1,721,016 research outputs found
Aurora Vent Field (82.9N, Fram Strait) surface sediment geochemistry, grain size and mineralogy
No full textSedimentological and geochemical datasets of sediment cores collected from Aurora Vent Field (82.9N) in the Fram Strait during HACON21 (MC-148, BlaC-01, BlaC-03, GC-191, GC-193) and HACON19 (MUC-33, MUC-34, MUC-37, MUC-39) expeditions. The sediment cores were collected via gravity coring (GC), multicoring (MC, MUC), and ROV-guided blade coring (BC) from the R/V Kronsprins Hakon. Gravity coring was conducted with a 6 m long steel barrel deployed which contains a PVC liner with an inner diameter of 10 cm. Here, we report the results for some laminated intervals in GC-191 (core lenght = 215 cm) and GC-193 (core lenght = 255 cm). These sites are located at various distances from the active vents. We used a KC Denmark DK8000 multicorer hosting up to six transparent plastic liners with a diameter of 10 cm and length of 70 cm. We report the results from surface (0-5 cm) sediment of the multicore MC-148 (25 cm) and some deeper samples from MUC-33, MUC-34, MUC-37, MUC-39. ROV-guided coring operations at the vent site were conducted with the ROV Aurora, owned and operated by REV Ocean (Norway). The blade cores are picked up from a compartment on the ROV by its manipulator arm and pushed into the seabed. Blade cores can reach a maximum depth of 32 cm below sea floor, have a thickness of 10 cm and a width of 25 cm. Here we report the data from the upper 5 cm of blade cores BlaC-01 (28 cm) and BlaC-03 (17 cm) and two deeper samples from BlaC-01 (19-20 cm and 25-26 cm). Sampling locations are reported in the separate the Core_location.txt file
Multibeam bathymetry of the Polaris Mud Volcano Complex, Southwestern Barents Sea
No full textMultibeam bathymetry data covering the 10 mud volcanoes constituting the Polaris Mud Volcano Complex, Southwestern Barents Sea. Data were collected on-board R/V Kronprins Haakon during the EXTREME24 cruise in 2024. During the cruise, multibeam bathymetry was processed and refined using QPS Qimera Software. Grid surfaces with a resolution < 10 m were generated
Replication Data for HgCl2 addition to pore water samples from cold seeps can affect the geochemistry of dissolved inorganic carbon ([DIC], d13CDIC)
No full textThe conventional use of mercuric chloride (HgCl2) as an antimicrobial agent in water samples for dissolved inorganic carbon (DIC) analysis poses health and environmental risks related to its handling and disposal. Even though there is an increasing interest in quantifying pore water DIC contribution to the ocean carbon cycle and deep-sea acidification, the paucity of comparative studies on marine pore waters prevents the modification of sampling protocols and HgCl2 still remains widely used. In this study we compared DIC concentrations and δ13CDIC composition in pore water samples from methane seepage areas in the Barents Sea and offshore N. Svalbard. Samples were extracted using 0.15 μm rhizon filters and split into two aliquots with 2–3 replicates each. Only one aliquot was treated with 10 μL saturated HgCl2(aq) and all samples were stored in the dark at 4 °C, prior to measurements ~30 days later. The samples yielded extremely wide ranges of DIC concentrations, from 1.8 mM to 20.1 mM, and δ13CDIC values, from −36.0‰ to −1.6‰ (VPDB), due to variable contributions of methane-derived DIC to the pore water system
Evolution of a Miocene carbonate shelf (northern Apennines, Italy) revealed through a quantitative compositional study
No full textThe evolution of the Miocene San Marino carbonate shelf (Torriana outcrop), developed on the accretionary prism of the northern Apennines, has been interpreted through a stratigraphic and compositional study. Modal analysis allowed to quantify the framework components and to identify four microfacies through which the main steps of the carbonate ecosystem were traced. The healthy phase of the carbonate shelf, dominated by bryozoans and echinoids, originated in a high-energy transgressive setting and evolved during a warm period characterized by a progressive increase of nutrients. The transitional stage is marked by a reduction of carbonate productivity and by terrigenous intermittent pulses associated with bioclast fragmentation. The drowning succession corresponds to deepening upward facies formed by fine-grained hybrid arenites to sandy marls with abundant planktonic foraminifera, glauconitic grains and clay matrix. The demise of the carbonate shelf might have resulted from a combination of regional and global factors that interplayed controlling the detrital input, the nutrient budget and the deepening of the basin. Synsedimentary tectonics triggered subsidence of the basin and enhanced terrigenous discharge. Moreover, the superposition of paleoclimatic and paleoceanographic events (Monterey and Middle Miocene Climate Optimum) could have contributed with the intense weathering and remarkable detrital and nutrients supply
Evoluzione sedimentaria del centro storico di Modena nel tardo Quaternario
No full textsondaggi eseguiti nella zona del centro storico di Modena, l’evoluzione sedimentaria del primo sottosuolo che interessa direttamente la Torre Ghirlandina e l’adiacente Duomo. Il tema centrale si sviluppa attorno al carotaggio eseguito nella primavera 2012 in prossimità dell’angolo sud-ovest della torre civica. Esso ha raggiunto la profondità di 21,30 m toccando il tetto ghiaioso appartenente all’acquifero più superficiale. È stata condotta una completa analisi dal punto di vista stratigrafico e sedimentologico, ponendo attenzione allo studio delle facies deposizionali; sono stati inoltre individuati e caratterizzati i livelli archeologici relativi al periodo romano e a quello medievale, fornendo un contributo di tipo cronologico. Elaborando una sezione stratigrafica sulla base di alcuni sondaggi
che attraversano in direzione NE-SO la zona del centro storico, è stata proposta una ricostruzione paleoambientale per gli ultimi 30 m di terreno che corrispondono all’ultimo periodo deposizionale tardo quaternario. A 21 m di profondità è stato rinvenuto il tetto dell’Unità di Vignola costituita dai sedimenti grossolani che si sono deposti durante l’ultimo periodo glaciale würmiano, quando lungo tutta la fascia pedeappenninica si estendeva una piana a canali braided. Su di essa poggiano sedimenti fini di piana inondabile relativi al periodo postglaciale che caratterizza la porzione inferiore del Subsintema di Ravenna. Gli orizzonti torbosi che si rinvengono all’interno di questi depositi testimoniano uno scarso drenaggio dell’area e frequenti episodi d’impaludamento. I livelli
organici cedono il posto, nell’intervallo tra -7 e -10 m, a corpi limo-sabbiosi di ventaglio di rotta. L’analisi di facies ha inoltre portato al riconoscimento di alcuni depositi riferibili ad argini naturali che indicano la presenza di canali nelle immediate vicinanze. L’insediamento romano nell’area di Modena occupa l’intervallo stratigrafico compreso tra -4 e -7 m, nel quale si registra la concentrazione di frammenti di laterizi e un livello di blocchi lapidei incontrato a 6 m di profondità in alcuni dei sondaggi studiati. La città fu sconvolta nel IV-VI secolo da ripetute alluvioni che ne causarono l’abbandono; a testimonianza di ciò rimane una spessa coltre di depositi di rotta fluviale che ricopre lo strato romano lungo tutta la sezione
Authigenic carbonates as tracers of methane-rich fluid emission into the sea floor: fossil examples (Miocene, northern Apennines, Italy) compared to modern analogues
No full textCold seepage is a worldwide widespread process recognized in different marine settings of both active and passive continental margins. Authigenic carbonates, deriving from anaerobic oxidation of methane, can be used as tracers for ancient hydrocarbon-rich fluid emissions. Seep-carbonates of the northern Apennines mainly formed during the Miocene, commonly located in the inner part of the foredeep, at the deformation front of the accretionary prism. They are concentrated in two different depositional settings: - in pelitic intervals included in Langhian-Serravallian basin-plain turbidites; - in slope hemipelagites (Burdigalian to Messinian) capping turbidites in proximity to the deformational fronts. Although many of these bodies have been studied yet, significant outcrops still have to be investigated. This study will focus on seep carbonates in the Tuscan-Romagna Apennines (Moggiona). Carbonate bodies have lenticular to stratiform morphologies extending along strike and concordant with the attitude of the enclosing marls. Dimensions vary from 10 to 40 m wide and from 3 to 8 m thick. Carbonates are very rich in lucinid-like clams; at the base, numerous conduits filled with coquina debris and breccias are present, as well as dense irregular networks of carbonate-filled veins and extensional fractures. Carbonates are depleted in δ13C ranging from -40.22 to -19.28‰ V-PDB. The comparison between fossil and modern methane-derived carbonates may allow a better definition of the evolution of the seepage system, and relationships with synsedimentary instability (intraformational slumps and extraformational slides) and diapiric processe
RECONSTRUCTING SEEPAGE DYNAMICS OF A MIOCENE SYSTEM THROUGH SEDIMENTOLOGICAL AND GEOCHEMICAL CHARACTERIZATION OF AUTHIGENIC CARBONATES AND HOST SEDIMENTS (CORELLA, NORTHERN APENNINES, ITALY)
No full textNew data from facies, stable isotopes (C and O) and CHN analyses on seep-impacted sediments and
authigenic carbonates provided insights into dynamics and geochemical background conditions at a Miocene
seepage system (Corella outcrops, northern Apennines, Italy).
The examined outcrops comprise 4 lenticular carbonate bodies with maximum length of 200 m and
thickness up to 12 m. These carbonates strike parallel to the bedding of the enclosing sediments and show
lateral pinch out terminations. Chemosynthetic fauna (mainly Lucinids and Vesycomids) are very common
and forms local concentrations of disarticulated or articulated shells; veins and conduits crosscut the
carbonate bodies. Microfacies show mottled micrite including clotted textures related to bacterial activity
and framboids of pyrite (rosette-like features observed at SEM). δ13C values of the carbonates (micrites and
sparry cement filling veins) range between -42.32‰ to -26.63‰ and are indicative of AOM. The δ18O range
between -5.67‰ to 1.13‰ (average -0.96‰) and is close to the Miocene seawater signature and therefore
considered unaffected by significative diagenetic alteration. The host sediments at the top of the carbonates
body is depleted in 13C compared to normal marine carbonates and range between -8.40‰ to -4.75‰ and
δ18O is comprised between -3.50‰ and 1.68‰. CHN analyses on the enclosing sediments revealed low TOC
values in the range 0.21-0.72% with an average of 0.37%, similar to other Miocene foredeep successions of
the northern Apennines. The atomic C/N ratio ranges from 8.93 to 14.05 (avg. 10.84) suggesting minor
admixture of land-derived and marine organic carbon.
We suggest, based on field data, geotectonic setting, and geochemical analysis, that a blind fault,
rooted in the underlyingTertiary turbidites, acted as a pathway for deep methane-rich fluids. Advective fluid
flow resulted in a shallow, near seafloor sulfate-methane transition zone (SMTZ), resulting in the anaerobic
oxidation of methane and the precipitation of massive authigenic carbonate. The presence and preservation
of chemosynthetic fauna throughout the authigenic carbonate body indicates much of the advective fluid
flow breached the seafloor, resulting in methane seepage that helped sustain these chemosynthetic
organism
MIOCENE SEDIMENTARY INSTABILITIES ASSOCIATED WITH METHANE DERIVED AUTHIGENIC CARBONATES: A NEW CASE STUDY FROM THE NORTHERN APENNINES (PALAZZUOLO OUTCROPS, ITALY)
No full textNorthern Apennines (Italy) host several outcrops of methane derived seep carbonates often associated
with sedimentary instabilities such as intraformational slumps, extraformational slides and diapiric
processes. Despite the vast body of literature on seep-deposits from the Monferrato to the Umbro-Tuscan
sectors of the mountain chain, only a few studies focus on the interplay between paleomethane seepage and
sedimentary instabilities (Conti and Fontana, 2002) because of the lack of good exposures.
In this study we investigate an outcrop located in the Mugello area of the Tuscan Apennines (Prati
Piani di Palazzuolo) characterized by the co-occurrence of methane derived authigenic carbonates,
chemosynthetic fauna and slump-like structures. The examined outcrop consists of several carbonate blocks
with max length of 3.5 m enclosed in a 100 m thick pelitic interval, interpreted as sedimentation above a
structural high in the inner foredeep at the front of the Middle Miocene accretionary wedge.
The blocks are mainly located at the base of the pelitic interval and have the same strike as the
enclosing sediments. At various levels, pelitic sediments show soft sediment deformation structures (folds,
slumps). Within the slumps, we sampled some concretions (silty-carbonate in composition).
The δ13C value in the carbonates ranges between -18.2‰ and -33.22‰, confirming they are methane
derived (AOM-related in origin). Pelites surrounding the carbonate blocks (in situ or transported for a short
distance. Isotopic δ18O values are comprised between -4.31‰ and 0.87‰. The concretions are slightly
depleted in 13C (-5.47‰; -10.95‰).
Preliminary data suggest the presence of a seepage system active before the onset of the instability
and able to sustain chemosynthetic communities at the seafloor. The interstitial overpressures might have
reduced the shear strength of the fine-grained sediments and constituted an important preconditioning factor
for diapiric or mass-transport structures. However, this conclusion is still speculative and needs further
investigation
A quantitative compositional approach to the study of a Miocene carbonate shelf in the northern Apennines
No full textThe petrography of 147 samples of carbonate and mixed siliciclastic-carbonate rocks has been
performed on shallow-water carbonates of early-middle Miocene deposited in a wedge-top basin
in the northern Apennines. High-frequency sampling of the Torriana log (Val Marecchia valley,
Romagna Apennines) covers the entire carbonate succession from the basal unconformity to the
terrigenous-rich sediments that mark the demise of the shelf. The modal analysis has been
performed by point counting (300 points) in order to quantify the main framework components:
an intrabasinal carbonate fraction (biogenic), a terrigenous fraction (largely siliciclastic), and an
authigenic intrabasinal component constitued by glauconitic grains.
On the basis of the relative amounts of these framework components, four different petrofacies
are distinguished and matched with lithofacies units. From the base to the top they are the
following:
- Rudstones and subordinate grainstones, made up almost exclusively of intrabasinal carbonate
grains, represented by bryozoans and subordinate echinoid spines and plates. Cement is
constituted by scarce sparry calcite.
- Rudstones to grainstones, made up almost exclusively of intrabasinal carbonate grains plus
very subordinate amounts of siliciclastic grains (quartz, feldspars). Intrabasinal carbonates
consist of shallow-water bioclasts such as bryozoan fragments, echinoid spines and plates, red
algae and benthic macroforaminifera (Amphisteginae, Gypsinae). Grains are cemented by sparry
calcite. Siliciclastic grains are concentrated in thin laminae; isorientation is also occasionally
observable in bioclastic grains (Amphisteginae).
- Hybrid arenites: the intrabasinal carbonate component (biogenic) is associated with variable
but subordinate amounts of terrigenous siliciclastic components dominated by quartz and
feldspar grains (both plagioclase and k-feldspar). The biogenic component is still represented by
bryozoans and echinoids but the bryozoan/echinoid ratio noticeably decreases. The siliciclastic
component is mainly concentrated in thin laminae. The interstitial fraction includes pore-filling
sparry calcite and micritic matrix.
- Arenites, from medium to fine-grained; the terrigenous input noticeably increases and
becomes dominant. It is made up of prevalent quartz and feldspars and few lithics (sedimentary,
metamorphic and volcanic). Intrabasinal grains are subordinate, made up of fragments of algae,
bryozoans, and planktonic foraminifera. Glauconitic grains are present (up to 7% of the whole
rocks); calcite is the dominant pore-filling cement.
The hierarchical cluster analysis of point counting data is in agreement with outcrop-scale facies
observations. Our data indicate an almost exclusively intrabasinal supply during deposition of
the basal portions. A vertical evolution is documented and it is evidenced by a progressive
increase in the terrigenous supply that replaces the bioclastic fraction. The terrigenous input
becomes significant in the upper unit marking the crisis of the shelf.
Abstrac
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