Adriana Bellanca

Palaeoceanographic significance of the Tethyan ‘Livello Selli’ (Early Aptian) from the Hybla Formation, northwestern Sicily: biostratigraphy and high-resolution chemostratigraphic records

High-resolution micropalaeontological and chemostratigraphic records for the Hauterivian–Aptian succession outcropping at Calabianca (NW Sicily) provide new insight into the palaeoclimatic and palaeoceanographic evolution of the Tethys Ocean. Calcareous nannofossil and planktonic foraminiferal biostratigraphy together with δ13C chemostratigraphy allowed the identification of a hiatus in the Barremian and a major one including most of the Upper Aptian, the entire Lower Albian and part of the Middle Albian. The Livello Selli equivalent was identified on the basis of lithology and well constrained by calcareous plankton biostratigraphy as well as by the δ13C curve. The multi-proxy record from the Calabianca section is consistent with previous documentation of Tethyan sections, and others worldwide. Early Aptian global events, such as black shale deposition, nannoconid crisis, C isotopic negative spike and positive excursion associated with the OAE1a, increase in abundance of leupoldinids and clavate hedbergellids are superimposed on local/regional events, being strictly related to climate changes and increased run-off. Based on micropalaeontological results and geochemical proxies (Ba, P, V, Ni), the Livello Selli equivalent is interpreted as a high-productivity event associated with variable but overall anoxic/dysoxic conditions in the lower water column. The onset of new physical, chemical and biological conditions in the oceans and of the mid-Cretaceous greenhouse climate are interpreted as consequences of the superplume episode.

Trace metal partitioning in Fe–Mn nodules from Sicilian soils, Italy

Concentrations of 20 elements (Mn, Fe, Na, Mg, Al, K, Ca, V, Co, Ni, Cu, Zn, Rb, Sr, Cd, Cs, Ba, La, Ce, Pb) were determined in 18 Fe–Mn nodules from two alfisols, which are subject to periodic waterlogging. The nodules are significantly enriched in most trace metals relative to the host soil, with Mn, Co, Ce, Pb, Ba, Cd, Ni more enriched than Fe, V, La, Cu, Sr, Zn. Cesium and rubidium show poor or no enrichment in the nodules, consistent with their aluminosilicate affiliation. Scanning electron microscopy (SEM) examination and energy dispersive X-ray spectrometer (EDS) microprobe analysis have shown different microstructures (an undifferentiated fabric and a distinctive Fe–Mn banded structure) in the nodules from the two soils. A clearer partitioning of trace elements between Mn and Fe oxide phases is observed in the nodules showing the Fe–Mn banded structure, with Ba, Sr, Ni, Cu, and Cd correlated with Mn, V, and Pb with Fe. The nodules with undifferentiated fabric exhibit lower element/Mn molar ratios, which could reflect a minor adsorption of trace elements by MnO2 in relation to a more rapid growth of the nodules. As shown by elemental associations, the Cd and Ce distribution appears to be closely linked to the redox cycling of Mn.

Influence of inheritance and pedogenesis on heavy metal distribution in soils of Sicily, Italy

Abstract The recognition of the potential health hazards associated with heavy metals has focused attention on the levels and behaviours of these elements both in natural and contaminated environments. Various soil types developed from different parent materials in Sicily, Italy, have been analysed in order to compare heavy metal distribution under different geopedological conditions. Total metal concentrations, metal partitioning and distribution profiles are discussed in relation to the inheritance factor and pedogenic processes. Parent material composition largely influences the contents of heavy metals in most of the analysed soils, mainly differentiating pedons for their metal concentration on the basis of sedimentary and volcanic parent materials. However, an exception is represented by the carbonate-free Alfisols and Mollisols, which are markedly enriched in heavy metals with respect to the underlying limestones and calcarenites. On the basis of chemical and mineralogical results, supported by data from sequential extraction (SEP), heavy metal enrichment in these soils is associated with the formation of common to abundant Fe–Mn oxides and clay accumulation. For Mollisols there is evidence for a major role of organic matter in heavy metal retention in surface horizons. In the other pedons, pedogenic processes appear to mainly influence the redistribution of heavy metals throughout the soil horizons rather than affecting the total content. Argillopedoturbation seems to be responsible for a uniform distribution of heavy metals in Vertisol profiles on marly clays. Accumulation of heavy metals in the topsoil of Inceptisols on clays with gypsum and Entisols on gypsarenites and diatomites is caused partially by adsorption on organic matter and mainly by dissolution of primary gypsum and opal-A. A pedogenic influence is less evident in young Andisols whose heavy metal composition greatly reflects that of hawaiitic pyroclastic deposits interbedded within the profiles. However, a certain redistribution of Cu accumulated as metal–organic matter complexes is evidenced in the surface horizon by SEP.

Rare earth elements in limestone/marlstone couplets from the Albian-Cenomanian Cismon section (Venetian region, northern Italy) : assessing REE sensitivity to environmental changes

Abstract We have studied the REE distribution through the Albian-Cenomanian interval of a stratigraphic succession (Cismon section, Scaglia Variegata Formation, Venetian Prealps) consisting of rhythmically alternating carbonate-rich and carbonate-poor strata which are the sedimentary expression of systematic variations of surface fertility and bottom-water redox conditions in the depositional basin. Limestone semicouplets show seawater-like shale-normalized patterns (HREE-enriched, with negative Ce anomalies and high Er/Nd ratios) indicating a clear dependence on the REE chemistry of surface seawaters. Marlstones and shales exhibit flatter patterns, more moderate Ce anomalies and low Er/Nd. Good correlations between Er/Nd, Ce/Ce∗ and Mn∗ suggest that, superimposed on REE signatures imparted by detrital and biogenic phases, the REE composition shows evidence of their sensitivity to palaeoredox conditions resulting in REE fractionation and Ce cycling. REE data are consistent with results from previous stratigraphic and geochemical (major and trace elements) investigations in reflecting palaeoenvironmental conditions rhythmically varying from efficiently mixed seawater during the limestone deposition to oxygen-depleted bottom waters at the time of marlstone deposition.

Orbitally induced limestone/marlstone rhythms in the Albian—Cenomanian Cismon section (Venetian region, northern Italy): Sedimentology, calcareous and siliceous plankton distribution, elemental and isotope geochemistry

Abstract A multidisciplinary study of the upper Albian—Cenomanian portion of the Cismon section (Venetian region, northern Italy) was undertaken in order to characterize the cyclic alternations of carbonate-rich and carbonate-poor layers and to investigate their possible origin and cyclic patterns. Limestone semicouplets are characterized by abundant radiolarians and micarbs (micron-sized calcitic fragments), common planktonic foraminifera, strong bioturbation, good oxygenation as expressed by the Mn* and V/(V+Ni) parameters, high Si/Al ratio, low K/Al, in the absence of pyrite and organic matter. The marlstone semicouplets are, on the contrary, frequently laminated, rich in pyrite and organic matter with common fish remains in the absence of radiolarians. The Mn* and V/(V+Ni) parameters indicate that the marlstone deposition occurred in dysoxic to anoxic conditions, which allowed the preservation of organic matter. The low Si/Al ratio and high K/Al ratio, the latter related to abundant feldspars, indicate that marlstones received a substantial contribution from a terrigenous source. The abundance of biogenic silica suggests that during limestone deposition surface waters were rather fertile due to an efficient recycling of nutrients from deeper waters. The enhanced fertility was coupled with an efficient current system at the welloxygenated sea floor which prevented the organic matter from accumulating. During marlstone deposition, surface waters were less fertile than in the limestone semicouplets, but still within the mesotrophic spectrum as indicated by the presence of fertility index species among calcareous nannofossils, whereas the bottom waters were oxygen-depleted. To accommodate fertility at the surface with stagnation at the bottom the scenario implies an enhanced stratification caused by an increase in freshwater runoff monitored by 18O-depleted δ values. In the meantime, the water discharge supplied the nutrients to the surface waters necessary for the calcareous nannofossils to proliferate. The cyclic organization of limestone/marlstone couplets as revealed by power spectral analysis seems to represent climatic cycles. The alternating conditions are (1) efficient mixing, highly fertile surface and near-surface waters, and a well-oxygenated seafloor to (2) enhanced water runoff or decreased evaporation, or both, and oxygen-depleted bottom waters. We suggest that this deterministic sedimentary cyclicity could be explained by periodic orbital-climatic cycles, in tune with the Milankovitch cycles. Within this scenario, the latest Cenomanian Bonarelli Level is an exceptional event marked by a large positive δ13C spike. It is characterized by high to very high fertility conditions in surface waters caused by increased upwelling that engendered high nutrient levels in near-surface waters. The enhanced production of organic matter was in excess for the oxygen available at the bottom floor, thus allowing the organic matter to accumulate in the sediments.

Recognition of lake-level changes in Miocene lacustrine units, Madrid Basin, Spain. Evidence from facies analysis, isotope geochemistry and clay mineralogy

Abstract The Miocene lacustrine sequence exposed near Esquivias, in the central area of the continental Tertiary Madrid Basin, is formed of two main lithostratigraphic units that represent two different stages of a palaeolake system. Unit I consists of five lithofacies: (A) nodular carbonates and marls, (B) massive dolostones, (C) bioclastic limestones, (D) mudstones, and (E) chert, which are characteristic of sedimentation and early diagenesis in a shallow lacustrine environment. Two main stages of the same general lowstand situation are reflected in mineralogy and isotope geochemistry results. An initial stage is suggested by the presence of non-stoichiometric dolomite and trioctahedral smectites. High δ18O and δ13C values of the dolomites (+5.5 and +2.9 δ‰, respectively) indicate strongly evaporative conditions. A second stage is characterized by the presence of calcite, fibrous clay minerals and by generally lower δ18O (from +1.5 to −6.5 δ‰) and δ13C (from −1 to −9.8 δ‰) values for carbonates, which suggest more diluted waters during this lowstand phase of the lake. Unit II comprises seven lithofacies: (A) conglomerates, (B) intraclastic mudstones, (C) laminated marls, (D) massive mudstones, (E) diatomaceous marls, (F) laminated bioclastic limestones, and (G) root-bioturbated limestones. Both conglomerates and intraclast mudstones fill sharply eroded contacts in the underlying deposits of Unit I. We demonstrate how the arrangement of facies, supported by isotopic results from the carbonates δ18O (from −0.7 to −7.2 δ‰; δ13C from −4.2 to −8.6 δ‰), is clearly indicative of deeper lake conditions. The basal reworked facies mark the initial phase of a lake transgression. In contrast with Unit I, the clay mineral assemblage from unit II is mainly detrital. Clay minerals thus also support the interpretation of a dilute water body, consistent with a highstand of the palaeolake.

Integrated stratigraphy of the Oligocene pelagic sequence in the Umbria-Marche basin (northeastern Apennines, Italy): A potential Global Stratotype Section and Point (GSSP) for the Rupelian/Chattian boundary

The Oligocene represents an important time period from a wide range of perspectives and includes significant climatic and eustatic variations. The pelagic succession of the Umbria-Marche Apennines (central Italy) includes a complete and continuous sequence of marly limestones and marls, with volcaniclastic layers that enable us to construct an integrated stratigraphic framework for this time period. We present here a synthesis of detailed biostratigraphic, magnetostratigraphic, and chemostratigraphic studies, along with geochronologic results from several biotite-rich volcaniclastic layers, which provide the means for an accurate and precise radiometric calibration of the Oligocene time scale. From this study, the interpolated ages for the Rupelian/Chattian stage boundary, located in the upper half of Chron 10n at meter level 188 in the Monte Cagnero section, and corresponding to the O4/O5 planktonic foraminiferal zonal boundary, are 28.36 Ma (paleomagnetic interpolation), 28.27 ± 0.1 Ma (direct radioisotopic dating), and 27.99 Ma (astrochronological interpolation). These ages appear to be slightly younger than those reported in recent chronostratigraphic time scale compilations. The Monte Cagnero section is a potential candidate for defining the Chattian Global Stratotype Section and Point (GSSP) and some reliable criteria are here proposed for marking the Rupelian/Chattian boundary according to International Union of Geological Sciences (IUGS) recommendations.

Sedimentology and isotope geochemistry of Carnian deep-water marl/limestone deposits from the Sicani Mountains, Sicily: Environmental implications and evidence for a planktonic source of lime mud

Abstract The upper Triassic Halobia-bearing marl/limestone deposits from the Sicani Mountains (Sicily) record the sedimentary evolution of the Sicanian Basin through the middle and late Carnian time. Dark marls and interbedded grey calcilutites of Julian age are characterized by abundant pyrite, sparse bioturbation and negative carbonate carbon δ13C values. They accumulated in a basin with dominantly anoxic to dysaerobic bottom waters. Lower Tuvalian dark-grey pyritic marls and calcilutites, which contain carbonate minerals with relatively high Mn contents and widely fluctuating δ13C signatures, were deposited under dysaerobic conditions. Middle and upper Tuvalian cherty limestones show intense bioturbation and nearly invariable positive δ13C values (around 2‰ for calcite). They form a thick and monotonous succession accumulated in a deeper and more oxygenated basin. The Halobia-bearing deposits preserve some calcareous nannoplanktonic forms. The nannofossils, varying in size from 7 to 32 μm, are significantly abundant in the cherty limestones pointing to a notable role of the calcareous nannoplankton as a source of carbonate mud in the deep-water basins of the southern Tethys during the late Triassic time.

Mineralogy and geochemistry of Terra Rossa soils, western Sicily: insights into heavy metal fractionation and mobility

Abstract The distribution of heavy metals in typical Terra Rossa soils and their partitioning in specific soil phases are estimated on the basis of the comparative evaluation of bulk contents, results from sequential chemical extraction procedure (SEP) and scanning electron microscopy/energy dispersive X-ray analysis ( SEM EDX ). A general natural enrichment of heavy metals with respect to average soil is observed. Cadmium proves to be remarkably high (up to 2.4 ppm). Large amounts of Fe, Cr, Cu, Ni, Pb, and Zn occur in the ‘residual’ fraction. The results indicate selective accumulation of the heavy metals in Fe oxides, present as hematite, goethite and maghemite. There is good evidence that Mn and Cd are subjected to similar influences, both elements mainly occurring in the ‘easily reducible’ fraction. The affinity of Cd for poorly crystallized Mn oxides governs its behaviour and mobility, which may significantly increase in moderate reducing conditions in relation to Mn phases stability.

Orbitally modulated black shale deposition in the upper Albian Amadeus Segment (central Italy): a multi-proxy reconstruction

Abstract The upper Albian Amadeus Segment, which falls within Oceanic Anoxic Event 1c, exhibits cyclical alternations of marls/black shales and carbonate-rich beds that record evidence of orbital climate and sedimentary dynamics. A combined micropalaeontological (planktic and benthic foraminifera, and palynomorphs) and geochemical (stable isotopes, clay mineralogy, and major element distribution) investigation allowed recognition of a remarkable influence of continental material within the black shales. Moreover, the palaeoproductivity record is characterised by a non-linear response to the orbital forcing. The micropalaeontological and geochemical record suggests that upper Albian bedded cycles in the Marne a Fucoidi Formation resulted from interplay of changes in atmospheric and hydrological parameters of the western Tethys and its drainage basin. In particular, deposition of the black shales occurred during precession minima, in times of increased precipitation, enhanced continental runoff and stratification of the upper water column. In this respect, the black shales of the Amadeus Segment share similarities with the Neogene Eastern Mediterranean sapropels.