Lagonegro Basin Research Articles

Weathering trends in the Norian through geochemical and rock magnetic analyses from the Pignola–Abriola section (Lagonegro Basin, Italy)

Abstract. We investigated the geochemical and rock magnetic properties of the magnetostratigraphically calibrated Pignola–Abriola section (Italy) in order to understand the climatic perturbations that characterize the late Norian–early Rhaetian interval (Late Triassic). We performed experiments on anhysteretic and isothermal remanence (ARM and IRM) and on magnetic susceptibility (χ) to obtain the rock magnetic parameters necessary for our paleoclimatic investigation. An episode of increase in the relative quantity of hematite, suggesting the enhanced subaerial oxidation of iron minerals, was identified in the Norian from ∼ 217 Ma in the Alaunian up to ∼ 211 Ma in the early Sevatian, followed by a decline up to 207–206 Ma at the end of the Norian (late Sevatian). The results of geochemical and multivariate statistical analyses support a long-term increase and reduction in rock weathering, confirming and extending previous 87Sr / 86Sr data from the Pizzo Mondello section (Italy). Possible causes of these long-term weathering trends are the multiphase uplifting of the Cimmerian orogen, occurring at mid-northern latitudes along the southern margin of Asia in the Late Triassic, and/or the northward motion of Pangea across the equatorial humid belt. Rapid excursions in oxidized iron minerals have also been observed across the Norian–Rhaetian boundary, the origin of which still has to be determined.

Geochemistry as a Clue for Paleoweathering and Provenance of Southern Apennines Shales (Italy): A Review

The southern Apennines (Italy) chain is a fold-and-thrust belt mainly derived from the deformation of the African–Apulian passive margin where shallow-water, basinal, and shelf-margin facies successions, including fine-grained sediments, occur. Here, we provide a review of the geochemistry of Meso–Cenozoic shales from the Lagonegro basin to elucidate provenance and paleoweathering. The different suites of these shales are dominated by 2:1 clay minerals and are Fe shales and shales. An R-mode factor analysis suggests Ti, Al, and LREE (F1) and K2O-MgO (F2) covariance, likely related to the illite → smectite → kaolinite evolution during weathering. HREE and Y are distributed by phosphate minerals, suggesting LREE/HREE fractionation. The CIA paleoweathering proxy rules out non-steady-state weathering conditions and indicates that the source area was affected by moderate to intense weathering. The paleoprecipitation values derived from the CIA-K and CALMAG indices show median values in the 1214–1610 mm/y range. The Eu/Eu*, Sm/Nd, and Ti/Al provenance ratios point toward a UCC-like source excluding any mafic supply and suggest that the Lagonegro basin was connected, through a southern area, with the African cratonic area. However, the Eu/Eu* median value of the southern Apennine shales is quite similar to the value of the Archean shales, possibly indicating a less differentiated component. This is consistent, in many samples, with the value of the (Gd/Yb)ch ratio, suggesting that the shales likely incorporated ancient sediments derived from African Archean terranes through a cannibalistic process.

Lateral Variations of P-Wave Velocity from Deep Borehole Data in the Southern Apennines, Italy

We have selected 28 deep wells in the Southern Apennine area, most of which are located along and around the Val d’Agri Basin. The Southern Apennines, one of the most seismically active regions of the Italian peninsula, is a NE-verging fold-and-thrust belt characterised by the Meso–Cenozoic Apulia carbonate duplex system overlain by a thick column of Apennine carbonate platform and Lagonegro basin units. These units are unconformably covered by Neogene siliciclastic successions. Among the many Quaternary tectonic basins in the area, the Val d’Agri Basin is the most important intramontane depression, and is bordered by a ~ NW–SE-trending active fault system that represents one of the main seismogenic structures of the region. Moreover, the Val d’Agri Basin is the largest onshore oil field basin in Europe. In this context, we have analysed sonic log records from 28 deep wells and compared them with the corresponding stratigraphy and the other geophysical logs. We have obtained detailed measurements of the P-wave velocity (Vp) for each well from 0 to ~ 6 km depth, and found important lateral variations of Vp over very small distances. From these values, we have retrieved the densities of the main units crossed by the wells and the range of the overburden gradient in this area.

Sedimentary record of Upper Triassic impact in the Lagonegro Basin, southern Italy: Insights from highly siderophile elements and Re-Os isotope stratigraphy across the Norian/Rhaetian boundary

The Norian and Rhaetian transition (Late Triassic) is characterized by a faunal turnover in major pelagic groups, such as radiolarians, conodonts, and ammonoids. Although catastrophic events such as emplacements of large igneous provinces and/or extraterrestrial impacts have been suggested to account for this biotic turnover, firm evidence based on geochemistry of sedimentary successions is still lacking. In order to assess environmental changes across the Norian/Rhaetian boundary (NRB), we report high–resolution stratigraphic variations for whole-rock major, trace, and highly siderophile element abundances, together with Re–Os isotope ratios for the Sasso di Castalda section in Lagonegro Basin, southern Italy. The section consists of a continuously exposed sequence of upper Norian (Sevatian) through the lower Rhaetian of a deep basinal deposits. Our data demonstrated that the upper Norian section records important events in stratigraphically ascending order: (1) a depositional environment moved below the Carbonate Compensation Depth, leading to the carbonate-biosilica transition associated with a slight depletion of elements favored in heavy minerals such as Zr, Hf, and Ti, (2) an input of Rochechouart impact components detected by platinum-group element anomaly, and (3) a transient change of redox state into low oxygen (dysoxic to suboxic) conditions marked by increases of V, U, and Re. This sequence of events suggests that the Rochechouart impact predates the major environmental changes resulting in faunal turnover at the NRB. Although their direct causal relationships are highly questionable given the small size of impactor and the interval between the impact horizon and the NRB, the possibility of triggering subsequent environmental and biotic collapses cannot be ruled out. This study provides the first identification of Rochechouart impact horizon in marine strata, which could be an important event marker for further studies on contemporaneous sections in the Lagonegro Basin and other localities.

The last phase of conodont evolution during the Late Triassic: Integrating biostratigraphic and phylogenetic approaches

For the Upper Triassic, conodonts are the primary tools utilized in biostratigraphic investigations. For an effective biostratigraphic zonation, the species should be constrained by clear phylogenetic relationships, in which the stratigraphic ranges and taxonomy are reliable. Unfortunately, a phylogenetic framework for the Late Triassic pectiniform conodonts is almost missing, except for particular intervals, such as the Carnian/Norian boundary. The purpose of this study is to examine the latest Norian and Rhaetian pectiniform conodonts in detail in an attempt to determine their phylogenetic relationships, by applying novel phylogenetic methodologies that incorporate both morphological and stratigraphic data. This work is based on the conodont assemblages from the Upper Triassic strata of the Lagonegro Basin (southern Apennines, southern Italy) and the Csővár area (north-central Hungary), complemented with data from the literature. The calibrated phylogenetic analysis of the latest Norian and Rhaetian conodonts supports a two-step evolutionary history: a first radiation (~211–210 Ma) of the Parvigondolella species and the first representative of the genus Misikella, followed by a second phase (~206.5–205 Ma) leading to the final radiation of the Misikella species. Furthermore, the systematic revision of uppermost Triassic conodonts is provided along with the description of Misikella kolarae n. sp.

The Norian “chaotic carbon interval”: New clues from the δ 13 C org record of the Lagonegro Basin (southern Italy)

A global carbon-isotope curve for the Late Triassic has the potential for global correlations and new insights on the complex and extreme environmental changes that took place in this time interval. We reconstruct the global δ 13 C org profile for the late Norian, improving on sparse published data from North American successions that depict a “chaotic carbon-isotope interval” with rapid oscillations. In this context, we studied three sections outcropping in the Lagonegro Basin (southern Italy), originally located in the western Tethys. The carbon-isotope profiles show four negative excursions correlatable within the Lagonegro Basin. In particular, a negative shift close to the Norian/Rhaetian boundary (NRB) appears to correlate with that observed in the North American δ 13 C org record, documenting the widespread occurrence of this carbon cycle perturbation. The 87 Sr/ 86 Sr and 187 Os/ 188 Os profiles suggest that this negative shift was possibly caused by emplacement of a large igneous province (LIP). The release of greenhouse gases (CO 2 ) to the atmosphere-ocean system is supported by the 12 C enrichment observed, as well as by the increase of atmospheric p CO 2 inferred by different models for the Norian/Rhaetian interval. The trigger of this strongly perturbed interval could thus be enhanced magmatic activity that could be ascribed to the Angayucham province (Alaska, North America), a large oceanic plateau active ca. 214 ± 7 Ma, which has an estimated volume comparable to the Wrangellia and the Central Atlantic Magmatic Province (CAMP) LIPs. In fact, these three Late Triassic igneous provinces may have caused extreme environmental and climate changes during the Late Triassic.

NEW EARLY TUVALIAN (CARNIAN, TRIASSIC) RADIOLARIANS FROM THE HUǦLU-PINDOS SUCCESSION IN THE SORGUN OPHIOLITIC MÉLANGE, SOUTHERN TURKEY

Three new radiolarian genera ( Paramonocapnuchosphaera , Monocoronella and Minicrampus ) and 8 new species are described herein from one of the most diverse and best preserved Carnian (Late Triassic) radiolarian faunas of the world, from the early Tuvalian sequence of the Sorgun Ophiolitic Melange, southern Turkey. The radiolarian fauna belongs to the Spongotortilispinus moixi Zone (equivalent to Paragondolella postinclinata - Paragondolella noah conodont Zone). The very similar late Julian-early Tuvalian radiolarian faunas from the Northern Calcareous, Alps through the Lagonegro Basin, Sicily, Rhodes Island, Greece and farther east in the Antalya nappes, in the Mersin Melange and in Elbistan, Turkey may confirm that the Pindos-type succession found in different units of early Mesozoic oceanic basins formed in a single oceanic basin.

New Middle Triassic radiolarian species from the Monte Facito Formation (Lagonegro succession, Southern Apennines, Italy)

Rich and well preserved radiolarian assemblages from the Middle Triassic radiolarian cherts of the Monte Facito Formation, Lagonegro succession (Southern Apennines, Italy), contain new Late Anisian taxa. These radiolarian cherts represent the oldest deep-water sediments of the Lagonegro Basin, representing pelagic conditions since the Late Anisian. Six new species are here described: Tiborella tribullata, Baratuna lucana, Hozmadia lagonegroensis, Hozmadia (?) simplex, Bulbocyrtium multiporatum, Planispinocyrtis curta.

Carbonate-to-biosilica transition at the Norian–Rhaetian boundary controlled by rift-related subsidence in the western Tethyan Lagonegro Basin (southern Italy)

The Lagonegro Basin, located in the Southern Apennines, Italy, records a transition from carbonate sediments of the Calcari con Selce Fm. (“Cherty Limestone”) to biosiliceous sediments of the Scisti Silicei Fm. (“Siliceous Shale”) around the Norian–Rhaetian boundary (NRB), Upper Triassic. Sedimentologic and chemostratigraphic analysis of three sections (Pignola-Abriola, Monte Volturino, and Madonna del Sirino) representing a proximal-to-distal transect across the basin document marine productivity, redox, and chemical weathering conditions. The basin was characterized by low to moderate productivity and mainly oxic deep waters, with no systematic secular variation throughout the ~10-Myr-long study interval. A weathering proxy, the chemical index of alteration (CIA*), shifts toward higher values (from ~0.70 to ~0.80) in all three study sections, suggesting development of warmer and/or more humid conditions just before the NRB. The lack of evidence for changes in marine productivity or redox conditions and the time-transgressive nature of the carbonate-biosilica transition suggests that the latter was caused not by changes in planktonic communities but, rather, by a rise in the CCD, the most likely cause of which was seafloor subsidence within the actively rifting Ionian Ocean (i.e., the westernmost branch of the Tethys Ocean). The tectonically active character of the Lagonegro Basin is also reflected in evidence of synsedimentary paleoseismic activity, e.g., numerous debris flows around the basin margins. The present study thus documents sedimentologic changes within a marginal basin in a geologically young ocean.

The Pignola-Abriola section (southern Apennines, Italy): a new GSSP candidate for the base of the Rhaetian Stage

The base of the Rhaetian stage (Norian/Rhaetian boundary, NRB) is still awaiting formal designation by the International Commission on Stratigraphy. At present, only the 4.30-m-thick Steinbergkogel section (Austria) has been proposed as GSSP (Global Stratotype Section and Point) candidate for the base of the Rhaetian. Here we present data from the 63-m-thick Pignola-Abriola section (Southern Apennines, Italy) that we consider an alternative candidate for the Rhaetian GSSP. The Pignola-Abriola basinal section, represented by hemipelagic–pelagic carbonate successions belonging to the Lagonegro Basin, matches all the requirements for a GSSP: 1, it is well exposed with minimal structural deformation; 2, it is rich in age diagnostic fossils (e.g. conodonts and radiolarians); 3, it yields a geochemical record suitable for correlation (e.g. δ13Corg/carb); and 4, it has a robust magnetostratigraphy and is correlated with the Newark APTS for age approximation of the NRB and additional Rhaetian bioevents. In the Pignola-Abriola section, we opt to place the NRB at the 44.4 metre level, coincident with a prominent negative shift of ca. 6‰ of the δ13Corg. This level is located 50 cm below the FAD of conodont Misikella posthernsteini s.s within the radiolarian Proparvicingula moniliformis Zone. Both the negative δ13Corg shift and the FAD of Misikella posthernsteini occur within Pignola-Abriola magnetozone MPA-5r, at ~205.7 Ma, according to magnetostratigraphical correlation to the Newark APTS. We also illustrate the coeval Mt. Volturino stratigraphical section deposited below the calcite compensation depth (CCD) within the same Lagonegro Basin and characterized by a detailed radiolarian biostratigraphy and strong δ13Corg negative shift around the NRB.

Determining the way-up of the Monte Facito Formation using new sedimentological data from the "La Cerchiara" succession, Southern Apennines

The Monte Facito Formation consists of Early-Middle Triassic sediments deposited during the first stages of the continental separation of Africa and Europe. This stratigraphic unit, located at the base of the Mesozoic succession of the Lagonegro Basin, appears as a chaotic complex, severely affected by contractional tectonics, and whose original stratigraphic order is very difficult to determine. Despite these complications, a first attempt to determine stratigraphic order was performed on the southern side of the Monte Facito locality. Another key section considered was the La Cerchiara outcrop. As the Monte Facito section is no longer accessible, the La Cerchiara outcrop remains the only locality were a significant stratigraphic portion of the Monte Facito Formation can be observed. Nevertheless, the problematic way-up of the succession has until now prevented consideration of this outcrop as the main Monte Facito Formation type-succession. Difficulty in determining way-up is a consequence of a lack of high-resolution biostratigraphic dating combined with a paucity of well-preserved way-up sedimentary indicators. A detailed field survey, involving sedimentological, stratigraphic and structural observations, has been conducted with the aim of definitively understanding the correct younging direction of the Monte Facito succession exposed at the La Cerchiara locality. The recognition of well-preserved way-up sedimentary indicators, as well as graded beds and ripples, allows an eastward direction of younging to be attributed to the study succession. These results permit a better understanding of the evolution of the passive northern African palaeomargin during the Triassic period, which led to the opening of the Lagonegro Basin.

Multiple Dolomitization Episodes In Deep-Water Limestones of the Triassic Lagonegro Basin (Southern Italy): From Early Reflux To Tectonically Driven Fluid Flow

Abstract Massive dolomitization does not commonly occur in deep-water carbonates. However, this regional study on outcrops and subsurface samples of Triassic Lagonegro basinal carbonates from the southern Apennines fold and thrust belt (Italy) shows that the evolution of the Lagonegro basin was punctuated by two events of massive dolomitization. These processes resulted in two distinct dolomite types, displaying different petrographic and geochemical features. A medium-crystalline and fabric-preservative dolomite in the northern area (Molise, Campagna, and San Fele–Mount Pierno) contrasts with a medium- to coarse-crystalline and fabric-destructive dolomite in the southern area (from Pignola to the high Val d'Agri). Geochemical data (increase in δ18O with respect to typical Late Triassic seawater values, high Sr and low Mn and Fe content, Sr isotopes consistent with Late Triassic seawater) indicate that the dolomite in the northern area is the result of an early replacement caused by a marine and possibly oxidizing fluid during shallow burial. Dolomitizing fluids likely were expelled through reflux from the Norian Apenninic carbonate platform towards the proximal Lagonegro basin. This reflux was promoted by the Norian peculiar paleoceanographic and climatic conditions in the Tethyan region, and affected only the proximal basinal facies. Dolomites in the southern area display a decrease in δ18O compared to Late Triassic seawater values and show lower Sr, higher Mn and Fe contents, and higher Sr isotope ratios compared to the early dolomites of the northern area. Fluid-inclusion microthermometry reveals homogenization temperatures between 70 and 120°C and salinities of 1.9 to 6.4 wt % NaCl eq. for saddle dolomites. These geochemical signatures indicate that the southern area was affected by late diagenetic burial dolomitization, interpreted to be the result of large scale tectonically driven fluid flow during the second compressional phase characterizing the southern Apennines fold and thrust belt emplacement. The dolomite distribution across the Lagonegro basin (northern and southern) is possibly controlled by the paleogeographic distribution of the facies (proximal vs. distal) as well as by their proximity to thrust faults. The Lagonegro case study demonstrates that basinal successions may undergo multiple dolomitization episodes in a manner similar to carbonate platform successions, from early shallow to deep-burial diagenesis. One of the relevant implications is that in areas of restricted oceanographic circulation, during periods of aridity, reflux dolomitization may extend beyond the platform margin, into deep-water carbonates, having the potential to alter their reservoir quality.

Frontal collapse during thrust propagation in mountain belts: a case study in the Lucania Apennines, Southern Italy

In thrust belts, low-angle tectonic contacts are common, and are associated with the stacking of tectonic units and the resulting regional shortening. The Southern Apennines of Italy, where basin and platform sediments are stacked along low-angle regional thrusts caused by the shortening of the Adria passive margin, are no exception. We studied a portion of a north–south-trending, low-angle regional thrust that separates Apennine platform sediments from Lagonegro basin rocks. To the east of the thrust, klippen composed of platform sediments overlying Lagonegro rocks along a low-angle tectonic contact are present. The klippen were first interpreted as remnants of the regional thrust. We performed a detailed structural analysis of the regional thrust, and we examined the structural setting of the klippen. Field evidence and analysis of map patterns revealed that emplacement of low-angle, foreland-propagating thrusts was followed by extensional deformation accommodated by regional east-dipping, low-angle normal faults. At the base of the klippen, we identified low-angle tectonic contacts with an extensional kinematics. We conclude that the klippen were the result of movements of platform sediments and Lagonegro rocks along low-angle normal faults, and not thrusts as previously interpreted. These faults are cut by more recent, high-angle normal faults associated with the opening of the Agri basin. Collectively, we show that evidence of changes in the tectonostratigraphic architecture, fault geometry and kinematics, and fabrics in the thrusts can reveal the presence of low-angle normal faults, the result of an extensional regime. We expect that our findings will contribute to the understanding of the deformation history of part of the Southern Apennines, and of other mountain belts. The results are also important to understand the transition from compression to extension in the Southern Apennines and in similar orogenic belts.

The Numidian Flysch: a guide formation for the reconstruction of the paleogeography and tectono-sedimentary evolution of southern Apennines

Abstract The Numidian Flysch shows constant lithological features from the strait of Gibraltar to central Italy. It is characterized by quartzarenites showing grains of monocrystalline, rounded and frosted quartz, and by kaolinitic mudstones. This research has pointed out that in the southern Apennines 1) the Numidian Flysch was deposited exclusively in the Campania-Lucania carbonate platform and in the Lagonegro-Molise basin, both located on the Apulian continental margin, and never is present in tectonic units originated from the oceanic area located west of that margin; 2) in the axial zone of the Lagonegro basin it stratigraphically follows a formation consisting of varicoloured clays (Argille Varicolori Auct.); 3) its age is limited to the early-middle Langhian, that is to say, it begins to sediment about 7 million years later than in the Maghrebian chain and deposited for a time span limited to 1–1.5 Ma. The thickness of the Numidian Flysch gradually decreases towards the north from about 600–1,000 meters to a few tens of meters and in some of the northeastern outcrops it is represented only by some layers of quartzarenites. This is accompanied by a decrease in size of the particles becoming more and more finer. In addition, northwards and frequently in the same section, a lower mineralogical and textural maturity (from quartzarenites to litharenites, and presence of abundant matrix, sub-angular, polycrystalline and deformed quartz grains) is well recognizable. In the Campania-Lucania carbonate platform the Numidian Flysch evolves to pelagic marly-clayey deposits, followed by mineralogically immature turbidite sandstones of Serravallian age. In the Lagonegro basin the Numidian Flysch replaces Cretaceous-lower Miocene turbidite deposits, consisting of limestones and red marls, on the western side of the basin, variegated clays in the axial zone and calcareous turbidites or variegated clays in the eastern side. Since the late Langhian, it evolves to pelagic sediments followed by lower Tortonian immature turbidite sandstones. In the successions of the Molise basin the Numidian Flysch is interbedded in a succession consisting of calcareous turbidites and pelagic limestones and marls, reaching the Messinian. The lithological features and the age of the Numidian Flysch in central-southern Apennines, therefore, point out an evolution different from that of the Numidian Flysch of the Maghrebian chain. During the early Miocene, a paleogeographic barrier or other unknown obstacles prevent Numidian sands from reaching the south-Apenninic domains. In the early Langhian, the disappearance of these obstacles allows sands to reach the deep basins located on the Apulian margin. In the late Langhian the Numidian sedimentation is canceled and replaced by mainly pelagic sediments, which will evolve to foredeep deposits in the Serravallian-Messinian time span. In addition, the significant presence of feldspathic and lithic grains testifies a double detrital supply: polycyclic quartzose sands and kaolinitic mudstones from the African craton and metamorphic and plutonic grains from the Hercynian or older rocks of the internal units of the southern Apennines. The Numidian Flysch of the southern Apennines allows to assign the tectonic units in which is present to the Campania-Lucania carbonate platform or to different zones of the Lagonegro-Molise basin and therefore is of great importance in the reconstruction of both the Mesozoic-Cenozoic paleogeography and a tectono-sedimentary evolution very difficult to decipher, given the convergence of sedimentary facies in the Apenninic deep basins since Cretaceous to Miocene, the presence of several tectonic phases and of out of sequence and back-thrusts.

The role of Mesozoic palaeogeography in the evolution of the Southern Apennines

Several lines of geophysical evidence suggest that the slab subducted underneath the Tyrrhenian sea is made up of oceanic lithosphere. This requires that an oceanic domain was present to the west of the Apulian Platform during the Mesozoic. The sediments of the Lagonegro basin were likely deposited within this oceanic domain, and related continental palaeomargin. The sinking and rolling back of the dense Ionian oceanic lithosphere controlled, to a large extent, the Neogene geological evolution of the Southern Apennines - Tyrrhenian system. In fact, most of the evolution of the Southern Apennines can be accounted for by an accretionary wedge tectonic. Only in the final stages, from Late Miocene-Early Pliocene, the accretionary wedge docked on the continental margin and was emplaced on the Apulian Platform, originating the present structural stack of the southern Apennines. It is here proposed that the Apennine Platform had an original intraoceanic position and was successively incorporated within the accretionary wedge, being detached from its infra-Triassic substratum.

Fluid channeling along thrust zones: the Lagonegro case history, southern Apennines, Italy

AbstractA regional study on late burial, syntectonic dolomites and syntectonic calcite and quartz veins occurring in the hemipelagic Triassic–Jurassic succession of the Lagonegro Basin (southern Apennines) was carried out by integrating fieldwork with structural, fluid inclusion, and geochemical investigations on both surface and subsurface samples. The main goal was to characterize the different parent fluids, channeled along a major, out of sequence thrust zone. We also investigated calcite veins from the deeper tectonic mélange zone. The results point out that the fluids at peak burial conditions, during the first deformation stage, were characterized by temperatures of 120–140°C and salinities averaging 2 wt% NaCl eq. Fluids channeled along the late, out of sequence thrust zone and responsible for partial dolomitization of the succession had lower temperatures (Th = 95 ± 10°C) and salinities in the range of slightly modified to normal marine seawater (mean at 3.7 wt% NaCl eq). Similar low salinities are encountered in late dolomites from other fold‐and‐thrust belts of Italy. The most probable source for the fluids channeled along the investigated out of sequence thrust zone is represented by Miocene marine pore waters expelled from the tectonic mélange zone. A comparison of the Lagonegro dolomites with similar late stages carbonates formed in other fold‐and‐thrust belts suggests that fluid salinities appear to be controlled by the different lithologies of the fold‐and‐thrust belts décollement surfaces.

The Geological Itinerary of Sasso di Castalda: A Journey into the Geological History of the Southern Apennine Thrust-belt (Basilicata, Southern Italy)

Sasso di Castalda (20 km south of Potenza in the Southern Apennines thrust-belt) is a village situated on spectacular outcrops of Mesozoic rocks. In order to illustrate the peculiar stratigraphic and structural features of the area, a geological itinerary comprising 15 stops has been developed around the Sasso di Castalda village. The itinerary illustrates the Mesozoic stratigraphy of the deep-sea Lagonegro Basin in an area where the Triassic to Cretaceous evolution of the basin has been studied in great detail. Extensive exposure allows the observation of tectonic structures related to the Miocene to Pleistocene evolution of the Southern Apennine orogeny. The choice of Sasso di Castalda as the starting point for this itinerary is due to the following reasons: (1) the opportunity to observe the thick sedimentary infill of the Lagonegro Basin, within deeply incised natural sections where lithology, stratigraphical contacts and the geometry of the sedimentary bodies are magnificently exposed; (2) the opportunity to examine 3D-fold geometry at different scales; and (3) the opportunity to observe well-exposed post-orogenic faults crosscutting the earlier contractional structures. The itinerary can be used for school teaching purposes at different levels, as well as university courses. In addition, non-geologists frequently follow the itinerary, often guided by expert volunteers.

Oxygen isotopic evidence for Late Triassic monsoonal upwelling in the northwestern Tethys

The oxygen isotopic composition of conodonts from the Pizzo Mondello section in the Sicani Basin (Sicily, Italy), on the northwestern Tethys margin, has been used to reconstruct regional paleoseawater conditions. The δ 18 O phos values (21‰–21.9‰) measured by sensitive high-resolution ion microprobe (SHRIMP II) are consistent with previously published δ 18 O phos data from the contemporaneous marginal Hallstatt-Meliata Basin (20.3‰–22.5‰) located farther north, but are distinctly higher than those previously reported from the open ocean setting of the nearby Lagonegro Basin (18.7‰–20.0‰). This ∼2‰ offset represents a temperature differential of ∼8 °C, suggesting that sea-surface temperatures along the northwestern margin (Sicani and Hallstatt-Meliata basins) of the Tethys Ocean were lower than in the open ocean (Lagonegro Basin) during the late Carnian (Tuvalian 2) to early Norian (Lacian). We interpret the cooler waters of the marginal basins to reflect coastal upwelling driven by strong monsoonal systems, as predicted by existing paleoclimate models for this region.

STRATIGRAPHY OF THE CARNIAN - NORIAN CALCARI CON SELCE FORMATION IN THE LAGONEGRO BASIN, SOUTHERN APENNINES

The Upper Triassic Calcari con Selce Formation, cropping out in the southern Apennines (S Italy), consists of 400 m of micritic limestones, often nodular, with chert beds and nodules, organized in dm to m beds intercalated with mm (rarely centimetric) marly horizons. Three intervals characterized by higher siliciclastic content have been recognized within this formation, and stratigraphically ordered after an accurate conodont biostratigraphical investigation: 1) the green clay-radiolaritic horizon, previously named in literature with the informal expression of “livello argilloso ad Halobia superba”, Tuvalian (upper Carnian); 2) an interval of some tens of meters of limestones and shales with abundant chert beds, here informally termed the brown member, Tuvalian/Lacian (upper Carnian/lower Norian; 3) the ca. 3 m thick red shale horizon, Sevatian (upper Norian) in age. All these intervals are characterized by micritic limestones or marly limestones with bivalves, radiolarians and conodonts alternating with shales (green, or red) having thicknesses of 50 cm or more. These intervals are also associated to an increase of calciturbidites, consisting of echinoderm fragments, isolated thin-shelled bivalves and reworked, partially lithified intraclasts of the Calcari con Selce Fm. The Carnian green clay-radiolaritic horizon and the Sevatian red siliciclastic interval are useful lithostratigraphic markers recognizable throughout the Lagonegro Basin and have been used as guide horizons to evaluate the lateral continuity of contiguous limestone beds. The green clay-radiolaritic horizon has been logged in 4 sections (Pignola 2, Mt. Armizzone, Pezza la Quagliara, San Michele). The sections are presently at approximately 50 km distance - but Tertiary thrusts occur between the sections, suggesting a larger separation at the time of the deposition of the Formation. Above the green clay-radiolaritic horizon, single carbonate beds or banks with the same stratigraphic position and common characteristics are recognizable in all sections. The thickness of these limestone beds may vary, but the shale interlayers and cherty beds are identical, thus, the carbonate beds have been correlated. The stratigraphic interval comprising the Sevatian red shale horizon has been acquired in two sections separated by 7 km, Monte Buccaglione (i.e lower portion of the Sasso di Castalda section) and Monte Cugnone, with a Terrestrial Laser Scanner (TLS). TLSs produce high resolution and high accuracy 3D representations of outcrops, stored as point-clouds. A regular sequence of limestone beds and shale interlayers, distinguished because of their different reflectance, has been recorded below the red shale horizon, and the thickness of single carbonate banks resulted identical within the instrumental resolution. Calcareous beds or banks thus can be correlated at the basinal scale. This implies that the Lagonegro Basin is characterized by laterally continuous carbonate sedimentation, most probably controlled by allocyclic factors, providing potential for cyclostratigraphic investigations. Original papers

The Norian-Rhaetian interval in two sections of the Lagonegro area: the transition from carbonate to siliceous deposition

New biostratigraphic data from two stratigraphic sections (Mt. St. Enoc and Mt. Volturino), of the Lagonegro Basin (Southern Apennines, Italy), define the age of the sedimentary events and delineate the sedimentary evolution for the Norian-Rhaetian time interval.The upper part of the Calcari con Selce Fm in the Mt. St. Enoc section is characterized by an alternation of cherty limestones rich in organic matter and thin silicified calcarenites with black cherty layers. The upper part of the Calcari con Selce Fm of the Mt. Volturino section exhibits instead intermediate characters between the Calcari con Selce and Scisti Silicei Fms, with cherty limestones, shales and radiolaritic beds. The biostratigraphic data based on conodonts and radiolarians allowed a good correlation among the Norian-Rhaetian successions throughout the Lagonegro Basin the two sections represent two different environments of the Lagonegro Basin. In fact, radiolarites (Scisti Silicei Fm) are present from the Misikella hernsteini-Parvigondolella andrusovi conodont Zone (late Sevatian) in the Mt. Volturino section while they appeared after the Misikella ultima conodont Zone (uppermost Rhaetian) in the Mt. St. Enoc section. This proves that euxinic carbonate facies and radiolaritic facies were deposited in the same time interval and in the same basin. On the basis of sedimentological analysis and with the support of biostratigraphy, the non-coeval beginning of biosiliceous sedimentation is discussed in order to point out the control factors: different paleobatimetry, upwelling areas or volcanic activity. Our preliminary results show that the Lagonegro Basin during the Norian-Rhaetian interval was probably characterized by an articulated physiography and that volcanism should have had an important role in changing pelagic sedimentation.