Astronomical dating of a tectonic rotation on Sicily and consequences for the timing and extent of a middle Pliocene deformation phase

A detailed palaeomagnetic study of long and continuous middle Pliocene sections from the Caltanisetta basin on Sicily reveals a differential clockwise rotation occurring around 3.21 Ma. The rotation appears to be a rapid event (80,000100,000 years) which suggests that the responsible tectonic processes also occur rapidly. Its timing corresponds closely to the transition from the Trubi to the Narbone Formation at 3.19 Ma. This transition marks a major change in sedimentary environment on Sicily and in Calabria, and it is coeval, for instance, with the onset of sapropel formation in the eastern Mediterranean. Apparently it marks a synchronous and centraleastern Mediterranean-wide event. Data from the oldest sediments overlying the Tyrrhenian basement (ODP Leg 107) suggest an acceleration in opening of the Tyrrhenian Sea during the middle Pliocene. We speculate that this acceleration is related to a transpressional event in the Sicilian fold-and-thrust belt and extension which formed troughs in the foreland, the Strait of Sicily. Thrust imbrication accompanying the transpressional event on Sicily induced the middle Pliocene clockwise rotation and resulted in shallowing of the Caltanisetta basin causing the change in sedimentation regime characterised by the TrubiNarbone transition. Following this middle Pliocene tectonic phase, no rotation took place in the southern Apennines, Calabria and Sicily until the middle Pleistocene (1.00.7 Ma). Ó 1998 Elsevier Science B.V. All rights reserved

Reply to: 'A late Pleistocene clockwise rotation phase of Zakynthos (Greece) and implications for the evolution of the western Aegean Arc'

During the 80s, a number of seminal papers were published by the Gif-sur-Yvette group of Carlo Laj and co-workers, on the late Neogene palaeomagnetic rotations of the Aegean and, in particular, of the Aegean Arc system. These studies shed new light on the tectonic evolution of the region (e.g. [1,2]). Then, similar work on the Calabrian^ Sicilian arc system established that major tectonic rotations were of very young (middle Pleistocene) age [3], and it became clear to us that it was warranted to have a closer and more detailed look at the tectonic history of the Aegean Arc. In particular, the advent of more accurate, astronomically calibrated time scales during the 90s provided the opportunity to correlate tectonic (or other, e.g. climatic) events over a large geographical area, and to constrain their age and duration and hence their (a)synchrony. This would aid in testing a dynamical model of subduction- related geodynamics of the (central) Mediterranean area [4]. Many studies, e.g. on numerical modelling of stress patterns, tomography, vertical motions and depot centre migration, and on tectonostratigraphy, have aided in testing this hypothesis (see [5] for references). Meanwhile, the accurate time control has provided increasing evidence for relatively short periods of rapid, pulsed tectonic rotations (see [5] for references and discussion). This is in contrast to a more continuous deformation over a longer time interval, as was earlier suggested by Laj et al. [1] for the western Aegean Arc

Post-early Messinian counterclockwise rotations on Crete: implications for Late Miocene to Recent kinematics of the southern Hellenic arc

Most geodynamical models for the kinematics of the central Mediterranean recognise that major tectonic rotations must have played an important role during the Neogene. The Hellenic arc is believed to have been subjected to clockwise rotations in the west and counterclockwise rotations in the east, while the southern part (Crete) shows no rotations (Kissel and Laj, 1988). Many qualitative and quantitative models are based on the idea that Crete did not rotate. We present new palaeomagnetic data which show that post-early Messinian counterclockwise rotations have occurred on Crete. The amount of counterclockwise rotation generally varies between 10º and 20º, but in central Crete much larger rotations (up to 40º counterclockwise) were found. Only a few sections did not show any rotation. The anisotropy of magnetic susceptibility (AMS) shows lineations, which are consistently WNWESE throughout Crete, indicating post-rotational WNW-ESE extension, or NNE-SSE compression. The observed counterclockwise rotations are consistent with the results of tectonic modelling by Ten Veen and Meijer (1998). The latter study compares the late-Middle Miocene to Recent kinematics with modelled intra-plate stresses for various possible distributions of plate boundary forces. Observations reveal that motion along left-lateral and right-lateral faults occurred during the Pliocene. The model analysis shows these motions to be consistent with transform resistance along the eastern segment of the overriding margin. The counterclockwise block rotations observed by us are probably a consequence of displacements along the left-lateral and right-lateral faults and could reflect a similar tectonic regime that involved transform resistance. Ó 1998 Elsevier Science B.V. All rights reserved

Neogene evolution of the Aegean arc: paleomagnetic and geodetic evidence for a rapid and young rotation phase

New paleomagnetic data of the entire Aegean outer-arc are presented. The results indicate a young Pleistocene and rapid clockwise rotation phase in the western Aegean arc, covering at least Zakynthos and the Peloponessos. The eastern Aegean arc, incorporating Kassos, Karpathos and Rhodos, also experienced Pleistocene anticlockwise rotations. The anisotropies of the magnetic susceptibility (AMS) data are in agreement with arc-parallel extension in the south and south-eastern Aegean arc and arc-normal compression in the north-west, in agreement with structural and geodetic observations. We compare the paleomagnetic results with the present-day pattern of rotation as computed from geodetic data, and we find good agreement. The onset of the Pleistocene rotations coincides with the beginning of uplift and a change in the stress pattern of extension. We compare our findings with existing models for the Aegean area

Comment on: 'A late Pleistocene clockwise rotation phase of Zakynthos (Greece) and implications for the evolution of the western Aegean Arc'

In a recent paper, Duermeijer et al. [1] report new palaeomagnetic results from the island of Zakynthos (Greece). In many cases, these authors have re-sampled the original sites of Laj et al. [2] and the results are virtually identical to those of the earlier study except for much more precise biostratigraphic age control. Three middle Pleistocene sites (Bochali, Zakynthos town and Porto Roma) which were not sampled by Laj et al. document signi¢cant clockwise rotations. From the results obtained from these three new sites, the authors conclude that the 25° clockwise rotation of Zakynthos described by Laj et al. as affecting the entire western Hellenic margin more or less progressively over the last 5 Myr is much more recent (early Pleistocene)

A Late Pleistocene clockwise rotation phase of Zakynthos (Greece) and implications for the evolution of the western Aegean arc

Palaeomagnetic measurements have been carried out on Eocene to Pleistocene sediments on the Ionian island of Zakynthos, NW Greece. Magnetostratigraphic constraints, biostratigraphic analyses of planktonic foraminifera and calcareous nannofossils provide a reliable time frame for these deposits. The results show that no significant rotation occurred between 8.11 and 0.77 Ma, but that Zakynthos underwent a 21.6º 7.4º clockwise rotation between 0.77 Ma and Recent. Thus, our data indicate a rapid rotational event, in contrast to continuous rotation since 5 Ma as previously postulated [Laj et al., Tectonophysics 86 (1982) 45 67]. We speculate this late Pleistocene tectonic rotation phase to be linked to rapid uplift in the Greek region which results from rebound processes caused by (African) slab detachment underneath the Ionian islands. Ó 1999 Elsevier Science B.V. All rights reserved

Neogene to recent tectonic evolution of the Central Mediterranean : an integrated paleomagnetic approach

Paleomagnetic studies of sediments from the Calabro-Peloritan block in southern Italy consequently imply a 15° clockwise rotation for the late Tortonian to middle Pleistocene sedimentary cover; but the results of older sediments are generally less consistent. Earlier paleomagnetic results of Tortonian sites from the Basilicoi section (Crotone basin, northern Calabria) suggested a major counterclockwise rotation of 97° (Scheepers, 1994b). Here, we studied the Basilicoi section in detail and we used anisotropy of the magnetic susceptibility (AMS) to reconstruct the bedding plane needed for tilt correction. This reduced the 97° counterclockwise rotation to a 25° counterclockwise rotation. The Lese section, also in northern Calabria, shows the same counterclockwise rotation in sediments with an age between 10.4 and 8.6 Ma, thus confirming the results from the corrected Basilicoi section. A comparison of the magnetostratigraphy and planktonic foraminiferal biostratigraphy with the magneto-biostratigraphic framework of the Mediterranean late Miocene allows a correlation of the Basilicoi and Lese sections to the GPTS and a timeframe for the rotation. It is concluded that the 25° counterclockwise rotation phase took place between -7.6 ± 0.1 and 8.6 Ma. We speculate that the timing of this tectonic phase is related to the opening of the Tyrrhenian Sea and the separation of Calabria from Sardinia. We compare our results with those of ODP leg 107 and we suggest an age between 8.6-7.8 Ma for the timing of the opening of the Tyrrhenian Sea

Paleomagnetic evolution of the Cankiri basin, central Anatolia, Turkey: implications for oroclinal bending due to indentation

Palaeomagnetic data in combination with palaeostress data and anisotropy of magnetic susceptibility orientations are utilized to develop a tectonic evolutionary model for the Early Tertiary part of the Omega(omega)-shaped Cankiri Basin (Turkey). The results reveal clockwise rotations in the northeast and anticlockwise rotations in the west and southeastern corner of the basin. The magnetic inclinations indicate a northward drift of the Cankiri Basin and support an indentation model for the Kirsehir Block. It is proposed that the Omega-shape of the Cankiri Basin was the result of indentation of the Kirsehir Block into the Sakarya Continent during northwards migration accompanying closure of Neotethys. It appears that the indentation started prior to Eocene and ended before Middle Miocene times

A late Pleistocene clockwise rotation phase of Zakynthos (Greece) and implications for the evolution of the western Aegean arc

Palaeomagnetic measurements have been carried out on Eocene to Pleistocene sediments on the Ionian island of Zakynthos, NW Greece. Magnetostratigraphic constraints, biostratigraphic analyses of planktonic foraminifera and calcareous nannofossils provide a reliable time frame for these deposits. The results show that no significant rotation occurred between 8.11 and 0.77 Ma, but that Zakynthos underwent a 21.6°± 7.4°clockwise rotation between 0.77 Ma and Recent. Thus, our data indicate a rapid rotational event, in contrast to continuous rotation since 5 Ma as previously postulated [Laj et al., Tectonophysics 86 (1982) 45-67]. We speculate this late Pleistocene tectonic rotation phase to be linked to rapid uplift in the Greek region which results from rebound processes caused by (African) slab detachment underneath the Ionian islands