Post-depositional history of the Miocene Gorgoglione Formation (southern Apennines, Italy): inferences from mineralogical and structural analyses

Abstract

The Gorgoglione Formation represents the infill of a thrust-top basin, which records the tectonic evolution of the southern Apennines (Italy) since Upper Miocene times. The Upper Miocene basin was divided into two main sub-basins, showing both about NNW-SSW elongation. During ongoing contractional deformation, the Gorgoglione basin was incorporated into the allochthonous units of the Apennine fold-and-thrust belt, as outlined by the emplacement of thrust sheets of internal provenance (Sicilide Unit) and by the development of two main generations of tight to open folds. In this work, the modalities of deformation associated to the incorporation of the Gorgoglione Formation into the fold-and-thrust belt has been documented by means of mineralogical and structural analyses. Mineralogical data show that, in the northeastern sub-basin of the Gorgoglione Formation, the illite content and the order of illite/smectite mixed layer increase near the contact with the overlaying Sicilide Unit. These data are hence used to estimate the relative tectonic load produced by thrusting of the aforementioned tectonic unit. Structural data are consistent with tight, NNW-trending, meso-scale folds particularly frequent in the upper pelitic/arenaceous portion of the Gorgoglione Formation. Within these folded pelitic levels, a well-developed axial-plane foliation, and an ordered I/S (R1 and R3) with higher illite content, is documented. Instead, other folds developed far away from the Sicilide klippen show an incipient axial-plane foliation and a random I/S (R0) with lower illite amount is found in pelites. The data suggest that the eastern sub-basin of the Gorgoglione Formation underwent variable tectonic load, increasing from E to W, as well as deformation produced by thrusting of Sicilide sheet. The mineralogical data also indicate that illitization process is favoured for the high availability of potassium due to the dissolution of k-feldspar. High potassium availability affects the samples subjected to the highest diagenetic degree, characterized by kaolinite illitization process. Histoire post-dépôt de la formation Gorgoglione (Miocène, Apennins du Sud, Italie) : apports d'études minéralogique et structurale Mots-clés. -Formation de Gorgoglione, Apennins du Sud, Charge tectonique, Interstratifiés illite/smectite, Analyse structuraleRésumé. -La formation de Gorgoglione représente le remplissage d'un bassin thrust-top qui enregistre l'évolution tectonique des Apennins du Sud (Italie) depuis le Miocène supérieur. Le bassin du Miocène supérieur comprenait deux sous-bassins allongés selon un axe NNW-SSE. Au cours de l'évolution de la déformation, le bassin Gorgoglione a été affecté par la deformation compressive et incorporé à l'unité allochtone des Apennins, recouvert par des nappes d'origine interne (unité Sicilide) et affecté par deux générations de plis, plus ou moins ouverts. Dans cette étude, les défor-mations de la formation Gorgoglione résultant de son implication dans le prisme orogénique, font l'objet d'analyses minéralogique...

Multi‐scale analysis of a migrating submarine channel system in a tectonically‐confined basin: The Miocene Gorgoglione Flysch Formation, southern Italy

“…The monocline represents the eastern flank of a NNW-SSE trending syncline ( Fig. 1) in which the GF formation was deformed during the post-Tortonian contractional tectonic phase of the Southern Apennines (Cavalcante et al, 2015).…”

Fracture stratigraphy of Mesozoic platform carbonates, Agri Valley, southern Italy

“…The presence of mixed illite/smectite layers with R1 and R3 ordering with a high percentage of illite is consistent with c. 130 °C thermal maturity, typical of high diagenetic conditions (Merriman & Peacor, 1999;Cavalcante et al, 2012;Perri et al, 2016;Waliczek et al, 2021). However, since smectite illitization and mixed-layer formation are also timedependent processes (McCubbin & Patton, 1981;Pollastro, 1993), and a function of K-availability (Cavalcante et al, 2007(Cavalcante et al, , 2015, we assess 100-130 °C diagenetic temperature range conditions. Assuming 20-25 °C temperature gradients, typical of accretionary wedges (Merriman, 2005), a c. 4-5 km burial is therefore estimated for the study carbonates.…”

Provenance and paleogeographic implications for the Cenozoic sedimentary cover of the Ghomaride Complex (Internal Rif Belt), Morocco

“…was obtained after heating the same very fine powder for 3 h at 900 • C. The mineralogy of the whole-rock powder and clay fraction was determined by X-ray diffraction (XRD) using a Bruker D8 Advance diffractometer at University of Calabria (Italy) and at the University of Granada (Spain), respectively. The mineralogical composition of the studied mudrocks were carried out on random and oriented powders measuring peak areas using the WINFIT computer program (Krumm, 1999), according to the procedure proposed by Cavalcante et al (2007). This procedure uses the strongest reflection of each mineral, except for quartz for which the line at 4.26 Å was considered instead of the peak at 3.34 Å because of its superimposition on that of the 10 Å minerals and of the mixed-layer clay minerals.…”

“…Clay fraction was evaluated according to the peaks at 10-15 Å (mixed-layer clay minerals), 10 Å (illite + micas) and 7 Å (kaolinite + chlorite) minerals; these latter phases were evaluated by considering the height of the peaks at 3.58 Å and 3.53 Å, respectively (e.g. Cavalcante et al, 2007). The mineralogical composition of the studied mudrocks was further recalculated using the vbAffina software program based on the combination of the XRD-determined phase percentages introduced into vbAffina (i.e., XRD results) and those determined using XRF (for the procedure see also Leoni et al, 1989Leoni et al, , 2008Cesarano et al, 2018).…”