reliminary cyclostratigraphic results on planktonic foraminifera from IODP-Hole U1406A

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Holocene hydrography evolution in the Alboran Sea: a multi-record and multiproxy comparison

A new high-resolution deglacial and Holocene sea surface temperature (SST) reconstruction is presented for the Alboran Sea (western Mediterranean), based on Mg=Ca ratios measured in the planktonic foraminifera Globigerina bulloides. This new record is evaluated by comparison with other Mg=Ca SST records and previously published alkenone SST reconstructions from the same region for both the Holocene and glacial periods. In all cases there is a high degree of coherence between the different Mg=Ca SST records but strong discrepancies when compared to the alkenone SST records. We argue that these discrepancies are due to differences in the proxy response during deglaciation which we hypothesize to reflect a resilience strategy of G. bulloides, changing its main growth season, and consequently Mg=Ca records a shorter deglacial warming than alkenones. In contrast, short-term Holocene SST variability is larger in the Mg=Ca SST than in the alkenone SST records. We propose that the larger Mg=Ca SST variability is a result of spring temperatures variability, while the smoothed alkenone SST variability represents averaged annual temperatures. The Mg=Ca SST record differentiates the Holocene into three periods: (1) the warmest SST values occurred during the Early Holocene (11.7-9 cal. kyr BP), (2) a continuous cooling trend occurred during the Middle Holocene that culminated in the coldest Holocene SST having a double cold peak structure centred at around 4.2 cal. kyr BP, and (3) the Late Holocene (4.2 cal. kyr BP to present) did not follow any clear cooling/warming trend although millennial-scale oscillations were enhanced. This SST evolution is discussed in the context of the changing properties in the Atlantic inflow water associated with North Atlantic circulation conditions and also with local hydrographical and atmospheric changes. We propose that a tight link between North Atlantic circulation patterns and the inflow of surface waters into the Mediterranean played a major role in controlling Holocene climatic variability of this region

La Piccola Era Glaciale e il suo clima tra mare, terra e arte

La Piccola Era Glaciale e il suo clima tra mare, terra e arte

Pleistocene Climate Change in Central Europe

Loess is terrestrial, clastic sediment formed by the accumulation of wind-blown dust. It is usually inter–bedded with paleosol horizons, forming loess-paleosol successions (LPS). Due to their characteristics LPS’s represent valuable records of climate changes during Pleistocene. The thickest LPS sections in Croatia are in the Baranja region. Stable oxygen (δ18O) and carbon (δ13C) isotope analysis were made on loess malacofauna in order to quantify paleo-temperature changes and describe paleo-vegetation in this part of Central Europe. δ18O values show significant paleotemperature changes during the Upper Pleistocene (130 ky - 20 ky) in Baranja region. Average growing season (AGS) temperature varied 13.2 °C or 9.5 °C during that time period, depending on which formula is applied for calculations. Magnetic susceptibility (MS) measurements show strong peaks in the paleosol horizons pointing to more humid climate. The overall climate was much cooler then present. Stable carbon isotope values point to dominance of C3 vegetation type during the Late Pleistocene in southern part of Central Europe. Climate change in the Late Pleistocene is very likely a significant but not the only factor that influenced the extinction of Neanderthal population which paved the way for the dominance of anatomically modern humans (AMH) in Central Europe

Persistent warm Mediterranean surface waters during the Roman period

Reconstruction of last millennia Sea Surface Temperature (SST) evolution is challenging due to the difficulty retrieving good resolution marine records and to the several uncertainties in the available proxy tools. In this regard, the Roman Period (1 CE to 500 CE) was particularly relevant in the socio-cultural development of the Mediterranean region while its climatic characteristics remain uncertain. Here we present a new SST reconstruction from the Sicily Channel based in Mg/Ca ratios measured on the planktonic foraminifer Globigerinoides ruber. This new record is framed in the context of other previously published Mediterranean SST records from the Alboran Sea, Minorca Basin and Aegean Sea and also compared to a north Hemisphere temperature reconstruction. The most solid image that emerges of this trans-Mediterranean comparison is the persistent regional occurrence of a distinct warm phase during the Roman Period. This record comparison consistently shows the Roman as the warmest period of the last 2 kyr, about 2 °C warmer than average values for the late centuries for the Sicily and Western Mediterranean regions. After the Roman Period a general cooling trend developed in the region with several minor oscillations. We hypothesis the potential link between this Roman Climatic Optimum and the expansion and subsequent decline of the Roman Empire

High resolution paleo-environmental changes during the Sapropel 1 in the North Ionian Sea, central Mediterranean

High-resolution paleoceanographic reconstruction of surface water properties during the most recent Sapropel event (S1) has been carried out by means of quantitative analyses of planktonic foraminiferal assemblages, planktonic foraminiferal oxygen isotopes (δ18O) and XRF elemental data from a 655 m depth core recovered in the North Ionian Sea. The results show that the S1 interval presents two distinctive warm phases (S1a and S1b), separated by a cold interruption event (S1i). High resolution faunal and geochemical analyses allow to identify two sub-phases within S1a interval, the oldest one has similar characteristics to S1b interval while the youngest sub-phase has less stratified surface waters with relatively lower nutrient content. The high abundance of Globigerinoides ruber white variety opposite to the low percentages of Neogloboquadrina pachyderma during the pre-S1 phase suggests that the onset of surface waters stratification occurred prior to the beginning of Sapropel deposition, acting as a pre-conditioning phase. Paleo-productivity proxies indicate that the deposition of S1 initiated after an increase in nutrient content, potentially related to increased fluvial inputs. Based on the integrated ecological interpretation of our records we argue that S1a and S1b are characterized as warm, stratified and nutrient rich surface waters in the Ionian Sea, while proxies related to oxygen content indicate dysoxic deep waters linked to a combination of the high nutrient content and stratified water column. The S1 interruption phase is characterized by the entrance of colder waters that caused mixing of the stratified water column and re-ventilation of the deep dysoxic waters

AN INTEGRATED CALCAREOUS PLANKTON BIOSTRATIGRAPHIC SCHEME AND BIOCHRONOLOGY FOR THE MEDITERRANEAN MIDDLE MIOCENE

The relative position of 30 main bioevents  pertaining to calcareous nannofossils and planktonic foraminifera was identified in the time interval between 13.75 Ma and 10.50 Ma, based on the quantitative study of the those microfossils in three Mediterranean sections spanning the late Langhian – lower Tortonian stratigraphic interval. The events were correlated  to the astronomic target curve using a cyclostratigraphic approach, resulting in a very detailed biostratigraphic and biochronologic subdivision of the interval. The zonal scheme proposed by Fornaciari et al. (1996) was adopted for the calcareous nannofossils, but three subzones were identified in the MMN7 Zone. For the planktonic foraminifera reference is made to the zonal scheme recently proposed by Foresi et al. (1998), slightly modified in order to increase its biostratigraphic resolution. The age of all the zonal boundaries is reported.&nbsp

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

Climate fluctuations and human impact during the late Holocene in a multi-proxy marine record from the Gulf of Gaeta (Tyrrhenian Sea, central Italy)

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