Bollettino SPI Vol. 58 (1) - OPEN ACCESS!
Environmental perturbations and biotic responses in the history of life: an Italian perspective
Published in June 2019
- Erwin D.H. (2019)
Crisis and Response: Current Trends and Future Prospects
New technologies have continuously expanded the questions palaeontologists and other geologists can explore about mass extinctions, biodiversity crises and the subsequent biotic rebounds. From international correlations in the 1950s, to stable isotopes, high- resolution geochronology and modeling efforts, mass extinctions have been revealed as more sudden in timing and often more catastrophic in extent than had been recognised. These and other tools are now being applied to understanding the dynamics of recovery after mass extinctions, which have been revealed to be quite complex. As the spatial and temporal resolution increases palaeontologists have increasingly been able to interrogate the ecological dynamics of these events, a trend that seems likely to expand in the future.
- Posenato R. (2019)
The end-Permian mass extinction (EPME) and the Early Triassic biotic recovery in the western Dolomites (Italy): state of the art
The Dolomites (Southern Alps, Italy) represent a key-area to study the biotic and environmental events connected to the end-Permian mass extinction (EPME) and the Early Triassic biotic recovery of shallow-marine ecosystems. Geological and palaeontological researches on these events began since in the early 19th century. The contributions of these studies to the stratigraphic setting, dating, intensity, pattern and causes of the EPME and Early Triassic biotic recovery are outlined herein. After almost two centuries of research, our present undestanding suggests the following multi-steps scenario. The EPME occurred during a short extinction interval, which started at the base of transgressive oolitic beds of the Tesero Member (Werfen Formation, latest Changhsingian). The early phase lasted only a few millennia. It caused a dramatic drop of fossil abundance and diversity and the extinction of about 65% of existing genera, including the large-sized brachiopods and molluscs. The second phase affected the sparse stenotopic marine organisms, most had survived within microbial communities, and finished just above the Permian/ Triassic boundary a few thousand years after the first phase. Stressed environmental conditions, recorded by low diversified benthic assemblages dominated by disaster taxa, lasted up to the lower Olenekian Campil Member (Werfen Fm.). The early biotic recovery phase, recorded by the reappearance of stenotopic organisms and an increase in biodiversity occurred about 1.3 Myr after the EPME witnessed in the Tirolites cassianus beds of the Val Badia Member.
- Preto N., Bernardi M., Dal Corso J., Gianolla P., Kustatscher E., Roghi G. & Rigo M. (2019)
The Carnian Pluvial Episode in Italy: History of the research and perspectives
The Carnian Pluvial Episode (CPE) was a perturbation of the Late Triassic climate that had a strong impact on marine and terrestrial ecosystems. The CPE is still a relatively neglected episode if compared to the other global ecosystem turnovers of the Mesozoic. Nevertheless, the CPE is synchronous with a major biological turnover, with both extinction among many marine and terrestrial groups and, remarkably, one of the most important evolutionary phases in the entire history of Life. The first significant radiation of dinosaurs, the spread of conifers and bennettitaleans, the first common occurrence of calcareous nannofossils, and the first reefs built by scleractinian corals all occurred during or soon after the CPE. Furthermore, the first common occurrence of amber dates to the CPE. Ammonoids and conodonts, the two most important groups for the biostratigraphy of the Triassic, were also subject to a significant turnover. Many localities in Italy had a primary role for the understanding of the CPE, and still represent benchmarks for new studies. Some of these localities are paradigmatic examples of the geological and biotic processes that were occurring during this interval of geologic time, and should be designated as geosites. While recent studies on the CPE focused on identifying the episode globally, and far from the best studied regions of Western Tethys and the European continent, the Italian CPE localities could still provide a wealth of information on this event, especially concerning the evolution of shallow marine and terrestrial groups. Indeed, the best deep-water record of the CPE (Pignola, Basilicata), the most expanded and complete shallow water successions (Raibl area, Friuli-Venezia Giulia), the most prolific amber sites and the best preserved reef associations (Dolomites, Veneto) all occur in Italy.
- Erba E., Bottini C., Faucher G., Gambacorta G. & Visentin S. (2019)
The response of calcareous nannoplankton to Oceanic Anoxic Events: The Italian pelagic record
Earth history is punctuated by phases of extreme global stress of concurrent warming, ocean fertilisation and acidification that impacted biologic diversity and function. Under excess CO2 and greenhouse conditions, the Mesozoic deep ocean became temporarily depleted of oxygen, promoting the accumulation of massive amounts of organic matter during Oceanic Anoxic Events (OAEs). Although global anoxia and enhanced organic matter burial are the most striking and intriguing palaeoceanograhic phenomena, OAEs can be studied also to decipher the oceanic ecosystem response to CO2 pulses. In Jurassic and Cretaceous oceans, calcareous nannoplankton were already common from coastal to open oceanic settings and of enough abundance and diversity to produce calcareous oozes. Indeed, Jurassic and Cretaceous pelagic micrites mainly consist of coccoliths and nannoliths, in addition to variable amounts of diagenetic carbonate. Therefore, pelagic limestones are ideal for epitomising variations in abundance and composition of calcareous phytoplankton at large scale to understand their response to global change. Italian pelagic successions are a reference for the Tethys Ocean and, in general, for low to middle latitudes. We consider herein well-dated sections with quantitative nannofossil data across OAEs to synthesise changes in abundance of the dominant, micrite-forming, nannofossil taxa and species-specific variations in size to trace the response of calcareous nannoplankton as expressed by biocalcification across the early Toarcian T-OAE, late Valanginian Weissert-OAE, early Aptian OAE1a and latest Cenomanian OAE2. In general, a major decrease in nannofossil abundance is recorded for the highly calcified dominant forms, evidenced by the “Schizosphaerella crisis”, the “nannoconid decline” and the “nannoconid crisis” during the T-OAE, Weissert-OAE and OAE1a, respectively. An even more dramatic drop in coccolith/ nannolith abundance characterises OAE2, with a nannoplankton biocalcification “blackout” through the Bonarelli Level in Italian sections. Despite these abundance crises, calcareous nannofloras recovered soon after the paleoenvironmental perturbation terminated, although the return to pre-OAE conditions occurred rather slowly and assemblage composition was renewed across the event. Species-specific changes in size were detected for Schizosphaerella across the T-OAE and for Biscutum constans (Górka, 1957) in the intervals of maximum perturbation within OAE1a and OAE2. Size of Nannoconus steimannii Kamptner, 1931, conversely, does not show variations across the Weissert-OAE and OAE1a. The T-OAE and OAE1a were preceded and accompanied by a few million-year-long origination phase, indicating the calcareous nannoplankton ability to positively respond to and overcome stressing oceanic conditions, as further evidenced by absence of extinctions. Calcareous nannoplankton reacted differently during the Weissert-OAE and OAE2 as the Valanginian “nannoconid decline” is gradual and followed by a symmetric increase in abundance, while the late Cenomanian nannofossil drop in abundance was as sudden as its recovery. In both cases, extinctions are paralleled by entry of new taxa, at a slower rate across the Weissert-OAE and at faster rates in the case of OAE2. The influence of palaeoenvironmental stress on calcareous nannofloral abundance and composition during the early Toarcian T-OAE, late Valanginian Weissert-OAE, early Aptian OAE1a and latest Cenomanian OAE2, are clearly recorded in Italian pelagic sections and at supra- regional to global scale. However, the effects on nannoplankton evolution, if any, was differentiated and resulted in overall originations. Calcareous nannofossil patterns underline the resilience of this phytoplankton group during OAE perturbations.
- Premoli Silva I. (2019)
The Cretaceous/Palaeogene Boundary: Italian souvenirs for the youngest of the “Big Five” extinctions
The aim of this contribution is to provide a brief introduction to the Italian section of the Bottaccione gorge, near Gubbio, and its bearing to the understanding of the end Cretaceous event. I provide an historical account of the main contributions that built the fundamental background knowledge to the famous hypothesis of an extraterrestrial cause for the extinction event, which was originally formulated grounding on observations and specimens collected in this section.
- Montanari A. & Coccioni R. (2019)
The serendipitous discovery of an extraterrestrial iridium anomaly at the Cretaceous-Palaeogene boundary in Gubbio and the rise of a far-reaching theory
It is not so frequent that in a scientific investigation using a deductive approach, an unforeseen result leads to a new hypothesis, which grows stronger through the same deductive approach of investigation, and eventually becomes a theory leading to a paradigm shift. The theory that a catastrophic impact of an extraterrestrial object, a comet or an asteroid, on the Earth caused a global mass extinction at the end of the Cretaceous Period strongly challenged the Lyellian paradigm of gradualism/uniformitarianism. In the 1980s, a nonconformist theory sprouted from the serendipitous discovery of an iridium anomaly in an inconspicuous clay layer marking the Cretaceous-Palaeogene boundary in the pelagic succession of Gubbio and opened the way to forty years of heated debates and thousands of scientific publications in the most disparate fields of Earth and planetary sciences. With this paper, our intention is to recount the scientific background, which led to the formulation of this theory.
- Giusberti L., Capraro L., Luciani V. & Fornaciari E. (2019)
The Italian record of the Palaeocene-Eocene Thermal Maximum
The present paper summarises the state of the art of the studies on Italian Palaeocene-Eocene Thermal Maximum (PETM) records. The PETM (~ 56 Ma) likely represents the most dramatic and rapid event of global climate warming of the whole Cenozoic. During the PETM, temperatures at the Earth’s surface probably increased by at least 5°C over a few thousand years, and remained thereafter exceptionally high for over 100 k.y. Hallmark of the PETM is a negative excursion in stable carbon isotopes globally recognised that is generally interpreted as the response to a massive and sudden input of isotopically light carbon into the ocean-atmosphere system, which eventually gave rise to a rapid and extreme global warming. Climatic perturbations associated with the PETM were severe and affected both the marine and terrestrial domains, triggering faunal and floral turnovers and radiations, migrations and the most dramatic Cenozoic deep-sea benthic foraminiferal extinction event. Since the beginning of the 2000s, insightful contributions to this topic have been provided by the investigations of lower Palaeogene marine Italian records from the Umbria-Marche (Northern Apennines, Italy) and Belluno (Southern Alps, Italy) basins. In particular, crucial reference sections found in Scaglia Rossa-type facies, such as the Contessa, Possagno, Forada and Cicogna sections, have significantly improved our knowledge of the biotic and abiotic events associated to the PETM. Among these, the Forada section (Belluno Basin) was the focus of accurate integrated micropalaeontological (calcareous plankton and benthic foraminifera) and geochemical-stratigraphical studies, which possibly offer the most complete reconstruction across the PETM available in Europe to date.
- Carnevale G., Gennari R., Lozar F., Natalicchio M., Pellegrino L. & Dela Pierre F. (2019)
Living in a deep desiccated Mediterranean Sea: An overview of the Italian fossil record of the Messinian salinity crisis
The events related to the Messinian salinity crisis have been extensively debated since the early 1970s. The spectacular scenario of a completely desiccated Mediterranean subsequently partially occupied by freshwater and brackish endorheic basins triggered a considerable amount of multidisciplinary research for almost five decades. Although the Italian geological record played a crucial role in the origin and complex development of the salinity crisis model, due to the hypothesised palaeobiotic apocalypse, the exploration of the fossil record has been limited or, in certain cases, nearly absent. In this paper, a cursory overview of the Italian fossil record of the Messinian salinity crisis is provided. The integrative analysis of the (primarily) Italian record of microbes, calcareous nannoplankton, dinoflagellates, diatoms, foraminiferans, ostracods, molluscs (and other invertebrates), and fishes reveals the persistence of marine organisms throughout the three stages of the MSC. Moreover, it clearly indicates that a more detailed exploration of the palaeobiological record at a Mediterranean scale is necessary to properly interpret the structure and composition of the biotic communities that inhabited the Mediterranean during the MSC.