Geological map of Tuscany (Italy)

The main map covers the territory of the Tuscany Region, in Central Italy and shows the main stratigraphic and tectonic features of the internal part of the Northern Apennines. This is characterized by nappe superposition well exposed in the Apennine chain (in the eastern part of the map), as well the effects of post-nappe extensional tectonics, originating in Miocene-Pliocene and younger basins bordered by metamorphic core complexes, covering most of the central and southern part of the Region. The map is at 1:300,000 scale and is based on 1:10,000 field mapping

Geology of the ‘Coltre della Val Marecchia’ (Romagna-Marche Northern Apennines, Italy)

A detailed geological map at 1:50,000 scale of the Marecchia Valley and adjoining areas (Northern Apennines, NA, Italy) is presented here. The Marecchia Valley represents a geological ‘unicum’ for the NA and it has been the focus of scientific debate for a long time, due to the occurrence in the area of the ‘Coltre della Val Marecchia (CVM)’, a complex stack of allochthonous and semi-allochthonous units emplaced in a foredeep basin during the Late Miocene to Early Pliocene. In order to clarify the geological evolution for this area, the lithostratigraphic relationships and the tectonic framework have been studied, allowing better understanding of the complex relationships between tectonics and sedimentation. The main result has been a new evolutionary framework for this sector of the orogen during the Late Miocene-Early Pliocene. Several new findings about the geological-structural setting and stratigraphy, result from the geological map presented here. These are overall supported by stratigraphic and tectonic evidence, which suggest time and modes of the CVM allochthonous emplacement within the Messinian-early Pliocene foredeep successions. Relationships between the allochthonous and autochthonous formations allowed recognition of two different bodies in the CVM, gravitationally emplaced following different trajectories and timing

Petrologic and Geochemical Composition of the AND-2A Core, ANDRILL Southern McMurdo Sound Project, Antartica

The compositional record of the AND-2A drillcore is examined using petrological, sedimentological, volcanological and geochemical analysis of clasts, sediments and pore waters. Preliminary investigations of basement clasts (granitoids and metasediments) indicate both local and distal sources corresponding to variable ice-volume and ice-flow directions. Low abundance of sedimentary clasts (e.g., arkose, litharenite) suggests reduced contributions from sedimentary covers while intraclasts (e.g., diamictite, conglomerate) attest to intrabasinal reworking. Volcanic material includes pyroclasts (e.g., pumice, scoria), sediments and lava. Primary and reworked tephra layers occur within the Early Miocene interval (1093 to 640 metres below sea floor). The compositions of volcanic clasts reveal a diversity of alkaline types derived from the McMurdo Volcanic Group. Finer-grained sediments (e.g., sandstone, siltstone) show increases in biogenic silica and volcanic glass from 230 to 780 mbsf and higher proportions of terrigenous material ca. 350 to 750 mbsf and below 970 mbsf. Basement clast assemblages suggest a dominant provenance from the Skelton Glacier - Darwin Glacier area and from the Ferrar Glacier - Koettlitz Glacier area. Provenance of sand grains is consistent with clast sources. Thirteen Geochemical Units are established based on compositional trends derived from continuous XRF scanning. High values of Fe and Ti indicate terrigenous and volcanic sources, whereas high Ca values signify either biogenic or diagenic sources. Highly alkaline and saline pore waters were produced by chemical exchange with glass at moderately elevated temperatures

Contrasting styles of (U)HP rock exhumation along the Cenozoic Adria-Europe plate boundary (Western Alps, Calabria, Corsica)

Since the first discovery of ultrahigh pressure (UHP) rocks 30 years ago in the Western Alps, the mechanisms for exhumation of (U)HP terranes worldwide are still debated. In the western Mediterranean, the presently accepted model of synconvergent exhumation (e.g., the channel-flow model) is in conflict with parts of the geologic record. We synthesize regional geologic data and present alternative exhumation mechanisms that consider the role of divergence within subduction zones. These mechanisms, i.e., (i) the motion of the upper plate away from the trench and (ii) the rollback of the lower plate, are discussed in detail with particular reference to the Cenozoic Adria-Europe plate boundary, and along three different transects (Western Alps, Calabria-Sardinia, and Corsica-Northern Apennines). In the Western Alps, (U)HP rocks were exhumed from the greatest depth at the rear of the accretionary wedge during motion of the upper plate away from the trench. Exhumation was extremely fast, and associated with very low geothermal gradients. In Calabria, HP rocks were exhumed from shallower depths and at lower rates during rollback of the Adriatic plate, with repeated exhumation pulses progressively younging toward the foreland. Both mechanisms were active to create boundary divergence along the Corsica-Northern Apennines transect, where European southeastward subduction was progressively replaced along strike by Adriatic northwestward subduction. The tectonic scenario depicted for the Western Alps trench during Eocene exhumation of (U)HP rocks correlates well with present-day eastern Papua New Guinea, which is presented as a modern analog of the Paleogene Adria-Europe plate boundary

Antarctic ice sheet sensitivity to atmospheric CO2 variations in the early to mid-Miocene

Geological records from the Antarctic margin offer direct evidence of environmental variability at high southern latitudes and provide insight regarding ice sheet sensitivity to past climate change. The early to mid-Miocene (23-14 Mya) is a compelling interval to study as global temperatures and atmospheric CO2 concentrations were similar to those projected for coming centuries. Importantly, this time interval includes the Miocene Climatic Optimum, a period of global warmth during which average surface temperatures were 3-4 °C higher than today. Miocene sediments in the ANDRILL-2A drill core from the Western Ross Sea, Antarctica, indicate that the Antarctic ice sheet (AIS) was highly variable through this key time interval. A multiproxy dataset derived from the core identifies four distinct environmental motifs based on changes in sedimentary facies, fossil assemblages, geochemistry, and paleotemperature. Four major disconformities in the drill core coincide with regional seismic discontinuities and reflect transient expansion of grounded ice across the Ross Sea. They correlate with major positive shifts in benthic oxygen isotope records and generally coincide with intervals when atmospheric CO2 concentrations were at or below preindustrial levels (∼280 ppm). Five intervals reflect ice sheet minima and air temperatures warm enough for substantial ice mass loss during episodes of high (∼500 ppm) atmospheric CO2. These new drill core data and associated ice sheet modeling experiments indicate that polar climate and the AIS were highly sensitive to relatively small changes in atmospheric CO2 during the early to mid-Miocene

Sand-rich turbidite system of the Late Oligocene Northern Apennines foredeep: physical stratigraphy and architecture of the "Macigno costiero" (coastal Tuscany, Italy

The 'Macigno costiero' turbidite system characterized the oldest foredeep clastic wedge of the Northern Apennines during the Late Oligocene collisional phase. The cropping-out thickness is about 500m. The features of the 'Macigno costiero' indicate a sand-rich, low-efficiency turbidite system. The system developed within a partially confined basin, which was part of a complex foredeep system. The stacking pattern of the turbidite system was determined through the analysis of facies and physical stratigraphy. It consists of a succession organized in sedimentary units, which are characterized by particular associations of facies linked to distinct depositional environments. Several architectural elements are seen: (1) unchannelized and channelized lobes; (2) distributary channels with channel-fill, overbank and channel-margin deposits; (3) main channel with channel-fill, channel-margin and interchannel deposits. Five turbidite stages were identified. From the bottom up they consist of four lobe stages and one proximal channel stage. The lobe stages are characterized by thickening-coarsening upward trends, from distal lobes to proximal lobes up to the channel-lobe transition zone. The uppermost, fifth stage is linked to a main channel complex with stacked channel-fill, channel-margin and interchannel deposits. This final stage also marks the maximum progradation of the system up to its closure due to the synsedimentary overthrusting of the orogenic wedge

Compositional evolution of the Macigno Fm. of southern Tuscany along a transect from the Tuscan coast to the Chianti Hills

The Macigno deep-sea turbidite unit was part of the diachronically migrating foredeep system that characterized the collisional phases of the Apennine orogen at the Oligocene-Miocene transition. Detrital modes of the Macigno sandstones along a transect transversal to the chain in southern Tuscany show homogeneity in the framework composition but differences in the composition of finegrained lithics. Three petrofacies characterize this portion of the foredeep system: the «petrofacies A», present in the innermost successions (Baratti area), shows considerable amounts of carbonate (CE) and volcanic (Lv) lithics; the «petrofacies B», occurring in the central section of the studied transect (Sassetta area) shows low CE and high Lv content; the «petrofacies C», seen in the external and eastern sections (Poggio Ritrovoli and Chianti area), has low CE and Lv contents. The modal analysis indicates that the occurrence of volcanic and carbonate grains tends to decrease from the internal to the external portions of the Macigno. The source of the «petrofacies A» sandstones was an area characterized by crystalline and volcanic terranes, associated with carbonate covers; they could be represented by the Corsica-Sardinia Massif. In contrast, the source of the «second » and «third» petrofacies sandstones is thought to be mainly in basement domains such as the Western-Central Alps crystalline terranes

Sedimentation in the Northern Apennines-Corsica tectonic knot (Northern Tyrrhenian Sea, Central Mediterranean): offshore drilling data from the Elba-Pianosa Ridge

The Northern Tyrrhenian Sea is located on the collisional zone between the Alpine Corsica and the Northern Apennines and is a key area for gaining a better understanding of the complex relationships between these two systems. The knowledge of the wide offshore part of this zone, located between Corsica (France) and mainland Italy, is based primarily on the analysis of several seismic profiles tied to the outcropping geology and unpublished preliminary reports of few offshore wells. The here presented study of two offshore wells provides a revision of the sedimentology, biostratigraphy and petrography of the thick, mainly siliciclastic, Tertiary successions (about 3,600 m) composing the Elba–Pianosa Ridge (EPR), a structural/ morphological high separating the Tuscan Shelf to the east from the Corsica Basin to the west. A comparison with similar deposits cropping out in the surrounding onshore areas (Northern Apennines, Corsica, Tuscan Archipelago, Piedmont Tertiary Basin) provides additional constraints for refinement of the complex geodynamic and regional setting in which the EPR evolved

The early depositional phases of the northern Apennine foredeep-thrust belt system: implications from the "Macigno costiero" (Late Oligocene, Italy)

The late Chattian "Macigno costiero" represents the innermost and the oldest portion of the well developed siliciclastic wedge of the migrating Oligo- Miocene foredeep-thrust-belt system of the Northern Apennine. Its stratigraphic features help to understand the early phases of the sin-collisional sedimentation and the evolution of such a thrust belt. In the turbiditic siliciclastic sequence, carbonates were found at different stratigraphic levels (chaotic-debris flow key-level, calcareous turbidites and Subligurian olistostromes and olistoliths). Stratigraphical studies of the sequence based on facies analysis, petrographical observations and biostratigraphical analysis of calcareous nannofossils allow to suggest some hypotheses of the palaeogeographic setting and the evolution of the foredeep-thrust belt system. The vertical distribution of the sediments and their sedimentological characters show a low efficiency sand-rich turbidite system (sensu Mutti and Normark, 1987), characterised by a prograding fan terminated by the emplacement of slices of the orogenic wedge. Olistostromes and olistoliths found in the turbidite succession were the precursor of the allochthonous nappe. The proposed hypothesis shows that turbidite sediments were probably fed transversally to the basin, from a shallow marine shelf adjacent to a crystalline basement. The "Macigno costiero" was deposited in an internal position of the foredeep system

Evoluzione deposizionale di un settore del sistema catena-avanfossa dell'Appennino settentrionale: stratigrafia fisica e sedimentologia del Macigno della Toscana meridionale

The Macigno deep-sea turbidite unit was part of the diachronically migrating foredeep system characterizing the collisional phases of the apenninic orogen at the transition between Oligocene and Miocene time. The Macigno Fm. stratigraphically rests above the Scaglia toscana, a pelitic and calcareous unit of basin plain environment, while it is superimposed by the ligurian and subligurian thrust sheets that formed the accretionary prism in the internal margin of the foredeep. The nappe was responsible, with its advancing, of the migration of the depocenter basin and of the progressive reduction and closure of the sedimentation. The turbidite deposition gradually moved from the inner Tuscan domain (Macigno clastic wedge) to the outer Tuscan domain (Cervarola-Falterona clastic wedge), and from here to the outermost Umbro-Marchean domain (Marnoso-arenacea clastic wedge), as fully explained in several papers. Here I have studied the lesser known southern Macigno outcrops of the southern Tuscany, along a transversal chain transect from the inner outcrops of the Piombino-Baratti area to west, to the outer outcrops of the Chianti region to east, through the outcrops of the Sassetta area in the inland Marittime Tuscany, and of the Poggio Ritrovoli area in the Colline Metallifere region. The aim is to contribute for a better knowledge of the depositional evolution of the Northern Apennines foredeep system. The methods of research have been a detailed 1:10.000 geological mapping and stratigraphical-sedimentological analyses aimed at reconstruction of the architecture of the depositional systems. The geological mapping has allowed to recognize the relationships between Macigno and others formations, and to define the tectonic units stack. The vertical distribution of nine sedimentological facies (of genetic type) has allowed defining five facies associations indicative of specific turbidite environments. The facies analysis shows for the innermost Baratti succession, multiple stages of prograding\aggrading lobe system moved until to a channel proximal to the slope stage that is previous to the closure of the basin through the allochtonous ligurian thrust sheet. Eastward, in the outer succession of Sassetta, the turbidite system is characterised by prograding\aggrading lobe system in turn replaced by starved basin deposits in the upper part. Olistostromes coming from the internal slope are embedded in the top part. The allochthonous thrust sheet closed the depositional system. Eastward again, the Poggio Ritrovoli succession has got the same features of the previous, with lesser evident thickening and coarsening upward trends for the middle part, and with peculiar presence of several carbonaceous turbidite bedsets interlayered to the siliciclastic deposits. Also in this succession, the normal-feeding turbidite system is superimposed by a thick interval of starved basin deposits topped by several olistostromes coming from the advancing nappe, and then closing it. The outermost succession, located in the southern sector of the Chianti region, has shown very developed facies and facies associations typical of distal lobe environment; carbonaceous turbidite beds are also recognized. The whole data suggest a complicated framework of the foredeep turbidite system at the Oligo-Miocene transition. Two main types of turbidite systems belonging to the same foredeep system have been distinguished. The internal and oldest succession of Macigno costiero reveals turbidite proximal conditions, and typical features of low-efficiency turbidite system, with feeding transversal to the basin coming from storage basins close to the Corso-Sardinian Massif. To follow the foredeep depositional system migrated toward outer position with changes in the turbidite fed, longitudinal to the basin, from farther source like western alpine crystalline terrain. The turbidite system changed to high-efficiency, migrating on space and on time, with progressively deactivation of the sedimentation, due to the approaching of the allochtonous thrust sheet, as showed by replacing of starved sediments and olisthostromes onto lobe turbidite sedimentation. In conclusion, the research has allowed to identify two turbidites system for the Macigno in Northern Apennines, the oldest and innermost, of low-efficiency type, transversal to the foredeep structural chain system deposited in open piggyback or inner complex foredeep basin, and the other, younger and wider long-lived migrating high-efficiency turbidite system deposited in wide foredeep basins