Paola Tuccimei

Sea-Level Highstand 81,000 Years Ago in Mallorca

Standing High Sea-level rises and falls as Earths giant ice sheets shrink and grow. It has been thought that sea level around 81,000 years ago—well into the last glacial period—was 15 to 20 meters below that of today and, thus, that the ice sheets were more extensive. Dorale et al. (p. 860; see the Perspective by Edwards) now challenge this view. A speleothem that has been intermittently submerged in a cave on the island of Mallorca was dated to show that, historically, sea level was more than a meter above its present height. This data implies that temperatures were as high as or higher than now, even though the concentration of CO2 in the atmosphere was much lower. Measurements from the island of Mallorca indicate that past sea levels were much higher than had been assumed. Global sea level and Earth’s climate are closely linked. Using speleothem encrustations from coastal caves on the island of Mallorca, we determined that western Mediterranean relative sea level was ~1 meter above modern sea level ~81,000 years ago during marine isotope stage (MIS) 5a. Although our findings seemingly conflict with the eustatic sea-level curve of far-field sites, they corroborate an alternative view that MIS 5a was at least as ice-free as the present, and they challenge the prevailing view of MIS 5 sea-level history and certain facets of ice-age theory.

Growth of fissure ridge travertines from geothermal springs of Denizli Basin, western Turkey

Fissure ridge travertines grown from geothermal springs of Denizli Basin, southwestern Turkey, are investigated through stratigraphic, structural, geochemical, and geochronological methods, with the aim of understanding the growth of these elongate mound-shaped structures. Two main types of travertine deposits are recognized: (1) bedded travertines, which grew as flowstone on sloping surfaces and form the bulk of fissure ridges, and (2) banded travertines, which grew as veins within the bedded travertine chiefly along its central feeding conduit. Stratigraphic and structural observations shed light on the bedded-banded travertine relationships, where the banded features grew through successive accretion phases, crosscutting the bedded travertine or forming sill-like structures. The bedded and banded travertines alternated their growth, as demonstrated by complicated crosscutting relationships and by the upward suture, in places, of banded travertine by bedded travertine that was, in turn, crosscut by younger banded travertine. The bedded travertine is often tilted away from the central axis of the fissure ridge, thus leaving more room for the central banded travertine to form. U-series ages confirm the bedded-banded travertine temporal relationships and show that the growth of the studied fissure ridges lasted up to several tens of thousands of years during Quaternary time. The banded travertine was deposited mainly during cold events, possibly in coincidence with seismic events that might have triggered the outflow of deep geothermal fluids. C and O stable isotope and rare earth element data indicate a shallow feeding circuit for the studied structures with a fluid component deriving from a deeper geothermal circuit. A crack-and-seal mechanism of fissure ridge growth is proposed, modulated by the interplay of local and regional influencing factors and mechanisms such as geothermal fluid discharge, paleoclimate, tectonics, and the progressive tilting of bedded travertine limbs over a soft substratum creating the necessary space for the central veins to grow.

226Ra-excess during the 1631-1944 activity period of Vesuvius (Italy): A model of alpha-recoil enrichment in a metasomatized mantle and implications on the current state of the magmatic system

Abstract The origin of the 226Ra-excess during the last cycle of Vesuvius activity was investigated by high-resolution γ-spectrometry, TIMS and EDXRF. Lavas display high initial 226Ra-excess (500–1000%), similar (230Th/232Th) activity ratios (0.87–0.91) and most samples show significant 238U-excess. During the period 1631–1944 the initial absolute 226Ra-excess reached the highest values (19–44 dpm g−1) recorded for earth volcanoes. Crystal fractionation and particularly leucite floating did not cause the 226Ra-excess in spite of the high 226Ra activity (21–85 dpm g−1) in leucite. The presence of phlogopite in the mantle source, documented by field and petrological evidences on local mantle-derived xenoliths, rules out that equilibrium partial melting can be responsible for the 226Ra-excess. This primary feature may be explained by a multistage process involving metasomatic mantle fluids (MMFs) flowing through a mantle wedge where U is concentrated as U-accessory minerals deposited along microfractures. Fluids, passing through the mantle wedge, are supplied of 226Ra, 230Th and 234U by α-decay recoil of parent nuclides from U-enriched microfractures. This model calculates that the ascent time of fluids through the mantle wedge was ≤ 12 ka. Successively MMFs mixed with mantle-derived melts, giving rise to 226Ra-enriched magmas, which entered the Vesuvius plumbing system less than 7 ka. Crystal fractionation did not affect extensively the initial 226Ra/Ba ratio, which varied in the 1631–1944 period according to a pattern reflecting periodic inputs of 226Ra-enriched magma, variable reservoir volumes and residence times in magmatic chamber(s). The temporal trend of the reservoir volumes, extrapolated to the present time, indicates a volume of magma of ∼ 0.021 km3, stored most probably in a shallow chamber.

Comparison of 14C and U-Th ages of two Holocene phreatic overgrowths on speleothems from Mallorca (Western Mediterranean): Environmental implications

Paola Tuccimei1, Mark Van Strydonck2, Angel Ginés3, *, Joaquín Ginés3, Michele Soligo1, Igor M. Villa4, 5, Joan J. Fornós3

U-series disequilibrium radionuclides in sulphur incrustations from the fumarolic field of Vulcano Island

Abstract U-series disequilibrium radionuclides ( 238 U, 234 U, 210 Pb, 210 Po) in sulphur incrustations deposited at La Fossa cone (Vulcano Island, Italy) were measured over the period 1990–1995 to collect information about changes in the feeding system of the fumarolic field. The 210 Po/ 210 Pb and 210 Pb /Pb ratios of the sulphur incrustations allowed the identification of a fumarolic vent which is free from magmatic contribution and remobilized sublimate contamination. In spite of the low temperature of the selected fumarole (280–350°C), kinetic data show that 210 Po is almost fully volatilized due to the relatively high velocity of the gas; as a result, the 210 Po/ 222 Rn activity ratio of the gas can be used to estimate fluid rising times (about 100 days). 234 U/ 238 U activity ratios of sulphur incrustations deposited in 1991–1993 showed a shift toward high values typical of nonmagmatic fluids. Both short-lived and long-lived U-series disequilibrium radionuclides contribute to volcanic forecasting and give information on fluid sources and rising times as well as the residence times of the aquifers involved in the degassing process of the fumarolic field.

Minimal mass transfer across dolomitic granular fault cores

The role of chemical changes and mass transfer in the formation of granular fault cores across carbonate strata is still unclear. Thirteen granular fault cores across strata of dolostone from Sperlonga, central Italy, are analyzed by chemical and physical methods. The analyzed faults are reverse or transpressional, up to about 1 m thick, and flanked by a host rock affected by a widely developed solution cleavage. Grain size distributions of fault core rocks are determined by a sieving procedure for grains larger than 63 μm. Mechanisms of grain comminution are inferred by microscopic analyses on a set of thin sections obtained from epoxy-impregnated fault rock samples. Concentrations of calcium and magnesium in the fault cores and in the adjacent host rock are determined by titrimetry. Results show that both the breccia and the gouge forming the fault cores show little evidence for mass transfer, regardless of the fault type and grain size distribution of fault rocks. We interpret these results as chiefly the effect, within the fault core, of a strongly reduced permeability, which impeded significant mass transfer processes through solute transport. It follows that grain comminution occurred mostly by brittle processes such as crushing and abrasive wear. Previous work suggests that these results are rather generalizable; some exceptions, however, compel further research on the role of circulating fluids and mass transfer in the formation of carbonate fault rocks.

Speleothems in a north Cuban cave register sea-level changes and Pleistocene uplift rates

A flight of marine terraces along the Cuban coast records Quaternary sea-level highstands and a general slowly uplifting trend during the Pleistocene. U/Th dating of these limestone terraces is difficult because fossil reef corals have been affected by open system conditions. Terrace ages are thus often based on geological and geomorphological observations. In contrast, the minimum age of the terraces can be constrained by dating speleothems from coastal mixing (flank margin) caves formed during past sealevel highstands and carving the marine limestones. Speleothems in Santa Catalina Cave have ages>360 ka and show various cycles of subaerial–subaqueous corrosion and speleothem growth. This suggests that the cave was carved during the MIS 11 sea-level highstand or earlier. Some stalagmites grew during MIS 11 through MIS 8 and were submerged twice, once at the end of MIS 11 and then during MIS 9. Phreatic overgrowths (POS) covering the speleothems suggest anchialine conditions in the cave during MIS 5e. Their altitude at 16m above present sea level indicates a late Pleistocene uplift rate of<0.1mm/ka, but modelling also shows uplift to have been insignificant over a long timespan during the middle Pleistocene since the cave was carved. Our study shows that some flank margin caves in the region of Matanzas are older than commonly believed (i.e. MIS 11 rather than MIS 5). These caves not only can be preserved but are good markers of interglacial sea-level highstands, more reliable than marine abrasion surfaces. Copyright

Tracing NAPLs contamination in the vadose zone using soil radon

Frequent spills of Non-Aqueous Phase Liquids (NAPLs), such as petroleum products or chlorinated solvents, occur all around the world contaminating the soil vadose zone or the aquifer. In order to trace the presence of these substances, radon concentration in soil gas can be employed because of its high solubility in NAPLs. Radon available in the soil pores accumulates in the NAPLs producing a local decrease of its concentration in the vicinity of contaminated areas. Thus radon minima in the vadose zone can be used to localize NAPL plumes indirectly.The suitability of this method is here checked by laboratory simulation of a gasoline spill within a known volume of soil. Radon activity concentration strongly drops down right after the injection of gasoline and progressively increases in the following days. This trend is compared with data from a simultaneous experiment carried out on a volume of the same soil, not contaminated by NAPL.Finally, an example of field measurements within a site affected by NAPL contamination is documented. Mapping of soil radon concentration at 80 cm depth shows an area where radon deficit is evident. This region is aligned along the directions of the groundwater flow induced by pumping for safety operation of the plant. Radon negative anomalies are not due to low gas permeability and are not correlated with soil CO2. The comparison of soil gas data with those from nearby background areas confirm the soundness of premises.

Laboratory simulation of recent NAPL spills to investigate radon partition among NAPL vapours and soil air

Soil radon is employed to trace residual NAPL (Non-Aqueous Phase Liquid) contamination because it is very soluble in these substances and is strongly depleted over polluted volumes of the subsoil. The solubility of radon into NAPL vapors, generally poorly considered, is investigated here, either as growth of radon exhalation from a material contaminated with increasing volumes of kerosene, or as radon partition between liquid kerosene, water and total air, considered ad the sum of kerosene vapors plus air.

Anatomy of a fumarolic system inferred from a multiphysics approach

Fumaroles are a common manifestation of volcanic activity that are associated with large emissions of gases into the atmosphere. These gases originate from the magma, and they can provide indirect and unique insights into magmatic processes. Therefore, they are extensively used to monitor and forecast eruptive activity. During their ascent, the magmatic gases interact with the rock and hydrothermal fluids, which modify their geochemical compositions. These interactions can complicate our understanding of the real volcanic dynamics and remain poorly considered. Here, we present the first complete imagery of a fumarolic plumbing system using three-dimensional electrical resistivity tomography and new acoustic noise localization. We delineate a gas reservoir that feeds the fumaroles through distinct channels. Based on this geometry, a thermodynamic model reveals that near-surface mixing between gas and condensed steam explains the distinct geochemical compositions of fumaroles that originate from the same source. Such modeling of fluid interactions will allow for the simulation of dynamic processes of magmatic degassing, which is crucial to the monitoring of volcanic unrest.