Emilia Le Pera

Detrital modes and provenance of Miocene sandstones and modern sands to the Southern Apennines thrust-top basins (Italy)

ABSTRACT The Cilento Group (Lower-Middle Miocene), the Monte Sacro Conglomerate (Upper Miocene), the Gorgoglione Formation (Upper Miocene), and the Crati submarine fan (Holocene) are four turbidite sequences deposited in northwest-southeast-trending thrust-top basins of the southern Apennines (Italy) foreland region. The Corigliano basin is a part of the modern Taranto Gulf foredeep basin that developed since the late Pleistocene. Sandstone detrital modes of the Miocene turbidite units are quartzofeldspathic (Petrofacies 1, 2a, 4, 5, 8; Q62F25L13), quartzolithic (Petrofacies 2b; Q60F16L24), and arkosic (Petrofacies 7; Q50F45L5, reflecting a collisional orogenic provenance. Volcanolithic sandstones (Petrofacies 3, Q23F11L66) suggest an important contribution also from a volcanic source area related to the convergent-continental-margin volcanism connected with the collisional tectonic regime that affected the western Mediterranean (e.g., Sardinia volcanic arc). Individual carbonatoclastic beds (hybrid arenite, biocalcarenite, and mudstone) are interbedded with sandstone units of the ilento Group. They have siliciclastic content of about 35% and are quartzofeldspathic (Petrofacies 6; Q53F23L24). These beds (0.10-65 m thick) record impulsive gravitational collapses of the carbonate-platform passive margin to the east and southeast. The petrologic parameters show a temporal evolution from metasedimentary to granitic-gneissic provenance ascribed to different tectonostratigraphic units of the Calabrian arc. Nine Miocene petrofacies suggest dynamic evolution of the source terranes from Laughian to Tortonian time. Facies, dispersal patterns, and petrologic parameters of the Miocene sandstones suggest a provenance from the northern and western margins of the basins. Comparison between the Holocene Crati Fan (Petrofacies 9; Q54F24L22) and Miocene detrital modes suggests that the sandstones of the Cilento Group, the Monte Sacro Conglomerate, and the Gorgoglione Formation were derived from unroofing of the thrusted basement block, transported by torrential-type, fluvio-deltaic systems and then funneled into a major turbidite dispersal system, analogous to the modern Crati submarine fan of the Corigliano thrust-top basin.

Sourceland controls on the composition of beach and fluvial sand of the northern Tyrrhenian coast of Calabria, Italy: implications for actualistic petrofacies

Abstract The northern Tyrrhenian margin of Calabria in southern Italy provides a natural laboratory for sampling sand at different scales: small drainages (first order), rivers draining mountain ranges (second order), and marine environments (beach to deep-marine; third order). Calabrian mountain ranges represent an uplifted and variable dissected thrust belt constituted by Palaeozoic through Pleistocene plutonic, metamorphic, ophiolitic, carbonate and siliciclastic rocks. The modern setting includes a mountainous coast, having high rates of fluvial discharge, and the deep-marine Paola Basin. The composition of modern fluvial and beach sands is useful for the interpretation of sediment transported into deeper-water environments. Modern beach and fluvial sands of the northern Tyrrhenian margin of Calabria define three distinct petrologic provinces, from north to the south: (1) the Lao Littoral Province has calclithite sand derived from erosion of dominantly carbonates of the southern Apennines; (2) the Coastal Range Littoral Province has quartzolithic sand derived from dominantly metamorphic (schist and phyllite) Coastal Range; and (3) the Santa Eufemia Littoral Province has quarzofeldspathic sand derived from dominantly metamorphic Coastal Range and Sila Massif and plutono-metamorphic Mount Poro provenances. Deep-marine turbidites of the Paola Basin have basinwide quartzolithic turbidite sands having close compositional relations with Coastal Range littoral petrofacies. Only at the northern boundary of the Paola Basin, calclithite turbidite sand record deep-water dispersal of the Lao littoral sands. Comparison of detrital modes from mainland to deep-marine environments contribute to the models of dispersal pathways and geographical extension of actualistic sand petrofacies.

Weathering of gneiss in Calabria, Southern Italy

Abstract The effects of weathering in a Mediterranean climate on the mineralogy and microfabric of Paleozoic gneiss of the Sila Massif, Calabria, southern Italy, have been studied. Field observations show highly weathered rock forms a residual soil. Micromorphological and mineralogical properties of bedrock and saprolite show that the weathering process is characterized by at least two major stages, having two distinct rock microfabrics. In the first stage, the morphological features of the original rock are preserved and weathering is manifested mainly by microfracturing, and large portions of the rock remain unaltered. The second stage of weathering involves further development of microcracks and progressive chemical attack on the minerals. This latter stage occurs along both compositional and microstructural discontinuities, with etch pitting of feldspar, and neoformation of clay minerals and ferruginous products replacing feldspar, biotite, and iron-bearing garnet. The determination of quantitative petrographic indices provides a measure of the various stages of weathering.

Post-Oligocene Sediment-Dispersal Systems and Unroofing History of the Calabrian Microplate, Italy

The composition as well as stratigraphic and structural relations of sandstone and sand derived from erosion of the Calabrian Arc provide constraints for paleogeographic and tectonic models of southern Italy. Clastic detritus in the following sedimentary assemblages was derived mainly from provenance terranes within the strongly deformed Calabrian Arc allochthon: (1) the Paleogene Liguride Complex accretionary wedge, deposited in a remnant ocean basin that lay east of the Calabrian Arc and west of the Adria margin; (2) Burdigalian to lower Messinian foreland basin successions, widely developed in the southern Apennines, representing progressively shifted foredeep basins and related wedgetop basins; (3) upper Tortonian to Messinian, mainly nonmarine to shallow-marine successions, cropping out in the western Calabrian Arc, representing synrift clastic wedges related to backarc rifting in the Tyrrhenian area; and (4) the Quaternary of the northern Calabrian Arc, represented by foredeep and related wedgetop b...

The Recycled Orogenic Sand Provenance from An Uplifted Thrust Belt, Betic Cordillera, Southern Spain

The Betic Cordillera of southern Spain represents an uplifted foreland fold–thrust belt. Source rock types of the Betic Cordillera include metamorphic (mainly phyllite, schist, quartzite, and gneiss), sedimentary (siliciclastic and carbonate), volcanic (felsic to intermediate pyroclasts), and mantle-derived (peridotite, gabbro, serpentinite, and serpentine schist) rocks. The fluvial systems range that transect the Betic Cordillera are the major detrital source of sediment along the southern Spanish coast, supplying sand to beaches and offshore depositional systems in the Alboran Sea basin. Three key sand petrofacies derived from the Betic mountain belt reflect the main clastic contribution of known source rocks. All the sands are quartzolithic, ranging from quartz-rich to lithic-rich. Fluvial systems draining the Sierra de Los Filabres, the Sierra Nevada, the Sierra de Gador, and the Ma´laga Mountains, and their related beaches constitute a metamorphic–sedimenticlastic quartzolithic sand petrofacies (Qm34610 F463 Lt6269; Lm72614 Lv264 Ls26613), derived dominantly from the Nevado–Fila´bride, Alpuja´rride, and Mala´guide complexes. This quartzolithic petrofacies extends from northeast of Almeria to Torremolinos (southwest of Ma´laga), and northeast of Algeciras. Only one beach sand sample, east of Cabo de Gata, is volcanolithic. Volcanic detritus (mainly having felsitic textures) is derived from Miocene (15–7 Ma) pyroclastic sequences cropping out in the southeast of the chain. This metamorphic–sedimenticlastic quartzolithic petrofacies changes in the coastal stretch from Torremolinos to Marbella, where drainage systems cut across the Serrania de Ronda. Here source rock types include peridotite, gabbro, and serpentinite of the Ronda Peridotite Massif, and metamorphic rocks of the Ma´laguide and Alpuja´rride units. The fluvial and beach sands of this area are quartzolithic (Qm32612 F1063 Lt58611), and include abundant peridotite and serpentinite grains. The latter quartzolithic petrofacies changes abruptly from Algeciras to Ca´diz, where the sand becomes quartz-rich (Qm7765 F462 Lt1964). This sand petrofacies is derived predominantly from recycling of sedimentary sequences, mainly the quartzarenite turbidite units of the Gibraltar Arc (the Algeciras Flysch). This petrofacies is characterized by higher proportion of quartz grains and abundant sedimentary lithic fragments (Lm163 Lv161 Ls9863). The three onshore petrofacies plot in the recycled-orogen provenance compositional field and the lithic to transitional to quartzose recycled subfields of Dickinson (1985). They vary from lithic, to transitional and quartzose depending on their source lithologies in the Betic foreland fold–thrust belt. These actualistic petrofacies best describe the nature and distribution of sand petrofacies derived from a collisional fold–thrust belt where primary and recycled source rocks are interfingered. Deep-marine turbidites of the Alboran Basin have basinwide quartzolithic sands having close compositional relations with Betic Cordillera onshore sand petrofacies. Comparison of detrital modes from mainland to deep-marine environments provides a suitable basis for interpreting the Miocene to Pleistocene sand dispersal history in the Alboran Basin. These modern quartzolithic petrofacies are used to interpret analogous ancient collisional sandstone petrofacies of the Alpine orogenic belt of the western-central Mediterranean region and of other collisional orogenic systems, as a broader point of view.

Sandstone petrology and mudstone geochemistry of the Peruc–Korycany Formation (Bohemian Cretaceous Basin, Czech Republic)

We have studied the petrography and the bulk-rock geochemistry of arenites and mudstones of the Cenomanian Peruc–Korycany Formation to characterize their provenance and sedimentary history, as well as the influence of weathering, hydraulic sorting, and recycling of the source rocks. The Peruc–Korycany Formation contains sedimentary facies reflecting both meandering- and braided-river systems and shallow-marine systems. Differences in the three depositional settings did not cause distinctly different modifications of the framework compositions of the arenites. The sand from the fluvial systems is very mature (Qm98F0Lt2). These fluvial arenites were subsequently modified by shallow-marine processes; reworking produced very slight decreases in the abundance of lithic fragments and polycrystalline quartz grains. The Cenomanian strata of the Bohemian Cretaceous Basin were derived dominantly from metasedimentary and crystalline rocks of the Palaeozoic Teplà-Barrandian and Cadomian Moldanubian units, respectively. Periods of low tectonic activity resulted in the deposition of arenites with quartzose framework compositions, indicating that climatic and/or transport/depositional-environmental controls overwhelmed factors such as source-rock compositions. Ultrastable dense minerals are useful indicators of sedimentary recycling within the Peruc–Korycanytarenites. Mudstone samples are characterized by abundant kaolinite, illite, chlorite, and quartz but by negligible amounts of goethite and gypsum. Concentrations normalized to the post-Archaean Australian shale (PAAS) show that the sediments are strongly depleted of Na, K, Ca, Sr, and Ba, probably because of the mobility of these elements during weathering. Chemical indices of alteration (CIA, CIW, and PIA) show that the degree of weathering of the source area was high. The data fall closer to the compositional fields of highly weathered minerals such as kaolinite, gibbsite, and chlorite on an A-CN-K diagram. The indices of compositional variability of the studied samples are much less than 1, suggesting that the samples are compositionally mature and were likely dominated by recycling. The elemental ratios critical of provenance (La/Sc, Th/Sc, Th/Co, Th/Cr, and Cr/Th) are similar to fine fractions derived from the weathering of mostly granitoids rather than mafic rocks.

Stratigraphy and Detrital Modes of Upper Messinian Post-evaporitic Sandstones of the Southern Apennines, Italy: Evidence of Foreland-Basin Evolution during the Messinian Mediterranean Salinity Crisis

During the Messinian, the southern Apennines thrust belt experienced a period of strong tectonic rearrangement and accretion, activation of overthrusts, and consequent migration of depocenters. The upper Miocene successions cropping out in the northern segment of the southern Apennine thrust belt have good potential for improving our understanding of the interplay between Messinian salinity-crisis events and foreland-basin evolution. The local Messinian stratigraphy includes: (1) pre-evaporitic thin-bedded euxinic marly clay, interbedded with diatomaceous marls; (2) evaporitic limestone, crystalline gypsum, and reworked gypsum; (3) post-evaporitic deposits subdivided into two main units: the Torrente Fiumarella unit and the Anzano Molasse Formation that grade upward into ostracod-rich deposits (Lago-Mare facies). The evaporitic and post-evaporitic sequences are separated by an angular unconformity. This paper deals with the stratigraphic and petrographic study of the post-evaporitic deposits. The Torrente Fiumarella unit includes lacustrine and alluvial conglomerates, quartzolithic sandstones containing abundant carbonate detritus, shale, and reworked clastic gypsum. The Anzano Molasse Formation includes thick-bedded deltaic to turbiditic conglomerates and sandstones passing upward to thin-bedded turbidite sandstones and marlyclayey siltstones. Sandstones are quartzofeldspathic with variable proportions of sedimentary (both carbonate and siliciclastic) and plutonic detritus. In particular, two populations are present, plutonic-rich and mixed plutonic-sedimentary. Volcaniclastic layers, composed of dominantly vitric particles (shards and pumice), are also interbedded within Anzano Molasse sandstones. The Anzano succession includes rare freshwater ostracods that increase in abundance in the uppermost Lago-Mare facies. The Lago-Mare facies deposits are represented by silty-marly clay with abundant Ostracoda shells (Ilyocypris gibba, Cyprideis torosa and Candona sp.) and intrarenite having abundant intrabasinal carbonate particles (ooids, peloids, and bioclasts) and subordinate extrabasinal noncarbonate and carbonate particles. The post-evaporitic sequences represent an infilled foredeep basin, with a lacustrine environment progressively deepening and experiencing gravity resedimentation. Detrital modes document complex provenance relations from upper Messinian accreted terranes of the southern Apennines thrust belt. Post-evaporitic sandstones in the Irpinia-Daunia sector of the southern Apennines foreland-basin system record both the effects of the foreland tectonic evolution and the Messinian Mediterranean salinity crisis. They may represent alternative models for foreland-basin evolution during a restricted time in late Messinian, which can be applicable also in other portions of the circum-Mediterranean orogen.

Provenance of volcaniclastic beach sand in a magmatic-arc setting: an example from Lipari island (Aeolian archipelago, Tyrrhenian Sea)

Lipari, an active volcanic island in the Aeolian magmatic arc, is an excellent area to determine the effects of multiple source lithology, climate, weathering, transport and depositional environment on epiclastic sand composition. Volcaniclastic sand samples from 12 modern beaches were petrographically characterized using the Gazzi–Dickinson method, and the proportions of source rocks in combination with topography in associated coastal drainage basins were quantified using GIS. Several types of bedrock in the 12 drainage basins that are the likely prominent sources for sand at each sampled beach were recognized, and divided into two categories of provenance lithotypes: lavas and pyroclastic rocks ranging in composition from basaltic andesitic, to andesitic, to rhyolitic. Volcanic lithic fragments from Lipari beach sand consist of colourless and black glassy volcanic fragments with lathwork, felsitic, vitric and microlitic textures. Moreover, high amounts of detrital less durable minerals, such as pyroxene, olivine and Fe oxides, illustrate how the analysed sands preserve the source rock(s) provenance signals. Applying the concept of Sand Generation Index we see that these lithotypes have different propensities to create detritus, in terms of both grain-size and composition. Clastic contribution from pyroclastic rock outcrops such as pumice is not found in the size ranges studied, suggesting that these pumiceous source rocks probably only produce gravel or very fine sand and silt. This finding has implications for the stratigraphic record because pumice clasts, ranging from medium to fine grain-size, could be underrepresented in older volcaniclastic deposits and overrepresented in other size fractions.

Behaviour of epoxide resin used to protect the Rupe di Tropea (southern Calabria, Italy)

The present work aims to study the behaviour of the protective resin tested on a small portion of sandstone rock along the Rupe di Tropea. The Rupe di Tropea, located on the northern coastal edge of the Capo Vaticano promontory (Southern Calabria, Italy), is characterized by frequent landslide phenomena involving large amounts of detritus related to the weathering processes of arenitic sediments. An experimental resin was used in a small portion (the tested surface) of the arenitic sediments of the Rupe di Tropea, in order to check its behaviour against fast erosion processes during the intervention of slope consolidation in 1998. The study of resin was performed trough laboratory tests and petrographic analysis. The results of analysis shown that the resin type was epoxy resin and it has penetrated the rock to a depth of about 2 mm. The tested surface of the arenitic sediments has shown during the last 17 years a good resistance to erosion with only a slight opacization of the applied resin. However, the tested surface is characterized by higher content of soluble salts then the non-treated surface due to the infiltration of water enriched in soluble salts related to the marine aerosol. In these conditions the soluble salts crystallize in the rock pores and between the prismatic cleavage of the micas producing an increase of physical stress and consequent exfoliation processes of the resin surface layer. After a long period, this produces a rock breakdown when these soluble salts evaporate, leaving salt crystals behind. Thus, the epoxy resin improves the resistance to erosion only in a restricted period and without infiltration of water. Over time the infiltration of moisture may introduce dangerous soluble salts. Thus, if the treated surface is not well isolated from the water infiltration, the resin produces after a long period an increase of the crystallization of the soluble salts with consequent important exfoliation processes of the treated area.