Simone Fabbi

Slab bending, syn‐subduction normal faulting, and out‐of‐sequence thrusting in the Central Apennines

In the Central Apennines, a Tertiary-Present eastward-vergent fold and thrust belt, thrusting mainly occurred in-sequence, cutting across a Mesozoic to Early Neogene succession, deposited in rifted (Early Jurassic) to passive continental margin, to foredeep (late Miocene) conditions. However, the Simbruini Mts were characterized by the occurrence of regional out-of-sequence thrusts (the Vallepietra-Filettino-Monte Ortara thrust fault) and ofTertiary prethrusting normal faults, associated with the deposition of thick breccia deposits (Brecce della Renga, Tortonian-early Messinian). A direct link between these two features is here proposed. Evidence for a prethrusting normal faulting origin for the Brecce della Renga is amply discussed. Although evidence for subduction-related normal faulting is growing in the Apennines literature, nowhere in the region are known extensional systems so vast and their syn-tectonic deposits so thick as in the Simbruini area. We propose that the Simbruini prethrusting normal faults were subduction related, i.e., they developed in the foreland due to anomalous bending of the lithosphere subducting in Late Tertiary time under the Apennines in the Simbruini Mts area. The associated breccia deposits were subsequently deformed during the development of the Simbruini Mts thrust front. We speculate that the prethrusting normal faults allowed the penetration of fluids within the subducting crust and possibly also in the mantle, weakening this part of the subducting plate. As a consequence, the weaker plate was anomalously down-bent, leading to a subcritical state of the Apennines wedge. The regional scale out-of-sequence thrust faults developed in order to bring the Apennines wedge back to the critical state.

Testing two open-source photogrammetry software as a tool to digitally preserve and objectively communicate significant geological data: the Agolla case study (Umbria-Marche Apennines)

The digital storage and communication of significant geological data became increasingly more objective and accessible through the development of new technologies or the implementation of already well-known techniques as photogrammetry. Digital acquisition of geometries (both structural and depositional) of significant geological outcrops is deemed necessary, especially if the site concerned is liable to be damaged or hopelessly involved in natural processes of geological and geomorphological evolution. In this paper, we tested the performances of two different open-source software (i.e. VisualSFM and ARC3D) on a small-scale but paradigmatic outcrop in the Umbria-Marche Apennines (Italy). The test showed that ARC3D provides an high-resolution model, employing a relatively short time and requiring inexpensive hardware support for processing hundreds of photos. In the text, 3D models of the selected outcrop are reported and discussed emphasizing the potential of the method to highlight structural, sedimentological and paleontological details. As a result, 3D photogrammetry proved to be a powerful and effective tool to digitally conserve and objectively communicate important geological observations and to facilitate accessibility and dissemination of the collected data within the scientific community.

Geology and Jurassic paleogeography of the Mt. Primo-Mt. Castel Santa Maria ridge and neighbouring areas (Northern Apennines, Italy)

This paper presents the results of a geological mapping project across the Mt. Primo ridge and neighbouring areas (Umbria-Marche Domain – Northern Apennines), where a thick Meso-Cenozoic carbonate succession is exposed. A geological map on the 1:15,000 scale, illustrates the main stratigraphic, paleogeographic and structural features of the area. The geometries of Jurassic stratigraphic units, were mainly controlled by the complex submarine topography resulting from an Early Jurassic extensional phase. The three-dimensional distribution of Jurassic rocks in turn conditioned the structural evolution of this part of the Apennines during the chain building phase.

Carbonate intercalations in a terrigenous foredeep: late Miocene examples from the Simbruini Mts. and the Salto Valley (Central Apennines - Italy)

Resedimented calcarenites and hybrid arenites are commonly found interbedded with various Upper Miocene terrigenous units (hemipelagic marls, “brecce della Renga fm.”, and siliciclastic turbidites) across the Simbruini Mts. and neighbouring areas of Central Apennines. Their distribution provides evidence for a complex, and rapidly evolving, paleogeography across a region that was experiencing the transition from foreland to accretionary wedge conditions during the Tortonian and Messinian. The bio-sedimentological features of the calcarenites indicate deposition through gravity flows (turbidity currents) sourced by areas of active benthic, heterozoan-type carbonate production, locally lying at photic depth. Thin-section analysis of >130 samples revealed that the resedimented levels are mainly composed by bioclastic calcarenites, with fragments of bivalves, echinoids, bryozoans, balanids, benthic foraminifera, anellids and red algae, along with subordinate planktonic foraminifera. The calcareous turbidites in the hemipelagic marls (Unita argilloso-marnosa) are characterized by the presence of Heterostegina sp., and their main source area was probably lying east, on the undeformed foreland. In contrast, evidence from field mapping, their common association with Cretaceous and Miocene carbonate lithoclasts, and the age of the encasing units, all suggest that the calcarenites in the “brecce della Renga fm.” and in the siliciclastic turbidites (“complesso torbiditico altomiocenico laziale-abruzzese”) could most likely have a different source. The presence of a carbonate ridge, corresponding today to the NW sector of the Simbruini range, bordered by normal faults exposing the Cretaceous substrate, is proven proven by mappable paleo-escarpment tracts onlapped by clastic and hemipelagic deposits. This ridge could have fed surrounding deeper areas with a mixture of lithoclasts and loose bioclastic material, produced through erosion of exposed bedrock coupled with export of sediment that was being produced topping and fringing the footwall blocks and their marginal downsteps. Carbonate production was apparently able to survive for a limited time in small productive areas until the early Messinian, shedding sediment into the siliciclastic foredeep.

Geology of the Northern Simbruini Mts. (Abruzzo – Italy)

ABSTRACT This paper presents the results of a geological mapping project across the northern portion of the Simbruini Mts. (Latium-Abruzzi Domain – Central Apennines), where a thick Cretaceous and Miocene carbonate succession, followed by a thick upper Miocene terrigenous foredeep succession, is exposed. The terrigenous succession also includes a peculiar lithoclastic unit (‘brecce della Renga fm.’), whose sedimentation is linked to pre-orogenic (Tortonian-Messinian) extensional tectonics. The study area experienced late Messinian-early Pliocene compression, which is the Apennine chain building phase, followed by Quaternary post-orogenic extension, related to the opening of the Tyrrhenian basin. A geological map, at 1:20,000 scale, illustrates the main stratigraphic and structural features of the area.

Discussion on «Geological map of the partially dolomitized Jurassic succession exposed in the central sector of the Montagna dei Fiori Anticline, Central Apennines, Italy» by

In their paper on the Montagna dei Fiori area, [Storti et alii (2017][1]) present a new geological map and discuss the dolomitization pattern and the Jurassic extensional architecture of this sector of the Central Apennines. They conclude that their “field evidence does not support the gravity-

Discussion on «Geological map of the partially dolomitized Jurassic succession exposed in the central sector of the Montagna dei Fiori Anticline, Central Apennines, Italy» by G. Storti, F. Balsamo & A. Koopman (2017)

In their paper on the Montagna dei Fiori area, [Storti et alii (2017][1]) present a new geological map and discuss the dolomitization pattern and the Jurassic extensional architecture of this sector of the Central Apennines. They conclude that their “field evidence does not support the gravity-

First report of hybodont shark from the Toarcian Rosso Ammonitico Formation of Umbria-Marche Apennine Polino area, Terni, Central Italy)

In this contribution we present the first material referable to hybodont shark from the Rosso Ammonitico Formation (Umbria-Marche-Sabina Palaeogeographic Domain). Two teeth were recovered isolated within Toarcian red marly-limestone (Bifrons Zone). The best-preserved tooth is characterized by a general structure well in accord with the classic crushing dentition typical of hybodont sharks within the Subfamily Acrodontinae. The gently domed occlusal surface of the tooth does not show any trace of occlusal crest and of wrinkles, and is characterized by densely pitted, finely reticulated ornamentation. The available characters allow a conservative classification of the material at the genus level as Asteracanthus sp. The best-preserved tooth can be referred to the most mesial area of the first row of lateral teeth, using as a reference the holotype of Asteracanthus medius. The new material represents the earliest evidence of Asteracanthus and the second one from the whole Northern Apennines (Central Italy), throwing new light on the dispersal of the genus on the Jurassic Tethys.

Forward modelling of the Montagna dei Fiori fault-related fold (Central Apennines, Italy), using combined kinematic models .

The Subandean Basins of South America extending from Trinidad to Tierra del Fuego have been the object of intensive exploratory activities (Fig. 1). The largest amount of hydrocarbons discovered during the last 30 years in these basins was found in complex structural terrains. A total of 59 Billion Barrels of Oil Equivalent (BBOE) have been discovered in areas affected by compressional tectonics. Of these basins, the largest discoveries are in the Furrial Trend of Venezuela (24 BBOE), followed by the Chaco area in Bolivia and Argentina (13 BBOE), the Llanos Foothills of Colombia (4.4 BBOE), and the Madre de Dios Basin of Peru (4.2 BBOE).

Geology of the eastern slopes of the Simbruini Mts. between Verrecchie and Capistrello (Central Apennines – Abruzzo, Italy)

ABSTRACT This paper presents the results of a geological mapping project across the eastern Simbruini Mts. and the higher Roveto Valley (Central Apennines). The study area belongs to the Latium-Abruzzi Domain, which is characterized by a Cretaceous and Miocene carbonate platform succession followed by a thick upper Miocene terrigenous succession. A unique feature of the study area is the existence of a thick clastic unit, the ‘brecce della Renga fm.’; this unit was produced by the dismantling of the margins of a large pre-orogenic extensional structural high, which rose within the foredeep basin starting in the early Tortonian. Following the Messinian-Pliocene Apennine chain building phase, the area was subjected to post-orogenic Quaternary extension, related to the opening of the Tyrrhenian sea. A geological map on the 1:20,000 scale illustrates the main stratigraphic and structural features of the area.