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Current Research

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1 - Mesozoic and Cenozoic global plate tectonic reconstructions

The goal of this research, which is being made with C. R. Scotese (Paleomap Project - University of Texas at Arlington), is to produce a sequence of 200 high-resolution plate tectonic reconstructions, starting from Early Jurassic. New computational methods have been developed in paleomagnetic analysis, in order to obtain high resolution and reliable apparent polar wander paths (APWPs) for the major continents. We are currently using marine magnetic anomalies, paleomagnetic and geologic data, as well as computer graphics to aid in understanding the break-up of Pangaea and the subsequent evolution of the continental blocks and oceanic basins. A new high-resolution definition of the plate boundaries for past tectonic configurations, the determination of age and depth of the ocean floor in the geologic past, the determination of the absolute velocity field, are the main features of this new approach to plate tectonic modeling.

 

2 - Mesozoic rifting events in the Central Mediterranean: Paleogeography and tectonic evolution

The main goal of this project, which is a collaborative effort with the Universities of Roma La Sapienza, Palermo, Napoli Federico II, and Bari, is to contribute to the study of the Mesozoic rifts of the central Mediterranean region, from the stratigraphic, petrologic, structural, kinematic and paleoecologic perspectives. It should also lead to the formulation of a paleotectonic model of the process of fragmentation of Pangaea during the Triassic and the lower Jurassic. New data and interpretations will be collected in a digital database.

The initial stage of fragmentation of Pangaea [Ladinic-Carnic] is coeval with an important stratigraphic and magmatic event that affected the whole Central Atlantic region, the Morocco Meseta and the Mediterranean region (Veevers, 1989). Starting from this time, a composite system of rifts formed in eastern N. America, in the Atlas and in the western Mediterranean. In this context, the Apenninic-Maghrebian belt, with its important Mesozoic successions, represents the easternmost segment of the rift system. A systematic study of the Mesozoic domains of this belt will contribute to the determination of the relative motions between north and south Pangaea during the rifting event and will constrain boundaries and kinematics of the Adriatic plate.

This tectonic element was located between two distinct Jurassic basins (Pindos and Ligurid) and represents an important kinematic element for the tectonic evolution of the Mediterranean region. On the other hand, its relative position in the area during the Mesozoic is still unclear,because of the lack of an identified southern boundary. Another problem that will be faced is related to the lack of basement rocks that could be associated with outcropping successions. Our contribution to the solution of this problem is a determination of the crustal thinning factor (beta) of the Adriatic margin, and a chronology of the events that led to the exumation of deep continental crust and upper mantle in the Calabrian arc. This segment includes a complete succession of rocks that formed at one margin of the Ligurid ocean, comprising fragments of continental crust, mantle, oceanic crust and associated sedimentary cover, now overthrusting the sedimentary Apenninic successions.

The completation of this project requires the following steps:

Finally, the formulation of a rigorous kinematic model will allow the realization of paleogeographic and paleotectonic maps, constrained by and consistent with the observed tectonic structures. The tectonic evolution of the rifts will be described through a series of maps, produced using specific software (PCME, Paleo Continental Map Editor). As the duration of this project is limited, these goals could appear too ambitious. However, a part of the work will consist in the reinterpretation, in the light of modern plate tectonic modeling, of the wide literature and data available.

 

3 - Adria: African promontory or independent microplate?

The main objective of the proposed research project is to find precise constraints to the motion of Adria in the context of the kinematic evolution of the Mediterranean region. In spite of the large amount of paleomagnetic data supporting the idea that the motion of Adria was coherent with that of Africa (Channell et al., 1979; Channell et al., 1996; Muttoni et al., 2001; Besse and Courtillot, 2002), important geological and geophysical evidences exist requiring that Adria was subject to independent motion relative to Africa during part of the Mesozoic. The most relevant evidences are:

In general, if we focus on the relative motion between Adria and Africa, paleomagnetic data cannot be considered as strong constraints, mainly because of their low resolution (typically 10 of uncertainty in paleolatitude). Conversely, plate tectonic reconstructions at the scale of the Mediterranean region require a lower degree of uncertainty, of the same order as that of marine magnetic anomaly data.

The relative motion between Africa and Eurasia, determined through an analysis of marine magnetic anomalies of the Atlantic Ocean, represents the fundamental framework for reconstruction of the tectonic history of the Mediterranean region. However, the presence of an intervening Adria microplate puts a serious limitation to the applicability of this approach. Although the motion of this tectonic element is responsible for the formation of four different orogenic belts (the Apennines, the Alps, the Dinarides, and the Hellenides), it still remains poorly constrained.

We propose, with the present research project, a new method for interpretating geologic data, in order to assign precise constraints to the motion of Adria. Testing of this approach, as illustrated below, represents an important objective of the research project.

Some intermediate goals are the following:

In order to reach this goal within the scheduled time, it is required a strong coordination between research units, which will involve specific themes in selected areas and use of commonly accepted methods. New data and interpretations will be collected in a common database, accessible by all participants. This aim of collaboration and data sharing is fully agreed with all research units.

 

4 - Physical models for absolute plate motions

This research project was started to test the idea of an invariant net rotation of the lithosphere across the geologic past. Physical models of plate kinematics have been developed since the beginning of 1970s. The No-Net-Rotation (NNR) and the hotspot models are two alternatives for the description of absolute plate motions. We are convinced that if the total torque exerted on the lithosphere is zero, then the total lithosphere rotation must be an invariant of the plate motion. This idea can be also tested through a PEP analysis of paleomagnetic data and the determination of a paleomagnetic reference frame for past plate motions. The z-axis of this frame coincides with the Earth's spin axis, according to the GAD hypothesis, whereas the remaining x and y axes would be defined by the non-dipolar components of the paleomagnetic field. Hence, this research attempts to reconcile three different approaches to modern and past plate kinematics, that is the NNR, the hotspot and the PEP approaches to absolute plate motions.

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