Transpressional deformations at lateral boundaries of propagating thrust-sheets: the example of the Meuse Valley Recess within the Ardennes Variscan fold-and-thrust belt (N France–S Belgium)

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.

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Thrust tectonics on Brøggerhalvøya and their relationship to the Tertiary West Spitsbergen Fold-and-Thrust Belt

Geological Magazine ◽

10.1017/s0016756801006069 ◽

2002 ◽

Vol 139 (1) ◽

pp. 47-72 ◽

Cited By ~ 12

Author(s):

K. SAALMANN ◽

F. THIEDIG

Keyword(s):

Middle Eocene ◽

Kinematic Model ◽

Thrust Belt ◽

Fold Belt ◽

Kinematic Evolution ◽

Fold And Thrust Belt ◽

Thrust Tectonics ◽

Tectonic Transport ◽

Thrust Sheets ◽

West Spitsbergen

The Tertiary fold-and-thrust belt on Brøggerhalvøya is characterized by a NE-vergent pile of nine thrust sheets. The sole thrust of the pile is located in Precambrian phyllites and climbs up-section to the northeast. Four lower thrust sheets consisting predominantly of Upper Palaeozoic sediments are overlain by two thrust sheets in the central part of the stack which contain a kilometre-scale syncline and anticline. The fold is cut by juxtaposed thrusts giving rise to the formation of three structurally higher basement-dominated thrust sheets. A multiple-stage kinematic model is proposed including (1) in-sequence foreland-propagating formation of the lower thrust sheets in response to N–S subhorizontal bedding-parallel movements, (2) a change in tectonic transport to ENE and out-of-sequence thrusting and formation of the kilometre-scale fold-structure followed by (3) truncation of the kilometre-scale fold and stacking of the highest basement-dominated thrust sheets by hind-ward-propagating out-of-sequence thrusting. The strain of the thrust sheets is predominantly compressive with the exception of the structurally highest thrust sheets, reflecting a temporal change to a more transpressive regime. Thrusting was followed by (4) N–S extension and (5) W–E extension. Comparison of the structural geometry and kinematic evolution of Brøggerhalvøya with the data reported for the fold belt further south allows us to assume a coeval evolution with the fold belt. A latest Paleocene/Early Eocene age for the main phase of thrusting is suggested for the West Spitsbergen Fold-and-Thrust Belt; the main phases therefore pre-date the separation of Svalbard and Greenland due to right-lateral movements along the Hornsund Fault Zone. The fold belt's temporal evolution followed by the formation of the Forlandsundet Graben can be linked with the plate-kinematic framework in the span between latest Paleocene and Middle Eocene times.

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A spatial statistics approach to the quantification of finite strain variation in penetratively deformed thrust sheets: an example from the Sheeprock Thrust Sheet, Sevier Fold-and-Thrust belt, Utah

Journal of Structural Geology ◽

10.1016/s0191-8141(97)00088-6 ◽

1998 ◽

Vol 20 (4) ◽

pp. 371-384 ◽

Cited By ~ 17

Author(s):

Malay Mukul

Keyword(s):

Spatial Statistics ◽

Finite Strain ◽

Thrust Belt ◽

Strain Variation ◽

Thrust Sheet ◽

Fold And Thrust Belt ◽

Thrust Sheets

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Timing and magnitude of vertical-axis rotations in the eastwards-flanking synorogenic sediments of the South-Pyrenean fold-and-thrust belt. Kinematics and origin of the salient curvature.

10.5194/egusphere-egu2020-7685 ◽

2020 ◽

Author(s):

Charlotte Peigney ◽

Elisabet Beamud ◽

Óscar Gratacós ◽

Luis Valero ◽

Ruth Soto ◽

...

Keyword(s):

Foreland Basin ◽

Structural Data ◽

Vertical Axis ◽

Central Unit ◽

Thrust Belt ◽

The South ◽

The North ◽

South Central ◽

Fold And Thrust Belt ◽

Thrust Sheets

The South-Pyrenean fold-and-thrust belt consists of three major thin-skinned thrust sheets (B&#243;ixols, Montsec and Serres Marginals) made up of uppermost Triassic to Oligocene cover rocks emplaced during Late Cretaceous-Oligocene times. In its central part, it forms a major salient (the Pyrenean South-Central Unit) whose geometry is controlled by the areal distribution of the pre-orogenic Upper Triassic and synorogenic Eocene salt d&#233;collement layers. Both westwards and eastwards, the salient is fringed by Paleogene synorogenic deposits that are deformed by detachment folds with orientations ranging from N-S to E-W. In the western edge of the salient, the varying trend of the folds is a result of synorogenic vertical axis rotations (VAR) which caused the clockwise rotation of the folds from an initial predominant E-W trend to the current NW-SE to NNW-SSE trend. The salient, at least on its western part, developed from a progressive curve originated from divergent thrust transport directions and distributed shortening.The aim of our study is to get a better understanding of the whole salient, by studying the kinematics of the deformation on the most frontal part of its eastern edge. Here, some sparse anticlockwise rotations have been reported but their origin and their possible relationship with the distribution of the salt d&#233;collements has not yet been addressed. For this purpose, 78 paleomagnetic sites have been sampled on the synorogenic upper Eocene-Oligocene materials of the NE Ebro foreland Basin, in the Artesa de Segre area, focusing on the limbs of oblique salt-cored anticlines (Ponts, Vilanova de l&#8217;Aguda, Cardona) which are detached above the synorogenic Eocene-Oligocene evaporites of the Cardona and the Barbastro formations. VAR analyses principally show anticlockwise rotations similar to those previously identified to the North in the Oliana Anticline, although a small number of clockwise rotations were also detected.In addition to the VAR analysis, a magnetostratigraphic study of the Eocene-Oligocene continental materials of the northern limb of the Sana&#252;ja Anticline has been conducted in order to constrain the age of these rotations from stratigraphic correlations. The demagnetization of 104 samples from a ca. 1100 m thick magnetostratigraphic section shows Priabonian to Rupelian ages for this succession. The integration of our results on timing, direction and magnitude of foreland VAR with previous paleomagnetic and structural data from both the western and eastern boundaries of the frontal thrust of the Pyrenean South-Central Unit will allow the understanding of the kinematics of the thrust salient as a whole.

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