Rodolfo Coccioni

Ontong Java Plateau eruption as a trigger for the early Aptian oceanic anoxic event

The Early Cretaceous Ontong Java Plateau was emplaced at almost the same time as marine biotic changes that culminated in oceanic anoxic event 1 (OAE1a). A causative link between these events has been suggested, but direct evidence has been lacking until now. New Os isotope measurements across the Lower Aptian “Selli Level” black shale deposited during OAE1a in central Italy reveal two negative excursions in marine 187 Os/ 188 Os ratios within a period of 2 Ma starting above the Barremian-Aptian boundary and ending just above the Selli Level horizon, suggesting an order-of-magnitude increase in the global fl ux of unradiogenic Os. The results are consistent with early and major phases of eruption of the Ontong Java Plateau. The latter phase is estimated to have been as short as ~1 Ma and may have induced widespread oceanic stratifi cation that triggered OAE1a.

Barremian-Aptian calcareous plankton biostratigraphy from the Gorgo Cerbara section (Marche, central Italy) and implications for plankton evolution

Abstract The Barremian-Aptian boundary interval of the Gorgo Cerbara section (Marche, central Italy) was revisited in order to improve stratigraphic correlations and investigate plankton evolution. A very close sampling at cm scale was carried out in the upper Maiolica and basal Scisti a Fucoidi formations. The latter formation includes the Livello Selli, the landward sedimentary expression of oceanic anoxic subevent OAE la. The study of closely spaced samples revealed that (1) the first diversification among planktonic foraminifera, marked by the appearance of the genus Globigerinelloides , occurred during the Barremian (this event was dated by means of ammonites); thus the first occurrence (FO) of both Globigerinelloides duboisi and Globigerinelloides blowi cannot be used to identify the Aptian; (2) the appearance of Rucinolithus irregularis is the biostratigraphic event which best approximates the Barremian-Aptian boundary; and (3) chron M0, being slightly younger than the FO of R. irregularis , is very close to this boundary. Semiquantitative and quantitative analyses of planktonic foraminifera, calcareous nannofossils and radiolarians show that the three groups fluctuate in abundance and assemblage composition throughout the studied interval. An important change in plankton distribution patterns occurs within the G. blowi foraminiferal Zone and C. litterarius nannofossil Zone, where planktonic foraminifera, radiolarians and calcareous nannofossils start to show large-scale, higher frequency fluctuations in abundance; fluctuations in the three groups are out of phase. These new plankton distribution patterns are interrupted by the Livello Selli, which is preceded and followed by ‘critical intervals’. The distribution and composition of all three planktonic groups lead to the interpretation of the ‘critical intervals’ as representing increased nutrient contents in the surface water and the Livello Selli as a very high fertility event. Among planktonic foraminifers the hedbergellids seem to indicate a more eutrophic habitat than the globigerinelloids. In calcareous nannofossil assemblages, the abrupt crisis affecting the nannoconids prior to deposition of the Livello Selli suggests that these nannofossils are characteristic of more oligotrophic conditions, whereas Zygodiscus erectus is indicative of a more eutrophic environment. Based on our data, the early Aptian Livello Selli has the same oceanographic significance as the latest Cenomanian Livello Bonarelli, i.e., it represents a high fertility event on a global scale.

Benthic foraminifera as bio-indicators of trace element pollution in the heavily contaminated Santa Gilla lagoon (Cagliari, Italy)

In order to assess the response of benthic foraminifera to trace element pollution, a study of benthic foraminiferal assemblages was carried out into sediment samples collected from the Santa Gilla lagoon (Sardinia, Italy). The lagoon has been contaminated by industrial waste, mainly trace elements, as well as by agricultural and domestic effluent. The analysis of surficial sediment shows enrichment in trace elements, including Cr, Cu, Hg, Ni, Pb and Zn. Biotic and abiotic data, analyzed with multivariate techniques of statistical analysis, reveal a distinct separation of both the highly polluted and less polluted sampling sites. The innermost part of the lagoon, comprising the industrial complex at Macchiareddu, is exposed to a high load of trace elements which are probably enhanced by their accumulation in the finer sediment fraction. This area reveals lower diversity and higher percentages of abnormalities when compared to the outermost part of the lagoon.

K-T boundary extinction: Geologically instantaneous or gradual event? Evidence from deep-sea benthic foraminifera

A stepped pattern of benthic foraminiferal decimation, survival, and recovery identified across the Cretaceous-Tertiary (K-T) boundary at Caravaca (southeast Spain) suggests that an exceptionally large influx of nutrients reached the sea floor suddenly, at the time of the K-T extinction event. Rapid reestablishment of pre-K-T boundary environmental conditions followed. Our data demonstrate a close coupling between the collapse of the ecologic system in the upper water column at Caravaca and a correspondent decimation of bottom dwellers on the sea floor. The dramatic environmental collapse of deep-water benthic foraminiferal communities at the end of the Cretaceous at Caravaca suggests that the K-T boundary event was geologically instantaneous and catastrophic.

Benthic foraminifera and trace element distribution: a case-study from the heavily polluted lagoon of Venice (Italy).

Living benthic foraminiferal assemblages were studied in surface samples collected from the lagoon of Venice (Italy) in order to investigate the relationship between these sensitive microorganisms and trace element pollution. Geochemical analysis of sediments shows that the lagoon is affected by trace element pollution (Cd, Cu, Ni, Pb, Zn and Hg) with the highest concentrations in its inner part, which corresponds to the Porto Marghera industrial area. The biocenosis are largely dominated by Ammonia tepida, Haynesina germanica and Cribroelphidium oceanensis and, subordinately, by Aubignyna perlucida, Ammonia parkinsoniana and Bolivina striatula. Biotic and abiotic factors were statistically analyzed with multivariate technique of cluster analysis and principal component analysis. The statistical analysis reveals a strong relationship between trace elements (in particular Mn, Pb and Hg) and the occurrence of abnormalities in foraminiferal tests. Remarkably, greater proportions of abnormal specimens are usually found at stations located close to the heaviest polluted industrial zone of Porto Marghera. This paper shows that benthic foraminifera can be used as useful and relatively speedy and inexpensive bio-indicators in monitoring the health quality of the lagoon of Venice. It also provides a basis for future investigations aimed at unraveling the benthic foraminiferal response to human-induced pollution in marine and transitional marine environments.

The middle Eocene climatic optimum event in the Contessa Highway section, Umbrian Apennines, Italy

We report a high-resolution paleomagnetic investigation constrained by new qualitative and semiquantitative analyses of planktic and benthic foraminifera, nannofossil assemblages, integrated with oxygen and carbon isotope measurements, for the middle Eocene Scaglia limestones of the Contessa Highway section, central Italy. Calcareous plankton assemblages enable recognition of several biostratigraphic events from planktic foraminiferal zone P11 to the lower part of zone P15 and from calcareous nannofossil zone NP15 to the upper part of zone NP17, which results in refi nement of the magnetobiostratigraphy of the Contessa Highway section. Correlation of the paleomagnetic polarity pattern with the geomagnetic polarity time scale provides a direct age interpretation for strata around the middle Eocene Scaglia limestones of the Contessa Highway section, from chrons C21n (47 Ma) through to subchron C18n.1n (38.5 Ma). Bulk carbon isotope values indicate a distinct carbon isotopic shift at 40 Ma that is interpreted to represent the fi rst evidence in the Northern Hemisphere of the middle Eocene climatic optimum, which has recently been observed as a stable isotope anomaly in multiple records from the Indian-Atlantic sector of the Southern Ocean. This demonstrates a global response of the carbon cycle to the proposed transient increased pCO 2 levels during the late middle Eocene and consequent global CO 2 -driven climate change.

Orbitally induced cycles in benthonic foraminiferal morphogroups and trophic structure distribution patterns from the Late Albian “Amadeus Segment” (Central Italy)

A detailed analysis was made of benthonic foraminiferal distribution patterns and morphogroups in the late Albian “Amadeus Segment” of the Aptian-Albian organic-rich Scisti a Fucoidi Formation outcropping over a widespread area of the Umbria-Marche region, Central Italy. Rhythmic changes in the trophic structures and composition of benthonic foraminiferal assemblages suggest cyclical fluctuations of the sea floor environment which appear to be orbitally induced. Benthonic foraminiferal assemblages varied significantly through the section and appear to contain a strong paleoecological signal. Fluctuations in both bottom water oxygenation and the surface primary productivity as a result of the orbital forcing are interpreted to have been the primary controls on benthonic foraminiferal distribution patterns.

Orbital control on carbon cycle and oceanography in the mid‐Cretaceous greenhouse

We established a new high-resolution carbonate carbon isotope record of the Albian interval of the Marne a Fucoidi Formation (Central Apennines, Italy), which was deposited on the southern margin of the western Tethys Ocean. Bulk carbonate sampled with 10–15 cm spacing was used for the construction of a continuous carbon isotope curve through the Albian stage. Spectral analyses reveal prominent 400 kyr cyclicity in the δ13C curve, which correlates with Milankovitch long eccentricity changes. Cycles occurring in our record resemble those observed in several Cenozoic δ13C records, suggesting that a link between orbital forcing and carbon cycling existed also under mid-Cretaceous greenhouse conditions. Based on comparisons with Cenozoic eccentricity-carbon cycle links we hypothesize that 400 kyr cycles in the mid-Cretaceous were related to a fluctuating monsoonal regime, coupled with an unstable oceanic structure, which made the oceanic carbon reservoir sensitive to orbital variations. In the Tethys these oceanographic conditions lasted until the Late Albian, and then were replaced by a more stable circulation mode, less sensitive to orbital forcing.

Strontium Isotopic Composition of Mid-Cretaceous Seawater

The 87Sr/86Sr ratio in fish teeth separated from mid-Cretaceous marl and black shale from the northeastern Apennines and Venetian Alps (Italy) define three periods of low 87Sr/86Sr ratio at 121 to 124 million years ago (Ma), 110 to 115 Ma, and 89 to 91 Ma. The 87Sr/86Sr excursions correspond to oceanic anoxic events represented by the Livello Selli, Livello 113, Livello Urbino, and Livello Bonarelli black shale marker beds and probably reflect an increase in the low-87Sr/86Sr hydrothermal strontium flux associated with the emplacement of the Ontong-Java and Kerguelen plateaus (120 to 110 Ma) and the Caribbean Plateau (89 to 91 Ma). The modeled flux is consistent with the volumes and eruption rates of the oceanic plateaus but is far smaller than expected from the proposed Cretaceous crustal production rates of 50 to 100 percent greater than modern.

Meiofauna of the Adriatic Sea: present knowledge and future perspectives

Owing to technical problems and difficult taxonomic identification, meiofauna have been generally less studied than macrofauna. However, the role of meiofauna in marine ecosystem functioning, and their effective and rapid response to anthropogenic alterations and climatic changes have recently been acknowledged, leading to increasing scientific and applied interest. At present, systematic and biogeographic knowledge of the meiofauna of the Adriatic Sea is extremely heterogeneous, because most of the data are limited to a few taxa and the sampled areas are scattered, being located mainly in the coastal areas of the northern basin. Analysis of the composition and distribution of meiobenthic groups in the Adriatic Sea highlights the presence of several endemisms. Meiofauna also include bioindicator taxa, which allow assessment of the quality of marine sediments; this is particularly useful in systems characterised by the synergistic effect of different forms of anthropogenic impact, such as the Adriatic basin. Current knowledge about the ecology of the meiofauna and use of this component in applied ecological studies, along with the availability of a standardised protocol for the analysis of meiofaunal assemblages, allows us to recommend formal acknowledgement of the need to integrate information derived from the analysis of macrofauna with information derived from the study of meiofauna. Future research based on the simultaneous use of both of these benthic components will allow faster and more accurate evaluation of the response of coastal marine ecosystems to anthropogenic disturbance.