Mercury is gaining prominence as a proxy for large igneous province (LIP) volcanism in the sedimentary record. Despite temporal overlap between some mass extinctions and LIPs, the precise timing of ...magmatism relative to major ecological and environmental change is difficult to untangle, especially in marine settings. Changes in the relative contents of Hg in sedimentary rocks through time, or ‘Hg anomalies’, can help resolve the timing of LIP activity and marine extinctions. However, major questions remain unanswered about the fidelity of Hg as a proxy for LIP magmatism. In particular, depositional (e.g., redox) and post-depositional (e.g., oxidative weathering) processes can affect Hg preservation in marine sediments. These factors pose challenges for confidently using Hg as a fingerprint of volcanism. Here, we use the Hg anomaly at the Triassic–Jurassic boundary to explore the opportunities and challenges associated with two approaches that may help build a more robust interpretation of the Hg proxy: (1) measurements of sediments from diverse depositional environments, including lithologies with low Hg and organic carbon content, and (2) the simultaneous use of Hg stable isotope ratios. We present and compare Hg records from five geographically disparate Upper Triassic–Lower Jurassic marine sections that represent nearshore, mid-shelf, deep-water, and carbonate platform settings. These sedimentary sections span the emplacement of the Central Atlantic magmatic province (CAMP) and the associated end–Triassic extinction (ETE). Total organic carbon contents, carbonate contents, and Hg contents and stable isotope compositions demonstrate the multiple ways in which different depositional environments impact how Hg anomalies are expressed in ancient marine sedimentary rocks. Although we observe an increase in Hg/TOC during the ETE in each section, the pattern and duration of Hg enrichment differ notably between sections, and the timing is not always coincident with CAMP activity, illustrating how the depositional filter complicates the use of Hg/TOC ratios alone as a fingerprint of LIP magmatism. Importantly, Hg isotope measurements support a volcanic origin for the Hg anomalies during the ETE, suggesting CAMP was the Hg source during the extinction interval. These data support the use of Hg isotopes to help distinguish Hg loading that results from LIP magmatism on a global scale and emphasize the importance of making Hg proxy measurements from diverse depositional environments.
Pressure solution processes taking place during diagenesis deeply modify the hydraulic properties of carbonates, affecting their mechanical layering and hence the dimension, distribution, and ...connectivity of high-angle fractures. The formation of stylolites is controlled by the texture of the host rock and therefore by the depositional environment and the diagenetic processes that involve it. This study reports the results of a multidisciplinary study carried out on a Jurassic–Cretaceous carbonate platform in southern Italy. The goal is to unravel the control exerted by single carbonate textures and specific diagenetic processes on the formation of bed-parallel stylolites. Microfacies analyses of thin sections are aimed at obtaining information regarding the composition and texture of the carbonates. Petrographic observations coupled with CL analyses are key to deciphering their diagenetic history. Results are consistent with carbonates originally deposited in a shallow-water realm in which carbonate mud is occasionally abundant. In this environment, early cementation inhibits their chemical compaction. In grain-supported facies, pressure solution is only localized at the grain contacts. During shallow burial diagenesis, precipitation of blocky calcite predates the formation of bed-parallel stylolites in the grain-supported facies. Contrarily, mud-supported facies favor chemical compaction, which results in stylolites showing a good lateral extension and thick sediment infill. A classification of different types of stylolite morphology is attempted in relation to facies texture. In detail, rougher morphology (sharp-peak) characterizes the stylolites nucleated in grain-supported facies, while smoother morphology (rectangular to wave-like) is observed in stylolites on mud-supported facies. Application of this knowledge can be helpful in constraining the diagenetic history of carbonate rocks cored from depth, and therefore predict the fracture stratigraphy properties of carbonates buried at depth.
The end-Triassic mass extinction (ETME) was associated with intensified deep-water anoxia in epicontinental seas and mid-depth waters, yet the absolute oxygenation state in the shallow ocean is ...uncharacterized. Here we report carbonate-associated iodine data from the peritidal Mount Sparagio section (Southern Italy) that documents the ETME (~ 200 Ma) in the western Tethys. We find a sharp drop in carbonate I/(Ca + Mg) ratios across the extinction horizon and persisting into the Early Jurassic. This records local dissolved oxygen and iodate decline in the near-surface ocean of low-latitude Tethys due to the development of depleted oxygen concentrations. Consequently, during the ETME even shallow-water animals, such as the megalodonts seen at Mount Sparagio, were likely the victims of oxygen-poor conditions. The shallow ocean deoxygenation coincides with the synchronous spread of deeper anoxic waters and widespread anoxic deposition on continental shelves and slopes. An upwards expansion of the mid-water oxygen minimum zone in the latest Triassic shoaled the oxycline and triggered a major marine crisis.
•I/(Ca + Mg) profile in a Triassic–Jurassic boundary shallow water carbonate succession of the western Tethys•Water column hypoxic conditions in the peritidal marine realm during the end-Triassic mass extinction•Oxygen decline was synchronous with the sudden local loss of benthic macrofauna•Shallow ocean deoxygenation driven by hyperthermal conditions and upwards expansion of mid-depth oxygen minimum zone
Xyloglucans are highly branched, hydroxyl rich polyglucans that for their abundance in nature, biocompatibility, film forming and gelation ability may take a prominent role in the design and ...fabrication of biomedical devices, including in situ forming scaffolds for tissue engineering, wound dressings and epidermal sensors. The understanding and exploitation of their self-assembly behavior is key for the device performance optimization. A multi-scale analysis, conducted combining small-angle X-ray scattering, both static and dynamic light scattering at large and small angles, and rheological measurements, provides a description of the supramolecular organization of this biopolymer, from the scale of a few nano-meter, to the meso- and macro-scale both in the sol and gel states. Xyloglucan self-assembly is described as multi-step and hierarchical process with different levels of organization.
The role of ocean anoxia as a cause of the end-Triassic marine mass extinction is widely debated. Here, we present carbonate-associated sulfate δ
S data from sections spanning the Late Triassic-Early ...Jurassic transition, which document synchronous large positive excursions on a global scale occurring in ~50 thousand years. Biogeochemical modeling demonstrates that this S isotope perturbation is best explained by a fivefold increase in global pyrite burial, consistent with large-scale development of marine anoxia on the Panthalassa margin and northwest European shelf. This pyrite burial event coincides with the loss of Triassic taxa seen in the studied sections. Modeling results also indicate that the pre-event ocean sulfate concentration was low (<1 millimolar), a common feature of many Phanerozoic deoxygenation events. We propose that sulfate scarcity preconditions oceans for the development of anoxia during rapid warming events by increasing the benthic methane flux and the resulting bottom-water oxygen demand.
A new δ13Ccarb curve was obtained from an expanded peritidal succession in western Sicily and was used to investigate the relationships between isotopic signatures and biological events on carbonate ...platforms across the Triassic-Jurassic boundary (TJB). The resulting curve shows two main negative carbon isotopic excursions (CIEs) that fit well with the “Initial” and “Main” CIEs that are recognized worldwide and linked to the End-Triassic Extinction (ETE). In the studied section, the first negative CIE marks the disappearance of the large megalodontids, which were replaced by small and thin-shelled specimens, while the “Main” CIE corresponds to the last occurrence (LO) of the megalodontids and, approximately 50 m upsection, to the total demise of the Rhaetian benthic foraminifer community. Upward, the carbon curve shows a positive trend (ca. +1‰) and a gradual recovery of the benthic communities after an approximately 10 m-thick barren interval populated only by the problematic alga Thaumatoporella parvovesiculifera.
A comparison between the Mt. Sparagio δ13Ccarb curve and other coeval Ccarb and Corg curves from carbonate platform, ramp and deep basin successions indicates similar isotopic trends; however, the diverse magnitudes and responses of benthic communities confirm that the carbon cycle perturbations have been globally significant, and were influenced by external forces such as CAMP volcanism. The multiphase nature of the extinction pulses could have been caused by local environmental changes related to transgression/regression phenomena. Overall, this study adds new data and a new timing to the effect of the acidification process on carbon productivity and benthic communities in different environments across the TJB.
The Triassic/Jurassic boundary section cropping out at Mt Sparagio in north-western Sicily (Italy) consists of a thick and continuous peritidal succession typical of a Tethyan carbonate platform. The ...combined chemostratigraphic and biostratigraphic study of this section allowed us to parallel the environmental variations inferred by the isotopic records and the extinction trends recorded by the benthic organisms. In the studied section, the isotope data of C, O, and S are indicative of serious environmental perturbations related to the Central Atlantic Magmatic Province (CAMP) activity, as recorded worldwide. Two negative excursions in the C-curve (Initial-CIE and Main-CIE) confirm the acidification processes that affected the benthic community. Moreover, the oxygen isotopes curve indicates a strong warming-trend that corresponds to the reduction in biodiversity and size of the megalodontoids in the upper part of the Rhaetian beds, probably due to the deterioration of the photosymbiotic relationships of these pelecypods. We here present some novel isotope data (Zn, Pb, Sr) from the Mt Sparagio section that offer additional clues on a tight control of CAMP volcanism on the End-Triassic Extinction.
The Custonaci marble district of western Sicily is known for the production of a valuable ornamental stone that has been, and nowadays is exploited due to its suitable properties and aesthetic ...qualities. The “Libeccio Antico” was, among the “marbles”, the most appreciated ornamental stone during the Baroque Age (the XVII–XVIII centuries), due to its strong polychrome contrasts from ivory to yellow, green or dark red. This polychrome pattern is the result of dissolution processes that involved an Upper Triassic peritidal limestone. The varicoloured sediments in paleocavities, collapse breccias, paleosols and neptunian dykes that occur in the “Libeccio Antico” represent the peculiar characteristics that have given this stone its particular ornamental interest.
This study provides an original sedimentological and stratigraphical analysis of the Upper Triassic carbonate succession in which most of the “Libeccio Antico” quarries occur. Petrophysic descriptions, accompanied by mineralogical and geochemical characterisations, are provided to comprehensively describe the diagenetic evolution of the carbonate host rock. This study emphasises as the “Libeccio Antico” represents a unique geoarchive among ornamental stones due to its origin, which involved diagenetic processes that occurred in a well-defined geological environment and over a restricted period of time. Moreover, this “marble” is frequently mentioned by architects, historians, naturalists and geologists in historical archives from the XVIII century in Sicily. All of these characteristics make the “Libeccio Antico” quarries a valuable geosite that should be promoted.
New biostratigraphic data, based on conodont investigations, were collected from the Ladinian limestones recently described at Sant’Otiero, a locality near the Village of Petralia Sottana in the ...Madonie Mountains (Central-Northern Sicily). At this locality a new calcareous succession lying at the base of a major tectonic unit of the Maghrebian chain is described. This succession consists of a lower massive part formed by a carbonate megabreccia, the elements of which are shallow water extraclasts with dasycladalean algae (Diplopora annulatissima Pia), benthic foraminifers, “Tubiphytes” and problematic organisms commonly described from Anisian carbonate platforms. Upward a well-bedded succession of dark-gray Daonella -bearing calcilutites follows. The presence of the bivalve Daonella tyrolensis Mojsisovics in a Lumachella bed from the upper part of the calcilutites can be related to the ammonoid Protrachyceras longobardicum Zone, upper Ladinian in age (lower Longobardian). Upward a sharp contact(decollement?) with the typical sediments of the Mufara Formation can be observed. A re-sampling of the Daonella -bearing calcilutites for conodont investigation has been carried out in order to better constrain the age of this succession. The distribution of conodont species such as Budurovignathus hungaricus (Kozur & Végh), B. mungoensis (Diebel) and Paragondolella trammeri (Kozur) among other conodonts, permits the correlation of the succession to the P. gradleri and P. archelaus ammonoid Zones, extending downwards the age of the calcilutites at Sant’Otiero to the upper Fassanian. This confirms that the Sant’Otiero succession is a key section to document Ladinian pelagic carbonate sedimentation in the westernmost termination of the Ionian Tethys.
In this study we present the results of a seismic-stratigraphic analysis of sub-bottom profiles in the north-westernmost area of the Malta Plateau in order to define the depositional mechanisms for ...the upper Quaternary sequences. During this interval the morphology of the Malta Plateau was characterized by a ramp and bathymetries not exceeding 200 m. Two major unconformities, related to MIS 6 and MIS 2 (the latter corresponding to the Last Glacial Maximum, LGM), characterize the upper Quaternary sequences. The geometries of the recognized seismic units indicate as depositional mechanisms were controlled by subsidence and sea-level fluctuations. In detail, deposits related to the last glacial event were recognized through their seismic pattern and have been interpreted as formed by the interaction between tide and wave dynamics. Contrary to the northern Sicilian continental margin, in the Malta Plateau ramp no LGM-related lowstand prograding wedge was recognized due to the absence of an effective shelf edge. It is considered as a consequence of the morphology and the dominant deposition processes in the Malta Plateau. Afterwards the ramp morphology allowed a rapid drowning of the Malta Plateau instead with the formation and preservation of transgressive deposits revealed as bedforms. The highstand deposits appear as prograding bodies and have been classified as infralittoral prograding wedge.
•In the Malta Plateau ramp, during Middle Pleistocene-Holocene, the regressive deposits occur as bedforms related to wave and tide dynamics.•During the last transgressive phase, the tidally-influenced sedimentation allows the formation of sand sheet deposits.•The highstand deposits formed prograding bodies comparable to the infralittoral prograding wedge.•Relict sand deposits represent potential offshore borrow area for beach nourishment and extraction of mineral resources.
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