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TS11.1

Salt and Shale Tectonics : Recent advances and challenges

This session is open to all recent works on salt-related tectonics, in various tectonic settings (extensional, contractional, strike-slip or simply gravitational, i.e. passive margins), areas of study (onshore or offshore), and types of approaches (subsurface or outcrop interpretation, seismic imaging and processing, numerical or analogue modelling, and rock-mechanics analysis). Likewise, we welcome contributions at various scales from the relationships between crustal-scale tectonics, evaporite deposition and salt tectonics within sedimentary basins and mountains, to the interaction between salt bodies and their surrounding sediments, to intra-salt deformation. Contributions on shale tectonics are also welcome.
The session will start with the speech of Jean-Paul Callot "The role of salt in mountain building, from minibasin formation to orogen dynamic" (invited speaker).

Convener: Virginie Gaullier | Co-convener: Gaia TravanECSECS
Presentations
| Mon, 23 May, 08:30–11:08 (CEST)
 
Room D1

Mon, 23 May, 08:30–10:00

Chairpersons: Virginie Gaullier, Gaia Travan

08:30–08:40
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EGU22-2767
|
solicited
Jean-Paul Callot et al.

Evaporites levels have long been considered to have a major impact on the evolution of tectonically-driven as well as gravity-driven fold-and-thrust belts. If initially thin and planar, the role of pre-tectonic salt can be limited to an efficient décollement level during the convergence. Nevertheless, as a décollement level, pre-kinematic salt rock already deeply modifies the shape of the orogenic wedge, favouring large and low taper prisms. In addition, a thick pre-kinematic evaporite level, triggering salt tectonics from the time of the deposition on, modifies the architecture of the sedimentary packages and subordinate basins later incorporated within the orogenic wedge, creating structurally deceiving inherited geometries. Syn-orogenic salt levels also controls the fold-and-thrust belt development, favouring large scale decoupling and strain partitioning. At a much larger scale, it appears that salt levels influences also the development of the orogenic prism itself, modifying the topographical evolution of the taper. Examples from the Western Alps, the Pyrenees and the Sivas basin illustrate the various roles of salt, generating strong inheritance at almost all scales of observation. In addition, two dimensional numerical experiments of collision built by the inversion of rifted margins reveal that mechanically, a weak décollement layer formed by salt rocks delays the formation of the collisional orogen. The thicker the salt layer, the wider is the orogen and the lower the altitude of the mountain belt, leading to a quasi-absence of topography and widespread salt tectonics, which obliterates classical thrusts propagation.

How to cite: Callot, J.-P., Célini, N., Jourdon, A., Legeay, E., Mouthereau, F., Le Pourhiet, L., and Ringenbach, J.-C.: The role of salt in mountain building, from minibasin formation to orogen dynamic, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2767, https://doi.org/10.5194/egusphere-egu22-2767, 2022.

08:40–08:46
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EGU22-1174
Jean-Claude, Raymond Ringenbach

Salt Tectonics Outcrops and 3D Drone Images from the Sivas Basin (Turkey) compared to High-Resolution Seismic Lines

Jean-Claude Ringenbach1*, Charlie Kergaravat1, Charlotte Ribes1, Alexandre Pichat2, Etienne Legeay2 & Jean-Paul Callot2

 

1 TotalEnergies s.e., Av. Larribau, 64018 Pau cedex, France.

2 LFC-R, Université de Pau et des Pays de l’Adour, Avenue de l’Université, BP 576, 64012 Pau cedex, France.

* Corresponding author: jean-claude.ringenbach@total.com

 

The outstanding outcrops of salt tectonic structures of the Sivas basin in Anatolia are now well known. A drone acquisition in November 2018 provides 3D images to visualize and interpret the structures in order to better analyze subsurface data from salt domains and since, many puctures have been acquired by the first author with a Mavic drone. Drone images, now widely used in structural geology, allow building 3D qualitative models of the outcrops. Seven structures among the most demonstrative of salt tectonics have thus been imaged in the secondary minibasins.

The Sivas basin, an elongated Oligo-Miocene north-verging multi-phased foreland basin, developed above the Neotethys suture zone. Evaporites deposited at the end of the early compression phase (Bartonian), filled the foreland basin and covered eroded thrust sheets and folds to the south. Primary minibasins formed during a period of quiescence from Late Eocene to Early Oligocene, associated to the building of an evaporite canopy. The system further evolved during convergence of the Arabian and Eurasian plates in the Late Oligocene-Early Miocene with a renewed compression on the north verging fold-and-thrust belt (FTB). This resulted in the formation of secondary minibasins, ultimately tilted and welded.

In the last decades, huge improvements in seismic imaging under thick allochthonous salt have been made in the Gulf of Mexico and Angola. Wide-azimuth towed-streamer (WATS) 2D as well as 3D seismic acquisitions allow far better imaging along steep subsalt diapiric flanks and welds. However, major drilling disappointments still do occur, due to unseen megaflaps and small-scale structures such as halokinetic sequences at various scales or small faults cannot be seen. Field analogs then become the only guide for a better assessment of the traps. Striking geometric analogies between the Sivas outcrops and seismic images from the classic petroleum provinces controlled by salt tectonics will illustrate the extraordinary quality of the Sivas basin as a geometrical field analog for the Angola and the Gulf of Mexico salt basins. Analog modelling imaged with X-ray tomography under a medical scanner will also be used for comparison.

How to cite: Ringenbach, J.-C. R.: Salt Tectonics Outcrops and 3D Drone Images from the Sivas Basin (Turkey) compared to High-Resolution Seismic Lines, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1174, https://doi.org/10.5194/egusphere-egu22-1174, 2022.

08:46–08:52
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EGU22-6252
Jean-Paul Callot et al.

Located in the center of the Anatolian Plateau in Turkey, the Tertiary Sivas Basin was built after the closure of the northern Neotethys oceanic domain from Upper Cretaceous to Pliocene times. It developed over an ophiolitic basement obducted from the north during the Late Cretaceous, initially separating the Kirshehir continental block from the Taurus microplate. During the Paleogene, the onset of the Tauride compression resulted in the development of a foreland basin within the Sivas domain, affected by north-verging thrusts reworking the foreland sequence and ophiolitic sheets. The flexural deepening of the basin resulted in the accumulation of a thick marine turbiditic succession in the foredeep area, followed by a rapid shallowing and the deposition of a thick evaporitic sequence during the late Eocene. This very special episode allowed for a second youth of the basin. Although studied for a quite long time, the Sivas Basin was indeed recently revisited as being likely the world’s finest open-air museum of salt tectonic structures. Despite huge difference with respect to known salt provinces, the Sivas basin provides outstanding outcrops of the classic geometries associated to the development of diapirs, i.e. halokinetic sequences along diapir walls, and associated stratal deformations, and more exotic structures such as bubble shaped minibasins, megaflaps and evaporites allochtonous glaciers and canopy. We will here review some of the results obtained thanks to a 5 year long project, during which the basin was dissected at the metric scale by a team including four PhD students to handle (1) the detailed mapping of a 60x30 km2 domain, (2) the coupled tectono-sedimentary analysis of the central, salt-controlled area, (3) decipher the complex and recurrent story of evaporite reworking and redeposition, (4) incorporate some matrix scale observations, and eventually (5) integrate the Sivas story within the Tethyan domain evolution. More generally, this fairy tale was also an opportunity to critically review the processes of geologic knowledge acquisition, basically here the trial and error game of building a coherent story, even based on fantastic outcrops.

How to cite: Callot, J.-P., Ringenbach, J.-C., Ribes, C., Kergaravat, C., legeay, E., and pichat, A.: The forgotten salt basin: Sivas Basin, Turkey, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6252, https://doi.org/10.5194/egusphere-egu22-6252, 2022.

08:52–08:58
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EGU22-4498
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ECS
Dan Mircea Tamas et al.

Numerous orogenic fold-and-thrust belts contain salt. It serves as an excellent décollement for folds and thrusts, and in some, diapirs had a profound influence on the structural styles. In salt-detached fold-and-thrust belts, decapitated diapirs can form due to thrusting but are poorly documented in the subsurface and not reported in outcrop. Here we present a surface exposure of a sub-horizontal intra-salt shear zone, which is interpreted to have formed as a result of partial decapitation of a deep-rooted salt-cored anticline. The Mânzălești diapir in the Romanian Eastern Carpathians forms the largest rock salt outcrop in Europe, with unique salt-karst geomorphology between the Tarcău and Subcarpathian nappes. Numerous wells show that the outcrop lies over a deep-seated salt diapir, the base of which is at >3500 m. Multi-scale observations using UAV-based digital outcrop models, fieldwork, and microstructure analysis show that the outcrop is characterised by sub-horizontal foliation with isoclinal folds. The halite is rich in clastic inclusions, with a power-law size distribution caused by tectonic reworking of originally dirty salt. Microstructures show that the halite matrix is strongly deformed by dislocation creep, forming subgrains with a dynamically recrystallised grain size of about 1.5 mm. This is indicative of relatively high differential stress, of around 4 MPa. After combining observations on all scales (cross-sectional, outcrop, and microstructural analyses), our preferred explanation is that the Mânzălești diapir has evolved from a salt-cored anticline to a thrusted diapir in front of the Tarcău nappe. Intense shear originating from a thrust partially decapitated the diapir, shifting its upper portion away from its base.

How to cite: Tamas, D. M., Tamas, A., Barabasch, J., Rowan, M., Schleder, Z., Krezsek, C., and Urai, J.: Do diapirs ever lose their heads? Insights from the Romanian Eastern Carpathians, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4498, https://doi.org/10.5194/egusphere-egu22-4498, 2022.

08:58–09:04
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EGU22-4580
Rodney Graham

                Allochthonous salt sheets in the external SW Alps

Rod Graham₁, Sam Brooke-Barnett₁, Naïm Célini₂, Jean Paul Callot₂, Adam Csicsek₁, Lidia Lonergan₁, Jean Claude Ringenbach₃.

₁ Imperial College London ₂Université de Pau et des Pays del’Adour ₃Total Energies SE

Understanding of the importance of salt tectonics in the Alpine fold and thrust belts of Europe has evolved considerably in the last few years. Our particular area of focus has been in the sub-Alpine chains of Haute Provence, an area where initial ground-breaking work on diapirism was published many years ago by Graciansky, Dardeau, Mascle and others.

 Our own work demonstrates that salt related phenomena like minibasins, megaflaps, welds and anomalous changes in stratigraphic thickness and facies are widespread over the region, but perhaps the most startling discovery is that, at several times in the past, salt was squeezed out over topographic surfaces to form allochthonous sheets of considerable extent. The salt breakouts were mostly submarine, comparable with the allochthonous salt in the Gulf of Mexico and coincided with times of shale deposition during Oxfordian, Albo- Cenomanian and , although breakout  onto land surfaces occurred in the Tertiary.

Graham et al (2012) described an allochthonous salt sheet overlying the inverted strata of the Barre de Chine north of Digne which covered some 25sq Km of the Oxfordian seabed,. North of this structure Célini et al. (2021) describe a major allochthonous sheet rooting in the Astoin diapir. 10 sq km of this remains as gypsum and cargneule, but the original extent of the salt glacier on the Oxfordian sea floor must have been much greater since stratigraphically out of place remnants of Liassic resting on Oxfordian black shales are found 10km north of the remnant allochthonous gypsum.

Further east on the flanks of the Dome de Barrot inlier near Daluis, there is evidence of Oxfordian breakout, renewed more extensively in the Apto-Albian with an extent of at least 10 sq km. More extensive Apto-Albian breakout is associated with the Gevaudan diapir near Barreme on which secondary minibasins developed from the Late Cretaceous to the Miocene. These include the hugely rotated minibasin containing the Poudingues d’Argens conglomerate, and, we suggest, much of the Barreme basin itself. The minimum extent of this sheet was about 80sq km, though it may have been larger.  

20km to the east, Eocene breakout is indicated by an enormously expanded growth in Nummulitic  shales - a possible Roho system, with salt expelled into the active strike slip system of the Rouaine-Daluis transcurrent fault zone. The most spectacular example of Tertiary allochthonous salt, however,  is  that into which the secondary minibasin of the famous  Esclangon Velodrome sank, providing a major depocentre for  Burdigalian to Pliocene sediments. Célini et al. (in press) have documented the evolution of the Velodrome and convincingly compared it with the Tuzlagözü minibasin of the Sivas basin in Turkey. The salt glacier into which the Velodrome sank must have flowed out onto an Oligocene land surface and may be analogous with the Salt Range of Pakistan.

How to cite: Graham, R.:                 Allochthonous salt sheets in the external SW Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4580, https://doi.org/10.5194/egusphere-egu22-4580, 2022.

09:04–09:10
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EGU22-7644
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ECS
Adam Csicsek et al.

The Upper Triassic evaporites of Western Europe, also known as the ‘Keuper’, are well-known and have been mostly considered as an efficient décollement level for the thrusts of the external fold-and-thrust belts. Numerous recent studies aimed to reappraise their role, and especially the role of salt tectonics, in the formation of several mountain belts such as the Pyrenees, the Betics, Provence, and the Alps.

The Western Alps represent a good laboratory to study the role of salt in shaping a mountain belt because it contains areas with (1) no evaporites, (2) evaporites involved as an efficient décollement level during orogeny and (3) evaporites mobilised in salt tectonics since the Lias rifting. We propose here, based on literature and our recent works regarding salt tectonics in the SW Alps, to present and discuss the different salt-related structural styles observed along-strike the Western Alps. A focus will be done on the SW Alps where evaporites influence their structure during the whole Alpine history from rifting until collision. They were mobilised by the Lias rifting through reactive diapirism. Salt tectonics carried on during the post-rift period by passive diapirism, controlled by sediment loading. A few structures were reactivated during the Oligocene and in places evaporites influenced the structure of the subalpine chains until the Mio-Pliocene.

Our study shows that evaporites strongly influence the structure of a mountain belt at different scales and that along-strike variations of structural style are observed along the strike of the Western Alps depending on the presence, the amount or the absence of evaporites.

How to cite: Csicsek, A., Célini, N., Callot, J.-P., Ringenbach, J.-C., Graham, R., Brooke-Barnett, S., and Lonergan, L.: Along-strike variations of salt-related structural style in the Western Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7644, https://doi.org/10.5194/egusphere-egu22-7644, 2022.

09:10–09:16
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EGU22-7092
Oscar Fernández et al.

Salt welds are frequent features in basins with halokinesis. They are profusely observed on reflection seismic and are common features on maps of salt-rich geological provinces (even though they may not always have been identified as such). Despite this abundance, detailed studies of salt weld outcrops are remarkably scarce, in part due to outcrop conditions being hampered by vegetation and weathering. This results in a significant paucity in the description of the structure of salt welds at the meter- to centimeter-scale.

In this contribution we present our observations on three non-primary salt welds from the Northern Calcareous Alps (NCA) in the Eastern Alps, an area that evolved from a Permian-Jurassic passive margin setting to the Cretaceous-Recent Alpine orogenesis. The NCA are dominated by Triassic to Jurassic shallow to deep water carbonates, underlain by an Upper Permian evaporitic unit (mainly salt, anhydrite and shales). The evaporite unit is preserved at present mostly in broad, poorly outcropping salt bodies (salt walls?) located between blocks of Triassic platforms, and in diapirs and allochthonous bodies that are mined or quarried for halite and anhydrite. These bodies have been affected by Alpine orogenesis to different degrees, but in general present a strong contractional and/or strike-slip overprint.

In this presentation we discuss welds that are associated to two diapirs and potentially to a strongly overprinted salt wall. Outcrop conditions for the welds are outstanding, with two of these welds being observed in the galleries of two salt mines. All welds occur in Middle to Upper Triassic platform carbonates and contain no major traces of evaporites but do contain either highly sheared syn-evaporite shales or fragments of Lower to Middle Triassic post-salt sediments. Hand samples and outcrop observations have been used to describe the millimiter- to hectometer-scale structure of the welds and provide a unique insight into the detailed architecture of salt welds. Furthermore, it reveals a different tectonic evolution for each weld, with different relative contributions of halokinesis and faulting during the passive margin stage, and of re-activation during Alpine orogenesis.

How to cite: Fernández, O., Grasemann, B., Ortner, H., Szczygiel, J., and Leitner, T.: Salt welds from up close: Examples from the Eastern Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7092, https://doi.org/10.5194/egusphere-egu22-7092, 2022.

09:16–09:22
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EGU22-11211
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ECS
Agathe Faure et al.

Recently, the understanding of the role of salt dynamics in the evolution of fold-and-thrust belts and foreland basins has significantly improved with the development of high-resolution seismics. Understanding a salt-related structure in the field as a mini-basin requires a thorough understanding of the 3-D geometries of folds.

In the western subalpine chain of Haute Provence, the Digne thrust area has undergone a complex tectonic history involving syn-sedimentary deformation, the migration of alpine front, late exhumation related to surface processes, and salt tectonics. In the front of the Digne thrust, the Vélodrome is an emblematic example of a complex fold displaying a 3D structure hardly explained by regional tectonics. The Vélodrome is an overturned syncline displaying a curved axis which direction changes from E-W in the north to N-S in the east and to E-W again in the south-eastern part. The Vélodrome is often interpreted as a growth fold with internal unconformities, but microstructural analyses (Fournier et al., 2008) have alternatively suggested a post-deposition folding. Moreover, recent studies (Graham et al., 2012; Celini, 2020) propose that the fold formed due to salt tectonics and interpret the Vélodrome as a mini-basin.

Thus, the Vélodrome complex tectonic structure requires a thorough understanding of the 3-D geometries to understand its tectonostratigraphic evolution.

This study aims at understanding the emplacement and the tectonic history of the Miocene Vélodrome series using in-situ field observations and drone field data to realize a 3-D geometrical model (GeoModeller - ©BRGM). More than 3000 structural data have been measured - both directly in the field and on 3D models obtained from drone image processing - and used in the GeoModeller to test the different hypotheses. The implicit approach offered by the GeoModeller and the field structural data-based approach bring an objective and new vision of 3-D geometries of the Vélodrome basin and confirm the Vélodrome as a syn-sedimentary fold. This study highlights several discontinuities inter- and intra-formations spatially localized. In the north of the Vélodrome, Aquitanian deposits do not present any unconformity, whereas internal unconformities can be observed in Burdigalian deposits. In the southeast of the fold, we observed internal unconformities both in the Aquitanian and Burdigalian deposits. This leads us to propose an early salt-related episode of deformation in the southeast part of the fold (Aquitanian) compared to the north, where deformation began only during the Burdigalian.

How to cite: Faure, A., Jolivet, L., Allanic, C., Gumiaux, C., Loget, N., Laurent, G., Callot, J.-P., and Guiomar, M.: Salt tectonic in the western subalpine foreland basin of Haute Provence? New insights on the Miocene Vélodrome syncline by a 3D geometrical modelling approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11211, https://doi.org/10.5194/egusphere-egu22-11211, 2022.

09:22–09:28
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EGU22-8216
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ECS
Amir Kalifi et al.

Most of the studies focusing on salt-tectonics are limited concerning high-resolution facies variations (seismic resolution/outcrop conditions) and reservoir distribution in salt diapir-flanking strata (few wells). As a consequence, many questions remain unsolved, such as the relation between the type of halokinetic sequences and the facies distribution, the interplay between sedimentary environments and the local halokinetic context. The aim of this study is to better understand spatial and temporal facies distribution and resulting sedimentary stacking pattern along the Cotiella mini-basins salt structures (Spanish Pyrenees).

Our approach is dedicated to detailed field mapping, sedimentological description of the stratigraphic succession as well as the investigation of the facies partitioning and depositional systems along within these exceptionally well exposed group of MBs. There, syn-halokinetic strata deposited during the Middle Coniacian to Early Santonian post-rift succession. Preliminary results show that:

  • The Cotiella mini-basin is characterized by a megaflap involving a 130° salt-controlled growth-strata. The Armeña mini-basin corresponds to a salt-expulsion roll-over characterized by a 80° salt-controlled growth-strata. Armeña formed mostly before Cotiella.
  • Depositional environments correspond to type-ramp mixed siliciclastic-carbonate platform. The sedimentological succession is composed by a parasequence stack characterized by proximal quartz-rich facies located mainly along the salt-weld and evolving laterally to more distal marine environments. Quartz are partly derived from the erosion of the salt-diapir, which correspond to the Keuper evaporitic facies containing authigenic quartz.
  • The stratigraphic successions of the Armena and Cotiella mini-basins is subdivided into 4 depositional sequences (S1a, S1b, S2, S3) but present specific thicknesses and facies partitioning, that suggest a strong control from the salt. These 4 sequences reveal the evolution from early to late stages of the rising salt-diapir.

Ultimately, and by integrating other mini-basins (i.e. mini-basins from the Sivas basin un Turkey), this study will help to better predict reservoir-facies and pinch-out locations along salt diapir-flanking strata.

How to cite: Kalifi, A., Ribes, C., Ringenbach, J.-C., Dujoncquoy, E., Muñoz, J. A., and Callot, J.-P.: Facies distribution along the salt diapirs of the Cotiella mini-basins (Southern Pyrenees, Spain), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8216, https://doi.org/10.5194/egusphere-egu22-8216, 2022.

09:28–09:34
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EGU22-2235
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ECS
Marine Lartigau et al.

Salt tectonics is responsible for typical structures associated with salt structures margins development: (i) minibasin subsidence, (ii) basin edge backfolding of basin margins, forming plurikilometric steep or overturned structures along the salt structures or their equivalent welds, called megahooks and megaflaps and (iii) smaller-scale halokinetic drape folding and composite halokinetic sequences (CHS). Mega-halokinetic structures like the megaflaps are of particular interest to us as they have been recently defined and their kinematics are poorly understood compared to those of CHS. They develop either during halokinetic drape folding, or during contractional squeezing of the diapirs or during some combination of both processes. It seems megaflaps form early in the salt reliefs development as opposed to more mature structures allowing the CHS development. Because of their geometry, megaflaps have also implications for reservoirs geometries and fluid pressures distribution, critical for successful exploration or potential storage. Megaflaps seem to have the same behaviour as detachment folds and could present same kinematics and deformations. Characterizing the multi-scale damage records, using fracturation network and matrix damage analyses, may allow us to reconstruct the megaflaps formation dynamics and to establish relationships between reservoir properties and structural evolution.

In the Cotiella Basin, recent studies have shown the role of salt tectonics associated with gravity in the creation of various minibasins during the post-rift system between the Cenomanian and the Santonian. The Cotiella minibasin s.s. presents a megaflap with vertical to completely overturned layers. The calcarenites composing this megaflap present numerous joints, veins and stylolites. The first observations and analyses show several stages of deformation, from Layer Parallel Shortening (LPS) to Late Stage Fold Tightening (LSFT) as observed in the folds. Moreover, preliminary results of matrix damage, using AMS, also indicate a record of LPS and even late deformation, LSFT, in the rocks. A detailed scenario of the damage acquisition chronology, from the multi-scale damage, is under contruction to understand the formation of this megaflap. We will then be able to compare the damage, the type of megaflap and the causal relationships such as geodynamic context and lithology with others such as the Sivas megaflap (Turkey).

How to cite: Lartigau, M., Callot, J.-P., Aubourg, C., and Kergaravat, C.: Megaflap formation and Damage recording: the case of the Cotiella Megaflap, South-Central Pyrenees., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2235, https://doi.org/10.5194/egusphere-egu22-2235, 2022.

09:34–09:40
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EGU22-1396
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ECS
Shan Zhao

The reserves of hydrocarbon reservoirs with gypsum-salt rock as cap rock account for 55% of the total hydrocarbon reserves in the world. The influence of cap rock sealing ability is an important problem to be solved in hydrocarbon accumulation analysis. Gypsum-salt rock belongs to evaporite, which is often associated with mudstone, limestone and dolomite, resulting in extremely complex lithologic composition of gypsum-salt rock caprock. At present, the analysis of sealing capacity of gypsum-salt rock caprock lacks the distinction between gypsum rock and salt rock, and the previous comprehensive evaluation of sealing capacity of caprock mainly focuses on the macro and micro characteristics of caprock. As one of the influencing factors of sealing capacity - mechanical properties, they are ignored in the evaluation system of sealing capacity of caprock.

Based on this, the classification standard of gypsum-salt rock caprock type is established, and the gypsum-salt rock caprock is divided into "three categories and five sub categories". Comprehensively considering the macro and micro characteristics and mechanical properties of the caprock, the lithology and rock combination type, lithology zoning, cumulative thickness of dominant lithology, caprock thickness, maximum thickness of thick single layer, ground coverage ratio, internal friction coefficient, tensile strength and peak strength are selected as the evaluation factors. The analytic hierarchy process (AHP) is introduced to determine the weight of each factor, formulate the evaluation standard, and establish the evaluation system of gypsum-salt rock caprock based on AHP to realize the quantitative evaluation of the sealing capacity of gypsum-salt rock caprock.

The evaluation method is applied to the Cambrian gypsum salt caprock in Tarim Basin, China. The results show that the C value in Bachu area of Tarim Basin is between 2.6-3.9, with an average value of 3.3, and the caprock quality is good; The C value in Tazhong area is 1.8-22, with an average value of 2.0, and the sealing capacity of caprock is generally general; The C value of Tabei uplift is less than 2, and it is in the range of poor caprock as a whole. On the whole, the evaluation value of sealing capacity of gypsum-salt rock caprock in Tabei—Tazhong—Bachu area gradually increases and the sealing capacity gradually becomes better. Combining the evaluation results with the vertical distribution of hydrocarbon, the corresponding vertical display type of hydrocarbon is mainly the distribution type under salt rock, and the corresponding hydrocarbon distribution position of poor caprock is above salt. The evaluation results are highly correlated with the vertical distribution of hydrocarbon, It shows that the evaluation system is of great significance for accurately evaluating the sealing hydrocarbon ability of gypsum-salt rock caprock and guiding hydrocarbon exploration.

Keywords: gypsum-salt caprock; lithological combination; sealing ability; quantitative evaluation; Tarim Basin

How to cite: Zhao, S.: Quantitative evaluation of the sealing ability of gypsum-salt rock caprocks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1396, https://doi.org/10.5194/egusphere-egu22-1396, 2022.

09:40–09:46
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EGU22-5173
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ECS
Niklas Ahlrichs et al.

As a part of the intracontinental Central European Basin System, the Baltic sector of the North German Basin has a long and complex history of basin evolution strongly influenced by salt tectonics. In the scope of the DFG project StrucFlow, we investigate the Triassic – Jurassic phase of basin evolution of the Baltic sector of the North German Basin to deepen the understanding of regional tectonics and their relation to the initial development of Zechstein salt structures. We use a dense network of modern marine high-resolution 2D seismic profiles together with older seismic data and both onshore and offshore wells. Thereby, we strive for a detailed regional tectono-stratigraphic interpretation of Triassic and Jurassic deposits with improved stratigraphic subdivision. We interpret local thickness variations across salt structures, imaged by the seismic data, to identify phases of salt withdrawal in rim-synclines and accumulation within the salt structure. Our analysis covers the northernmost part of both the eastern Glückstadt Graben and the Eastholstein Mecklenburg Block as well as the northeastern basin margin close to Rügen Island. Relatively quiet tectonic conditions characterized by thermal subsidence during the Early and Middle Triassic persisted in the study area. In the Late Triassic, during deposition of the Keuper, Paleozoic faults were reactivated at the northeastern basin margin, which created a local depocenter with increased thickness of Keuper and Lower Jurassic deposits. We interpret this zone with increased Triassic – Jurassic sedimentary thickness as a transtensional graben system connected to deeper Paleozoic structures. Local thickness variations of Triassic units across salt structures and crestal faulting indicate initial salt movement in the eastern Glückstadt Graben and at the Kegnaes Diapir contemporaneous with the onset of Late Triassic regional extension and faulting at the northeastern basin margin. Salt movement continued at least until the early Jurassic. During the Triassic, the Eastholstein Mecklenburg Block formed a more stable area at the transition between the Glückstadt Graben and the fault systems of the northeastern basin margin. Within the Eastholstein Mecklenburg Block, salt movement started only in the latest Triassic and was of decreased intensity. From Middle Jurassic times until the Albian, the North Sea doming event subjected the study area to uplift and erosion, which removed much of the Jurassic and partly Upper Triassic deposits resulting in a study area-wide erosional unconformity.

How to cite: Ahlrichs, N., Noack, V., Seidel, E., and Hübscher, C.: Triassic-Jurassic tectonic evolution of the Baltic sector of the North German Basin: regional extension, salt movement and large-scale uplift, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5173, https://doi.org/10.5194/egusphere-egu22-5173, 2022.

09:46–09:52
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EGU22-12073
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ECS
Gaia Travan et al.

The Algerian margin (Western Mediterranean) reactivated in compression 8 My ago due to the convergence between Africa and Eurasia, and is nowadays subjected to a strain regime of several mm/y, resulting in destructive earthquakes as the M 6.8 Boumerdès event in 2003.

The MARADJA I seismic reflection data acquired in 2003 allowed to image in detail the Messinian Salinity Crisis Mobile Unit (mostly halite) and its brittle sedimentary overburden offshore Algiers. Particularly interesting in the area are the salt-related geometries and the presence of crustal tectonic structures -consequence of the compressional setting of this margin- that created an uplifted plateau offshore Algiers (Déverchère et al., 2005; Domzig et al., 2006). The comparison with the MARADJA II (2005) data offshore Béjaia allowed to better distinguish between the regional trends and the local peculiarities.

Together with the general analysis of the structures due to the salt tectonics, as well as the influence of crustal tectonics on salt deformation on the Algerian margin, this study is particularly focused on the geometry, position and triggering processes of a localized minibasins field, which started to form very early –possibly before the end of the Messinian Salinity Crisis- and is still active nowadays. This minibasins field position corresponds to both the external limit of a sedimentary body and the western limit of the previously mentioned uplifted plateau, raising the question of the relative influence of these two contributing factors in the formation of the minibasins. The analogue modelling contribution in this analysis is crucial.

How to cite: Travan, G., Gaullier, V., Vendeville, B. C., and Déverchère, J.: Messinian salt deformation offshore Algeria: the role of crustal tectonics and sedimentary load on the observed geometries, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12073, https://doi.org/10.5194/egusphere-egu22-12073, 2022.

Mon, 23 May, 10:20–11:50

Chairpersons: Gaia Travan, Virginie Gaullier

10:20–10:26
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EGU22-11751
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ECS
Débora Duarte et al.

The southwestern margin of Iberian (SWIM) underwent a complex tectonic evolution, related to its proximity to the plate boundary between Africa and Europe, and the Betic-Rif Orogeny. The Algarve, Doñana, Sanlucar and Cadiz Basins developed on the Betics’ foreland since the late Miocene, and their sedimentary infill is composed of deep-water turbiditic, hemipelagic and contourite deposits. This work aims to understand the influence of diapiric structures on the development and evolution of deep-water sedimentation associated with these sedimentary basins. It has been accomplished with the analysis of regional 2D and 3D seismic datasets and a chronological framework from well data.

Extensive diapiric activity was recorded throughout the Late Miocene-Quaternary basins. Salt and shale structures were identified characterized by their internal transparent to chaotic reflections with moderate to low amplitude. Three types of diapirs were observed: i) squeezed, vertical diapiric stocks, ii) vertical elongated diapirs related to compressive deformation, and iii) salt-cored normal faults. Eight diapiric pulses occurred during the late Miocene-Quaternary timeframe. Deep-water sedimentation is influenced by these diapiric pulses in two ways: i) diapiric-related reliefs on the seafloor control down- and along-slope current circulation, and consequently the turbidite and contourite sediment distribution and their deposits architecture, and by ii) changeable accommodation space: depocenter size and capacity for sediment accumulation are variable over time, being directly related to the intensity of the diapiric activity. Contourite deposits also respond to changes in depocenter characteristics by altering drifts geometry and size, from sheeted to mounded to confined, with the increasing intensity of diapiric activity.

This work demonstrates the influence of diapirism in shaping the seafloor paleo-morphology, with diapiric-related reliefs and depocentres, controlling the distribution of deep-water depositional systems. Thus, this study emphasizes the importance of an integrated basin analysis, considering sediment supply, regional tectonics, including diapiric activity, as well as climatic and sea-level variations in controlling deep-water sedimentation.

 

Acknowledgements: D.D. thanks the Portuguese Foundation for Science and Technology (FCT) for a PhD scholarship (reference SFRH/BD/115962/2016). This research has been conducted under the framework of ‘The Drifters Research Group’, Department of Earth Sciences, Royal Holloway University of London (UK). We thank DGEG (Direção-Geral de Energia e Geologia) and Dr. José Miguel Martins for the supply of the 3D seismic dataset. The bathymetric data used in this work is from the European Marine Observation and Data Network (EMODnet) Bathymetry Project (http://www.emodnet.eu/bathymetry).

How to cite: Duarte, D., Hernández-Molina, F. J., Magalhães, V. H., Roque, C., and Ng, Z. L.: Late Miocene-Quaternary diapiric activity in the SW Iberian Margin: Interaction between salt and shale structures and deep-water sedimentation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11751, https://doi.org/10.5194/egusphere-egu22-11751, 2022.

10:26–10:32
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EGU22-674
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ECS
Aurio Erdi et al.

The geometry and evolution of continental margins can be influenced by gravity-driven, thin-skinned deformation above mobile shale. The response of the mobile shale and its overburden to gravitational collapse is complex due to: (i) spatial and temporal variations in the timing and magnitude of extension within prograding deltaic systems driving deformation; and (ii) the behavior of the weak, basal shale layer. This complexity, together with the difficulties in seismically imaging mobile shales and their strongly deformed overburden, mean we have a relatively poor understanding of the distribution and evolution of syn-sedimentary extension in large, supra-shale deltaic systems.

In this study we use a 3D pre-stack time migration (PSTM) seismic dataset located on the shelf-edge to upper slope of the Offshore Tarakan, North East Borneo. We combine our seismic-stratigraphic analysis and a detailed seismic interpretation with published well data, producing six age-constrained structural and thickness maps that document the Neogene tectonic evolutions of this shale-rich delta system. Our study reveals that the Tarakan delta system, including its underlying basal mobile shales, is deformed by a range of NE-trending shale structures, and NE-SW-striking, basinward- (i.e., eastwards) and counter-regional (i.e., westwards) dipping shale-detached (i.e., basement-decoupled) extensional faults. The extensional faults typically have a listric geometry, merging towards the top of an interval inferred to be within the mobile shales. Lateral throw distributions of each extensional listric faults appear to decrease southwestward. Hangingwall rollover-related deformation is accommodated by planar crestal faults. In relatively distal locations we document broad, shale-cored anticlines. We also observe mud volcanos and diapirs that are located above and along the shale-detached normal faults and shale-cored anticlines, respectively. Isochrone maps document complex thickness patterns through time, reflecting the complex interplay between mobile shale flow, supra-shale extension, and sea-level variations. Taken together, we identify three main tectonic stages: (i) Middle Miocene - fault nucleation, growth, and local linkage in the proximal domain, and formation of a shale-cored anticline more distally; (ii) Upper Miocene-Pliocene – lateral propagation and eventual retreat of the extensional faults, and mud diapirism; and (iii) Pleistocene-Holocene – extensional faults reactivation, decay and death, accompanied by mud volcanism.

We suggest that the extensional faults in the Tarakan delta system formed in response to Neogene tilting and gliding of supra-shale sequence in response to the uplift of Borneo. Updip extension was accommodated by and kinematically linked to, downdip contraction, and the formation of shale-cored anticlines. We speculate that mud volcanoes and shale diapirs formed above these extensional and contractional structures in response to mobile shale ascending fault- and fold-related fracture. Our careful analysis of the supra-shale faults and underlying shale structures can provide insights into the three-dimensional kinematic evolution of other mobile-shale provinces in deltaic systems, such as those characterizing North West Borneo, the Niger Delta, and the Ceduna shelf margin in Southern Australia.

How to cite: Erdi, A., Jackson, C. A. L., and Soto, J. I.: Neogene Shale Tectonics in Offshore Tarakan Basin, North East Borneo (Kalimantan): Insights from 3D Seismic Interpretation , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-674, https://doi.org/10.5194/egusphere-egu22-674, 2022.

10:32–10:38
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EGU22-9559
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ECS
Sian Evans et al.

Welds form due to the tectonically-induced thinning and/or dissolution of salt, with their composition and completeness thought to at least partly reflect their structural position within the salt-tectonic system. Despite their importance as seals or migration pathways for accumulations of hydrocarbons and CO2, we have relatively few examples of drilled subsurface welds; such examples would allow us to improve our understanding of the processes and products of welding, and to test analytical models of the underlying mechanics. In this study we integrate 3D seismic reflection and borehole data from the Green Canyon Area of the northern Gulf of Mexico, USA to characterize the geophysical and geological expression of a tertiary weld, as well as its broader salt-tectonic context. These data show although it appears complete on seismic reflection data, the weld contains c. 38 m of pure halite. This thickness is consistent with the predictions of analytical models, and with observations from other natural examples of subsurface welds. Our observations also support a model whereby compositional fractionation of salt occurs as the salt-tectonic system evolves; in this model, less mobile and/or denser units are typically stranded within the deeper, autochthonous level, trapped in primary welds, or stranded near the basal root of diapirs, whereas less viscous and/or less dense units form the cores of these diapirs and, potentially, genetically related allochthonous sheets and canopies. We also show that shearing of the weld during downslope translation of the overlying minibasin did not lead to complete welding.

How to cite: Evans, S., Alshammasi, T., and Jackson, C.: Salt welding during canopy advance and shortening in the Green Canyon area, northern Gulf of Mexico, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9559, https://doi.org/10.5194/egusphere-egu22-9559, 2022.

10:38–10:44
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EGU22-12981
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ECS
Alexander Peace et al.

Polyphase deformation on passive margins, including fault reactivation, has been documented globally. These processes form complex structures that can be integral to petroleum systems and can provide essential constraints on the kinematic and structural evolution of rifts and passive margins. In some cases, inversion structures can also be used as global markers for far-field stress changes and help us to understand how plate tectonics operates on Earth. Despite the importance of reactivated faults, their identification, extent mapping, controls on kinematic evolution, and knowledge of interaction within fault populations are often poorly constrained. As such, there is need for detailed investigations of such structures, including their relationship with halokinesis, which can lead to complex and sometimes misleading structural observations.

We present a new structural interpretation of the Penobscot 3D seismic reflection survey, and associated relay ramp, imaged offshore Nova Scotia, Canada, down to ~3.5 s TWT, constrained by two exploration wells. The relay ramp comprises two dominant faults that dip approximately SSE and are associated with smaller antithetic and synthetic faults. The wider fault population is dominated by ~ENE-WSW striking normal faults that dip both NNW and SSE. The two major normal faults display evidence for reverse deformation in their lower portions (below ~2.5 s TWT), which manifests as anticlinal folding and reverse offsets. However, in their upper portions the faults display normal offset. Smaller faults tend to only affect the uppermost strata and do not show evidence of reactivation. Analysis of fault throw demonstrates that movement on the two main faults was coupled during both the reverse and normal deformation intervals. Through our structural analysis and previous regional interpretations of widespread salt kinesis, we determine that the observed style of deformation likely occurred due to normal (extensional) reactivation of reverse faults that had initially formed due to halokinesis of underlying salt. The timing of salt movement broadly corresponds to documented times of kinematic reorganisation on many Atlantic margins, and thus salt kinesis may have been in response to this. The kinematic dichotomy with depth along the two dominant faults is important to document as this style of polyphase reactivation may go unrecognised where seismic data does not image the full depth of a structure. Therefore, reactivation may be more widespread than previously thought if only uppermost parts of structures have been imaged. The interpretation of salt as an important contributor to kinematic reactivation of faults is crucial as it likely provides a mechanism to explain inversion at many other locations globally.

How to cite: Peace, A., Schiffer, C., Jess, S., and Phethean, J.: Fault reactivation and halokinesis: an example from the Penobscot 3D seismic volume, offshore Nova Scotia, Canada, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12981, https://doi.org/10.5194/egusphere-egu22-12981, 2022.

10:44–10:50
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EGU22-1093
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ECS
Leonardo Pichel et al.

Many rifted passive margins are associated with widespread and thick evaporite (i.e., salt) deposits, and pronounced syn-and post-rift salt tectonics. The majority and largest salt basins known-to-date formed during the latest stages of rifting, immediately prior to continental breakup. We use 2D thermo-mechanically coupled finite-element modelling of lithospheric extension to investigate the interplay between variable styles of rifted margin, syn-rift architecture, and consequences for the distribution of late syn-rift salt, and post-rift salt tectonics. We simulate the formation of salt basins in different types of continental margins: narrow, intermediate, wide, and ultra-wide margins. For each of these, we evaluate: 1) the interplay between rifting, post-rift sediment progradation, base-salt topography and margin scale salt tectonics, 2) the spatial and temporal distribution of salt-related structural domains, and 3) the contrasting styles of salt tectonics for different margin types. We show that narrow and intermediate margins form partially isolated salt basins in their proximal domain with limited translation and significant vertical diapirism. Their distal portions are associated with significant translation, development of updip listric normal faults and rollovers passing downdip to squeezed diapirs. Wide and ultra-wide margins form wide salt basins with a more subtle base-salt topography which result in significant basinward salt expulsion and overburden translation towards their distal domains. These margins are characterized by updip extensional and/or expulsion rollovers and downdip salt inflation, diapirism and shortening in the form of diapir squeezing, buckle-folding and development of allochthonous salt sheets. All margins present a distal salt nappe that varies in width for each margin type and forms as a consequence of syn-rift distal salt stretching and post-rift thrusting. These models are the first to integrate lithospheric extension with long-lived post-rift salt tectonics using a geodynamically self-consistent modelling approach where the geometries of the lithosphere and salt basins are not prescribed, allowing a natural evolution of syn and post-rift deformation. They also incorporate a more realistic style of post-rift progradation using a dynamically evolving profile and present unprecedented detail for salt, syn- and post-rift stratigraphy. The results can be directly compared to examples from various salt-bearing continental margins and provide an improved understanding on the kinematics and relative timing of rift and salt deformation, and on the controls and variability of salt tectonics for different margin types.

How to cite: Pichel, L., Huismans, R., Gawthorpe, R., Faleide, J. I., and Theunissen, T.: Coupling crustal-scale rift architecture with passive margin salt tectonics: a geodynamic modelling approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1093, https://doi.org/10.5194/egusphere-egu22-1093, 2022.

10:50–10:56
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EGU22-1117
Jörg Lang and Andrea Hampel

Subsurface salt movement is primarily driven by differential loading, which is typically caused by tectonics or sedimentation. During glacial periods, the weight of an ice sheet may represent another source of differential loading. In salt-bearing basins affected by Pleistocene glaciations, however, it often remains unresolved if young deformations at salt structures were triggered by ice loading or represent a continuation of late Cenozoic activity. Numerical modelling can help distinguishing ice-load-induced deformation from halotectonic movement unrelated to salt-ice interaction. A prerequisite for obtaining conclusive model results is the appropriate choice of the rheological behaviours and parameters of the modelled materials.

Finite-element simulations (ABAQUS) were conducted to test and improve existing models of the interaction between salt structures and ice sheets. The models comprise two-dimensional plane-strain sections based on a simplified geological cross-section of a viscoelastic salt structure with elastic overburden and basement rocks. Different parameter sets for the rheology of salt and overburden rocks, including linear versus non-linear viscosity of the salt, were tested to gain insight into the main controlling factors.

All tested configurations show ice load-driven salt flow and deformation of the salt structure and the overburden rocks. The advance of an ice sheet towards the salt structure causes lateral salt flow away from the load into the salt structure and thus uplift at the surface above the salt structure. Complete ice coverage leads to downward displacement of the salt structure and subsidence at the surface. The downward displacement is accompanied by lateral expansion of the salt structure, which is controlled by the elasticity of the overburden rocks. After unloading, the displacements are largely restored by the elasticity of the materials. In all models, the observed deformation was limited to a few metres and no permanent reactivation of salt structures occurred. The deformation is generally larger in models with linear viscous salt than in those applying non-linear viscosity. Considering the low stress caused by a several hundreds of metres thick ice sheet and the time scales of several thousands of years, the application of a linear viscosity appears to be appropriate. The elastic parameters strongly impact the results, with lower Young's moduli leading to larger deformation. Our model results highlight the importance of a careful parameter choice, regarding both the viscous and elastic behaviour of the modelled materials.

How to cite: Lang, J. and Hampel, A.: Ice-load induced salt movement – insights into the controlling parameters from numerical modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1117, https://doi.org/10.5194/egusphere-egu22-1117, 2022.

10:56–11:02
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EGU22-6980
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ECS
Michael Warsitzka et al.

Growing salt diapirs emerging at the sedimentary surface can produce outflowing salt extrusions, as observed, for instance, in many locations in the Zagros fold-and-thrust belt (Southern Iran). Flow patterns of such salt extrusions are controlled by gravity spreading and gliding. Furthermore, internal structures and shapes of salt extrusions are affected by factors like the local topography, the width of the diapir and the tectonic stress field. Many field examples of outcropping diapirs reveal, however, that the highly soluble evaporites (mainly halite) are already dissolved at the surface and that extrusions are covered by a ‘caprock’ layer, which is built of a multi-compositional residuum of less soluble minerals and rocks. Thickness, composition and mechanical properties of the caprock (density, shear strength, etc.) strongly vary between individual diapirs depending on the original composition of the salt layer, overlying host rock sediments, erosion rate, etc. Hence, the influence of such a caprock on the dynamics of the salt extrusion might also be highly variable and has not yet been investigated. It is unclear, if the caprock deforms by ductile shearing similar as viscous rock salt or if it acts as competent, brittle cover layer deforming by fracturing and brecciation during flow of the underlying salt.

We present a series of 3D analogue experiments and 2D numerical models in which we systematically investigated deformation patterns of the caprock layer during diapiric extrusion of a viscous material. In the analog experiments, we tested different types of granular materials as caprock equivalent to simulate different rheologies. Specifically, a fine-grained powder was used to mimic a competent, high-cohesive rock and a coarse-grained, low-density granulate for a less competent rock. In the numerical models, we tested a wide range of caprock parameters, such as thickness, viscosity, and shear strength. Our study is specifically focused on salt extrusions of the Iranian Zagros fold and thrust belt. Thus, the extrusion patterns in both, analog and numerical models, were tested on 1. passively growing diapirs and 2. diapirs reactivated by lateral shortening.

The results of this modelling study provide insights into the conditions (e.g. minimum thickness or strength) under which a caprock layer has a significant influence on the style of the salt extrusion or only acts as a passive veneer floating on top of the flowing salt. The model results show that a competent or thick caprock forms a polygonal fracture pattern at the beginning of the extrusion, while the separated blocks slide downslope during later stages of the extrusion. An incompetent or thin caprock rather deforms by flow, shear thinning and folding coupled to the flow of the underlying salt. These characteristics can help us to interpret deformation structures observed on natural salt extrusions, in terms of thickness and deformation behavior of the caprock.

How to cite: Warsitzka, M., Słotwinski, M., Krýza, O., and Závada, P.: The deformation of caprock on extruding salt diapirs – insights from analog and numerical modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6980, https://doi.org/10.5194/egusphere-egu22-6980, 2022.

11:02–11:08
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EGU22-6470
Mjahid Zebari et al.

In emergent salt diapirs, the volume of the salt at the surface represents an equilibrium state between the salt supplied from the underlying orifice and that lost by dissolution and erosion at the surface. Therefore, the salt volume at the surface represents the surplus of the salt supply over the dissolution and erosion neglecting any volume changes from the decompaction. Both dissolution and erosion processes occur at or near surface and can be estimated, while estimating salt supply remains challenging because it occurs at depth. At the surface, the salt moves away from the central dome above the diapir’s orifice toward the flanks by gravity spreading in the direction of the slope.

In this work, the salt volume change at the surface was estimated using Persistent Scatterer Interferometry (PSI) data to estimate the salt supply into the surface. While the salt tends to move in the direction of slopes, maximum deformation signal can be detected from the PSI data where the slope direction aligns with the line-of-sight (LOS) of satellite in the east- and west-facing slopes of salt diapirs. The salt deformation was estimated from both the east-west and up-down components of the decomposed PSI data along an east-west trending swath profile across the symmetrical Finu salt diapir to obtain salt gain (surplus) along this profile. During the PSI processing, areas with surface erosion and dissolution (sinkholes) were mostly filtered out, and the relevant salt loss was already accounted when analyzing the salt deformation.  However, the down (subsidence) signal of the analyzed PSI data in nearly horizontal areas in the flanks of the Finu diapir, where salt movement is expected to be horizontal, is assumed to be associated with the subsurface salt dissolution. The used PSI data cover a period of four years from October 2014 to December 2018.

Our results show that salt area surplus is c. 14 m2 a-1 along the profile crossing the Finu diapir. With the profile length of 4.6 km, the surplus rates along it are c. 3.1 mm a-1. The average subsidence rate on the diapirs flat flanks, which is supposed to be associated with the subsurface dissolution, was estimated at c. 1.0 mm a-1. Thus, the total supply rate along the profile is c. 4.1 mm a-1. Along the profile length, these rates mean that a total section area of c. 19 m2 a-1 of salt is added to the profile. Considering the semi-circular and symmetrical shape of the diapir and assuming uniform salt supply rates, the total volume of the salt delivered to the surface is in the order of c. 70,000 m3 a-1 from the underlying orifice. The orifice is approximately circular with a diameter of c. 1.7 km and an aperture covering c. 2.3 km2 area. This means the salt is extruded at a rate of c. 30 mm a-1 averaged over the period of four years.

How to cite: Zebari, M., Friedrich, A., Plattner, C., Rieger, S., and Parizzi, A.: Quantifying salt extrusion rates in active emergent salt diapirs from Persistent Scatterer Interferometry data and salt budget estimates: Finu Diapir in Zagros (Iran) as a case study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6470, https://doi.org/10.5194/egusphere-egu22-6470, 2022.