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TS10.1

EDI
Rates and dates of tectonic plate processes from geomorphic and sedimentary records

The rates and dates of processes occurring at tectonic-plate scale can be quantified using evidence derived from actively deforming settings, including geomorphic markers (e.g., topography and rivers, fluvial deposits, marine terraces) and sedimentary archives (e.g., syntectonic sedimentation, stratigraphic evidence).
When used as key natural laboratories at adequate time spans, such evidence provides essential clues to understand large-scale tectonics. These focused studies may contribute to unravel the motion, deformation, and evolution of tectonic plates, as well as changes in their potential geodynamics and boundary conditions.
We invite contributions focusing on understanding the dynamics and evolution of deforming plate interiors and active plate boundaries through interdisciplinary, geomorphic, or sedimentary data-based approaches. We welcome all types of studies that aim to quantify the rates of active plate deformation and the dates of tectonic events, regardless of their spatio-temporal scale or methodology.

Co-organized by GM9/SSP2
Convener: Silvia CrosettoECSECS | Co-conveners: Gino de GelderECSECS, David Fernández-BlancoECSECS, Jorien L.N. van der WalECSECS
Presentations
| Fri, 27 May, 10:20–11:50 (CEST)
 
Room K2

Fri, 27 May, 10:20–11:50

10:20–10:26
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EGU22-11284
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ECS
Luca C. Malatesta and Kimberly L. Huppert

Crustal deformation along active coastline can be constrained with age and elevation of marine terraces. These are essentially the product of an erosive process (waves eroding bedrock) and a preservation process (rock uplift moving terraces up and away from subsequent wave erosion). The morphology that results from this combination depends nonlinearly on the characteristics of the two processes. In particular, variations in rock uplift rate can promote or hinder the creation of marine terraces at specific age and elevations (e.g., past sea level high stands).  While widespread and well-outlined in some coastal settings, marine terraces can be rare or absent from other areas despite the coexistence of the two driving processes. If they do not produce discrete terraces, wave erosion and rock uplift still contribute to shaping the coastal landscape in conjunction with subaerial processes, and their history is somehow encoded in the topography. Using the logic of a “sea level occupation map” that we introduced to describe the cumulative effect of wave erosion during the eustatic seesaw (Malatesta et al., 2022), we inspect the hypsometry of numerical and real landscapes whether or not they hold terraces. Hypsometry allows for a continuous representation, and inspection, of parameters in numerical models. In real landscapes, a hyspsometric survey does not require very high resolution digital elevation models, and produces tractable information from the entire topography. In this contribution we 1) explain our approach to create a metric that can be equally applied to numerical and real landscapes; 2) highlight threshold effects in numerical outputs that were difficult to identify previously; and 3) present preliminary results extracting valuable information about rock uplift rate and sea level occupation from coastal landscapes with limited or no marine terraces.

How to cite: Malatesta, L. C. and Huppert, K. L.: The topographic signature of relative sea level in numerical and real landscapes., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11284, https://doi.org/10.5194/egusphere-egu22-11284, 2022.

10:26–10:32
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EGU22-5139
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On-site presentation
Cretaceous Rapid uplift of the Transantarctic Mountains-not due to rift-flank-uplift
(withdrawn)
Audrey Huerta et al.
10:32–10:38
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EGU22-529
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ECS
Ian Pierce et al.

The Tien Shan are an intracontinental mountain belt experiencing shortening as a result of far field deformation from the ongoing India-Eurasian collision. At the longitude of Kyrgyzstan the Tien Shan accommodate ~20 mm/yr of shortening. In central Kyrgyzstan, the most well studied faults include the northwest-striking right-lateral Talas Fergana fault and the series of east-striking reverse & thrust faults that form the basins and subranges that accommodate most of this compression. Yet in satellite imagery, some of the most prominent fault ruptures appear on a series of east-northeast-striking left-lateral strike slip faults. Little is known about the paleoseismology, rate of slip, or tectonic role of these faults. Here we present new drone-based high resolution topography and imagery along with geomorphic, geochronology, paleoseismic, and slip rate data for four of these sinistral faults. The studied faults are in the Aksay, Kazarman, Issyk Kul, and Song Kol basins. These data reveal that each fault has produced Holocene surface ruptures with single event displacements as great as 5-7 m along faults as long as ~100 km, corresponding to M~7.5 earthquakes. We propose a structural model to explain how these faults may have evolved from reverse faults that have rotated about their horizontal axis and then reactivated as strike slip faults due to their optimal alignment in the current stress field. How the existence of these faults affects seismic hazards is a question of discussion, as they are currently not considered in the regional strain budget that is largely based on compression.

How to cite: Pierce, I., Abdrakhmatov, K., Baikulov, S., Rakhmedinov, E., Tilek Kyzy, G., Johnson, B., Seitz, G., Arrowsmith, R., Rizza, M., and Walker, R.: Sinistral Strike Slip Faults of the Kyrgyz Tien Shan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-529, https://doi.org/10.5194/egusphere-egu22-529, 2022.

10:38–10:44
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EGU22-3222
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ECS
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On-site presentation
Malte Froemchen et al.

Many rifts are influenced by pre-existing structures and heterogeneities during their evolution, a process known as structural inheritance. During a rift’s evolution, these heterogeneities may aid the nucleation of the rift, growth and segmentation of faults, aid linkage of various segments or even inhibit the formation of faults in various places. Structural inheritance is well explored in offshore rift settings due to the availability of high-quality 3D seismic, which enables good constraint on the structural evolution. However, the degree of structural inheritance in onshore active rifts is more difficult to constrain due to a lack of subsurface datasets. Yet, understanding how structural inheritance influences early rift evolution is vital to better understand seismic risk in areas of active rifting. The Shanxi Graben in the North of China is a densely populated active rift system that is believed to have formed along the trend of the Precambrian Trans North China Orogen. However, the influence of these Precambrian structures on the present-day rifting is poorly constrained. Here we show how the impact of structural inheritance on a young active rift may be investigated using tectonic geomorphological techniques - e.g., hypsometric integral, channel steepness (KsN) and drainage network analysis (chi analysis). Using the geomorphic expression of active faults, we can quantify their geomorphic response and identify faults that show higher levels of activity. Our results show that large basin bounding faults broadly follow the trends of basement fabrics but show a lower geomorphic response, while smaller faults that link the main basins show higher levels of geomorphic response but seemingly crosscut the basement fabrics. We interpret that those large faults formed first in regions with basement fabrics that were preferably orientated to the principal stress direction. Faults in the linkage zones between major basins likely formed later due to local perturbations of the stress field by the major rift faults. This means that there is no need for a changing stress field during the evolution of the Shanxi Graben, as previously proposed, but that the graben evolved under a relatively uniform stress field. Using the hypsometric integral or drainage network analysis may prove useful when applied to other areas with active rifts influenced by structural inheritance such as East Africa. Due to the lack of data in these regions, geomorphic analysis might prove useful in the study of the temporal evolution of structural inheritance in young active rifts.

How to cite: Froemchen, M., McCaffrey, K., Allen, M., van Hunen, J., and Phillips, T.: Unraveling the role of ancient orogens in present-day rifting using tectonic geomorphology in Shanxi, North China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3222, https://doi.org/10.5194/egusphere-egu22-3222, 2022.

10:44–10:50
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EGU22-4432
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On-site presentation
Chandreyee Chakrabarti Goswami et al.

The tectonic landscape of the Himalayas is mainly depicted by the E-W trending major regional thrusts, the southernmost being the Himalayan frontal Thrust (HFT) or the Main Frontal Thrust (MFT. But there are also out of sequence transverse faults and back thrusts that play important role in strain adjustment.

The map traces of thrust faults make cuspate-lobate patterns suggesting differential fault growth. These orogen-scale curvatures at an intermediate scale are expressed as salients and recesses. Salients are normally associated with mountain fronts defined by frontal imbricate faults, whereas recesses are open to the foreland. Himalayan salients, recesses, and associated cross-structures help in determining the deformation kinematics along the length of the Himalayan arc over space and time.

In the Eastern Himalaya, east of the Tista River, the sequential and out-of-sequence structures are well observed in the Jaldhaka recess. Here the splay on the HFT is marked by southerly sloping Chalsa and Matiali scarps whereas the northerly sloping Thaljhora scarp represents the Frontal Back Thrust (FBT).

In this study, we are presenting the geometry and structural detail of the back thrust below the Thaljhora scarp. The attitude of the thrust plane, folding of the bedding, and displacement is evident from an excavated trench perpendicular to the strike of the fault scarp. The folded beds join against the thrust plane to form a piggyback structure. The thrust plane dips 20→ S. The maximum displacement of the bed is recorded at 4.5cm along the thrust plane. There are liquefaction structures, convolute laminations and flame structures within the deformed sediments. The attitude of the gentler limb of the fold is about 400→S and that of the steeper climb is around 55-60 degrees towards North.

From earlier works (Guha et al. 2010, Singh et al, 2016, Goswami et al., 2019) the age of deposition of different sediments of this area varies from 70ka to 22ka. The oldest sediment here from the north bank of Thaljhora River, below the deformed boulder bed, is around 70 ka., eastward from the same bank from an upper stratum, comprising of black sandy clay dated around 27ka, a black clay around 6m high from the river bed, on the Thaljhora scarp itself dated as around 37 ka whereas from somewhere within that scarp dated as around 22ka. From the present study, the sediments which are deformed and displaced gives the depositional dates varying from 14 to 17ka. So, it can be said that the faulting or thrusting which has formed the scarp is at least as young as 14ka.

The movement on the splay of HFT in the adjacent Matiali fan started earlier than 70 ka and the major upliftment forming the T2 terrace was around 20ka.

The movement along the Thaljhora fault started somewhere between 20-30ka. This movement may have started to adjust the stress along the northerly dipping fault. These two northerly and southerly dipping thrust systems may be interpreted as a conjugate thrust which maybe adjust the stress in this particular area.

How to cite: Chakrabarti Goswami, C., Jaiswal, M., Dasgupra, S., and Singh, A.: Paleoseismological findings along the identified back thrust in the Eastern Himalayan foothills near the India-Bhutan border, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4432, https://doi.org/10.5194/egusphere-egu22-4432, 2022.

10:50–10:56
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EGU22-6740
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ECS
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Virtual presentation
Pin-Ju Su et al.

The Ilan Basin, located at the southwestern end of the Okinawa Trough, was mostly believed to be formed due to the expansion of the Okinawa Trough. However, recent marine surveys show that they may not be directly related. On the other hand, existing terrestrial surveys concentrated on the Oligocene to Miocene formations instead of the tectonic activities during the Last Glacial period to Holocene, and contradictions remain in the interpretation of the paleo-environment. This study analyzed 40 cores of Ilan Plain, reconstructed the paleo-sedimentary environment, and interpreted the seismic profiles. We found that the transgression of the Ilan Plain in the Last Glacial period was controlled by tectonic activities. The subsequent main transgression that happened in 17.5 ka and 15~14ka was driven by the rapid sea-level rise after the Last Glacial Maximum and the Melting-water Pulse 1A event. The tectonic subsidence of the Ilan Basin was centered on the deepest part of the basement. The combination of subsidence rate and sediment supply was generally stable before 4,000 years ago, but the subsidence rate has increased significantly since then, and the sediments supply has also been increased. The sediments not only filled the deepest area in the north of Lanyang River but also left the seismic facies of forwarding propagation on the Ilan shelf. In addition, there may be another sinking center in the south before 10 thousand years ago. This study continues to establish the complete sedimentary model of the Ilan Basin and to discuss the timing and causes of the main changes in the sedimentary environment. This study will improve our understanding of the tectonic subsidence model of the Ilan Basin and the sedimentary system in the basins with significant tectonic subsidence.

How to cite: Su, P.-J., Chen, K.-Y., and Lin, Y.-J.: Late Quaternary Stratigraphic Features in the Ilan Basin, an Active Tectonic Subsidence Basin in Taiwan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6740, https://doi.org/10.5194/egusphere-egu22-6740, 2022.

10:56–11:02
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EGU22-11435
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ECS
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On-site presentation
Roland Freisleben et al.

Abstract. The tectonically active western coast of South America is characterized by the accumulation of deformation that contributes to permanent uplift of the Andean forearc at glacial-cycle timescales. However, the individual mechanisms responsible for long-term coastal uplift are still debated, mostly because analyses at continental-scale have not been carried out as yet. In coastal realms, permanent deformation is often estimated from marine terraces, which depict the interplay between wave erosion, tectonic uplift, and sea-level changes. Based on ~2000 elevation measurements of last interglacial marine terraces, we performed wavelength analyses using fast Fourier transforms. We compared the resulting uplift-rate signal with various tectonic processes and subduction parameters associated with the accumulation of permanent deformation. We detected a constant background signal of uplift along the South American margin (median rate: 0.22 mm/yr), which is disturbed by short-, intermediate- and long-wavelength changes between ~20 and ~800 km wavelengths, with the most prominent wavelengths at scales of ~500 km. Similarities between the wavelength spectra of uplift rate and signals from tectonic parameters suggest potential correlations, although multiple individual mechanisms usually contribute to a larger wavelength peak or to a certain range of wavelengths. For instance, crustal faulting is responsible for short-wavelength deformation (<100 km) and strong megathrust earthquakes (MW>7.5) mostly cover wavelength ranges from ~100 to 200 km, despite reaching wavelengths over 600 km as well. The subduction of bathymetric anomalies and the extent of interseismic locking correlate with intermediate wavelengths (~200 to ~500 km), whereas residual gravity anomalies, basal friction, and background seismicity correlate with long-wavelength deformation (>500 km). We suggest that the constant background signal of uplift rate results from two possible mechanisms: (a) a combination of multiple processes acting at different wavelengths, times and locations over millennial timescales or (b) a single unidentified process acting homogeneously along the western South American margin. With this study, we highlight the application of novel signal analysis approaches to elucidate the mechanisms driving surface deformation in subduction zones on different spatial and temporal scales.

How to cite: Freisleben, R., Jara-Muñoz, J., Melnick, D., Strecker, M., and van der Beek, P.: Tectonic processes responsible for various wavelengths of permanent deformation on the western coast of South America, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11435, https://doi.org/10.5194/egusphere-egu22-11435, 2022.

11:02–11:08
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EGU22-3299
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ECS
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Virtual presentation
Paulina Vergara and Carlos Marquardt

Abstract: Most of the coastal areas along the South Pacific are mainly uplifting due to subduction processes. The geomorphology of the Mejillones Peninsula, located in one of the seismic gaps of northern Chile at 23°S, is characterized by Quaternary alluvial fans, marine terraces, coastal cliffs, and fault scarps, among others. These features are very well preserved due to hyper-aridity conditions recognized in the area from the Plio-Pleistocene and represent the evidence of the uplift during that time. Quaternary marine terraces (QMT) have been studied to understand the permanent deformation of the forearc, in particular the differences in the uplift rates along the coast. A morpho-metric analysis using ALOS-PALSAR remote sensors and local differential GPS data, besides the use of software, as well as fieldwork, allows us to define the best-preserved QMT sequences and the height at which they are found with respect to the current mean sea level. From this, we correlate the platforms of each marine terrace with the corresponding Marine Isotope Stage (MIS) during the Quaternary, and we estimate associated uplift rates in order to study the role of the Quaternary faults in the differential uplift along the coastal area. From our morpho-metric analysis we determined 3 representative areas with well-preserved marine terraces: Punta Angamos (~12x10 km²), Hornitos (8x4 km²) and Punta Chacaya (4x4 km²). Hornitos and Punta Chacaya are both located in the continent, while Punta Angamos is located in the north part of the peninsula. The results show significant differences both in the morpho-structural features and in the estimates of the uplift rates. We have identified at least 13 QMT in Punta Angamos that can be separated into 2 groups: the last 9 platforms would be associated to the last 570 ka, with uplift rates between 0.42 to 0.55 m/ka; and the highest 4 platforms, that would be associated with Early Pleistocene and Pliocene, where it is not possible to obtain reliable uplift rates for the moment. In Hornitos, we have identified 3 QMT, with uplift rates between 0.24 to 0.31 m/ka for the last 225 ka, and in Punta Chacaya, we identified 4 QMT, with uplift rates between 0.14 and 0.29 m/ka for the last 321 ka. We also identified a platform that could be correlated to the last interglacial (MIS 1) in Hornitos and Punta Angamos, with an estimated uplift rate of 0.92 m/ka and 1.7 m/ka respectively. These preliminary results suggest that, for the last ~20 ka, there has been an acceleration in the uplift rates. That change can be interpreted as the result of the distance to the trench – the closer to the trench, the subduction process affects the most –, which could indicate a change in the subduction regime, as well as the Quaternary activity of the Morro and Mejillones faults, among other faults, that allows differential uplift.

Keywords: Morro fault, Mejillones fault, MATLAB, TerraceM, differential GPS.

How to cite: Vergara, P. and Marquardt, C.: Uplift rates accelerations along 23°S Chilean coast in the Quaternary: preliminary results from the case of Mejillones Peninsula, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3299, https://doi.org/10.5194/egusphere-egu22-3299, 2022.

11:08–11:14
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EGU22-12690
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ECS
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On-site presentation
Pedro Guzmán-Marín et al.

The Salar de Atacama (SdA) endorheic basin is a low topographic anomaly located in the Central Andes forearc, and it has been suggested as an independent block that subsides with respect to their neighbouring morpho-structures: Cordillera de Domeyko at the west, and the Altiplano and Puna volcanic plateaus to the east. Within the SdA depression, we focus on the Cordillera de la Sal (CdS), a ridge that emerges at its western margin and extends to the northeast for more than 100 km towards the volcanic arc, where the SdA basin closes. The core of the CdS ridge is formed by a fold-and-thrust belt affecting the Oligocene-Miocene continental sedimentary sequences of the San Pedro Formation. Unconformably overlaying this sequence, Upper Miocene-Pliocene tuffs and clastics with varying intensities of deformation are recognised along the northern segment of CdS, where it ends covered by the volcanic arc.

The deformation of CdS and the western border of the SdA have been suggested as a consequence of the inversion of a normal fault that delimits the basin or as an eastward propagation of the thrusting of Cordillera de Domeyko. Moreover, the presence of salt intervals and domes within the San Pedro Formation made some authors propose the existence of halokinesis. In the present work, we aim to investigate the actual tectonic regime of the CdS fold-and-thrust belt. Our objective is to determine spatial and temporal strain variability of CdS to contribute to the understanding of how this mountain belt evolved and how deformation is partitioned at its northern prolongation under the volcanic edifices.

Detailed geological mapping and the construction of seriated cross-sections will allow us to determine variable spatial patterns of deformation affecting the tuff-rich succession, spanning from 9 to 1 Ma. In addition, we will obtain temporal patterns of deformation at the scale of 103 to 105 yr using tectonic geomorphology indicators, such as deformed strath terraces and Holocene salt cave conduits.

Our preliminary results suggest that a compressional tectonic regime is progressively deforming the Upper Miocene-Pleistocene succession of CdS. Moreover, the evolution of drainages from the south-facing slope of the volcanic arc towards the SdA competed with the folds and thrusts, and the major channels developed along thrusts and synclines. This competition is going on also in the Middle to Late Pleistocene as documented by deformed fluvial strath terraces, which we are currently dating with Infra-Red Stimulated Luminescence. The age assessment of deformed terraces and cave conduits will allow us to model the slip rates of the thrust structures at different time scales.

How to cite: Guzmán-Marín, P., Picotti, V., Schmidt, C., and King, G.: Variability of active deformation of the Cordillera de la Sal fold-and-thrust belt, Salar de Atacama, Central Andes, Chile. Preliminary data on deformed fluvial features., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12690, https://doi.org/10.5194/egusphere-egu22-12690, 2022.

11:14–11:20
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EGU22-13302
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ECS
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Virtual presentation
Valentina Cortassa et al.

The distal Andean foreland basin (Chaco-Pampean Plain) is thought to have been tectonically inactive during the Cenozoic. However, re-interpreted industry seismic reflection data, borehole information and gravity surveys document a rich and complex history of tectonic activity. Our new data synopsis and re-analysis reveals two, regionally extensive and approximately N-S oriented, basement highs beneath the flat present-day surface. The Quirquincho (or Rincón Caburé) and Pampeano-Chaqueño highs have been observed by previous authors, but the mechanism that elevated these features and the timing has remained elusive. Here, we discuss several viable mechanisms of their formation. The morphology, wavelength and stratal terminations suggest that the Quirquincho high could represent a forebulge due to Paleogene orogenic processes. In contrast, the Pampeano Chaqueño high farther east might correspond to a Neogene forebulge, implying forebulge migration. Alternatively, both highs could have been caused by blind and associated with a major crustal detachment. In this case these processes may have been facilitated by vertical mechanical strength contrasts in the foreland crust that have been invoked to drive spatially and temporally disparate thick-skinned deformation during the Andean orogeny. The fact that the arches occur in the vicinity of Cretaceous normal faults and rift basins suggests that these highs could also have been linked with extensional processes; in this case basement uplift and erosion would have been followed by sedimentary processes that finally caused the onlap of the Paleogene strata on the arches. Finally, we also consider the possibility they are Paleozoic, inherited features with posterior reactivation.

How to cite: Cortassa, V., Rossello, E., Back, S., del Papa, C., Ondrak, R., and Strecker, M.: Subsurface basement topography in the Cenozoic Andean foreland basin of northern Argentina: manifestations of long-wavelength deformation vs. inherited structures related to earlier orogeny and extensional processes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13302, https://doi.org/10.5194/egusphere-egu22-13302, 2022.

11:20–11:26
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EGU22-13402
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ECS
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Virtual presentation
Marlise Colling Cassel et al.

The South Atlantic present-day configuration is the result of remarkable paleogeographic and paleoclimate events that occurred during the Cenozoic. These tectono-climatic events include opening and closing ocean gateways, hyperthermal events, climate changes, and the rise of the Andean Mountain Chain. This work aims to define how these events affected the evolution of the Pelotas Basin in the southern Atlantic Ocean passive margin regarding their sedimentary and geomorphic records. To reach this objective, a multiproxy and multiscale analysis based on subsurface data and regional information using seismic interpretation, backstripping, and numerical modeling was performed to identify the influence of climatic, eustatic, and tectonic triggers. Our results point that the interaction between Naszca, South America, and Antarctic tectonic plates are the root to explain the Cenozoic events registered in the South Atlantic passive margins. The Andean Mountain Chain Uplift on the west side of South America and their retroarc foreland system, the forebulge and back-bulge provinces conducted a strong tectonic control over the Pelotas Basin. On the other hand, the climatic control resulting from the Drake Passage widening and consequent development of the Antarctic Circumpolar Current changed the contour currents dynamics. In response to these tectonic-induced climatic changes, the Pelotas Basin records over the Cenozoic: a) depocenter change, b) alterations in oceanic currents described through contourite deposits, and c) formation of a huge fan-like feature (Rio Grande Fan) during an accelerated increase in the sedimentation rate and consequent gravitational collapse driven by overpressure occurred in undercompacted shales.

How to cite: Colling Cassel, M., Girelli, T. J., Medina Ketzer, J. M., and Chemale Jr., F.: Cenozoic tectonic plate interaction registered in a South Atlantic passive margin basin (southern sector, Pelotas Basin), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13402, https://doi.org/10.5194/egusphere-egu22-13402, 2022.

11:26–11:32
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EGU22-3588
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ECS
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On-site presentation
Marco Meschis et al.

In order to investigate crustal deformation within the upper plate of the Ionian Subduction Zone (ISZ) at different time scales, we have (i) mapped and modelled sequence of Late Quaternary raised marine terraces tectonically deformed by the West Crati normal fault, in northern Calabria, and (ii) refined geodetic rates of crustal extension from continuous GNSS measurements. Indeed, this region experienced damaging earthquakes such as the “1184 Valle del Crati” (M 6.7) and the “1638 Crotonese” (M 6.7) events, possibly on the West Crati Fault; however, an in-depth evaluation of the deformation rates inferred from geologic and GNSS data has not yet been performed. Furthermore, fault slip-rates and earthquake recurrence intervals for the understudied West Crati Fault are still debated and poorly-constrained. Raised Late Quaternary marine terraces are preserved on the footwall of the West Crati Fault; however, it is still debated if the “local” effect of the footwall uplift is affecting the “regional” signal of uplift likely related to the deformation associated either with the subduction or mantle upwelling processes. Within the investigated region lying in the northern part of the uplifting Calabrian-Peloritani Arc there are 32 regionally distributed permanent GNSS stations, for 18 of which the coordinate time series are adequately long (at least 4.5 years) to allow the study of the crustal kinematics. The data of these 18 stations are used to geodetically estimate fault slip-rates and then earthquake recurrence intervals for the West Crati Fault, with the aim of at least partially solve the aforementioned problem of the poor constrains. In particular, velocity and strain across this fault, based on reasonable hypotheses about the fault dip and the mechanical properties of the involved material, are computed starting from GNSS data about the surface kinematics.

Our preliminary results show that GIS-based elevations of Middle to Late Pleistocene palaeoshorelines, as well as temporally constant uplift rates, vary along the strike of the West Crati Fault, mapped on its footwall. This suggests that the fault slip-rate governing seismic hazard has also been constant through time, over multiple earthquake cycles. We then suggest that our geodetically-derived fault slip-rate for the West Crati Fault may be a more than reasonable value to be used over longer time scales for an improved seismic hazard approach, allowing to derive new earthquake recurrence intervals. These results thus suggest a significant yet understudied seismic hazard for the investigated area also because the regional extension might be likely accommodated by a few more active faults across-strike in northern Calabria. These facts highlight the importance of mapping crustal deformation within the upper plate above subduction zones to avoid unreliable interpretations relating to the mechanism controlling regional uplift.

How to cite: Meschis, M., Teza, G., Elia, L., Lattanzi, G., Di Donato, M., and Castellaro, S.: Refining rates of active crustal deformation in the upper plate of subduction zones, implied by geologic and geodetic data: The E-dipping West Crati Fault, southern Italy., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3588, https://doi.org/10.5194/egusphere-egu22-3588, 2022.

11:32–11:38
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EGU22-11349
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ECS
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Virtual presentation
Julius Jara-Muñoz et al.

The coastal morphology of islands may furnish valuable information regarding deformation rates, their controlling mechanisms and the dynamics of the upper crust in offshore areas along subduction zones. Here we study active deformation and faulting at glacial-cycle time scales in the Kythira island, located at the western part of the Hellenic subduction zone, between Crete Island and the Peloponnese. The island exposes an outstanding sequence of more than twelve successive levels of marine terraces that depict the Pleistocene active uplift of the island. The marine terraces are offset by several NNW-SSE and NNE-SSW active faults. We use high-resolution topography combined with morphometric analysis to map the sequence of marine terraces and active faults. We divide the marine terrace sequence into two groups, the higher marine terraces (260 – 480 masl) include polygenic rasa surfaces, the lower terraces (20 – 220 masl) are characterized by staircase morphologies. Based on a proposed correlation with sea level curves, we estimated ages ranging between MIS 17 and MIS 22 (712 – 1000 ka) for the higher terraces and between MIS 5 and MIS 15 (125 – 620 ka) for the lower terraces. We focus on the two main faults of the island, defined as F1 and F2, they display right- and left-lateral and dip slip displacements, offsetting the marine terrace risers and treads and producing local drainage anomalies. Based on the proposed terrace ages we derived preliminary heave rates between 0.3 and 0.5 m/ka for the right-lateral fault F1 and between 0.8 and 1 m/ka for the left-lateral fault F2. Mean throw rates vary between 0.01 m/ka and 0.03 m/ka for F1 and F2 respectively. We link the activity of these faults with the occurrence of intermediate-depth and strong magnitude earthquakes such as the Mw 6.6 and 6.7 occurred in the area of Kythira in 1903 and 2006, respectively. Further dating of marine terrace deposits and surfaces, and structural analysis will be carried soon to refine our preliminary estimates. Our work emphasizes on the importance of studying islands to elucidate vertical and horizontal deformation rates in offshore areas of subduction zones.

How to cite: Jara-Muñoz, J., Tsanakas, K., Karymbalis, E., Yildirim, C., Pedoja, K., Batzakis, D.-V., and Griva, D.: Quantifying active faulting using marine terraces, Kythira island, Greece, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11349, https://doi.org/10.5194/egusphere-egu22-11349, 2022.

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