The new 1:10.000 Geological Map of eastern Elba Island, northern Tyrrhenian Sea, Italy: novelties on its tectonic and structural evolution

Andrea Brogi^1,2,3 & Domenico Liotta^1
1University of Bari, Department of Earth and Geoenvironmental Sciences, Bari, Italy.
²CRUST - Centro inteRUniversitario per l’analisi Sismotettonica Tridimensionale, Chieti, Italy.
³OGS, National Institute of Oceanography and Applied Geophysics, Trieste, Italy.
Corresponding author e-mail: domenico.liotta@uniba.it

A new geological map at 1:10,000 scale has been produced in the framework of the 7th Framework Programme for Research of the European Commission (Project IMAGE-FP7, n.608553, 2014-2018), which aimed at the relationships between geological structures and geothermal fluid flow. Indeed, eastern Elba represents an exhumed, fossil geothermal system, active during the late Messinian, as testified by the widespread hydrothermal fluid circulation which originated the well-known Fe-ore deposits. The fieldwork and data collection were completed in 2022, after eight years of fieldwork. In the geological map, outcrops are highlighted to make clear the level of interpretation. The main novelties are: a) the structural setting, now defined by seven main tectonic units (from oceanic and continental domains), of which stacking and geometrical setting was inherited from the collisional tectonics and then modified by the subsequent post-collisional extension; b) the occurrence of subunits consisting of parts of the successions belonging to the main tectonic units, and bounded by subtractive contacts (i.e. extensional duplexes); c) the role of the transfer fault zones in controlling the emplacement of the Late Miocene magmatic systems and the circulation of hydrothermal fluids; d) a new definition of the Palaeozoic ages of the protoliths of the HT-metamorphic units; e) the occurrence of foreland deposits involved in the stacking of tectonic units and affected by metamorphism (Pseudomacigno Fm, late Oligocene-Early Miocene); f) the occurrence of two main regional Miocene extensional shear zones: the upper, located at the boundary between the uppermost oceanic and the continental units; the lower, mainly defined by ductile shear zones, decoupling the Triassic-upper Oligocene sedimentary units from the Palaeozoic successions in the lowermost continental units. In contrast to the main previously published geological maps (i.e., Bortolotti et al., 2015 and Trevisan & Marinelli, 1967), the new map differs from that of Bortolotti et al., (2015) in terms of structural reconstruction and paleogeographic attribution of geological bodies, while it is quite similar to the map proposed by Trevisan & Marinelli (1967), apart from the distribution of faults and the use of tectonic units instead of complexes. In the supplementary material accompanying this paper, the reader can find the revision of the oversights occurred during the editing of the geological map (attached to this paper), as well as the paleontological implementations gained in the time being of this publication. Accordingly, the electronic copy of the geological map (PDF format) has been revised to incorporate corrections and improvements.

collisional tectonics, extensional tectonics, transfer faults, Northern Apennines, Elba Island.