reconstruct the cyclical changes in surface and deep water hydrographic conditions during the Late Miocene prior to the Messinian salinity crisis. Oscillations in winter and summer temperatures lin...

The hydrographic evolution of the Ra de Vigo (NW Spain) during the last 3000 years has been reconstructed using benthic foraminiferal assemblages, stable oxygen isotopes, molecular biomarkers and sea-surface temperatures (SST) reconstructed from the U K 9 37 index. Benthic oxygen isotopes and SST records provide evidence of episodic salinity contra...

We identified three coccolithophores assemblages in core VIR-18, in the Ria de Vigo. We will use these assemblages together with other biogeochemical data to make paleoenvironmental interpretations about this area and thus determine fluctuations between marine and continental influences over the last 3000 years.

RESUMEN En este trabajo se presenta la comparación de los sedimentos superficiales de la plataforma proximal de tres complejos playeros situados en las inmedia-ciones de la embocadura de la Ría de Muros y Noia. En cada uno de ellos, se han identificado las distintas poblaciones sedimentarias en función de los aná-lisis granulométricos realizados. L...

Cited By (since 1996): 26, Export Date: 30 June 2012, Source: Scopus, CODEN: PPPYA, doi: 10.1016/S0031-0182(00)00058-4, Language of Original Document: English, Correspondence Address: Vazquez, A.; Earth Sci. Institute 'Jaume Almera', C.S.I.C., c/Sole Sabaris sn, 08028 Barcelona, Spain; email: avazquez@ija.csic.es, References: Abrantes, F., Diatom p...

En este trabajo se presenta la comparación de los sedimentos superficiales de la plataforma proximal de tres complejos playeros situados en las inmedia-ciones de la embocadura de la Ría de Muros y Noia. En cada uno de ellos, se han identificado las distintas poblaciones sedimentarias en función de los aná-lisis granulométricos realizados. La aplica...

En este trabajo se han analizado las asociaciones actuales y subactuales de foraminíferos bentónicos a lo largo del eje central de la ría de Vigo con tres ob-jetivos fundamentales: establecer los parámetros ambientales que controlan los microhábitats de estos organismos, determinar el efecto tafonómico y sentar las bases para una interpretación pal...

The relative space distributions of single mineral constituents in mixed terrigenous-carbonated sediments of the Bayona Bay have been analysed. In order to determine the existence of different mixing mechanisms, a study comparing the general sedimentary trends resulting from the average patterns and the single mineral behaviour, reflected in the si...

Cyclical fluctuations in planktic foraminiferal assemblages have been recognized in the pre-evaporitic Messinian in a marginal basin of the western Mediterranean. The fluctuations coincide with a dominantly precession-controlled sedimentary cyclicity (sapropels). During sapropel deposition, high planktic foraminiferal diversities are indicative of...

Foraminiferal studies provide a key to understanding the dynamics of a shallow marine environment from Baiona Bay, N.W. Spain. Preliminary data describing the foraminiferal distributions and associated physical and oceanographic setting are presented. A new species list is provided for this regíon, which includes both autochthonous and allochthonou...

A quantitative analysis was carried out on coccolith assemblages from two Pleistocene cores (K1 and K10) from the western Mediterranean. The distribution of selected coccolithophore species provides new paleoclimatic and paleoceano-graphic data. A continuous sequence from the top of Isotope Stage 5 to the Holocene was recorded. The reversal in domi...

The Bransfield Basin is a narrow, extensional, back-arc basin located between the north-eastern tip of Antarctic Peninsula and the South Shetland Islands, around 60-63º S. Recent sediments accumulated on this basin may be determinant in finding the role played by Southern Ocean in carbon and silica cycles during late Holocene times. It is furthermo...

Cyclical fluctuations in planktic foraminiferal assemblages have been recognized in the pre-evaporitic Messinian in a marginal basin of the western Mediterranean. The fluctuations coincide with a dominantly precession-controlled sedimentary cyclicity (sapropels). During sapropel deposition, high planktic foraminiferal diversities are indicative of...