Rita Catanzariti

Lower Oligocene thrust-system in the epi-Ligurian succession: evidence from the Enza Valley (northern Apennines, Italy)

Abstract Within the lower part (Upper Eocene-Oligocene) of the epi-Ligurian succession, outcropping in the Emilian side of the northern Apennines (Enza Valley), duplications by thrust tectonics were recognized through the systematic integration of field geology with calcareous nannofossil biostratigraphy. This thrust system, derived from the overthrusting of two thrust-sheets over a footwall, is unconformably overlain by a Rupelian succession. The thrust structure of the Enza Valley, affected by a subsequent wide overturned syncline together vith the unconformable succession, shows a remarkable Lower Oligocene contractional tectonics, previously not recognized in the northern Apennines. The comparison of this thrust system with other outcropping areas of the epi-Ligurian succession makes probable the wide-spread occurrence of the Lower Oligocene tectonics in the uppermost structural levels of the chain (epi-Ligurian domain). In a regional tectonic framework, the Rupelian thrust tectonics affecting the epi-Ligurian succession can be related to the Lower Oligocene closure of the innermost portion of the Subligurian basin (Aveto-Petrignacola Formation) due to the NE-verging overthrusting of the External Ligurian Units. In this context the unconformable succession of the Enza Valley seems correlable with the basal portion of the Subligurian Eratica Sandstone (Rupelian-Chattian) which unconformably overlies a deformed substratum (Mesoalpine Phase).

MIDDLE PLIOCENE CETACEANS FROM MONTE VOLTRAIO (TUSCANY, ITALY). BIOSTRATIGRAPHICAL, PALEOECOLOGICAL AND PALEOCLIMATIC OBSERVATIONS

The historic collection of fossil odontocetes (Cetacea) from Monte Voltraio, near Volterra (Tuscany, Italy) has been examined and lithostratigraphical and biostratigraphical investigations on the find locality have been carried out. The Monte Voltraio outcrop is referred to the Middle Pliocene, in particular to Globorotalia aemiliana and Discoaster tamalis zones. The odontocete remains are assigned to the families Kogiidae ( Kogia pusilla ) and Delphinidae ( Globicephala ? etruriae and two indeterminate specimens which might belong to Hemisyntrachelus and Stenella giulii ). The Middle Pliocene cetacean fauna from the Mediterranean basin (Monte Voltraio and Rio Stramonte associations) includes extinct taxa or extant taxa no longer represented in this basin. The disappearance of these taxa may be linked with the Pliocene and/or Quaternary climatic deteriorations (e.g. the climatic crisis at about 2.6-2.4 MA).

Updated picture of the Ligurian and Sub-Ligurian units in the Mt. Amiata area (Tuscany, Italy): elements for their correlation in the framework of the Northern Apennines

The Mt. Amiata region (Southern Tuscany, Italy) represents the southernmost area of the Northern Apennines in which different lithologies belonging to the Ligurian and Sub-Ligurian units crop out widely. This paper provides an update on the stratigraphic, paleontological and structural features of the Ligurian and Sub-Ligurian units in the Mt. Amiata area by integrating new data from the Regional Geological Mapping project with those available from the existing literature. In the study area, the Sub-Ligurian units are represented by the Canetolo unit, which comprises the middle Eocene (Zone NP15) Argille e Calcari and Vico Fms showing heteropic relationships. The Ligurian units are represented by the Ophiolitic and Santa Fiora units. The Ophiolitic unit consists mainly of Early Cretaceous Palombini Shale associated with scattered Middle-Late Jurassic ophiolites. The age of the Palombini Shale spans from late Hauterivian-Barremian Zone CC5 to Aptian Zone CC7 of [Sissingh (1977)][1]. The Ophiolitic unit overlies the Santa Fiora unit consisting of the Pietraforte Fm and Varicoloured Shales topped by the Santa Fiora Fm. The Pietraforte Fm shows heteropic relationships with the Varicoloured Shale, and both formations can be referred to the ?Aptian to middle Coniacian. The age of the Santa Fiora Fm seems to span from the late Coniacian-early Santonian (Zone CC14) to middle-late Campanian (Zones CC21-CC22). Structural analyses indicate that all the Ligurian and Sub-Ligurian units experienced complex polyphase deformation through several folding phases during the closure of the Ligurian-Piemontese oceanic basin and the subsequent continental collision, which began in the middle Eocene. The Ligurian and Sub-Ligurian units now come into contact through low-angle shear zones developed during the last deformation phase identified in these units, i.e. middle Miocene extensional tectonics. This tectonic phase produced strong delamination through low-angle faults with staircase geometry, so that not only several stratigraphic levels but also entire tectonic units were omitted. Despite the extensional tectonics, the collected stratigraphic and structural data suggest a correlation between the Ligurian and Sub-Ligurian units of the Mt. Amiata area and the units cropping out in Southern Tuscany and the Ligurian-Emilian Apennines. [1]: #ref-77

CHRONOSTRATIGRAPHIC FRAMEWORK OF THE EXTERNAL LIGURIAN UNITS (LATE CRETACEOUS, NORTHERN APENNINES, ITALY) BASED ON CALCAREOUS NANNOFOSSILS

The study of calcareous nannofossil assemblages recovered from the External Ligurian Units allows us (1) to reconstruct the distribution patterns of selected Late Cretaceous taxa; (2) to identify the biohorizons helpful in recognizing and characterizing the standard zones of Sissingh (1977); some of which have been grouped; and (3) to propose a synthesis of the ages achieved until now for the External Ligurian Units. According to the available dataset; rooted on published and unpublished data; the here proposed biostratigraphic scheme is based on 24 age-indicative taxa and 16 first occurrences; and its biostratigraphic resolution is comparable with the resolution of the scheme of Sissingh (1977); only considering FOs. Calcareous nannofossils are hence a fossil group useful to furnish a new and more complete chronostratigraphic framework of the main External Ligurian Units; helpful to better constrain the tectono-sedimentary and the geodynamic evolution of the Western Tethys Domain.

Calcareous nannofossil biostratigraphy: a tool for understanding the stratigraphic evolution of the Mt. Modino Unit (Northern Apennines, Italy)

The Mt. Modino Unit succession (Northern Apennines) is mainly composed of turbiditic sediments deposited during the collisional and post-collisional stages of the Northern Apennines fold-and-thrust belt. Within this succession we have studied a thick interval of shales with arenitic beds, marls and arenites, of the Fiumalbo Shale, the Marmoreto Marl and the Mt. Modino Sandstone formations. Calcareous nannofossil assemblages of the eight investigated stratigraphic sections contain middle-late Eocene to Oligocene-early Miocene biozones. Zones CNE12 to MNN1 have been identified through quantitative analyses of a set of 200 samples, and the precise ages of the Fiumalbo Shale, the Marmoreto Marl and the Mt. Modino Sandstone were identified as well.The biostratigraphic analyses enable stratigraphic correlations between the investigated sections which were used to propose a stratigraphic architecture of the Mt. Modino Unit succession.Physical and biostratigraphic data available for the Mt. Modino Unit succession suggest a subsiding wedge-top basin fed since the Rupelian by both Apennine and Alpine sources. After the late Oligocene shortening phase, the Mt. Modino Basin occupied the inner part of the foredeep basin, sharing the same turbiditic deposits with the Macigno formation.

CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY OF PALEOCENE TO MIDDLE EOCENE SUCCESSIONS (TERTIARY FLYSCH AUCTT.) OF THE NORTHERN APENNINES

An accurate biostratigraphic study of the Paleocene-middle Eocene calcareous nannofossils was performed on the turbiditic successions that characterize the Northern Apennines Mt. Caio, Farini d’Olmo, Mt. Sporno and Mt. Penice Units, belonging to the “Tertiary Flysch Auctt .” and referable to the External Ligurides. This geologic complex accumulated in a link key area, located between the oceanic Ligure-Piedmontese domain and the Adria continental margin. The reference biostratigraphic scheme used in the study is the recently published calcareous nannofossil biozonation proposed for the Paleogene by Agnini et al. (2014). The obtained biostratigraphic and chronostratigraphic data suggest that further investigation is needed to clarify the tectono-sedimentary evolution and to unravel the complex architecture of the External Ligurides.

The geodynamic evolution of the Intra-Pontide suture zone, Central Turkey: evidence from the ophiolite bearing Arkot Dağ Mélange

Lucchi, Renata G. ... et. al.-- 87° Congresso della Societa Geologica Italiana e 90° Congresso della Societa Italiana di Mineralogia e Petrologia, The Future of the Italian Geosciences - The Italian Geosciences of the Future, 10-12 September 2014, Milan, Italy.-- 1 pageThe Montellina Spring (370 m a.s.l.) represents an example of groundwater resource in mountain region. It is a significant source of drinking water located in the right side of the Dora Baltea Valley (Northwestern Italy), SW of Quincinetto town. This spring shows a morphological location along a ridge, 400 m from the Renanchio Torrent in the lower sector of the slope. The spring was investigated using various methodologies as geological survey, supported by photo interpretation, structural reconstruction, NaCl and fluorescent tracer tests, discharge measurements. This multidisciplinary approach, necessary due to the complex geological setting, is required for the importance of the Montellina Spring. It is interesting in the hydrogeological context of Western Alps for its high discharge, relatively constant over time (average 150 l/s), and for its location outside a fluvial incision and suspended about 40 m above the Dora Baltea valley floor (Lasagna et al. 2013). According to the geological setting, the hydrogeological reconstruction of the area suggests that the large amount of groundwater in the basin is essentially favoured by a highly fractured bedrock, covered by wide and thick bodies of glacial and gravitational sediments. The emergence of the water along the slope, in the Montellina Spring, is essentially due to a change of permeability between the deep bedrock and the shallow bedrock and/or surficial sediments. The deep bedrock, showing closed fractures and/or fractures filled by glacial deposits, is slightly permeable. The shallow bedrock, strongly loosened as result of gravitational phenomena, and the local gravitational sediments are, on the contrary, highly permeable. The concentration of water at the spring is due to several reasons. a) The spring is immediately downward a detachment niche, dipping towards the spring, that essentially drains the water connected to the change of permeability in the bedrock. b) It is along an important fracture, that carries a part of the losses of the Renanchio Torrent. c) Finally, it is favored by the visible and buried morphology. Although it is located along a ridge, the spring occurs in a small depression between a moraine and a landslide body. It also can be favored by the likely concave trend of buried base of the landslide. At last, tracer tests of the Renanchio Torrent water with fluorescent tracer are performed, with a continuous monitoring in the Montellina Spring. The surveys permit to verify and quantify the spring and torrent hydrogeological relationship, suggesting that only a small fraction of stream losses feeds the spring.