In this paper we illustrate the stratigraphic and structural features of the Sibillini Mountains on the basis of a 1:40.000 geological map. Following the “Foglio 132 Norcia” (Geological Map of Italy at 1:100.000 scale; SCARSELLA, 1941), this new geological map is the first cartographic document that covers the whole area of the Sibillini Mts. This area is key for understanding the geological evolution of the external zones of the Apennine orogen, mostly owing to the pronounced structural elevation of the Apennine ridge at the Sibillini Mts. area. This allowed us to: a) carry out stratigraphic and structural analyses for the Umbria-Marche sedimentary cover to the oldest units; b) analyze the paleo-tectonic setting of this sector of the Afro-Adriatic continental margin and the behavior of pre-existing structures during the subsequent deformation events; c) investigate in depth the major Apennine thrust front (“Sibillini Mountains Thrust”) exposed in several sites (Fiastrone, Ambro, Tenna and Tronto valley) and its relationship with the units of the adjacent Messinian foredeep
13 December 2017 in Journal of Geophysical Research: Solid Earth
This paper presents a new southern North Atlantic plate model from Late Cretaceous to present, with the aim of constraining the kinematics of the Iberian plate during the last 83.5 Myr. This model is presented along with a detailed isochron map generated through the analysis of 3 aeromagnetic tracks and ~400 ship tracks from the National Centers for Environmental Information database. We present a new technique to obtain well‐constrained estimates of the Iberia‐North America plate motions from magnetic anomalies, overcoming the scarcity of large‐offset fracture zones and transform faults. We build an integrated kinematic model for NW Africa, Morocco, Iberia, Europe, and North America, which shows that the deformation is partitioned between Pyrenees and Betic‐Rif orogenic domain during the Late Cretaceous‐Oligocene time interval. In the Eastern Betics domain, the calculated amount of NW Africa‐Iberia convergence is ~80 km between 83.5 and 34 Ma, followed by ~150 km since the Oligocene. The motion of Iberia relative to Europe in the Central Pyrenees is characterized by overall NE directed transpressional motion during the Campanian and the Paleocene, followed by NW directed transpressional movement until the Lutetian and overall NNW directed convergence from Bartonian to Chattian. This motion occurs along the axis of the Bay of Biscay from the Santonian–Campanian boundary to the middle Priabonian, subsequently jumping to King's Trough at Anomaly 17 (36.62 Ma).
The Red Sea and Gulf of Aden represent two young basins that formed between Africa and Arabia since the early Oligocene, floored by oceanic crust or by transitional and thinned continental crust. While in the easternmost Gulf of Aden the rift–drift transition can be dated chron C6 (∼20.1 Ma), here we show that in the Red Sea the first pulse of sea floor spreading occurred during chron C3n.2n (∼4.6 Ma) around ∼17.1°N (present–day coordinates) and propagated southwards from this location, separating the Danakil microplate from Arabia. It is also shown that sea floor spreading between Arabia and Nubia started later, around chron 2A (∼2.58 Ma), and propagated northwards. At present, there is no magnetic evidence for the existence of a linear spreading center in the northern Red Sea at latitudes higher than ∼24°N and in the southern Red Sea below ∼14.8°N. The present–day plate kinematics of this region can be described with high accuracy by a network of five interacting plates (Nubia, Arabia, Somalia, Sinai, and Danakil) and six triple junctions. For times older than anomaly 2A (∼2.58 Ma) and up to anomaly 3, the absence of marine magnetic anomalies between Arabia and Nubia prevents a rigorous kinematic description of the five–plates system. However, there is strong evidence that the unique changes in plate motions during the last five Myrs were a dramatic slowdown at chron C2 (∼1.77 Ma) in the spreading or extension rates along the ridge and rift axes, thereby a good representation of the real plate motions can be obtained anyway by backward extension of the oldest Arabia – Nubia and Arabia – Danakil stage rotations determined on the basis of marine magnetic anomalies, respectively C2 – C2A and C2A – C3. The proposed kinematic reconstructions are accompanied by a geodynamic explanation for the genesis of large continent–continent fracture zones at the rift–drift transition and by an analysis of the strain associated with plate motions in Afar, northeastern Egypt, and Sinai.