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The application of Ground Penetrating Radar (GPR) prospecting to the search of fossil structures, particularly using advanced techniques like Finite-difference time-domain (FDTD) modelling and GPR attribute analysis, is currently poorly exploited in paleontology. Here, we promote the use of such a GPR workflow at Bargiano (Umbria, central Italy), a unique paleontological site known for the discovery of cetacean skeletons, dolomitized sperm-whale cololites (Ambergrisichnu salleronae), and layered fossil assemblages. The study site is characterized by a very uneven topography shaping highly conductive clayey deposits, representing not exactly ideal conditions for GPR surveying. After generating models encompassing a real topography and variable electrical properties of media, we simulated buried fossil structures at variable depth with different size and geometry, using different operative frequencies. After obtaining information on the characteristics of reflections, investigation depth, and detectability, we provide a comparison with experimental data, also used to compute instantaneous amplitude and phase attributes. Upon depicting a peculiar GPR signature for our targets, we discuss the results in light of ground-truthing performed through trenching. Our workflow allowed us to restrict the excavation areas, extending the surface information in depth in a non-invasive way, and optimizing the field operations, necessary for the preservation of the study site.

The latest Triassic was an interval of prolonged biotic extinction culminating in the end-Triassic Extinction (ETE). The ETE is now associated with a perturbation of the global carbon cycle just before the end of the Triassic that has been attributed to the extensive volcanism of the Circum-Atlantic Magmatic Province (CAMP). However, we attribute the onset of declining latest Triassic diversity to an older perturbation of the carbon cycle (delta13Corg) of global extent at or very close to the Norian/Rhaetian boundary (NRB). The NRB appears to be the culmination of stepwise biotic turnovers that characterize the latest Triassic and includes global extinctions of significant marine and terrestrial fossil groups. These biotic events across the NRB have been largely under- appreciated, yet together with a coeval disturbance of the carbon cycle were pivotal in the history of the Late Triassic. Here, we present new and published delta13Corg data from widespread sections (Italy, Greece, ODP, Australia, New Zealand, USA, Canada). These sections document a previously unknown perturbation in the carbon cycle of global extent that spanned the NRB. The disturbance extended across the Panthalassa Ocean to both sides of the Pangaean supercontinent and is recorded in both the Northern and Southern Hemispheres. The onset of stepwise Late Triassic extinctions coincides with carbon perturbation (delta13Corg) at the NRB, indicating that a combination of climatic and environmental changes impacted the biota at a global scale. The NRB event may have been triggered either by gas emissions from the eruption of a large igneous province pre-dating the NRB, by a bolide impact of significant size or by some alternative source of greenhouse gas emissions. As yet, it has not been possible to clearly determine which of these trigger scenarios was responsible; the evidence is insufficient to decisively identify the causal mechanism and merits further study.

The Global Boundary Stratotype Section and Point (GSSP) of the Jurassic–Cretaceous boundary (JKB) is the last among the GSSPs in the Phanerozoic to be chosen. The Berriasian Working Group of the International Subcommission on Cretaceous Stratigraphy decided in 2016 to use the base of the Calpionella alpina Subzone as the primary marker for the formal definition of the JKB. This definition is satisfactorily applicable for near continent, shallow offshore deposits within the Western Tethys, North Atlantic and central-south America. Unfortunately, the primary marker taxon cannot be found in the Pacific and circum-Pacific regions since the distribution of calpionellids is limited to the Western Tethys and neighboring regions. Radiolarians are good candidates for defining the JKB, because they are widespread and can be found both in shallow and deep pelagic sedimentary facies worldwide. We carried out detailed field observations and careful sample collections in a 5-m thick interval around the JKB in the Bosso Valley section (Northern Apennines), which is one of potential candidates for GSSP of the JKB. The Maiolica Formation, which includes the JKB, is characterized by white to light gray, well-bedded micritic limestones with abundant light gray to black chert layers and nodules. In this study, after selection of samples acid-etched in the field, we observed the etched surface with a scanning electron microscope in the laboratory. Our detailed observations revealed that both micritic limestone and chert generally contain abundant radiolarian tests. Most of them in limestones are replaced by calcite, so that it is impossible to isolate radiolarian tests from rock samples with acid treatment. On the other hand, radiolarian tests within chert layers or nodules are too recrystallized to preserve their original surface ornamentation. The best preserved radiolarian tests are included in micritic limestone near chert layer or nodules. Careful and systematic sampling enabled us to get enough material to establish phylogenetic analysis on radiolarians.

Rich and well preserved radiolarian assemblages from the Middle Triassic radiolarian cherts of the Monte Facito Formation, Lagonegro succession (Southern Apennines, Italy), contain new Late Anisian taxa. These radiolarian cherts represent the oldest deep-water sediments of the Lagonegro Basin, representing pelagic conditions since the Late Anisian. Six new species are here described: Tiborella tribullata , Baratuna lucana , Hozmadia lagonegroensis , Hozmadia (?) simplex , Bulbocyrtium multiporatum , Planispinocyrtis curta .

The base of the Rhaetian stage (Norian/Rhaetian boundary, NRB) is still awaiting formal designation by the International Commission on Stratigraphy. At present, only the 4.30-m-thick Steinbergkogel section (Austria) has been proposed as GSSP (Global Stratotype Section and Point) candidate for the base of the Rhaetian. Here we present data from the 63-m-thick Pignola-Abriola section (Southern Apennines, Italy) that we consider an alternative candidate for the Rhaetian GSSP. The Pignola-Abriola basinal section, represented by hemipelagic-pelagic carbonate successions belonging to the Lagonegro Basin, matches all the requirements for a GSSP: 1, it is well exposed with minimal structural deformation; 2, it is rich in age diagnostic fossils (e.g. conodonts and radiolarians); 3, it yields a geochemical record suitable for correlation (e.g. d13Corg/carb); and 4, it has a robust magnetostratigraphy and is correlated with the Newark APTS for age approximation of the NRB and additional Rhaetian bioevents. In the Pignola-Abriola section, we opt to place the NRB at the 44.4 metre level, coincident with a prominent negative shift of ca. 6& of the d13Corg. This level is located 50 cm below the FAD of conodont Misikella posthernsteini s.s within the radiolarian Proparvicingula moniliformis Zone. Both the negative d13Corg shift and the FAD of Misikella posthernsteini occur within Pignola-Abriola magnetozone MPA-5r, at ~205.7 Ma, according to magnetostratigraphical correlation to the Newark APTS. We also illustrate the coeval Mt. Volturino stratigraphical section deposited below the calcite compensation depth (CCD) within the same Lagonegro Basin and characterized by a detailed radiolarian biostratigraphy and strong d13Corg negative shift around the NRB.

Comparison of radiolarian assemblages from marls in the Gorgo a Cerbara section in the Umbria–Marche Basin in central Italy and a siliceous sequence (BB1 section) near Babazhadong in southern Tibet indicates similar faunas comparable to those in the Aurisaturnalis carinatus zone and the Turbocapsula costata zone. Several significant species, Archaeodictyomitra lacrimula (Foreman), A. excellens (Tan Sin Hok), Dictyomitra communis (Squinabol), and Aurisaturnalis carinatus perforatus Dumitrica and Dumitrica-Jud, which are common in older strata, make their last occurrences near the base of the Turbocapsula costata zone in these two areas. Comparison with the Gorgo a Cerbara section provides an accurate age constraint for the siliceous succession in southern Tibet, which contains no fossils other than radiolarians. The comparison indicates a close connection between the western and eastern Tethys during the Barremian to early Aptian. The correlation testifies that the radiolarian zonation in southern Tibet is applicable for the whole Tethys. The siliceous succession in BB1 section encompasses the early Aptian Oceanic Anoxic Event 1a (OAE 1a). The early Aptian OAE 1a is located in the upper part of the Aurisaturnalis carinatus perforatus subzone. The first occurrence biohorizon of the genus Turbocapsula and the evolutionary first appearance biohorizon of T. costata costata (Wu) are useful markers for constraining the OAE 1a in the Tethys.

New biostratigraphic data from two stratigraphic sections (Mt. St. Enoc and Mt. Volturino), of the Lagonegro Basin (Southern Apennines, Italy), define the age of the sedimentary events and delineate the sedimentary evolution for the Norian-Rhaetian time interval. The upper part of the Calcari con Selce Fm in the Mt. St. Enoc section is characterized by an alternation of cherty limestones rich in organic matter and thin silicified calcarenites with black cherty layers. The upper part of the Calcari con Selce Fm of the Mt. Volturino section exhibits instead intermediate characters between the Calcari con Selce and Scisti Silicei Fms, with cherty limestones, shales and radiolaritic beds. The biostratigraphic data based on conodonts and radiolarians allowed a good correlation among the Norian-Rhaetian successions throughout the Lagonegro Basin the two sections represent two different environments of the Lagonegro Basin. In fact, radiolarites (Scisti Silicei Fm) are present from the Misikella hernsteini-Parvigondolella andrusovi conodont Zone (late Sevatian) in the Mt. Volturino section while they appeared after the Misikella ultima conodont Zone (uppermost Rhaetian) in the Mt. St. Enoc section. This proves that euxinic carbonate facies and radiolaritic facies were deposited in the same time interval and in the same basin. On the basis of sedimentological analysis and with the support of biostratigraphy, the non-coeval beginning of biosiliceous sedimentation is discussed in order to point out the control factors: different paleobatimetry, upwelling areas or volcanic activity. Our preliminary results show that the Lagonegro Basin during the Norian-Rhaetian interval was probably characterized by an articulated physiography and that volcanism should have had an important role in changing pelagic sedimentation.

Giordano, N., Rigo, M., Ciarapica G. & Bertinelli A. 2010: New biostratigraphical constraints for the Norian/Rhaetian boundary: data from Lagonegro Basin, Southern Apennines, Italy. Lethaia. 10.1111/j.1502-3931.2010.00218.x. Four stratigraphic sections belonging to Lagonegro succession (Southern Apennines) at Mt S. Enoc, Pignola-Abriola, Sasso di Castalda and Mt Volturino have been studied in detail under to provide a new micro-palaeontological data set based on conodonts and radiolarians for the characterization of the Norian/Rhaetian interval. The studied sections represent the different settings of the Lagonegro Basin (from proximal to distal facies) and permit a detailed, integrated, biostratigraphy of the Calcari con Selce (cherty limestones) and Scisti Silicei formations (bedded cherts with radiolarians) to be drawn up. The upper portion of the Calcari con Selce Formation, exhibits intermediate characteristics between the Calcari con Selce and Scisti Silicei Formation, in particular the progressive decrease in carbonate content against an increase in shales and cherts. Within the four sections studied, the Norian/Rhaetian interval has been documented both with conodonts and radiolarians. Because of the continuity and the absence of condensed facies, it has been possible to recognize the morphocline between species Misikella hernsteini and Misikella posthernsteini, here represented by all the transitional forms characterized by common features between the two species, gathered in three evolutionary steps. Moreover, the morphocline between M. hernsteini and M. posthernsteini has been involved in the definition of the Norian/Rhaetian Boundary, recognizing thus the FAD of M. posthernsteini, one of the possible biomarkers proposed for the boundary. The rich, well-preserved, radiolarian associations of Pignola-Abriola, Sasso di Castalda and Mt Volturino permit the correlation of Tethyan and American conodont successions, highlighting the importance of the mostly coincident occurrences of M. posthernsteini and Epigondolella mosheri morphotype A, which correspond to the base of Proparvicingula moniliformis A. Z. and the disappearance of bivalve Monotis. These coincident bioevents are used here to define the base of the Rhaetian stage. □Biostratigraphy, conodonts, Lagonegro Basin, Late Triassic, Norian/Rhaetian boundary, radiolarians.