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Brandano, M. & Policicchio, G. 2011: Strontium stratigraphy of the Burdigalian transgression in the Western Mediterranean. Lethaia, Vol. 45, pp. 315-328. A 87Sr/86Sr analysis of selected pectinid shells has been performed to refine the stratigraphical framework of the Burdigalian transgressive event. Samples were collected from shallow water successions of the Western Mediterranean area (North-Eastern Sardinia, Southern Corsica, Central Apennines). The Western Mediterranean is the result of the interaction between the European and the African plates. Sardinia and Corsica were extended and rifted apart from the Iberian Peninsula during the opening of the Liguro-Provencal basin, between 30 and 15 Ma. In the outcrops of Northern Sardinia and Southern Corsica, Burdigalian deposits nonconformably overlie Varisican granites. In the central Apennines the Burdigalian deposits paraconformably overlie the Cretaceous platform. These are transgressive deposits, characterized by the presence of Miogypsina globulina, which points out early to middle Burdigalian age. The Sr isotope ages indicate that marine transgression in Northern Sardina and Southern Corsica took place between 18.6 and 18.3 Ma, which could correspond to the eustatic sea level rise of the Bur3 third-order sequence. In the Central Apennines the Burdigalian transgression was anticipated (18.8 Ma) by subsidence input linked to the eastward migration of the orogenic system. This input allowed the Miocene carbonate ramp to develop on the Cretaceous platform substrate, while successive eustatic rise controlled the evolution of the stratigraphical architecture. The following regressive phase is recorded in both the Apennine and Corsica successions. The end of this phase is dated between 17.6 and 17.5 Ma and corresponds to sea level drop corresponding to the occurrence of the Mi 1b event. □ Burdigalian, pectinids, strontium stratigraphy, transgression, Western Mediterranean [ABSTRACT FROM AUTHOR]

The Eocene-Oligocene represents the last greenhouse-icehouse transition faced byEarth. This relevant climate change affected the global carbon cycle in ways that arestill under debate. In this work, the upper Eocene-lower Oligocene δ13CCarb andδ13CTOC records of a shallow-water and a basinal carbonate settings within the CentralMediterranean area are presented and discussed. The bulk-rock carbon isotope recordhas been analysed in the northern portion of the Apula Platform, cropping out inthe Majella Mountain, Central Apennines (Santo Spirito Formation), while theorganic C-isotope signal has been investigated in the Umbria-Marche hemipelagicsuccession in the Massignano section (Conero area, Central Italy). Aims of this workare: (i) to discriminate between the global and the regional factors affecting theNeotehys C-isotope record; (ii) to evaluate the complex C-cycle dynamics across theEocene-Oligocene Transition; (iii) to estimate the influence of this C-cycle perturbation onthe shallow-water carbonate production. The results show that the Neotethys C-isotoperecord matches the global trend. Overall, the upper Eocene δ13CCarbdecreaseswhile the δ13CTOCincreases. The decoupling of the curves is due to a reducedfractionation effect by primary producers, consistent with the decreasing of theatmospheric CO2concentration during the late Eocene. However, regional factorsaffected the Neotethys record. The upper Eocene hemipelagic δ13CTOC curve ismarked by transient negative spikes that testify for high productivity pulses whichare related to enhanced nutrient availability triggered by the subtropical EoceneNeotethys current that, entering from the Arabian-Eurasian gateway, carried iron-richwaters. On the contrary, the shallow-water δ13CCarbrecord does not show theseshort-term peaks. However, a change in the carbonate factory is recorded at theEocene-Oligocene transition, witnessed by a demise of the larger benthic foraminiferaoccurring concomitantly with a spread of seagrass and corals. Lastly, no positive C-isotopeshift is recorded in the Santo Spirito ramp associated to the Oi-1, since the normal bedding isdisrupted by extensive slumps. These slumps are a clear evidence of the sea-leveldrop linked to the onset of the Antarctic glaciation, which triggered the deepeningof the storm wave base, leading to an increased instability over the entire ramp. [ABSTRACT FROM AUTHOR]

The 87Sr/86Sr isotope ratio has been widely used as a physical tool to date and correlate carbonate successions due to the long Sr residence time in comparison with the ocean mixing time. If this method works on oceanic successions, marginal basins may show different Sr isotope records in comparison with the coeval ocean one due to sea-level variations, continental run-off and restricted water exchanges. In this work, we present the 87Sr/86Sr isotope record of the upper Miocene carbonate ramp of the Lithothamnion Limestone (Majella Mountain, central Apennines), as an example of the onset of restricted water exchanges between a marginal basin and the ocean water masses. The overall latemost Tortonian-early Messinian Sr isotope record of the Lithothamnion Limestone fits below the global reference line. This deviation has been interpreted as due to the strong control that freshwater input and enhanced continental run-off, linked to the migration of the Apennine accretionary wedge and foredeep system, have had on the central Adriatic water chemistry. These results imply that an accurate oceanographic and geodynamic framework along with diagenetic overprint investigation has to be taken into consideration prior to apply SIS on carbonate successions on marginal basins, even when facies analyses indicate fully marine conditions. This seems to be the case for the upper Miocene Central Mediterranean carbonate successions, but may have more general validity and be extended to other recent or past marginal basins. [ABSTRACT FROM AUTHOR]

Changes in stacking patterns of facies, stratal architecture and shoreline trajectory along depositional strike are mainly dependent on along-strike differences in factors such as physical processes (rivers, waves, tides), tectonics, eustatic changes, sediment supply, and local physiography. The lower-upper Ordovician successions (Lashkerak Formation) deposited in a Peri-Gondwana shallow continental shelf have been interpreted using the sequence stratigraphic concepts. This approach allowed to highlight main differences along-strike in the co-existing depositional systems (coastal plains, estuaries, deltas, and shoreline to shelf systems) in the Alborz basin along the northern edge of Gondwana. On the basis of sedimentary and ichnological characteristics, the siliciclastic successions are divided into four facies associations: (i) Wave-dominated estuarine, (ii) Wave-dominated shoreface-offshore complex, (iii) Mixed fluvial (F)- and wave (W)-influenced delta (Fw and Wf), and (iv) Tide-dominated, fluvial-influenced delta (Tf). Six third-order depositional sequences (DS1-DS6) were recognized, each of them are bounded by unconformities and pronounced shifts in the facies. Along depositional strike (NE/SW- a distance of c. 150 km), significant intrabasinal changes in sediment supply produced evident lateral changes in the shoreline trajectory and stratal architecture, of the DS1-DS3 (Tremadocian-Floian), may be attributed to differences in physical processes (rivers, waves, tides activity) and topographic irregularities derive probably by different rates of subsidence in the basin. During the deposition of the DS1-DS3, a significant along-strike differences in the composition of ichnological suites and the lifestyle of benthonic organisms, dependent on the relative supremacy of wave, storm, river, and tidal processes. Sedimentary supply and processes are the main controlling factors for the stratigraphic architecture rather than the tectonic activity between Tremadocian and Floian. While during the Darriwilian-Katian interval (DS4-DS6), the tectonic activity predominates with the beginning of extensional phases related to the rifting in the Alborz basin causing the activation of syn-depositional normal faults and the development of block-faulted craton-ward margin. Typically, differential subsidence due to extensional tectonic activity causes the uplift of tectonic blocks west of the Alborz Basin into the emerging areas, on one hand, and simultaneous deepening-upward stacking patterns (i.e., increased subsidence rates) in the hanging-wall depocenters of east of the Alborz Basin, on the other hand. This outcrop-based study suggests that the identification of genetically related depositional units in a larger paleogeographic context is fundamental for understanding along-strike variability in controlling mechanisms of the spatial distribution and stratigraphic architecture of coexisting and linked depositional systems. • Analyze along-strike variations in stratigraphic architecture of the Ordovician successions. • Synthesis of autocyclic and allocyclic controls on changes in accommodation space along depositional strike. • Interpreting along-strike variability in controlling mechanisms of stratigraphic architecture. • Unravelling the palaeogeography of continental shelf of the Prototethys margin along the northern edge of Gondwana. • Results are useful for correlation to Ordovician strata in other parts of Gondwana. [ABSTRACT FROM AUTHOR]

Oligocene carbonate ramps and platforms are widespread and though they are important carbonate reservoirs, detailed studies on the facies organization, platform type and internal architecture are scarce. Within this context, the Chattian carbonate units cropping out in Salento (southern Italy) allow detailed study of the distribution of skeletal components and facies architecture. The lower Chattian Castro Limestone, previously considered as a fringing reef, is reinterpreted as a distally steepened ramp with a distal talus induced by a paleo-escarpment in the substrate. Epiphytic biota and sediment dweller organisms thriving in seagrass meadows dominated production in the shallow-water euphotic zone. Seawards, large rotalid foraminifers dominated a detritic mesophotic zone. Near the edge of the escarpment, also in the mesophotic zone, luxurious growth of corals built discrete mounds with no evidences of wave-resistant growth fabrics. Basinward, 25° to 30° dipping clinobeds abut against the escarpment where coral rudstone/floatstone textures resulted from downfall of corals and sediments. The upper Chattian Porto Badisco Calcarenite represents a homoclinal ramp dominated by packstone textures. In the euphotic inner ramp, autochthonous biota suggests the occurrence of extensive seagrass meadows. Basinward, large rotalid packstone and small coral mounds developed in mesophotic conditions, and rhodolithic floatstone to rudstone and large lepidocyclinid packstone characterize the sediments of the deeper oligophotic zone. Comminuted skeletal debris, depleted of light-dependent organisms, typifies deposition in the dysphotic/aphotic zone. In both examples, the middle ramp (meso-oligophotic zones) was the most prolific in terms of carbonate production, whereas shallow-water seagrass-related production (euphotic) was much less important. Corals built mounds, also in the mesophotic zone but never reached sea level. Hydrodynamic conditions in the meso-oligophotic zone are better explained by breaking of internal waves, and their induced up- and down-slope currents, instead of the surface storm waves. [ABSTRACT FROM AUTHOR]

Abstract: Analyses of facies associations and biotic assemblages integrated with backstripping analysis are presented to improve understanding of the development of a shallow water Miocene carbonate ramp in the Central Apennines (Italy), with special reference to the relationships between tectonic subsidence and the internal architecture of the ramp. Subsidence curves were calculated for six measured sections located in different sectors of the platform. Dating is derived from Sr isotope analyses (from previous studies) and regional correlations. Corrections for eustasy and paleobathymetry were deduced from biota and facies analyses. The subsidence curves show rates that vary both in space and time. By analysing the vertical motions in different sectors of the ramp over a fixed time span (Burdigalian to Tortonian), it was possible to evaluate the control on platform architecture exerted by tectonically induced changes in sea-floor bathymetry and highlight the effects of tectonic migration. Most analysed sites experienced a short period of tectonic uplift or stability followed by a period of slow subsidence. This preceded increased subsidence which resulted in drowning of the shallow-water carbonate platform. The stability/uplift is progressively younger towards the north-eastern sectors that correspond to progressively more external zones of the foreland relative to the Apenninic orogenic belt. The subsequent drowning is related to the diachronous down-flexure of the Adriatic lithosphere due to its eastward retreating subduction under the Apennines. The small magnitude of the uplift suggests that the formation of a foreland bulge due to subduction-related flexure of the Adriatic plate was probably not the responsible mechanism. Hence, this uplift is related to the development of proto-thrusts or to the propagation of compressive stresses in the foreland. These vertical motions influenced the geometry of the platform during the 17.5–16 Ma stage. During this period the platform was characterised by exceptional progradation of the bryomol-dominated proximal outer ramp facies belt. This rapid spreading may be induced by the combined effect of increased eutrophic conditions and a contemporaneous decrease in the sea-floor bathymetry resulting from the tectonic uplift. From the Tortonian onwards, when the platform became involved in the eastward migrating foredeep system, the tectonic subsidence curve records a short period of fast tectonic subsidence rates followed by a period of slow subsidence or slight uplift during basin drowning and infilling, respectively. [Copyright &y& Elsevier]

The small Plio-Quaternary volcanic centre of Cabezo Negro de Tallante in SE Spain includes a thick deposit of polymictic pyroclastic tuff-breccia, whose fragments are agglutinated by a carbonate-rich component. This feature is also observed in other monogenetic volcanic centres cropping out in the Tallante-Cartagena volcanic district. The carbonate fraction has been recently interpreted in literature as representing a mantle component, therefore pointing to the existence of a diffuse carbonatitic activity in the area. Based on detailed sedimentological (presence of pisoids and root remnants), petrographic (presence of plagioclase and absence of euhedral silicate minerals in the calcite plagues), mineral chemistry (Ba-Sr-poor calcite composition), whole-rock chemistry (overall low incompatible element content in the pure carbonate fraction and a monotonous trace element negative correlation with CaO) as well as isotopic constraints (perfect correlations between Sr-Nd-Pb isotopic ratios with CaO in the basaltic and carbonate fraction, as well as heavy δ18O and light δ13C isotopic composition of the carbonate fraction), we propose a secondary origin for the carbonate component, excluding any contribution of mantle carbonatite melts. The presence of carbonates infiltrating the abundant mantle and crustal xenolith fragments found in the pyroclastic breccia is not related to the presence of carbonatitic melts at mantle to lower crustal depths, but to in-situ fragmentation of the Strombolian tuff-breccia deposit, followed by secondary carbonate infiltration. The pyroclastic breccia was indeed affected by an alternation of carbonate precipitation and dissolution in a vadose zone, where the activity of bacteria, fungi, roots and meteoric water led to the formation of a calcrete (caliche)-type deposits. Basaltic rocks (hawaiites and basanites) occur in the area as scoria and lava fragments in the pyroclastic breccia as well as small lava flows. They have been modelled with a low-degree partial melting of an amphibole-bearing peridotitic mantle close to the lithosphere-asthenosphere boundary. The origin of the mildly alkaline sodic basaltic activity in SE Spain post-dates the abundant and long-lasting subduction-related volcanic phase in the Betic Chain. Its origin is explained without requiring the presence of any thermal anomaly, but simply as consequence of the difference of lithospheric depths and edge-driven-type small-scale convection. • Carbonate-rich volcaniclastic breccias have been found in Cabezo Negro de Tallante volcano in SE Spain. • The whitish carbonate matrix of the breccias has been interpreted in literature as a carbonatitic melt. • This work re-interprets this matrix as a sedimentary component of calcrete-type, unrelated to any • carbonatite involvement. [ABSTRACT FROM AUTHOR]

Despite data coming from fully developed oil fields are fundamental to validate reservoir models, they are rarely publishable because of confidentiality. In this work, we benefit from an exceptionally dense public dataset represented by 43 wells logs drilled in a carbonate-heavy oil-rich reservoir of the Majella Mountain (Central Italy) over a grid of 200 m × 200 m, with depths in the range of 90–200 m. We tested different modelling solutions, to assess the best modelling approach that fits the available data on hydrocarbon distribution. Both deterministic (using Kriging) and stochastic simulations (using Sequential Gaussian Simulation- SGS) were tested. The role of the variogram resulted as a fundamental parameter for both simulation methods. Wells-derived variogram agrees with the size and orientation of carbonate dunes that drive the hydrocarbon distribution highlighting the importance of an accurate depositional model. Kriging was faster in terms of computation time and better in maintaining the lateral continuity of the layers, however, it excessively smoothed the results. SGS gave a better distribution of computed values but the lateral continuity was not preserved. By adding a main vertical trend derived from the upscaled logs to the SGS, results become more accurate. We then applied the best model to estimate the total volume of hydrocarbon in place in an already exploited area starting from just one well. The computed reserves show a good fit with historical production data demonstrating the reliability of the model. • We benefit from a public dense well dataset to test carbonate-reservoir models. • Deterministic solutions are faster but mostly inaccurate. • Stochastic simulation with vertical trend improves simulations of single well profile. • Variogram shape is crucial to improve the 3D stochastic simulation results. • Wells-derived variogram agrees with size and shape of carbonate dunes. [ABSTRACT FROM AUTHOR]

Understanding the factors controlling fracture frequency distribution can greatly improve the assessment of fluid circulation in fault damage zones, with evident implications for fault mechanics, hydrogeology and hydrocarbon exploration. This is particularly important for relay zones that are usually characterized by strong damage and structural complexity. We investigated the fracture frequency within an outcrop adjacent to the front fault segment of a relay ramp, hosted within peritidal carbonates that forms part of the Tre Monti fault (Central Italy). We analysed the distribution of fracture frequency in the outcrop through (1) scanlines measured in the field, (2) oriented rock samples, and (3) scan-areas performed on a virtual outcrop model. Fracture frequency increases with distance from the front segment of the relay ramp. Moreover, supratidal and intertidal carbonate facies exhibit higher fracture frequency than subtidal limestones. This trend of increased fracture frequency has two main explanations. (1) The number of subsidiary faults and their associated damage zones increases moving away from the front segment. (2) The supratidal and intertidal carbonate facies content increases toward the centre of the relay ramp. Our results indicate that the fracture frequency pattern is very complex in relay ramps hosted in shallow-water limestones and that its prediction necessitates a good control on structures and sedimentary facies distribution. • Analysis of fracture distribution within a carbonate-hosted relay ramp. • Integration of scanlines, oriented rock samples and a virtual outcrop model. • Fracture frequency increases with distance from the front segment of the relay ramp. • Subsidiary faults and carbonate peritidal facies control fracture distribution. [ABSTRACT FROM AUTHOR]

Shallow-marine sediment records have the strong potential to display sensitive environmental changes in sedimentary geometries and skeletal content. However, the time resolution of most neritic carbonate records is not high enough to be compared with climatic events as recorded in the deep-sea sediment archives. In order to resolve the paleoceanographic and paleoclimatic changes during the Oligocene-Miocene transition in the Mediterranean shallow water carbonate systems with the best possible time resolution, we re-evaluated the Decontra section on the Maiella Platform (central Apennines, Italy), which acts as a reference for the correlation of Oligocene-Miocene shallow water deposits in the Mediterranean region. The 120-m-thick late Oligocene-late Miocene carbonate succession is composed of larger foraminiferal, bryozoan and corallinacean limestones interlayered with distinct planktonic foraminiferal carbonates representing a mostly outer neritic setting. Integrated multi-proxy and facies analyses indicate that CaCO 3 and total organic carbon contents as well as gamma-ray display only local to regional processes on the carbonate platform and are not suited for stratigraphic correlation on a wider scale. In contrast, new biostratigraphic data correlate the Decontra stable carbon isotope record to the global deep-sea carbon isotope record. This links relative sea level fluctuations, which are reflected by facies and magnetic susceptibility changes, to third-order eustatic cycles. The new integrated bio-, chemo-, and sequence stratigraphic framework enables a more precise timing of environmental changes within the studied time interval and identifies Decontra as an important locality for correlating not only shallow and deep water sediments of the Mediterranean region but also on a global scale.