Understanding Paleomagnetic Rotations in Sicily: Thrust Versus Strike‐Slip Tectonics

Abstract

The paleomagnetic investigation of the western Sicily Maghrebian belt has revealed since the 1970s that large clockwise rotations up to 140° with respect to the Hyblean‐African foreland occurred synchronous with Tertiary shortening of the chain. The observation that rotations decrease stepwise from internal to external tectono‐stratigraphic units led in the 1990s to a widely accepted model postulating that rotational thrust‐sheet emplaced during forward orogenic propagation. More recently, other authors suggested that clockwise rotations from Sicily are conversely the result of late orogenic dextral strike‐slip tectonics. Here we report on a paleomagnetic investigation of 30 Jurassic‐Eocene sedimentary sites sampled mainly across the WNW‐ESE Mt. Kumeta and Rocca Busambra ridges (Trapanese Unit), both bounded to the north by high‐angle reverse faults with dextral strike‐slip components. We find rotations of 110°–120° at faults of northern ridge margins, which decrease to 80°–90° at ~200 m to the south and rise again moving further south. Thus, an excess rotation of 20°–40° due to dextral‐strike‐slip shear is annulled to the regional rotational background of the Trapanese Unit at only 200 m from fault traces, translating to paleomagnetically calculated strike‐slip offsets not exceeding 600 m. Further north, seven sites sampled in the Imerese Unit, tectonically stacked above the Trapanese Unit, yield a ~130° rotation. Thus, our data confirm that CW rotations in Sicily are predominantly related to thrust‐sheet emplacement. Strike‐slip tectonics has very limited relevance and gives local rotations that fade out at only 200 m from fault planes.

Paleomagnetic Evidence for 25–15 Ma Crust Fragmentation of North Indochina (23–26°N): Consequence of Collision With Greater India NE Corner?

“…Crustal rotations that have taken place in deformed orogens have been either related to block rotation due to strike‐slip shear (Hernandez‐Moreno et al, , and references therein) or to emplacement of rotational thrust sheets (e.g., Cifelli & Mattei, ; Shaanan et al, ; Speranza et al, ; Weil et al, ). Both kinematics are possible in the study area, as the Lanping and Simao domains are characterized by both strike‐slip faults, and thrust structures (Bureau of Geology and Mineral Resources of Yunnan Province, ; Wang & Burchfiel, ).…”

Structural and tectono-stratigraphic review of the Sicilian orogen and new insights from analogue modeling

“…As previously noticed, moderate differential rotation between coeval tectonostratigraphic units within the wedge, and major decreasing rotation through time, evidenced by paleomagnetic data (Cifelli et al, 2007;Speranza et al, 2018), are not consistent with large displacements between long thrust sheets (Butler et al, 2019).…”

“…This period was also characterized by large vertical-axis clockwise rotations of the thrust system in response to the convergence obliquity. Up to 70° regional rotations of Upper Triassic-Middle Miocene successions are recorded by paleomagnetic measurements (Channell et al, 1990;Oldow et al, 1990;Speranza et al, 2003Speranza et al, , 2018 and structural analysis (Monaco and De Guidi, 2006;Avellone et al, 2010;Barreca and Monaco, 2013).…”

Strong Neotectonic Block Rotations, Related to the Africa‐Eurasia Convergence in Northern Algeria: Paleomagnetic Evidence From the Mitidja Basin

“…The remaining question is whether a similar evolution may occur along the North African margin toward the West and East of the Mitidja‐Cheliff‐Northwestern Algeria areas, that is, in Morocco and Eastern Algeria‐Tunisia. Further East, paleomagnetic investigation of the western Sicily Maghrebian belt has revealed that large clockwise rotations with respect to the Hyblean‐African foreland have occurred since the Tertiary (Channell et al, ; Schult, ; Speranza et al, ).…”