Mauro De Donatis

FRONTAL PART OF THE NORTHERN APENNINES FOLD AND THRUST BELT IN THE ROMAGNA-MARCHE AREA (ITALY) : SHALLOW AND DEEP STRUCTURAL STYLES

In this study, surface geological data resulting from a detailed field survey, including structural and biostratigraphic analysis, have been integrated with subsurface (seismic lines and well logs) data in order to reconstruct the tectonic evolution of the external zones of the northern Italian Apennines in the Romagna-Marche foothills and Adriatic Sea areas. This integrated analysis shows: (1) a late Messinian to lower Pleistocene progression of structural development from the hinterland to the foreland of the studied sector of the thrust belt; (2) relatively limited (≤20%), southward increasing, amounts of shortening (obtained by the construction of line-length balanced and restored geological cross sections); (3) a regional deformation style characterized by the presence of backthrusts associated with most foreland-vergent thrust ramps, leading to quasi-symmetric uplift and a low critical taper for the wedge, typical of foreland fold and thrust belts with a weak basal decollement (Triassic anhydrites in the present case); (4) an important influence of basement faulting which, despite a general basement-cover decoupling, appears to control stress localization in the latter, producing linkage of basement and cover stuctures in a combination of thin- and thick-skinned tectonic styles; and (5) contrasting structural styles characterizing deep features, as imaged by seismic reflection profiles, and shallow ones. Deep stuctures consist of growth anticlines bounded by major thrust ramps and back limb back thrusts, separated by broader, open synclines, both involving a Mesozoic-Paleogene, mainly carbonate, passive margin succession. In the crestal zones of major anticlines, shallow structures, affecting Neogene terrigenous foredeep sediments, show a complex pattern of upright to recumbent folds (of tens to hundreds of meters wavelength) related to minor thrusts and backthrusts. Deformation of the Mesozoic-Paleogene multilayer appears to be dominated by thrust propagation in the cores of early formed anticlines developed by buckling instabilities. The overlying Neogene deposits are detached from the carbonate substratum along the base of the foredeep succession. Bedding-parallel slip occurring along this detachment level appears to be accommodated by the complex structures in the crests of major anticlines, where the thrusts lramp to the surface cutting up section. Complex shallow structures, interpreted to accommodate at shallow structural levels the deep deformation, would therefore represent a geometrical requirement for maintaining strain compatibility across the shallow detachment level located at the base of the foredeep succession.

Time and space variability of “thin-skinned” and “thick-skinned” thrust tectonics in the Apennines (Italy)

In the Apennine fold and thrust belt of Italy, «thin-skinned» (i.e. detachment-dominated) and «thick-skinned» (i.e. crustal ramp-dominated) structures coexist, but with marked differences in both time and space. The external part of the northern Apennines and the deeper and younger portions (buried Apulian carbonates) of the thrust belt in the central and southern Apennines show limited amounts of shortening (in the range of 5–14 km). These result from similar deformation styles, involving the occurrence of relatively low-displacement, thick-skinned thrust ramps. The latter represent, at least in the northern Apennines, preexisting basement structures reactivated and inverted during contractional deformation. Interposed between the northern and southern parts of the fold and thrust belt, the central Apennines appear to constitute a transitional area in which strike-slip tectonics is relevant and carbonate platform units become predominant over pelagic basin ones, whereas the overall structure of the thrust belt becomes similar to that of the southern Apennines. In the latter, a peculiar structural style is revealed by the integrated analysis of surface and subsurface data. Structurally, the upper part of the thrust belt consists of allochthonous units made of Mesozoic peritidal carbonate platform and pelagic basin successions, and of Miocene foredeep sediments. These are completely detached from their original substratum and transported onto the 6–7 km thick, foreland carbonates of the Apulian platform. Based on available seismic data, the latter appears to be involved, together with the underlying Permo-Triassic clastics and, we infer, also the basement, in relatively low-displacement, thick-skinned structures. Therefore, in the southern Apennines, a transition from thin-to thick-skinned tectonics appears to have occurred through time. Thin-skinned structures characterise the shallower — and older — part of the thrust belt made of detached units, while a thick-skinned tectonic style is dominant in the buried Apulian carbonates of most recent accretion. The present boundary between the two different, superposed portions of the thrust belt consists of a low-angle, large-displacement thrust fault penetrated by numerous oil wells. Different styles and modes of contractional deformation in the investigated sectors of the Apennines appear to result from the geometrical requirement of maintaining strain compatibility and overall displacement continuity along a highly segmented orogen characterised by variable mechanical stratigraphy and southward increasing amounts of shortening.RiassuntoNella catena a pieghe e sovrascorrimenti dell’Appennino coesistono strutture che vedono coinvolto nella deformazione il basamento (tipo «thick-skin») e strutture scollate da questo (tipo «thin-skin»). La parte esterna dell’Appennino Settentrionale e le parti più profonde e più giovani (i carbonati della piattaforma Apula sepolta) dell’Appennino Centrale e Meridionale mostrano un raccorciamento limitato (compreso tra i 5 e i 14 km). Ciò deriva da stili deformativi simili, che producono rigetti relativamente bassi per la presenza di rampe di sovrascorrimento di tipo «thick-skin». Queste ultime rappresentano, almeno nell’Appennino Settentrionale, delle preesistenti strutture di basamento riattivate e invertite durante la deformazione contrazionale. Interposta tra le porzioni settentrionali e meridionali della catena, l’Appennino Centrale costituisce un’area di transizione in cui la tettonica trascorrente risulta di rilevante importanza e le unità carbonatiche di piattaforma divengono predominanti su quelle dei bacini pelagici, mentre la struttura generale della catena a pieghe e sovrascorrimenti diventa simile a quella dell’Appennino Meridionale. In quest’ultimo, lo stile strutturale tipico è rivelato dall’analisi integrata dei dati di superfice e di sottosuolo. Nella parte strutturalmente superiore di questo settore di catena sono presenti unità alloctone costituite da piattaforme a carbonati peritidali del Mesozoico e da successioni bacinali, sopra le quali sono presenti sedimenti miocenici di avanfossa e di bacini satelliti. Tale parte superiore è completamente scollata dal substrato di origine e trasportata sulla piattaforama carbonatica dell’avampaese apulo, che raggiunge potenze di circa 6–7 km. Sulla base dei profili sismici diponibili, la piattaforma apula appare coinvolta, insieme ai sottostanti sedimenti clastici permo-triassici e quindi anche al basamento, in strutture con basso rigetto di tipo «thick-skin». Di conseguenza, nell’Appennino Meridionale, un passaggio da un regime tettonico di tipo «thin-skin» ad uno di tipo «thick-skin» sembra essere avvenuto nel tempo. Le strutture «thin-skin» sono caratteristiche della parte più superficiale (e più vecchia) della catena costituita da unità scollate, mentre lo stile «thick-skin» è dominante nei carbonati apuli sepolti di più recente accrezione. Il limite attuale tra le due diverse, sovrapposte porzioni della catena è costituito da una importante superficie di sovrascorrimento a basso angolo, penetrata da numerosi pozzi petroliferi. Gli stili geometrici e le modalità di deformazione contrazionale differenziati nello spazio e nel tempo sembrano essere il risultato di esigenze di compatibilità geometrica della deformazione e di continuità dei rigetti lungo un orogene fortemente segmentato e caratterizzato da una stratigrafia variabile nelle sue caratteristiche meccaniche e da un aumento del raccorciamento verso Meridione.

MAP IT: The GIS software for field mapping with tablet pc

Map IT is a proper Geographic Information System (GIS) software designed for digital mapping and data capture with tablet pc that ought to be tested and evaluated by field geologists and people who project and use field systems and geologic databases. It can be easily used at different levels of digital knowledge. The digital pen writing on the sunlight readable screen of a rugged tablet pc is similar to the traditional way by which geologists draw lines and other features on a base map and write hand notes on a field book. If the entry level of this software is very simple, going ahead, step by step, Map IT keep its user-friendly interface. Global Positioning System (GPS) connected device allows to capture points (i.e. bedding measurements), lines (i.e. faults and stratigraphic boundaries) and polygons (i.e. landslides, large outcrops) and to georeference any file created by the surveyor via date and time through an intuitive method. Then a slip of yellow paper (Easy Note) can be used to take short notes and link any files (hand notes, recorded sound and/or voice notes, hand sketches, digital photos) by drag-and-drop. After the picture, downloaded from digital camera into the computer, has been linked in Easy Note, a photo display allows to visualize and sketch the photos for outcrop or landscape interpretations and notes. Moreover any kind of software useful for data capturing (i.e. spreadsheets, stereoplots, etc.) can be used to generate files which can be linked to Map IT database. If the mapping project is pre-organized by standardized symbology and conventional ontology for interoperability, the project manager can easily customize forms to be filled by the surveyors to input data directly into the database. However, the field geologist can keep flexibility in unexpected field situations using Easy Note and other digital note and sketch recorder in addition. In case of working with groups of surveyors, the data can be sent via communications technologies (GPRS or UMTS) to a central server with high reduction of time for building a GIS or more simply a real-time cartography, which would be important, for example, when natural or anthropogenic disasters occur. rs occur.

Three-Dimensional Visualization of the Neogene Structures of an External Sector of the Northern Apennines, Italy

A three-dimensional (3-D) visualization technique is used to build a structural model linking a complex series of thrust sheets in an external area of the northern Apennines, central Italy. This foreland fold and thrust belt consists of faulted anticlines and broad syn clines, involving a Triassic-Paleogene succession that is detached from the underlying basement. Reactivation of basement faults has influenced the geometry and kinematics of the overlying structures in a mix of thin-skinned and thick-skinned tectonics. Upper de tachment horizons within the sedimentary succession form shallow structures in the crestal zone of the major anticlines. All the struc tures are scantily cylindrical, and the model demonstrates the soft linkages between oblique and frontal structures through relay ramps.

Sheet 280-Fossombrone 3D: A study project for a new geological map of Italy in three dimensions

The goal of this project is to define and test a method for building a three-dimensional (3D) geological model of Italy based on maps at a 1:50,000 scale, using the new national geological mapping program (CARG project). A structural model of Sheet 280-Fossombrone (Northern Apennines, central Italy) was produced using recently developed 3D visualization techniques. This area is characterized by faulted anticlines and broad synclines, involving a Triassic-Palaeogene succession detached from its underlying basement. Exhaustive knowledge of the regional and local geology, combined with available subsurface (well and seismic) data, makes this area a good test site for developing a 3D geological modeling method. The model of Sheet 280-Fossombrone was built in two steps. In the first step, we built a 2.5D geological model using the digital elevation model combined with the new 1:50,000 scale geological map of the area. This 2.5D model shows relationships between topographic elements, geology and major structures much better than traditional 2D geological maps. In the second step, we constructed an in-depth model integrating a large amount of subsurface data with field data from the recent mapping project. The geological model of Sheet 280-Fossombrone clarifies structural geometries and kinematics of this external part of the Northern Apennines. Structural and geomorphic analyses were performed on the 3D model to evaluate how additional information can be obtained from 3D cartography in order to improve knowledge of the study area. We present results of these analyses as examples.

Representation and transfer of geological knowledge in IT-supported projects

Information Technologies (IT) have the capability to improve the clearness and the usefulness of scientific information, and related applications in earth sciences could allow to make geological data more sharable among different users. This paper illustrates an approach to represent the knowledge paths followed by field geologists involved in assessment and description of complex structuralgeological settings and processes, through the use of specific IT applications. The proposed approach is based on three working steps: i) building of a conceptual map (cMap) that defines the project approach to the study matter, drives the acquisition of field data and gives rules for GIS representation of interpreted geological features (prefieldwork stage); ii) capturing of data directly in the field by means of digital devices, in a way suitable to retrace the acquisition data steps and to separate the observed features from the interpreted ones (fieldwork stage); iii) management of information in relational GIS databases by means of «geological» metadata that could define the «weight» of data and explain the adopted interpretations (postfieldwork stage). An application of these working steps is given in a case study of the stability evaluation of a quarry rock mass. In the example, different conceptualizations and investigation methods are combined so that they are sharable among field geologists and engineering geologists in order to allow crucial decision in characterization and modelling of the quarry slope. Besides, ITbased approaches should get retraceability of decisional processes possible

3D model of a sector of the South Scotia Ridge (Antarctica)

A three-dimensional geological model was built to show and analyse a northern sector of the Scotia-Antarctica transform plate boundary. The South Scotia Ridge is a 400km long submerged continental structural high representing the eastern continuation of the Antarctic Peninsula. South Scotia Ridge runs approximately in the E-W direction, separating Scotia Sea Plate from Antarctica Plates. Structures, due to the transform plate margin, are considered to be concentrated inside this continental high. The three-dimensional model, built using seismic profiles and a digital elevation model, is a powerful tool to visualize and help to understand deep geological structures. Maps and profiles, on the contrary, only give a two-dimensional view, and do not show the structure of the continental-oceanic boundary at depth. The model shows that the deformation style of the continental-oceanic boundary, and of the oceanic crust nearby, is related to the left-lateral movement of the main transform fault system. Furthermore, it seems to be connected to the orientation and geometry of the South Scotia Ridge with respect to the homogeneous deformation regime, which affects the entire Scotia Plate. Moving from west to east, the NW-dipping main fault surface becomes almost vertical with a sinistral strike-slip movement in the central sector. To the east, a south-dipping plane decreases its inclination and changes orientation (from E-W to ESE-WNW): here shortening features are visible. The three-dimensional geological model presents a western and central province wherein the continental-oceanic boundary involves the fragmented continental blocks, the continental slope, the oceanic basement and sediments. The sedimentary cover and the oceanic basement are not deformed in the eastern province.

Outdoor GPS and Indoor Magnetic Field Positioning: combining survey technology and app development

This work tested a solution for outdoor and indoor positioning. In order to find a suitable solution for geo-applications like in caves and mines, we tested the GPS and Open Street Map cartography for outdoor and Magnetic Field positioning and Indoor Atlas technology for indoor in the Urbino University residences. The results of this work can be already used for university students and hosts in Urbino; moreover, these could be also easily applied to geotouristic sites by means of the development of an app for Android smartphones.

Preface: Geology and information technology

The image of geologist is often associated with a “tough natural scientist” operating in the field without technology. This has changed with the large diffusion of information and communication technology; today, geologists face the digital world. The geological maps and cross sections have been fundamental for synthesizing the geological knowledge of a region, but GIS, 3D digital modelers, and web-based applications allow to easily analyze, interpolate, showing and sharing data, information, interpretations, and thoughts. This new way of operating has deeply affected the new generations of earth scientists and it changed the approach to the knowledge management in geology. In 2005, the need for communication among people working with digital tools in the earth sciences in Italy lead to the constitution of an informal group called GIT (Geology and Information Technology—www.gitonline.eu) which became later a section of the Italian Geological Society. This special issue showcases some of the main contributions to the second meeting hold in Bevagna (Perugia-, Italy) on 4–6 June 2007.