Geological and geophysical study of a thin-skinned tectonic wedge formed during an early collisional stage: the Trasimeno Tectonic Wedge (Northern Apennines, Italy)

AbstractThe presence of a set of well-known turbidite successions, deposited in progressively E-migrating foredeep basins and subsequently piled up with east vergence, makes the Northern Apennines of Italy paradigmatic of the evolution of deepwater fold-and-thrust belts. This study focuses on the early Apenninic collisional stage, early Miocene in age, which led to the accretion of the turbidites of the Trasimeno Tectonic Wedge (TTW), in the central part of the Northern Apennines. Based on the interpretation of previously unpublished seismic reflection profiles with new surface geology data and tectonic balancing, we present a detailed tectonic reconstruction of the TTW. In the study area, the TTW is characterized by a W-dipping shaly basal décollement located at a depth of 1–5 km. The tectonic wedge is c. 5 km thick at its central-western part and tapers progressively eastwards to c. 1 km. The total shortening, balanced along a 33 km long cross-section, is c. 60 km, including 20 km (40%) of internal imbrication, c. 23 km of horizontal ENE-wards translation along the basal décollement and c. 17 km of passive translation caused by the later shortening of footwall units. Deformation balancing, constrained through upper Aquitanian – upper Burdigalian (c. 21–16 Ma) biostratigraphy, provides an average shortening rate of c. 8.6 mm a–1. Internal shortening of the TTW shows an average shortening rate of c. 4 mm a–1 for this period.

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Grenville Foreland Deformation and Sedimentation in Southwest Ohio Indicated by Reprocessed Seismic Reflection Profiles near Middletown, Ohio, USA

The Ohio Journal of Science ◽

10.18061/ojs.v120i2.7260 ◽

2020 ◽

Vol 120 (2) ◽

pp. 39

Author(s):

David J. Peterman ◽

Ernest C. Hauser ◽

Doyle R. Watts

Keyword(s):

Cross Section ◽

Seismic Reflection ◽

Vertical Displacement ◽

Reverse Fault ◽

Seismic Line ◽

The North ◽

North American Craton ◽

Tectonic Style ◽

Seismic Reflection Profiles ◽

Depositional Setting

The late Mesoproterozoic to early Neoproterozoic Middle Run Formation contains vital information about the crustal evolution of the North American Craton. Four reprocessed seismic reflection lines in the vicinity of the AK Steel facility in Middletown, Ohio, provide new insights into the structural and depositional setting of the Middle Run Formation in this region. A residual statics solution improved the resolution and coherency of reflections in these profiles that underlie the Cambrian Mount Simon Sandstone. Reprocessing revealed gently inclined, west-southwest-dipping reflectors and the occurrence of an angular unconformity between the Middle Run Formation and the overlying Paleozoic strata. The weak and discontinuous seismic reflection character of the Middle Run Formation in these seismic lines overlies a sequence of stronger parallel reflections that are like those observed on the eastward ODNR-1-88 seismic line located near core hole DGS 2627, the stratotype of the Middle Run Formation. This inferred thickness indicates that the basin in which the Middle Run Formation was deposited ranges from at least 670 to 1,128 m (2,200 to 3,700 ft) deep at the AK Steel area and dips gently west-southwest, which is in contrast with the moderate easterly dip observed on the ODNR-1-88 seismic line to the northeast. Correlation of these features across the 10 km (approximately 6 mi) cross-strike gap between the AK Steel lines and the ODNR-1-88 seismic line suggests the presence of a reverse fault with approximately 792 m (2,600 ft) of estimated vertical displacement. A regional cross section—including the WSU 1990 seismic line eastward of the ODNR-1-88 line—exhibits a faulted west-verging asymmetric syncline in near proximity to the Grenville Front. This cross section also shows that deformation of the Middle Run Formation and the underlying layered sequence exhibits a consistent tectonic style of reverse faulting and folding that developed in response to Grenville Front tectonism.

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Conceptual model of basement deformation beneath the Southern Atlassic front of Tunisia from gravity modeling, seismic reflection profiles and seismotectonic data

10.5194/egusphere-egu21-216 ◽

2021 ◽

Author(s):

Nesrine Frifita ◽

Mohamed Gharbi ◽

Kevin Mickus

Keyword(s):

Seismic Reflection ◽

Geological Mapping ◽

Gravity Modeling ◽

Basement Faults ◽

Geophysical Study ◽

Half Graben ◽

Basement Structures ◽

Tectonic Style ◽

Basement Deformation ◽

Seismic Reflection Profiles

<p>The nature of the basement beneath the Southern Atlassic front of Tunisia is relatively unknown. To study the basement, a geophysical study was undertaken using gravity, seismic reflection and seismicity data. Additionally, these data were used to determine the relationship and the tectonic environment between the known seismicity and basement structures under the Chotts fold belt and the surrounding basins. Based on 2.5D gravity modeling, 2D seismic reflection profiles and known geological mapping, the geometry of the basement was modeled as consisting of horsts,grabens and half-grabens. Specifically, the Sidi Mansour and El-Fejej basins are located on basement uplifts. The variations in the depths of the known earthquakes reveal that the deepest events occurred on basement faults beneath the Metlaoui and Sidi Mansour basins. While the surrounding anticlines within the northern Chotts range are probably inverted into graben and half-graben structures by both thin- and thick-skinned tectonic events. The geophysical findings indicate that the geometry of the basement to consist of a series of uplifted and downdropped regions, where the depth to basement increases from south to north and from east to west. This basement structure can explain the concentration of earthquakes in the northwestern portion of the study area by linking a reactivation of pre-existing east trending fault systems that formed during Alpine Orogeny. The results provide a coherent model showed a mixed thick and thin-skinned tectonic style was active within the study area.&#160;</p>

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Structural reconstruction, fault parameterization, and slip rate analysis in the northern Adriatic Sea (Italy): implications for the Plio-Pleistocene tectonic activity of long-lived offshore buried thrusts.

10.5194/egusphere-egu21-15554 ◽

2021 ◽

Author(s):

Yuri Panara ◽

Francesco Emanuele Maesano ◽

Chiara Amadori ◽

Jakub Fedorik ◽

Manlio Ghielmi ◽

...

Keyword(s):

Seismic Reflection ◽

Adriatic Sea ◽

Residual Activity ◽

Distribution Functions ◽

Northern Apennines ◽

Tectonic Activity ◽

Thrust Faults ◽

Northern Adriatic ◽

Moderate Earthquake ◽

Seismic Reflection Profiles

<p>The northern Apennines foredeep is characterized by a Plio-Pleistocene tectonic activity whose driving structures (thrust faults and related anticlines) are always buried by a high amount of syntectonic sediments, both onshore (Po Plain) and offshore (Adriatic Sea), thereby leaving subtle or none apparent signatures in the topo-bathymetry. Compared to the rest of Italy, this area has a relatively moderate earthquake hazard, but historical reports and instrumental recordings testify for significant seismicity. Seismological analyses of recent sizeable earthquakes (e.g., the Mw 6.1, Emilia earthquake in 2012) confirmed that the seismic activity is mainly due to the outermost northern Apennines buried thrusts. In this work, we reconstructed and parameterized the 3D geometry of such buried faults in an offshore sector just south of the Po River delta by interpreting a dense network of 2D seismic reflection profiles. The availability of two regional seismic reflection profiles, coupled with a detailed reconstruction of Plio-Pleistocene horizons, allowed us to restore the deformation cumulated by these thrusts. Our analysis was aimed at (1) establishing the age of inception of the main crustal thrusts, (2) reconstruct the main Plio-Pleistocene tectonic events affecting the study area, and (3) calculate the Plio-Pleistocene slip rates at different time slices and reporting them through probability distribution functions that take into account the uncertainties associated with horizon ages and restoration parameters. Our results show that the Plio-Pleistocene tectonic activity is variably distributed on different thrust faults and decreases exponentially over time after the Gelasian. The analysis performed on the most recent reflectors suggests that a low but not negligible tectonic activity characterizes the main thrusts in the studied region in the last 4-500 ka and hints at a residual activity that may last until the present.</p>

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