Donatella Insinga

Insights into flood-dominated fan-deltas: very high-resolution seismic examples off the Amalfi cliffed coasts, eastern Tyrrhenian Sea

Abstract A high-resolution (IKB-Seistec) seismic survey calibrated with gravity-core data, off the Amalfi coast, a rocky coastal area on the southern side of the Sorrento Peninsula (Italy), documents the internal stratigraphic architecture of a series of small fan-deltas that develop at the mouth of major bedrock streams. The fan-delta system mostly postdates the Plinian eruption of Vesuvius of ad 79 and displays various phases of development associated with periods of high sediment supply from the adjacent river basins. During these periods landscape-mantling loose pyroclastic deposits (mostly air-fall tephra from Vesuvius) were quickly eroded and delivered to the continental shelf by sheet wash and flash flood events. Depositional processes on the foresets were dominated by sediment gravity flows originating from hyperpycnal river flow and pyroclastic fall deposits. This in turn created favourable conditions for sea-floor instability, soft sediment failure, slumping and sliding, which characterize the deltaic stratigraphic architecture. The intermittently increased sediment yield during the various phases of the evolution of the fan-delta system was probably influenced also by the morphoclimatic regime. This may have resulted in varying rates of progradation of the delta foresets, tentatively correlated with the main climatic oscillations of the last 2000 years. The Amalfi fan-delta system represents a small-scale analogue for larger flood-dominated fan-deltas of the world and may be regarded as a useful example for a better understanding of inner-shelf, mixed siliciclastic–volcaniclastic fan-delta systems in the stratigraphic record.

Chapter 6 The Late-Holocene evolution of the Miseno area (south-western Campi Flegrei) as inferred by stratigraphy, petrochemistry and 40Ar/39Ar geochronology

Abstract This study on terrestrial and marine successions increases the understanding of the Late-Holocene volcanological and stratigraphical evolution of the south-western part of Campi Flegrei caldera. Stratigraphic data derived from field studies of two major tuff vents located along the coastal zone, namely Porto Miseno and Capo Miseno, clearly indicate that the Porto Miseno tuff ring slightly predates the Capo Miseno tuff cone. 40Ar/39Ar step-heating experiments, carried out on fresh sanidine separates from pumice samples, yielded a plateau age of 5090±140 yr BP for Capo Miseno and 6490±510 yr BP for Porto Miseno vent, thus confirming field observations. The volcanoclastic input derived from this recent and intense eruptive activity played a major role in the inner-shelf stratigraphic evolution of the Porto Miseno Bay deposits that have been drilled up to 40 m depth off the crater rim. The cored succession is characterised by transgressive marine deposits (mostly volcanic sand) with two intercalated peat layers (t1 and t2), dated at 3560±40 yr BP and 7815±55 yr BP (14C), respectively, interbedded with a 1–5 m thick pumice layer (tephra C). Peat layers have been chronostratigraphically correlated with two widespread paleosols onland while petrochemical analyses allowed us to correlate tephra C with the Capo Miseno tuff cone deposits. The results presented in this study imply a Late-Holocene volcanic activity that is also well preserved in the marine record in this sector of the caldera where a new chronostratigraphic reconstruction of the eruptive events is required in order to better evaluate the hazard assessment of the area.

Volcanic ash hazard in the Central Mediterranean assessed from geological data

Volcanic ash produced during explosive eruptions can have very severe impacts on modern technological societies. Here, we use reconstructed patterns of fine ash dispersal recorded in terrestrial and marine geological archives to assess volcanic ash hazards. The ash-dispersal maps from nine Holocene explosive eruptions of Italian volcanoes have been used to construct frequency maps of distal ash deposition over a wide area, which encompasses central and southern Italy, the Adriatic and Tyrrhenian seas and the Balkans. The maps are presented as two cumulative-thickness isopach maps, one for nine eruptions from different volcanoes and one for six eruptions from Somma-Vesuvius. These maps represent the first use of distal ash layers to construct volcanic hazard maps, and the proposed methodology is easily applicable to other volcanic areas worldwide.

Reply to the comment on the article “40Ar/39Ar dating of tuff vents in the Campi Flegrei caldera (southern Italy): toward a new chronostratigraphic reconstruction of the Holocene volcanic activity” by Isaia et al.

We agree wholeheartedly that integrated geochronologic and stratigraphic studies are necessary to constrain the eruptive history of the Campi Flegrei. Ar/Ar geochronology of Holocene eruptive products is difficult due to the long (1.25 billion years) half-life of K to Ar decay. The minute quantity of radiogenic Ar is easily overwhelmed by atmospheric argon contained within samples or by various corrections associated with irradiation or analytical techniques, so tremendous care is necessary to determine reliable ages. Sample homogeneity is important to avoid older, xenocrystic grains that can yield spuriously old ages, but equally important is generating enough signal to overcome analytical backgrounds (instrumental noise). Demonstration of homogeneity can be by single-crystal work and/or by incremental heating [note that Fedele et al. (2011) and Insinga et al. (2006) employed incremental heating in a resistance furnace, not with a laser]. However, simply choosing the younger age determination does not guarantee reliable results, as implied by Isaia et al. (2011). Excess argon, not xenocrystic contamination, yielded old apparent ages for the AD 79 eruption of Vesuvius in samples collected from the Villa of Poppea (Renne et al. 1997), but not from the Casti Amanti site (Lanphere et al. 2007). The excess argon was best characterized by incremental heating in a resistance furnace. We remain reasonably confident that the Editorial responsibility: J.D.L. White

On the occurrence of the Neapolitan Yellow Tuff tephra in the Northern Phlegraean Fields offshore (Eastern Tyrrhenian margin; Italy)

A main volcanic marker has been identified for the first time on the continental shelf of the northern Phlegraean Fields in the Gulf of Gaeta (Campania region, eastern Tyrrhenian margin, Italy) by means of Subbottom Chirp profile grid and stratigraphic analysis of a core collected on the slope. In the seismic sections, the core bottom corresponds to the top of a continuous and parallel reflector (V) interbedded within the transgressive deposits of the Late Quaternary-Holocene depositional sequence. The Transgressive System Tract deposits are particularly thick compared to the majority of the transgressive deposits of other shelf settings. This might be due to the input of pyroclastic and volcaniclastic deposits related to the intense eruptive activity of the Campania Plain during the Late Pleistocene-Holocene time span. Undulations and pockmarks are the main morphological features of the sea floor and they might be linked to gas uprising, widely detected in the study area. The V reflector is located on the shelf from northeast to southwest at different depths, ranging from 10 ms (about 8 m) to 30 ms (about 25 m) below sea floor and it can be mapped down to the continental slope. The tephrostratigraphic analysis of this continuous reflector allowed to correlate it with the Neapolitan Yellow Tuff deposits emplaced at Phlegraean Fields at ca. 15 ka.

Deltaic and Coastal Sediments as Recorders of Mediterranean Regional Climate and Human Impact Over the Past Three Millennia

This work was financially supported by the MISTRALS/PaleoMex program and by the Project of Strategic Interest NextData PNR 2011–2013 (www. nextdataproject.it). Lionel Savignan is thanked for his participation in the biomarker analysis. Radiocarbon datings for core KESC9-14 have been funded by Institut Carnot Ifremer-EDROME (grant A0811101). We also thank the Holocene North-Atlantic Gyres and Mediterranean Overturning dynamic through Climate Changes (HAMOC) project for financial support. The biomarker data presented here are available in the supporting information.

Marine sediment cores database for the Mediterranean Basin: a tool for past climatic and environmental studies

Abstract Paleoclimatic data are essential for fingerprinting the climate of the earth before the advent of modern recording instruments. They enable us to recognize past climatic events and predict future trends. Within this framework, a conceptual and logical model was drawn to physically implement a paleoclimatic database named WDB-Paleo that includes the paleoclimatic proxies data of marine sediment cores of the Mediterranean Basin. Twenty entities were defined to record four main categories of data: a) the features of oceanographic cruises and cores (metadata); b) the presence/absence of paleoclimatic proxies pulled from about 200 scientific papers; c) the quantitative analysis of planktonic and benthonic foraminifera, pollen, calcareous nannoplankton, magnetic susceptibility, stable isotopes, radionuclides values of about 14 cores recovered by Institute for Coastal Marine Environment (IAMC) of Italian National Research Council (CNR) in the framework of several past research projects; d) specific entities recording quantitative data on δ18O, AMS 14C (Accelerator Mass Spectrometry) and tephra layers available in scientific papers. Published data concerning paleoclimatic proxies in the Mediterranean Basin are recorded only for 400 out of 6000 cores retrieved in the area and they show a very irregular geographical distribution. Moreover, the data availability decreases when a constrained time interval is investigated or more than one proxy is required. We present three applications of WDB-Paleo for the Younger Dryas (YD) paleoclimatic event at Mediterranean scale and point out the potentiality of this tool for integrated stratigraphy studies.

The TEA C6 record: a reference archive from the Gulf of Taranto (Ionian Sea)for the last 15 ka

Abstract from 88th Congress of the Italian Geological Society, 2016-09-07 - 2016-09-09, NaplesAbstract from 88th Congress of the Italian Geological Society, 2016-09-07, 2016-09-09, Naplesbook Edited by D. Calcaterra, S. Mazzoli, F.M. Petti, B. Carmina & A. Zuccari doi: 10.3301/ROL.2016.79

Sessione S 23. Tephras and cryptotephras in Quaternary sciences

Abstract from 88th Congress of the Italian Geological Society, 2016-09-07 - 2016-09-09, NaplesAbstract from 88th Congress of the Italian Geological Society, 2016-09-07, 2016-09-09, Naplesbook Edited by D. Calcaterra, S. Mazzoli, F.M. Petti, B. Carmina & A. Zuccari doi: 10.3301/ROL.2016.79

The Large Explosive Activity of Mt. Etna as Recorded in Distal Tephrostratigraphy

Mt. Etna is renowned for being the most active and highest volcano in Europe. Lava flows and weak explosive eruptions characterize its activity, but intermediate to large explosive eruptions have punctuated its eruptive history. Marine and lacustrine distal records are excellent archives for the recognition of past large explosive activity at Mt. Etna, as testified by the recognition of distal tephra layers of Pleistocene to Holocene age. These data are, to date, neither organised nor correlated to the proximal stratigraphic and chronological records. Here, we propose the reorganisation and correlation of the distal tephra layers from Mt. Etna in order to decipher the timings and frequency of its major explosive eruptions.