Compressional and extensional tectonics inside collisional belts: the case of the western portion of the Northern Apennines

Coeval extensional and compressional tectonics are a common feature in orogenic belts, especially in post-collisional phases. The attempt to constrain their relative timing and the responsible mechanisms led to several models taking into account different geodynamic contexts of various mountain chains. In peri-Mediterranean collisional orogens, extension and compression are commonly associated and coeval to the emplacement of far-travelled/allochthonous units. The deformation acquired by these units during their translation across collisional belts, thus, are very likely imprinted by the development of extensional and compressional tectonics affecting the orogen. In the western portion of the Northern Apennines of Italy, one of the northernmost peri-Mediterranean Tertiary orogens, the far-travelled/allochthonous units, i.e., the Ligurian and Subligurian units, are widely exposed. The present study integrates published and newly acquired surface geological data (geological maps, cross-sections), subsurface geological data (seismic lines, boreholes), paleothermal data (vitrinite reflectance, mixed layer illite-smectite) and thermochronological data (apatite fission tracks) in order to investigate the deformation history and, consequently, the record of the extension-compression relationships inside these far-travelled/allochthonous units. The integrated approach allowed us to: 1) build a 3D representation of the Ligurian and Subligurian units present-day geometry; 2) document an early tectonic thinning of the Ligurian and Subligurian units occurred in the late Miocene, followed by a later reshaping in the Pliocene to Recent (?) times; 3) identify the tectonic exhumation and uplift of the deepest foredeep units as one of the main causes which led to the activation of low-angle extensional faults responsible for the thinning of the far-travelled/allochthonous units since late Miocene; 4) relate the later Pliocene to Recent (?) reshaping phase to both high-angle extensional faults and increased erosion rates; 5) recognize lateral variations in the extent of uplift, exhumation and thinning inside the western Northern Apennines. These results allowed us to strengthen the hypothesis that in the Northern Apennines extensional and compressional tectonics were coeval and tightly connected by a cause/effect relationship, explained by an over-thickened orogenic wedge which decreased its surface slope’s angle and returned to its gravitational equilibrium state. This latter was achieved by means of tectonic and surface erosional processes, acting during two major evolutionary stages: 1 - late Miocene) low-angle extension of the shallowest portion (the uppermost 4-6 km) of the orogenic wedge causing the thinning of the far-travelled/allochthonous units; 2 - Pliocene to Recent?) high-angle extensional tectonics coupled with increased surface erosion. The study of the late orogenic deformation and reshaping of the far-travelled/allochthonous Ligurian and Subligurian units, thus, revealed that the western Northern Apennines were dominated by an overall compressional regime which induced episodes of gravitational instability in the shallower portion of the Apennines orogenic wedge. Then, this study provides elements indicating the possibility that the processes characterizing the second stage were active till Recent times, because of the relationships highlighted between deep Apenninic compressional structures and Holocene surface gravitational processes. The importance of surface erosion processes during the second stage led to the attempt to quantify these processes through the use of numerical modelling, which gave an average erosion/exhumation rate of 0.64 km/My over the last 5.35 My). The new data and results presented in this work have important implications on the geodynamic framework characterizing the Northern Apennines. They reveal that, from middle Miocene to Recent, the western Northern Apennines were affected by underplating processes spaced out by episodes of frontal accretion possibly related to the subducting slab retreat.L’attività coeva di tettonica compressiva ed estensionale è una caratteristica comune a molte catene montuose, specialmente durante le loro fasi post-collisionali. Il tentativo di vincolare le tempistiche e i meccanismi responsabili di questi processi hanno portato alla produzione di numerosi modelli che prendono in considerazione diversi contesti geodinamici, all’interno di diverse catene montuose. Nelle catene collisionali peri-Mediterranee estensione e compressione sono comunemente associate e coeve alla messa in posto di unità alloctone. La deformazione acquisita da queste unità durante la loro traslazione attraverso la catena, perciò, con tutta probabilità conserva tracce dello sviluppo della tettonica compressiva ed estensionale relativa all’intero orogene. Nella porzione occidentale dell’Appennino Settentrionale (Italia), uno degli orogeni terziari più settentrionali tra quelli peri-Mediterranei, le unità alloctone Liguri e Subliguri affiorano estesamente. Il presente lavoro integra dati nuovi e già pubblicati relativi alla geologia di superficie (carte e sezioni geologiche), alla geologia di sottosuolo (linee sismiche e pozzi), con dati paleotermici (riflettanza della vitrinite e strati misti illite-smectite) e dati termocronologici (tracce di fissione in apatite), allo scopo di investigare la storia deformativa e, di conseguenza, il record delle relazioni tra compressione ed estensione all’interno di queste unità alloctone. L’approccio integrato ci ha permesso di: 1) costruire una rappresentazione tridimensionale della geometria attuale delle unità Liguri e Subliguri; 2) documentare un primo assottigliamento tettonico delle unità Liguri e Subliguri avvenuto durante il Miocene superiore, seguito da un ulteriore rimodellamento avvenuto tra il Pliocene e il Recente (?); 3) identificare l’esumazione tettonica e il sollevamento delle unità di avanfossa come una delle cause principali che hanno condotto all’attivazione di faglie estensionali a basso angolo, responsabili dell’assottigliamento delle unità alloctone, a partire dal Miocene superiore; 4) collegare la più recente fase di rimodellamento (dal Pliocene al Recente (?)) all’attività di faglie estensionali ad alto angolo e tassi di erosione superficiale in forte aumento; 5) riconoscere variazioni laterali relative all’estensione del sollevamento, esumazione e assottigliamento delle diverse unità tettoniche, all’interno della porzione occidentale dell’Appennino Settentrionale. Questi risultati ci hanno permesso di rafforzare l’ipotesi che in Appennino Settentrionale la tettonica compressiva ed estensionale sono coeve e collegate da una forte relazione di causa/effetto, spiegata attraverso il modello di un cuneo orogenico sovra-ispessito, che ha diminuito il proprio angolo di inclinazione superficiale per ritornare ad uno stato di equilibrio gravitativo. Quest’ultimo è stato raggiunto per mezzo di processi tettonici ed erosivi superficiali che hanno agito principalmente durante due stadi evolutivi: 1 – Miocene superiore) estensione a basso angolo della porzione più superficiale del cuneo orogenico, la quale, a sua volta, ha portato all’assottigliamento delle unità alloctone; 2 – Pliocene – Recente?) estensione ad alto angolo associata con l’aumento dei tassi di erosione superficiale. Lo studio della deformazione tardiva e del rimodellamento delle unità alloctone Liguri e Subliguri, perciò, ha rivelato che la porzione occidentale dell’Appennino Settentrionale è stata dominata da un regime complessivamente compressivo, il quale ha indotto episodi di instabilità gravitativa nelle porzioni più superficiali del cuneo orogenico Appenninico. Questo studio fornisce, inoltre, elementi che indicano la possibilità che i processi attivi durante il secondo stadio siano stati attivi fino all’attuale, a causa delle relazioni evidenziate tra strutture compressionali profonde e processi gravitativi superficiali di età olocenica. L’importanza dei processi di erosione superficiale durante il secondo stadio ha portato al tentativo di quantificare l’entità di tali processi attraverso l’uso di modelli numerici, dai quali è stato ottenuto un tasso di esumazione/erosione medio di 0.64 km/Ma negli ultimi 5.35 Ma. I nuovi dati e i risultati presentati in questo lavoro hanno importanti implicazioni sul quadro geodinamico che caratterizza l’Appennino Settentrionale. Tali risultati rivelano che a partire dal Miocene medio fino al Recente la porzione occidentale dell’Appennino Settentrionale è stata coinvolta in processi di underplating, intervallati nel tempo da episodi di accrezione frontale, possibilmente legati al ritiro dello slab in subduzione

Stability and Control for Energy Production Parametric Dependence

The activities of plant cultivation in Italy are provided by prefabricated structures that are designed to avoid any preliminary study of optical and thermal exchanges between the external environment and the green house. Designers mainly focused on the heating and cooling system to obtain climate beneficial effects on plant growth. This system involves rather significant operating costs which have driven the interests of designers, builders, and farmers to pursue constructive solutions such as the optimization and control of energy flows in the system. In this paper we take into account a model of greenhouse for plant cultivation to be located in Central Italy. For the optimal design of a greenhouse, simulations of heat exchange and flow of energy have been made in order to maximise the cooling system consumption of energy

Deformation, fluid flow, and mass transfer in the forearc of convergent margins: A two-day field trip in an ancient and exhumed erosive convergent margin in the Northern Apennines

This guide provides background information and an itinerary for a two-day fi eld trip in the Northern Apennines leaving from Modena and ending at Riolunato (Modena). The proposed fi eld trip route leads through the Po Valley side of the Northern Apennines, in the Emilia region. The fi eld trip provides opportunities to examine the exposed geological features related to a phase of early-middle Miocene convergence between the European and Adria plates. In particular, outcrops have been selected that exhibit features characterizing deformation in an exhumed plate boundary shear zone, interpreted as an erosive plate boundary shear zone. The sedimentary evolution and deformation of the upper and lower plates are also highlighted

Deformation, fluid flow, and mass transfer in the forearc of convergent margins: A two-day field trip in an ancient and exhumed erosive convergent margin in the Northern ApenninesDeformation, Fluid Flow, and Mass Transfer in the Forearc of Convergent Margins: Field Guides to the Northern Apennines in Emilia and in the Apuan Alps (Italy)

This guide provides background information and an itinerary for a two-day field trip in the Northern Apennines leaving from Modena and ending at Riolunato (Modena). The proposed field trip route leads through the Po Valley side of the Northern Apennines, in the Emilia region. The field trip provides opportunities to examine the exposed geological features related to a phase of early-middle Miocene convergence between the European and Adria plates. In particular, outcrops have been selected that exhibit features characterizing deformation in an exhumed plate boundary shear zone, interpreted as an erosive plate boundary shear zone. The sedimentary evolution and deformation of the upper and lower plates are also highlighted

Deformation, fluid flow, and mass transfer in the forearc of convergent margins: A two-day field trip in an ancient and exhumed erosive convergent margin in the Northern Apennines

This guide provides background information and an itinerary for a two-day fi eld trip in the Northern Apennines leaving from Modena and ending at Riolunato (Modena). The proposed fi eld trip route leads through the Po Valley side of the Northern Apennines, in the Emilia region. The fi eld trip provides opportunities to examine the exposed geological features related to a phase of early-middle Miocene convergence between the European and Adria plates. In particular, outcrops have been selected that exhibit features characterizing deformation in an exhumed plate boundary shear zone, interpreted as an erosive plate boundary shear zone. The sedimentary evolution and deformation of the upper and lower plates are also highlighted

Mass Transport Deposits and geo-hazard assessment in the Bradano Foredeep (Southern Apennines, Ionian Sea)

Seafloor bathymetry, combined with multi-scale seismic reflection profiles, were used to describe the morphostructural setting of the Bradano Foredeep (Gulf of Taranto, northern Ionian Sea), where a submerged portion of the Southern Apennines is facing the Apulia Platform in the Calabrian Arc convergent margin. In this complex area, marine geophysical data highlight the presence of two mega-slide deposits at the shelf-slope transition, which are most likely the largest ever described in the region. These slid masses, named the Bradano Basento MegaSlide (BBMS) and Bradano Basento MegaSlide 1 (BBMS1), form a Mass Transport Deposit Complex (MTDC) affecting and eroding the topmost portion of the outer Apennines deformation front and the Apulian Foreland Ramp. It was emplaced in late Pleistocene times inside the narrow (about 10 km wide) Bradano Foredeep basin, a Plio-Pleistocene submarine trough developing at the chain front. The youngest of these deposits (BBMS1) likely predates the Last Glacial Maximum. Location of the MTDC within the subduction complex suggests that active tectonics and seismic shaking might represent the main triggering mechanisms for gravitative instability in this area, although gravitational tectonics and sediment creeping mechanisms cannot be excluded. On the other hand, size and distribution of the MTDC in the sedimentary record of the Bradano Foredeep suggest the need of re-evaluating the potential for large earthquakes/tsunamis, and more in general geological hazard related to submarine sliding masses, along the coast of this highly populated area