Surface processes versus kinematics of thrust belts: impact on rates of erosion, sedimentation, and exhumation – Insights from analogue models

Abstract The mechanical equilibrium of an orogenic wedge is maintained thanks to interactions between tectonic processes and surface processes. To better constrain the influence of erosion and sedimentation on the evolution of orogens, we performed a series of analogue models based on the tapered wedge principle, varying the amounts of erosion and sedimentation. The models develop by frontal accretion in the foreland basin and by simple underthrusting and subsequent underplating in the hinterland. The variations in rates of erosion and sedimentation strongly modify the extent, the morphology, the structures, the timing of development and the material paths in the different models. Under certain conditions, entire structural units can be formed and subsequently eroded out of the geological record, leading to important underestimations when restoring sections. Particles located in the converging lower-plate or in the upper-plate show complex uplift paths related to tectonic stages. The correlation between models and three Alpine tectonic cross-sections emphasizes the role of erosion and sedimentation on the dynamics and development of the orogen and adjacent Molasse basin. Along strike changes in the present structure of the orogen could be explained in part by differences in surface processes.

Download Full-text

Contractional salt tectonics and role of pre-existing diapiric structures in the Southern Pyrenean foreland fold–thrust belt (Montsec and Serres Marginals)

Journal of the Geological Society ◽

10.1144/jgs2020-085 ◽

2021 ◽

pp. jgs2020-085 ◽

Cited By ~ 1

Author(s):

Laura Burrel ◽

Antonio Teixell

Keyword(s):

Cross Sections ◽

Foreland Basin ◽

Salt Tectonics ◽

Structural Development ◽

Field Observations ◽

Content Type ◽

Growth Strata ◽

Structural Style ◽

Supplementary Material

Triassic Keuper evaporites have long been recognized as the main detachment level for thrusting in the Pyrenean fold–thrust belts. The deformed Late Cretaceous–Eocene foreland basin of the Southern Pyrenees has structures and stratal geometries that can be interpreted as related to salt tectonics (e.g. unconformities, rapid thickness variations, long-lived growth fans and overturned flaps), although they have been overprinted by shortening and thrusting. Based on field observations and published maps, we build new structural cross-sections reinterpreting two classic transects of the Southern Pyrenees (Noguera Ribagorçana and Noguera Pallaresa river transects). The sequential restoration of the sections explores the variations in structural style, addressing the role of halokinesis in the tectonic and sedimentary development. In the Serres Marginals area, we propose that salt pillows and diapirs started developing locally during the Mesozoic pre-orogenic episode, evolving into a system of salt ridges and intervening synclines filled with early synorogenic sediments. Rapid amplification of folds recorded by widespread latest Cretaceous–Paleocene growth strata is taken as marking the onset of contractional folding in the area. During Pyrenean compression, folding mechanisms transitioned from dominantly halokinetic to a combination of buckling and differential sedimentary loading. Squeezing of salt diapirs and thrust welding occurred as salt ridges were unroofed. We provide new field observations that lead to a reinterpretation of the regional structural development and contribute to the debate about the role of salt tectonics in the Pyrenees.Supplementary material: Table S1, giving the thickness of the main stratigraphic units, is available at https://doi.org/10.6084/m9.figshare.c.5287737

Download Full-text

The Barreme Basin and the Gevaudan diapir - an example of the interplay between compressional tectonics and salt diapirism

10.5194/egusphere-egu2020-3655 ◽

2020 ◽

Author(s):

Rod Graham ◽

Adam Csicsek

Keyword(s):

Foreland Basin ◽

Finite Geometry ◽

Driving Mechanism ◽

Salt Diapirism ◽

Sedimentary Evolution ◽

Tectonic History ◽

Thrust Belts ◽

Fold And Thrust Belt ◽

History Of

The Barreme Basin and the Gevaudan diapir - an example of the interplay between compressional tectonics and salt diapirism &#160;Adam Csicsek and Rod GrahamImperial College London&#160;Our understanding of the role of salt diapirism in determining the finite geometry of fold and thrust belts has grown apace in the last few years, but the interplay between the two remains a significant problem for structural interpretation. The Gevaudan diapir in the fold and thrust belt of the sub-Alpine chain of Haute Provence is well known and has been documented by numerous eminent alpine structural geologists. Graciansky, Dardot, Mascle, Gidon and Lickorish and Ford have all described and illustrated the geometry and evolution of the structure, and Lickorish and Ford&#8217;s interpretation is figured as an example of&#160; diapirism &#160;in a compressional setting by Jackson and Hudec in their text on salt tectonics. We review these various interpretations and present another.The differences between the various interpretations say much about the complex interplay of salt diapirism and thin-skinned thrusting and have profound implications for the way we interpret the tectonic and sedimentary evolution of the Barreme basin which lies adjacent to the diapirThe Barreme basin is a thrust-top fragment of the Provencal foreland basin and has been described in detail from both sedimentological (e.g. Evans and Elliott, 1999) and structural (e.g. Antoni and Meckel, 1997) points of view. Here we make the case that it is also a salt related minibasin - a secondary minibasin developed on a now welded allochthonous Middle Cretaceous salt canopy. &#160;We believe that within the basin it is possible to interpret successive depocentres which may record progressive salt withdrawal. We argue that though thrust loading must be the fundamental driving mechanism responsible for salt movement late in the tectonic history of the region, thrusting has not done much more than modify existing salt related geometry. &#160;&#160;&#160;

Download Full-text

Role of rift-inheritance and segmentation for orogenic evolution: example from the Pyrenean-Cantabrian system

BSGF - Earth Sciences Bulletin ◽

10.1051/bsgf/2020021 ◽

2020 ◽

Vol 191 ◽

pp. 18 ◽

Cited By ~ 1

Author(s):

Rodolphe Lescoutre ◽

Gianreto Manatschal

Keyword(s):

Cross Sections ◽

Seismic Data ◽

Large Scale ◽

Sedimentary Cover ◽

First Order ◽

Segment Boundary ◽

Orogenic Wedge ◽

Mountain Belts ◽

Two Phases

The Basque-Cantabrian junction corresponds to an inverted rift accommodation zone at the limit between the former hyperextended Pyrenean and Cantabrian rift segments. The recognition of an inherited rift segment boundary allows to investigate the reactivation associated with large-scale rift segmentation in an orogenic system. We use criteria from published field observations and seismic data to propose a new map of rift domains for the Basque-Cantabrian junction. We also provide balanced cross-sections that allow to define the along-strike architecture associated with segmentation during rifting and subsequent Alpine reactivation. Based on these results, this study aims to characterize and identify reactivated and newly formed structures during inversion of two rift segments and its intermitted segment boundary. It also aims to describe the timing of thin-skinned and thick-skinned deformation associated with the inversion of segmented rift systems. During convergence, two phases have been recognized within the rift segment (eastern Mauléon basin). The Late Cretaceous to Paleocene underthrusting/subduction phase was mostly governed by thin-skinned deformation that reactivated the former hyperextended domains and the supra-salt sedimentary cover. The Eocene to Miocene collisional phase, controlled by thick-skinned deformation that took place once necking domains collided and formed an orogenic wedge. At the rift segment boundary, the underthrusting/subduction phase was already controlled by thick-skinned deformation due to the formation of shortcutting thrust faults at the termination of overlapping V-shaped rift segments. This led to the formation of a proto-wedge composed of the Basque massifs. We suggest that this proto-wedge is responsible for the preservation of pre-Alpine structures in the Basque massifs and for the emplacement of subcontinental mantle rocks at a crustal level beneath the western Mauléon basin. These results argue for a first order cylindrical orogenic architecture from the Central Pyrenean segment to the Cantabrian segment (up to the Santander transfer zone) despite rift segmentation. They also highlight the control of 3D rift-inheritance for the initial phase of orogenic evolution and for the local architecture of mountain belts.

Download Full-text

Tectonic evolution of the Himalayan syntaxes: the view from Nanga Parbat

Geological Society London Special Publications ◽

10.1144/sp483.5 ◽

2018 ◽

Vol 483 (1) ◽

pp. 215-254 ◽

Cited By ~ 7

Author(s):

Robert W. H. Butler

Keyword(s):

Strain Localization ◽

Tectonic Evolution ◽

Ductile Deformation ◽

Surface Processes ◽

Feedback Mechanisms ◽

Tectonic Processes ◽

New Models ◽

Nanga Parbat ◽

Namche Barwa

AbstractCurrent tectonic understanding of the Nanga Parbat–Haramosh massif (NPHM) is reviewed, developing new models for the structure and deformation of the Indian continental crust, its thermorheological evolution, and its relationship to surface processes. Comparisons are drawn with the Namche Barwa–Gyala Peri massif (NBGPM) that cores an equivalent syntaxis at the NE termination of the Himalayan arc. Both massifs show exceptionally rapid active denudation and riverine downcutting, identified from very young cooling ages measured from various thermochronometers. They also record relicts of high-pressure metamorphic conditions that chart early tectonic burial. Initial exhumation was probably exclusively by tectonic processes but the young, and continuing emergence of these massifs reflects combined tectonic and surface processes. The feedback mechanisms implicit in aneurysm models may have been overemphasized, especially the role of synkinematic granites as agents of rheological softening and strain localization. Patterns of distributed ductile deformation exhumed within the NPHM are consistent with models of orogen-wide gravitation flow, with the syntaxes forming the lateral edges to the flow beneath the Himalayan arc.

Download Full-text

Oxygen K near edge structures studied with multiple scattering calculations

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104583 ◽

1988 ◽

Vol 46 ◽

pp. 504-505

Author(s):

Xudong Weng ◽

Peter Rez

Keyword(s):

Cross Section ◽

Cross Sections ◽

Partial Cross Section ◽

Energy Window ◽

Edge Structure ◽

Fine Structures ◽

Hydrogenic Model ◽

Electron Energy Loss ◽

Quantitative Chemical

In electron energy loss spectroscopy, quantitative chemical microanalysis is performed by comparison of the intensity under a specific inner shell edge with the corresponding partial cross section. There are two commonly used models for calculations of atomic partial cross sections, the hydrogenic model and the Hartree-Slater model. Partial cross sections could also be measured from standards of known compositions. These partial cross sections are complicated by variations in the edge shapes, such as the near edge structure (ELNES) and extended fine structures (ELEXFS). The role of these solid state effects in the partial cross sections, and the transferability of the partial cross sections from material to material, has yet to be fully explored. In this work, we consider the oxygen K edge in several oxides as oxygen is present in many materials. Since the energy window of interest is in the range of 20-100 eV, we limit ourselves to the near edge structures.

Download Full-text

An Study of Influence of Imperfections on the Delamination of Diamond-Like Carbon Films

MRS Proceedings ◽

10.1557/proc-719-f8.36 ◽

2002 ◽

Vol 719 ◽

Author(s):

Myoung-Woon Moon ◽

Kyang-Ryel Lee ◽

Jin-Won Chung ◽

Kyu Hwan Oh

Keyword(s):

Cross Sections ◽

Focused Ion Beam ◽

Imaging System ◽

Ion Beam ◽

Carbon Films ◽

Diamond Like Carbon ◽

Glass Substrates ◽

Atomic Force ◽

Initiation And Propagation

AbstractThe role of imperfections on the initiation and propagation of interface delaminations in compressed thin films has been analyzed using experiments with diamond-like carbon (DLC) films deposited onto glass substrates. The surface topologies and interface separations have been characterized by using the Atomic Force Microscope (AFM) and the Focused Ion Beam (FIB) imaging system. The lengths and amplitudes of numerous imperfections have been measured by AFM and the interface separations characterized on cross sections made with the FIB. Chemical analysis of several sites, performed using Auger Electron Spectroscopy (AES), has revealed the origin of the imperfections. The incidence of buckles has been correlated with the imperfection length.

Download Full-text