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Litostratigrafia e petrografia delle areniti di Monte Tiriolo (Trias superiore), Calabria Centrale
No full textLitostratigrafia e petrografia delle areniti di Monte Tiriolo (Trias superiore), Calabria Centrale
No full textReconstructing parental affinity and climatic and physiographic conditions from the compositional signatures of Triassic-Early Jurassic continental redbeds, Peloritani Mountains, Sicily, Italy.
No full textMn- and Fe-carbonate rich layers in Meso.Cenozoic shales as proxies of environmental conditions: a case study from the southern Apennine, Italy
No full textMn-rich layers and interbedded shales from a well exposed natural section of the Northern-Calabrian Unit (Late Jurassic–
Early Oligocene) in the surroundings of the Terranova del Pollino village, southern Italy, have been mineralogically and
chemically analyzed, in order to reveal the factors controlling their formation. Mn-rich layers are composed of micas/clay
minerals, rhodochrosite, siderite, chlorite and quartz whereas shales are formed by micas, clay minerals, chlorite, quartz,
and feldspars. The MnO abundances in the Mn-rich layers, which are depleted relatively to the UCC in SiO2, TiO2, Al2O3,
Na2O, K2O, and P2O5, are in the range of 11.01 18.41 (wt. %). R-mode Factor analysis indicate that SiO2, Al2O3, TiO2,
Na2O and K2O have high positive weights in the first factor (59.8% of the total variance) whereas high negative weights
are observed for Fe2O3, MnO, and CaO. This factor accounts for the competition between the terrigeneous component, the
authigenic carbonate phases accumulating Mn and Fe which likely formed during paucity of detrital supply. The negative
weight of CaO and MnO in this factor, the higher Ca contents in the Mn-rich layers compared to shales, and the lack of
calcite, suggest the presence of a mixed Mn–Ca carbonate rather than pure rhodochrosite. It is generally retained that Ca–
rhodochrosite precipitates within the pore waters of reducing sediments since neither rhodochrosite nor siderite can form
in equilibrium with bottom seawater. Thus the resulting sediment should be a mixing between the detrital component and
the authigenic one. Assuming Al2O3 as an index of the detrital component, it is clearly envisaged that in the Al2O3/MnO
vs. Al2O3 diagram the carbonate-rich samples fall on the mixing curve having as end members the average shale and the
richest MnO sediment. This supports the idea that carbonate-rich samples formed through precipitation of carbonate
minerals in the pore waters of the terrigenous detritus accumulating at the sea bottom. Further the REE distribution of
unaltered marine carbonates is expected to be representative of ambient seawater where carbonates precipitated. Carbonates
normalized to fine-grained siliciclastic sediments, have typical HREE enrichment, negative Ce-anomaly, and lower
total REE. In our case, the carbonate-rich samples normalized to the average composition of the interbedded freecarbonate
shale, show HREE enrichment, lower total REE contents, and the lack of negative Ce-anomaly, due to the
anoxic environment of formation for Mn– and Fe–carbonate. Finally was observed that the mineralization is enhanced if
the site of accumulation is protected from dilution by clastic sediment input. The alternation between Mn– and Fe–carbonate
silts and carbonate-free shales along the studied sedimentary succession, were likely controlled by eustatic sea-level
oscillations which are well documented in the western Tethys during Middle and Late Triassic
Sedimentary recycling, provenance and paleoweathering from chemistry and mineralogy of Mesozoic continental redbeds mudrocks, Peloritani Mountains, Southern Italy.
No full textThe Triassic to Lowermost Jurassic mudrocks from continental redbeds of the Longi-Taormina Unit (Calabria-Peloritani
Arc; southern Italy) have been mineralogically, chemically and petrographically analyzed, in order to reveal their complex
history, which record an important phase of the geological evolution of the Mediterranean area.
The Late Triassic corresponds with a low first-order sea level stand and a time of high continental emergence whereas
the Early Jurassic was the time of the initiation of the first-order sea level rise in the mid-Mesozoic, generally marked by
a transgressive trend.
The mineralogical assemblage, dominated by the occurrence of illite and illite/smectite mixed layers, coupled to the
CIA index and to the A-CN-K plot, indicates post-depositional K-enrichments.
Palaeoweathering indices (CIW and PIA ratios) suggest that the source experienced intense weathering and that they
likely record a recycling effect from their metasedimentary basement rocks. A recycling effect is also suggested by the
distribution of Al2O3, TiO2, and Zr. In the Zr/Sc vs. the Th/Sc plot the redbeds are not clustered along the primary
compositional trend but fall along a trend involving zircon addition and thus sediment recycling. Recycling could significantly
affect the weathering indices which likely monitor a cumulative effect including a first cycle of weathering at the
source rocks. Weathering occurred under hot, episodically humid climate with a prolonged dry season. Wet-humid conditions
favored the formation of stream channels that eroded the soil profiles, whereas the dry season promoted the sedimentation.
The climate alternation in the Early Jurassic favored recycling.
An additional provenance terrane occurring in the basement, including metavolcanic rocks having mafic composition
cannot be excluded, since the Eu anomaly is slightly higher than the PAAS value. Although the effects of recycling on
REE distribution are uncertain, the Eu/Eu* should increase, as more feldspar is destroyed during weathering and diagenesis.
This involves that the Eu/Eu* ratio could monitor a supply of low Eu/Eu* mafic detritus which compensate for the recycling
effect by reducing Eu/Eu*. Eu released during the dissolution of feldspar could be retained by clay minerals contributing
to minimize the recycling induced increase of the Eu-anomaly. This may involve that the recycling effect on the Euanomaly
was minor and that the low Eu/Eu* mafic detritus supply was also minor. The subordinate importance of a mafic
supply is confirmed also by other provenance proxies including the La-Th-Sc plot and the Cr/V and Y/Ni ratios.
The proportions of illitic layers in I/S mixed layers coupled with the illite crystallinity values, expressed as Kübler
Index (KI), suggesting an estimated temperature experienced by the Longi Units in the range of 100–150°C. Starting fro
Le successioni silicoclastiche nell'evoluzione tettonica cenozoica dell'Appennino meridionale. Studi Geologici Camerti, Vol. Spec. 1995/2, 155-165.
No full textCompositional variations in Mn- and Fe-carbonate rich layers of Meso-Cenozoic shales from the southern Apennine, Italy.
No full textZircon compositions of Lower mesozoic redbeds of the tethyan margins, west-central mediterranean area
No full textTypologic study and chemistry of zircon populations from Middle Triassic–Lower Liassic arenitic
continental redbeds of the Internal Domains successions of the Mediterranean chains, from the
Gibraltar Arc to the Calabria–Peloritani Arc, allow assessment of whether this type of study may be
used to obtain more comprehensive inferences on the sedimentary evolution of ancient clastic rocks.
Calabria-Peloritani Arc zircons are primarily euhedral, with subordinate rounded and subrounded
grains. Rifian Maghrebides samples contain abundant euhedral zircons, with minor rounded and
ovoid zircons. Betic Cordillera zircons are rounded or subrounded, with minor euhedral elongate
grains; rounded zircons of these samples cannot be typologically classified. Electron-microprobe
analyses (Si, Zr, Hf, P, and HREE) indicate homogeneous compositions, suggestive of common
source areas characterized by granitoid rocks, whereas typology suggests the existence of two
distinct groups. The first group includes arenites from the Calabria-Peloritani Arc and the Rifian
Maghrebides. The second group includes arenites from the Betic Cordillera. Differences between
the two zircon groups may be related to recycling effects, in agreement with a geochemical study of
Triassic to lowermost Jurassic mudrock redbeds. Recycling likely was more significant for the Betic
Cordillera samples. These results suggest that zircon typology and mudrock geochemistry can be
useful tools for provenance, especially in complex sedimentary contexts where arenite-mudrock
couplets occur
Chemistry and mineralogy of mesozoic continental redbed mudrocks from the calabrian arc, southern Italy: implication for provenance, paleoweathering and burial history.
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