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The detailed study of diatom laminations conducted by means of backscattered electron imaging serves as tool to unravel details of past ocean dynamics. In this paper we apply this method to the analysis of the diatomites of Cerro Los Quesos, Upper Miocene Pisco Fm, Peru. Numerous studies have been conducted on the Pisco Fm; however, a focus on its paleoceanographic significance is still lacking. In this work, we provide information on the oceanographic setting in the area at the time of diatomites deposition. The high abundance of deep‐living Coscinodiscus laminae, proceeded by either a mixed lamina or a terrigenous one, let us hypothesize a deep position of the thermocline during the deposition of the Pisco diatomites; together with the scarcity of Chaetoceros Hyalochaete spp. resting spores, this evidence confutes the belief that equals high biogenic silica content in marine sediments with enhanced upwelling. Conversely, the depositional setting of the Pisco Fm diatomites is more similar to what is known as "permanent El Niño" (or "El Padre") state, meaning a constant weakened upwelling (or upwelling of nutrients‐poor waters). Climate modeling warns that an increase in atmospheric CO2 may lead to this mean state in the near future. Thanks to this study we also obtained refined information on the diatomites sedimentations rates. The comparison of the Pisco diatomites sedimentation rates with those of Quaternary diatomites gave strength to the hypothesis that the formation of the vertebrate Lagerstätte may have been enhanced, among others, by the so‐called "impact‐burial" mechanism. Plain Language Summary: Some sedimentary rocks are formed by the remains of small organisms. This is the case of diatoms, microscopic algae with a siliceous exoskeleton. As we know the ecological conditions of the modern oceans in which different diatom species live, when we found them in sedimentary rocks, we can infer the ecological conditions of the oceans millions of years ago. Here, we present the species that we found in some Peruvian rocks, the so‐called Pisco Formation, which dates back to 7/6 Million of years ago. Different species are preserved in these rocks in the same order in which they bloomed, so that we can identify small "laminae" (horizontal strips in the rock with thicknesses smaller than 1 mm) for each blooming season. The species that we recognize are those that today bloom during "El‐Niño," a climatic warm condition that causes loss of large fishery stocks, inundations and droughts. This small finding helps us hypothesize how climate may evolve if the Earth's temperatures keep on rising. Also, the Pisco formation is famous because of their huge content of fossil whales and dolphins, thus the study of this rock helps us understand how these large mammals got preserved trough millions of years. Key Points: Laminae of the Upper Miocene diatomaceous Pisco Formation reveal that the fall dump mechanism regulated marine export productionThe predominance of fall dump over upwelling implies a drop of the temperature gradient between the Western and Eastern PacificEvidences highlight a need of caution when using biogenic silica as a proxy for paleo upwelling [ABSTRACT FROM AUTHOR]

Recent restoration work on Pisa Cathedral provided the opportunity for a multidisciplinary analysis of the monument that identified interesting aspects of its history, preservation, and structural safety. In particular, the study of the matroneum provided clues about the role of the structures in the well-known fire that occurred in 1595. Alteration patterns and damage forms on the stone masonry walls were analysed to better understand their relationship with this catastrophic event. The investigation of the stone specimens enabled textural and mineralogical features typical of fire damage to be identified on the surface. The evidence of fire also provided a terminus ante quem to correctly interpret and diachronically date a damage pattern consisting of cracks in the eastern arch supporting the dome. The cracks were likely to have been induced by a soil consolidation phenomenon related to the renowned leaning of the Pisa tower, centuries before the fire. [ABSTRACT FROM AUTHOR]

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The Miocene Pisco Formation, broadly exposed in the Ica Desert of southern Peru, is among the most outstanding Cenozoic marine Fossil-Lagerstätten worldwide. It is renowned for its exceptional preservation and abundance of vertebrate fossils, including a rich assemblage of whales and dolphins (Cetacea). Here, we integrate taphonomic data on 890 marine vertebrate fossils, gathered through 16 different localities. Our observations range from the taxonomic distribution, articulation, completeness, disposition and orientation of skeletons, to the presence of bite marks, associations with shark teeth and macro-invertebrates, bone and soft tissue preservation, and the formation of attendant carbonate concretions and sedimentary structures. We propose that the exceptional preservation characterising many Pisco vertebrates, as well as their exceptionally high abundance, cannot be ascribed to a single cause like high sedimentation rates (as proposed in the past), but rather to the interplay of several favourable factors including: (i) low levels of dissolved oxygen at the seafloor (with the intervention of seasonal anoxic events); (ii) the early onset of mineralisation processes like apatite dissolution/recrystallisation and carbonate mineral precipitation; (iii) rapid burial of carcasses in a soupy substrate and/or a novel mechanism involving scour-induced self-burial; and (iv) original biological richness. Collectively, our observations provide a comprehensive overview of the taphonomic processes that shaped one of South America's most important fossil deposits, and suggest a model for the formation of other marine vertebrate Fossil-Lagerstätten. [ABSTRACT FROM AUTHOR]

The pyroclastic rocks belonging to the Late Eocene-Miocene volcanic activity that occurred in Sardinia between 38 and 15 Ma ago were widely used as construction materials in several Romanesque churches of the easternmost Logudoro area, as well as in large parts of the Sardinia territory. In this work, the ancient Cathedral of Nostra Signora di Castro (twelfth century) was taken as a representative case study. There is no historical or archaeological evidence of ancient quarries. Based on the geochemical, petrographic, and volcanological data on several samples from an extensive field area (approximately 150 km2), a geographical zoning of the volcanics has been recognised. In the Oschiri sector, there are three different sub-zones, which can be identified with different volcanic rocks: less fractionated rocks (Differentation Index ∼70–78); intermediately fractionated rocks (D.I. ∼76–79); and more fractionated rocks (D.I. ∼77–82). To identify the origin of the ignimbrite rocks of the Church of Nostra Signora di Castro, two statistical methods were used: stepwise linear discriminant and canonical analysis. Moreover, to define the geochemical transformation processes induced by the alteration, a comparative study of concentrations of major and trace elements measured by XRF and SEM-EDX analyses on the surface portion and the innermost areas of the stone was made. [ABSTRACT FROM AUTHOR]

Field mapping and sedimentological study of outcrop sections exposed along the Ica River valley permitted the establishment of a regional allostratigraphic framework for the upper Miocene portion of the Pisco Formation. The stratigraphy of the studied interval is illustrated using a new 1:20,000-scale geological map which reveals that this formation is a cyclical sedimentary succession composed of three fining-upward allomembers. The bounding surfaces defining each allomember are transgressively modified subaerial unconformities. They converge and merge landward into a single composite surface representing the time-transgressive lower boundary of the Pisco Formation. Accordingly, the extent of the stratigraphic gap associated with the basal unconformity varies significantly throughout the basin and increases toward the basin margins. The timing of allomember-bounding surfaces coincides with that of major oxygen-isotope maxima in the deep-sea oxygen isotopic record and matches the ages of eustatic sequence boundaries identified elsewhere, indicating glacio-eustatic falls due to the growth of Antarctica ice sheets as a viable mechanism for their development. [ABSTRACT FROM AUTHOR]

Baleen is a comb-like structure that enables mysticete whales to bulk feed on vast quantities of small prey, and ultimately allowed them to become the largest animals on Earth. Because baleen rarely fossilises, extremely little is known about its evolution, structure and function outside the living families. Here we describe, for the first time, the exceptionally preserved baleen apparatus of an entirely extinct mysticete morphotype: the Late Miocene cetotheriid, Piscobalaena nana, from the Pisco Formation of Peru. The baleen plates of P. nana are closely spaced and built around relatively dense, fine tubules, as in the enigmatic pygmy right whale, Caperea marginata. Phosphatisation of the intertubular horn, but not the tubules themselves, suggests in vivo intertubular calcification. The size of the rack matches the distribution of nutrient foramina on the palate, and implies the presence of an unusually large subrostral gap. Overall, the baleen morphology of Piscobalaena likely reflects the interacting effects of size, function and phylogeny, and reveals a previously unknown degree of complexity in modern mysticete feeding evolution. [ABSTRACT FROM AUTHOR]

The sequence stratigraphic framework and a summary of the fossil fauna of the Upper Miocene portion of the Pisco Formation exposed along the western side of the Ica River (southern Peru) is presented through a new geological map encompassing an area of about 200 km2 and detailed chronostratigraphic analyses. Extensive ield mapping and sedimentological study of outcrop sections have shown that the Pisco Formation is a cyclical sediment unit composed of at least three ining-upward, unconformity-bounded depositional sequences, designated P0, P1, and P2 from oldest to youngest. In the study area, these sequences progressively onlap a composite basal unconformity from southwest to northeast. Integration of biostratigraphic and tephrochronologic age determinations constrains the ages of the three Pisco sequences within the study area. Based on the age of surrounding sediments, a conservative estimate of the age of P0 suggests deposition of these strata between 17.99 ± 0.10 Ma and 9.00 ± 0.02 Ma, whereas diatom biostratigraphy and calculated 40Ar/39Ar ages converge to indicate that strata of the P1 sequence were deposited sometime between 9.5 Ma and 8.9 Ma and that those of the P2 sequence are younger than 8.5 Ma and older than 6.71 ± 0.02 Ma. Our survey for both vertebrate and macro-invertebrate remains in the three sequences conirms the outstanding paleontological value of the Pisco Formation and contributes to depict regional faunal shifts in the fossil assemblage. [ABSTRACT FROM AUTHOR]

Exceptionally preserved delicate baleen microstructures have been found in association with the skeleton of a late Miocene balaenopteroid whale in a dolomite concretion of the Pisco Formation, Peru. Microanalytical data (scanning electron microscopy, electron probe microanalysis, X-ray diffraction) on fossil baleen are provided and the results are discussed in terms of their taphonomic and paleoecological implications. Baleen fossilization modes at this site include molding of plates and tubules, and phosphatization. A rapid formation of the concretion was fundamental for fossilization. We suggest that the whale foundered in a soft sediment chemically favorable to rapid dolomite precipitation, allowing the preservation of delicate structures. Morphometric considerations on the baleen plates and bristles coupled with the reconstructed calcification of the latter permit speculation on the trophic preferences of this balaenopteroid whale: the densely spaced plates and the fine and calcified bristles provide evidence for feeding on small-sized plankton, as does the modern sei whale. [ABSTRACT FROM AUTHOR]

One-hundred and ninety-two fossil marine vertebrate specimens, preserved as bone elements cropping out at Cerro Los Quesos (Pisco Basin, Peru), are identified and reported on a 1:4,000 scale geological map and in the corresponding stratigraphic section. All the fossils originate from the Pisco Formation, which is dated in this area to the late Miocene (from 7.55 Ma to ≥6.71 Ma, based on40Ar/39Ar analyses of three volcanic ash layers along the section). Specimens are particularly concentrated near the top of the two main hills, where the geologically youngest portion of the examined section crops out. The impressive fossil assemblage includes cetaceans (91.6%), represented by mysticetes (balaenopteroids and cetotheriids) and odontocetes (phocoenids, physeteroids, and ziphiids, including the holotype ofNazcacetus urbinai). Seals, a crocodile, a seabird, bony fish, and sharks are also reported. Isolated large teeth ofCarcharoclesandCosmopolitodusare common and, in several instances, associated to mysticete skeletons. Together with a similar work recently published for the other late Miocene locality of Cerro Colorado, this work represents a case study for the detailed inventory of the extraordinary paleontological heritage of the Pisco Basin. As such, it constitutes the basis for future taphonomic, paleoecological, and systematic studies, as well as for a much-needed conservation effort. [ABSTRACT FROM PUBLISHER]

Hundreds of fossil marine vertebrates cropping out at Cerro Colorado (Pisco Basin, Peru) are identified and reported on a 1:6500 scale geological map and in a joined stratigraphic section. All the fossils are from the lower strata of the Pisco Formation, dated in this area to the late middle or early late Miocene. They are particularly concentrated (88%) in the stratigraphic interval from 40 to 75 m above the unconformity with the underlying Chilcatay Formation. The impressive fossil assemblage includes more than 300 specimens preserved as bone elements belonging mostly to cetaceans (81%), represented by mysticetes (cetotheriids and balaenopteroids) and odontocetes (kentriodontid-like delphinidans, pontoporiids, ziphiids, and physeteroids, including the giant raptorial sperm whaleLivyatan melvillei). Seals, crocodiles, sea turtles, seabirds, bony fish, and sharks are also reported. Isolated large teeth ofCarcharoclesandCosmopolitodusare common throughout the investigated stratigraphical interval, whereas other shark teeth, mostly of carcharinids, are concentrated in one sandy interval. This work represents a first detailed census of the extraordinary paleontological heritage of the Pisco Basin and the basis for future taphonomic, paleoecological, and systematic studies, as well as a much needed conservation effort for this extremely rich paleontological site. [ABSTRACT FROM PUBLISHER]

Volcanic activity focuses along plate boundaries. However, large volcanoes are also found in intraplate settings. For these volcanoes, geodynamic processes responsible for magma generation and structural controls on magma rise and extrusion need to be evaluated. We merge original (field and remote sensing) and available (geodetic, geophysical, and petrological) data to consider the tectono-magmatic relationships of three large intraplate volcanoes in the E-Anatolian-Iranian plateau; Sar'akhor (NE Iran), Damavand (Central Alborz) and Ararat (E Anatolia). In NE Iran, a Miocene-Pliocene NW-trending compression activated E-W dextral faults to the NW of Sar'akhor and N-S sinistral faults to the SE, creating an extruding wedge to the west of this volcano. Since Quaternary, NE-trending compression inverted fault movement, hindering further block extrusion and volcanism terminated. The adakitic composition of the Sar'akhor rocks suggests post-collisional melting of oceanic slab and/or mafic lower crust, possibly triggered by an asthenospheric rise after slab break-off or intramantle delamination. For the active Damavand and Ararat volcanoes, available data suggest magma generation due to rising hot asthenosphere, following lithospheric delamination or slab break-off in a transtensional environment. The features common to Sar'akhor, Damavand and Ararat allow proposing a model, where transtension focuses the rise of magma in intraplate settings overlying hot asthenosphere produced by delamination or slab break-off. [ABSTRACT FROM AUTHOR]

The northward-flowing Humboldt Current hosts perpetually high levels of productivity along the western coast of South America. Here, we aim to elucidate the deep-time history of this globally important ecosystem based on a detailed palaeoecological analysis of the exceptionally preserved middle–upper Miocene vertebrate assemblages of the Pisco Formation of the East Pisco Basin, southern Peru. We summarise observations on hundreds of fossil whales, dolphins, seals, seabirds, turtles, crocodiles, sharks, rays, and bony fishes to reconstruct ecological relationships in the wake of the Middle Miocene Climatic Optimum, and the marked cooling that followed it. The lowermost, middle Miocene Pisco sequence (P0) and its vertebrate assemblage testify to a warm, semi-enclosed, near-shore palaeoenvironment. During the first part of the Tortonian (P1), high productivity within a prominent upwelling system supported a diverse assemblage of mesopredators, at least some of which permanently resided in the Pisco embayment and used it as a nursery or breeding/calving area. Younger portions of the Pisco Formation (P2) reveal a more open setting, with wide-ranging species like rorquals increasingly dominating the vertebrate assemblage, but also local differences reflecting distance from the coast. Like today, these ancient precursors of the modern Humboldt Current Ecosystem were based on sardines, but notably differed from their present-day equivalent in being dominated by extremely large-bodied apex predators like Livyatan melvillei and Carcharocles megalodon. [ABSTRACT FROM AUTHOR]

The eruptive products of the last 1000 years at La Fossa volcano on the island of Vulcano (Italy) are characterized by abrupt changes of chemical composition that span from latite to rhyolite. The wide variety of textural features of these products has given rise to several petrological models dealing with the mingling/mixing processes involving mafic-intermediate and rhyolitic magmas. In this paper, we use published whole-rock data for the erupted products of La Fossa and combine them in geochemical and thermodynamic modelling in order to provide new constrains for the interpretations of the dynamics of the active magmatic system. The obtained results allow us to picture a polybaric plumbing system characterized by multiple magma reservoirs and related crystal mushes, formed from time to time during the differentiation of shoshonitic magmas, to produce latites, trachytes and rhyolites. The residing crystal mushes are periodically perturbated by new, fresh magma injections that, on one hand, induce the partial melting of the mush and, on the other hand, favor the extraction of highly differentiated interstitial melts. The subsequent mixing and mingling of mush-derived melts ultimately determine the formation of magmas erupted at La Fossa, whose textural and chemical features are otherwise not explained by simple assimilation and fractional crystallization models. In such a system, the compositional variability of the erupted products reflects the complexity of the physical and chemical interactions among recharging magmas and the crystal mushes. [ABSTRACT FROM AUTHOR]

Invertebrate taphonomy can provide significant information about the post-mortem processes that affected the fossil record. In the East Pisco Basin of southern Peru, a Panopea Ménard de la Groye, 1807 shell bed was found in the upper Miocene strata of the Pisco Formation, hinting at a peculiar biostratinomic and diagenetic history. This bed contains abundant invertebrate fossil molds cemented by dolomite. The specimens of the deep infaunal bivalve, Panopea sp., occur together with bivalves representative of shallow infaunal species (Trachycardium sp. and Dosinia ponderosa [Gray, 1838]) and balanid barnacles, which are sessile encrusters. The Panopea specimens host compound molds evidencing an abundant encrusting fauna, including serpulids, ?foraminifera, bryozoans, and barnacles that colonized the inner surfaces of the valves before their final burial. We hypothesize that short-term, storm-related processes exhumed the living bivalves, resulting in a sedimentological concentration of relatively well-preserved shells. After the death of the exhumed bivalves, the inner surfaces of the articulated Panopea shells, representing hard-substratal, sheltered environments on an otherwise unstable sandy seafloor (i.e., "benthic islands"), were colonized by different encrusting organisms. Following the final burial, dolomite precipitated, cementing the sediment infill of the valves. Lastly, a decrease of pH occurred at the sulfate reduction-methanogenesis boundary, inducing the dissolution of the shell carbonate. [ABSTRACT FROM AUTHOR]

The Danakil depression marks a progressive change from continental rifting in Afar to seafloor spreading further north in the Red Sea. Extension and volcanism in this incipient spreading centre is localised to the ~70-km-long, 20-km-wide active Erta Ale volcanic segment. Here, we combine remote sensing and major element geochemical analysis to determine the structure and composition of three volcanoes on the Erta Ale Volcanic Segment: the Alu dome, the Dalafilla stratovolcano and the Borale stratovolcano. We investigate the evolution and compositional variation within and between these volcanic complexes. Our results show that most flows are sourced from scoria cones and fissures, representing in total 15 phases of volcanism that occurred within four major eruptive stages, most likely occurring in the last 80 thousand years (kyr). The first stage represents large-scale fissure volcanism, comprising submarine basaltic phases. Stage two involves basaltic fissure volcanism around Alu. The third stage is dominated by trachy-andesite to rhyolitic volcanism from the volcanic edifices of Alu, Dalafilla and Borale and the fourth by a resumption of small-scale basaltic/trachybasalt fissure systems. Geochemical modelling indicates a paucity of crustal assimilation and mixing within the sub-volcanic magmatic system. Spatial analysis of volcanic cones and fissures within the area indicate the presence of a cone sheet and ring faults. The fissures are likely fed by sills connecting the magma source with the volcanic edifices of Alu and Borale. Our results reveal the cyclic nature of both eruption style and composition of major volcanic complexes in rift environments, prior to the onset of seafloor spreading. • Alu-Dalafilla and Borale have had four main eruptive stages in their evolution. • Activity is dominated by fissure eruptions producing basaltic lavas. • Intermediate and felsic activity occurred at all three volcanic centres. • Modelling shows compositions can be achieved through fractional crystallisation. • Radial fissures, dykes and curvilinear faults suggest changing magma pressures. [ABSTRACT FROM AUTHOR]