Episodes Of Compression Research Articles

Late Cretaceous Ophiolite Emplacement and Cenozoic Collisional Tectonics in the Northeastern Arabian Plate: Insights From New Broadband Magnetotelluric Data

AbstractThe Late Cretaceous obduction of the Semail Ophiolite onto the rifted passive Arabian margin and the Cenozoic collisional tectonics with the final closure of the Neo‐Tethys Ocean, are major contributors to the present‐day crustal architecture of the northern United Arab Emirates (UAE). We acquired the first 3D grid magnetotelluric observations from 73 stations in the northern UAE in order to image deep crustal electrical structures associated with the two significant compressional episodes. Inversion of the broadband magnetotelluric data reveals the subsurface geometry of the high‐resistivity ophiolite blocks, the underlying conductive thrust sheet (Haybi‐Hawasina nappe), a “wedge‐shaped” conductive foreland basin flanking the Hajar mountain ranges, and at depth, a high‐resistivity structure associated with a fold‐thrust belt adjacent to the allochthonous units, or Proterozoic crystalline basement. The ophiolite along the eastern coast (from cities Khor Fakkan to Fujairah) is more than 20 km thick and dips eastward. Across the Wadi Ham fault, the resistive ophiolite lies against less resistive materials that may represent Bani Hamid metamorphic rocks. The thin‐skinned thrust sheets of the proximal‐distal Tethyan sedimentary units (Haybi‐Hawasina complexes) exhibit low resistivity in the Dibba zone. In contrast to its gently east‐dipping geometry in the Dibba zone, the conductive Haybi‐Hawasina structure in the southern portion of the study area appears nearly vertically (>20 km) beneath the dense Khor Fakkan and Aswad ophiolite blocks. This result suggests extensive deformation of the thrust sheets beneath the southerly dense ophiolite blocks.

Open and Endoscopic Endonasal Optic Nerve Decompression for Craniofacial Fibrous Dysplasia in an Adolescent: 2-Dimensional Operative Video.

Craniofacial fibrous dysplasia (CFFD) is a benign, bony disease that may affect the skull base.1,2 Most cases are asymptomatic and observed; however, advanced disease can present with cranial neuropathy or craniofacial deformity requiring intervention.3-5 A 16-year-old adolescent girl with known CFFD involving the sphenoid and frontal bones with severe bilateral optic canal narrowing developed progressive right eye visual decline and frontal cosmetic deformity. Visual acuity worsened oculus dextrus (OD) to 20/30 with a new superior nasal scotoma and 20% loss in the retinal nerve fiber layer and remained oculus sinister (OS) 20/20. The patient was recommended a staged subfrontal craniotomy for right optic decompression and simultaneous correction cosmetic deformity followed by endonasal right optic decompression. On postoperative day one, visual acuity OD improved to 20/20; however, she developed OS visual decline to 20/800. Curiously, there were no episodes of intraoperative hypotension or additional iatrogenic compression. Use of methylprednisolone led to improvement OS 20/400. Given persistent visual decline, urgent second stage endonasal bilateral optic nerve decompression, rather than unilateral, was performed. Postoperatively, vision improved to OS 20/200. At one month, her vision improved to OD 20/15 and OS returned to 20/20 with a paracentral scotoma and 29% decline in left retinal nerve fiber layer with further improvement anticipated. This video describes a multidisciplinary, multistaged approach in treatment of optic nerve compression due to CFFD in addition to the management of unanticipated contralateral visual decline. The patient consented to the procedure and publication of her image. No Institutional Review Board/ethics committee approval was necessary for this case report.

The present-day stress field and paleo tectonics in offshore Brunei Darussalam

Present-day maximum horizontal stress orientation is one of the fundamental inputs for well design and stability analysis. Since the previous stress orientation map in Brunei Darussalam published in 2005, more borehole image data have been acquired to evaluate both reservoir geology and hole damages of different causes. The image-based breakout orientations in recent wells not only filled critical data gaps but also replaced the low-confident stress orientations from dipmeter data on the previous map. Integration with seismic interpretation also gives new insights into the present-day stress variations in relations to the tectonic evolution.The new map suggests three main stress domains transitioning to each other. Domain A in the deepwater to shelf slope region is compressional, characterized by northwest-southeast maximum horizontal stress, consistently perpendicular to the associated delta toe thrust structures near the well locations. The shelf to onshore region is divided into domain B in the east and domain C in the west as result of different evolutions and interactions between shallow deltaic and deep plate tectonics. This contrasts with the 2005 stress map, which divided the region into inversed inner shelf and extensional outer shelf provinces. The domain B is possibly in strike slip state with margin normal maximum horizontal stress, which is a reversal from the paleo extensions expressed by collapse faults and a large counter regional normal fault. The counter regional normal fault is interpreted as the result of rapid sediment load over thick ductile shales prior to the toe thrust system. The domain C in the west exhibits extension with east-west maximum horizontal stress, parallel to the normal faults but oblique to the thrust faults and the coastline. It is reversed from the latest compressional episode. Restoration of the structural deformation history suggests that tectonic reversals occurred several times in the domain C. Between the two shelf domains, where two sets of structural lineaments intersect, the maximum horizontal stress rotates across the two systems.

Anesthetic Management of a Pediatric Patient with Midline Neck Mass Causing Significant Tracheal Compression in Stridor for Resection of Tumor

Abstract A 1-year-old female child weighing 10 kg, with a mass over the lower part of the neck presented with stridor. Computed tomography showed a solid enhancing lesion in the lower neck causing marked tracheal compression with complete apposition of the anterior and posterior walls of the trachea causing almost complete obliteration of the tracheal lumen. The child was posted for resection of the tumor under general anesthesia. She was induced with sevoflurane 8% in oxygen and intubated following a flexible bronchoscopic assessment with a 4.0 mm cuffed endotracheal tube using C-MAC videolaryngoscope. After positioning, she developed airway compression, and using a fiber-optic bronchoscope, ETT tip was repositioned distal to the area of tracheal compression. There were repeated episodes of airway compression with desaturation intraoperatively. Postoperatively, the child was ventilated. Due to tracheomalacia and bilateral vocal cord palsy, the extubation trials failed, and she was eventually tracheostomized on the 5th postoperative day to maintain airway.

Time constraints on the geological evolution of the main sedimentary basins and tectono-magmatic events on Livingston Island, South Shetland Archipelago, Antarctica: a review

The Lower Cretaceous to Miocene South Shetlands Islands’ volcanic arc is a result of the subduction of the Phoenix Oceanic Microplate (part of the Pacific Plate) beneath the Antarctic Peninsula. The magmatic activity on Livingston Island has been going on for a long time: since the Early Cretaceous to the present. The evolution of the volcanic arc resulted in the formation of various sedimentary basins and paleoenvironments (turbiditic to shallow marine and continental) that formed varied sedimentary successions and tholeiitic to potassium calc-alkaline subduction-related magmatic rocks. Considering the magmatic activity on Livingston Island, a general trend of rejuvenation can be observed from the WNW (Byers Peninsula) to the ESE (to Hannah Point, Point Williams and further to the Hurd Peninsula and the Tangra Mountain). The rejuvenation of the magmatic rocks in the direction of the thrust plate can be explained as an effect of a flattening subduction that was active from the Early Cretaceous (135 Ma) up to around 90–70 Ma. The mixed ages of the dikes and small intrusions in the Hurd Peninsula are most probably due to periods of rotation and probably beginning of а slab-roll back. A regional Paleocene–Eocene (65–47 Ma) compressional episode that caused a low temperature to high-pressure metamorphism is registered on Smith and Elephant islands. The regional metamorphism was followed by a vast extension between 50–30 Ma that culminated with the opening of the Drake Passage around 34–30 Ma. The magmatic response of that regional scale extension was the intrusion of the Eocene Barnard Point Pluton (46–40 Ma) and dikes with youngest ages of around 30 Ma. The major uplift phase and the exhumation of the Tangra Mountain happened between 22–16 Ma as indicated by the Ap FT thermochronology. The last magmatic event on the island produced the contrastingly different in composition Quaternary alkaline mafic rocks that occupy the area between Innot Point and Burdick Peak. This episode is interpreted as related to a process of crustal extension that culminated in asthenospheric upwelling and rifting along the Bransfield Strait. The latter is due to a slab roll-back that led to the break-up of the South Shetlands from the Antarctic Peninsula and consequent subduction termination.

Does the syn- versus post-rift thickness ratio have an impact on the inversion-related structural style?

Abstract. Many extensional basins worldwide are modified by subsequent compressional episodes, which lead to inverted structures. The structures associated with the reactivation of pre-existing faults are critically important in the formation of suitable subsurface traps for hydrocarbons. Major concerns regarding inverted structures are the trap integrity and fault seal. In general, the preferred structures have simple four-way closures due to the minor forced folding of the post-rift cover, as opposed to (reverse) fault-related structures, which have a higher risk of breaching. Such reverse-fault-bounded structures have been generally observed in basins with a thick syn-rift fill and a relatively thin post-rift sequence at the time of inversion (Mode I). In contrast, gentle/open forced folds have been described in basins with thicker post-rift sequences than the syn-rift basin fill (Mode II). Five physical sandbox models, coupled with particle image velocimetry (PIV) analysis, have been performed to address the influence of the syn- versus post-rift thickness ratio on the inversion-related structural style of the post-rift cover. The main control on the development of Mode I or Mode II inversion structures within the post-rift sequence appears to be different due to the amount of compressional displacement accommodated by the inherited listric fault and the thickness of the post-rift cover. These observations do have a direct impact on the understanding of the geo-energy systems associated with inverted structures and are broadly comparable with natural data examples from Aotearoa/New Zealand, Israel, Romania, and the Republic of Türkiye.

The role of surface processes in basin inversion and breakup unconformity

In the context of continental extension, transient compressional episodes (stress inversion) and phases of uplift (depth inversion) are commonly recorded with no corresponding change in plate motion. Changes in gravitational potential energy during the rifting process have been invoked as a possible source of compressional stresses, but their magnitude, timing, and relationship with depth inversions remain unclear. Using high-resolution two-dimensional numerical experiments of the full rifting process, we track the dynamic interplay between the far-field tectonic forces, loading and unloading of the surface via surface processes, and gravitational body forces. Our results show that rift basins tend to localize compressive stresses; they record transient phases of compressional stresses as high as 30 MPa and experience a profound depth inversion, 2 km in magnitude, when sediment supply ceases, providing an additional driver for the breakup unconformity, a well-documented phase of regional uplift typically associated with continental breakup.

The role of surface processes in basin inversion and breakup unconformity

Abstract In the context of continental extension, transient compressional episodes (stress inversion) and phases of uplift (depth inversion) are commonly recorded with no corresponding change in plate motion. Changes in gravitational potential energy during the rifting process have been invoked as a possible source of compressional stresses, but their magnitude, timing, and relationship with depth inversions remain unclear. Using high-resolution two-dimensional numerical experiments of the full rifting process, we track the dynamic interplay between the far-field tectonic forces, loading and unloading of the surface via surface processes, and gravitational body forces. Our results show that rift basins tend to localize compressive stresses; they record transient phases of compressional stresses as high as 30 MPa and experience a profound depth inversion, 2 km in magnitude, when sediment supply ceases, providing an additional driver for the breakup unconformity, a well-documented phase of regional uplift typically associated with continental breakup.

UNDERSTANDING Cu DEFICIENCY AND Mo ENRICHMENT IN THE JURASSIC ZHANGGUANGCAI-LESSER XING’AN CONTINENTAL ARC (NE CHINA): INSIGHTS FROM THE LUMING PORPHYRY MO DEPOSIT

Abstract Continental arcs are favorable sites for porphyry Cu ± Mo deposits. In contrast, the Jurassic Zhangguangcai-Lesser Xing’an continental arc, northeastern China, hosts numerous porphyry Mo deposits with only minor total Cu endowment. The reasons for this remain elusive. Here, we address the issue by tracking the origin and evolution of a long-lived (ca. 12 m.y.) magmatic suite associated with one of the largest Mo deposits in the Zhangguangcai-Lesser Xing’an range continental arc—the Luming porphyry Mo deposit. In combination with previous geochronological data, our results indicate that the pre- (187.5–186.5 Ma) and syn-ore (178.6–175.6 Ma) intrusions at Luming represent separate magma batches from isotopically similar parental magmas with the signature of subduction-metasomatized mantle-derived magmas mixed with crustal melts. The Sr/Y, La/YbN, Dy/YbN, and Eu/Eu* values, together with fO2 and apatite S and Cl concentrations of the syn-ore intrusions, however, are systematically higher than pre-ore intrusions. These data indicate that there is a distinct change in magma chemistry during the period of magmatism quiescence between the pre- and syn-ore magmatism. The marked change in magma chemistry is coincident with an episode of major compression and crustal thickening in the Zhangguangcai-Lesser Xing’an range. We, therefore, interpret that the chemical changes most likely reflect a deepening of the locus of lower crustal magma evolution, linked to increased crustal thickness and/or melt H2O contents accompanying an increase in orogenic stress. Considering the tectonic setting, magmatic evolution in the deep crust, emplacement depth, fractionation degree, and oxygen fugacity of the porphyry Mo-related intrusions at Luming, they are very similar to porphyry Cu deposits worldwide. Accordingly, we propose that the deficiency in Cu and enrichment in Mo of the porphyry deposits in the Zhangguangcai-Lesser Xing’an range most likely formed due to mantle-derived magmas interacting with reduced crustal materials or melts in the deep crust. This resulted in substantial sequestration of Cu and S, decreasing porphyry Cu potential. Such an inference is supported by the distinctly lower S and Cl concentrations of the Mo-related intrusions in the Zhangguangcai-Lesser Xing’an range compared to those associated with porphyry Cu deposits. Our results confirm the fundamental role of increasing compressive stress, crustal thickening, and transcrustal petrologic processes in the formation of porphyry deposits and highlight the role of crustal components in modulating the Mo/Cu ratio of porphyry deposits in a continental arc setting. In addition, we tentatively propose that magmatic apatite SO3 and/or Cl contents can be used to discriminate porphyry Mo-related intrusions from those associated with porphyry Cu deposits in continental arcs.

Forearc tectonics and volcanism during the Devonian–Carboniferous evolution of the North Patagonian segment, southern Chile (41,3°S)

Late Paleozoic to early Mesozoic subduction complexes formed during the evolution of southwestern Gondwana and extensively crop out along the Chilean continental margin. Recent findings in northern Patagonia (40°–43°S) revealed that accretionary processes were active since the Devonian when enhanced lithosphere stretching in the forearc led to the formation of Chaitenia island arc. The extension in the crust consecutively developed a backarc basin, which culminated during a compressive episode that re-amalgamated the Chaitenia island arc with the margin. This episode produced intermediate grade metamorphism in the sedimentary rocks that were formed throughout the extension. To constrain the tectonic evolution of these processes, we combined petrology, structural analysis, whole-rock geochemical, and whole-rock isotopic tracing (Sr-Nd-Pb) data along with thermodynamic modelling. Two petro-tectonic domains are here defined. The Western Coastal Range Domain is composed of Carboniferous to Permian metapsammopelitic rocks, which are mainly schists with a metasedimentary Carboniferous protolith exhibiting a penetrative northeast to southwest dipping main foliation associated with basal accretion. The Eastern Coastal Range Domain is comprised by garnet micaschists, metabasalts, metarhyolites, and metasandstones. This unit is folded by three ductile structures: The first is related to rootless isoclinal folds, the second is associated with kilometric scale west-verging tight folds, and the third is associated with west-verging cylindrical folds. The volcanic rocks of this domain are comprised by middle Devonian alkaline metarhyolites and metabasalts with enriched-MORB and normal-MORB affinities. Trace element composition suggests that the metabasalts formed through shallow melting in an extensional setting over a supra-subduction zone. Nd and Pb isotope data point to a mantle source change for the basaltic melts from an EM1-like to a DM-like and are interpreted to reflect the embryonic to mature evolution of the early Devonian to Carboniferous backarc system. The calculated P–T evolution of the garnet micaschists follows: 1) a clockwise IP–IT prograde Barrovian path, 2) an isobaric thermal increase at ∼7 kbar and 540°C, and 3) an adiabatic decompression. Finally, after the metamorphism, these rocks were uplifted by thrusting processes that probably occurred during the late Permian.

Review: Louis Kahn: The Importance of Drawing and Our Days Are Like Full Years: A Memoir with Letters from Louis Kahn

Review: <i>Louis Kahn: The Importance of Drawing</i> and <i>Our Days Are Like Full Years: A Memoir with Letters from Louis Kahn</i>

Analogue modeling of the role of salt in the structuration of thin-skinned pull-apart basins: The case study of El Hamma basin, Central Tunisia

Pull-apart basins are structurally complex features that typically form in between two laterally offset strike-slip zones. The vast majority of analogue experiments on the formation of this type of basins have been conducted using basal discontinuities that transmitted from the bottom up strike-slip motion into the overlying sedimentary cover. Here, we present a series of models whose aim is to demonstrate that pull-apart basins above a viscous layer can be initiated not from the base up, but by the sole effect of lateral forces that allow two blocks to move laterally one past the other. This occurs independently from the basement, from which the brittle cover is fully decoupled by the viscous layer. This work was inspired by a natural example, the El Hamma Basin, located in Central Tunisia West of the city of Gabes and is bounded by two N100-110 trending major fault corridors, the Oum Ali- Fejij corridor in the North, and the Oglet Merteba-Matmata in the South. The area underwent multiple tectonic episodes of both extension and compression from Late Liassic to the Plio-Quaternary times. The region was subjected to regional NE-SW extension during the upper-cretaceous and major NW-SE compression during upper Miocene (Tortonian) and early quaternary (Early Pleistocene). The latter stage resulted in right-lateral strike slip along both corridors with faults forming a pull-apart basin that comprises two lateral mega-grabens separated by a central horst. Although one sub-circular diapir in the area (the El Melah diapir) crops out along the northern wrench zone, whether or not the mobile Triassic series extend farther South of it, beneath the pull-apart basin, is still debated.Through a series of analogue experiments using an innovative technique that generates two narrow, parallel strike-slip zones located within the sedimentary cover, rather than in the basement. Experimental results show remarkably similar geometry and evolution with those of the El Hamma basin. Moreover, from a regional perspective, our results suggest that the pinch out of the Triassic evaporites extends further South than previously thought and underlies at least part of the El Hamma basin.

Lineaments Extraction and Analysis Using Landsat 8 (OLI/TIRS) in the Northeast of Morocco

Northeastern Morocco is made up of several units belonging to the Alpine belt and its foreland. Miocene to plio-quaternary volcanic rocks with variable mineralogy and geochemistry dominate the geology of this region. The presence of active faults in different directions explains the high tectonic instability and the high frequency of earthquakes. This study contributes to the effort of understanding the geothermal potential of the Northeast of Morocco. Heat source and permeability are both key factors in the geothermal process. Indeed, lineaments analysis constrains the structures and their directions and indicates severely faulted zones, which are the most promising areas for geothermal exploration. For this purpose, we used Landsat data combined with geological and structural maps available in this region. Different image processing techniques were applied including band ratio (6/2) and directional filters. To validate the results, we conducted a comparative study between linear structures, available geological data, and previous studies. Results of the automatic extraction method of lineaments from Landsat 8 OLI/TIRS indicate three main lineament systems: 1) a NE-SW system ranging from N40 to N70; 2) an N-S system ranging from N10 to N45; 3) an EW to WNW-ESE systems ranging from N80 to N120. Most of lineaments extracted are localized in Kebdana, Amejjaou, Nador and Melilla regions. Compared to previous studies, the NE-SW system is consistent with an extensive period (Tortonian to Pliocene); the NW-SE system is consistent with the last compressive episode (Pliocene); the N-S system is consistent with the first compressive period (Late/End Tortonian).

The geology of the Capiru Group, Curitiba Terrane, Southern Ribeira Belt (Brazil)

ABSTRACT The Capiru Group is a Neoproterozoic metasedimentary unit that crops out in the Curitiba terrane, Southern Ribeira Belt, Brazil. A detailed geological mapping of this unit was performed during 2016 to 2020. Original interpretations and the new geological map were compiled and integrated with the past field data of the state (MINEROPAR) and national (CPRM) geological surveys, and to unpublished and recent published studies. This compilation represents the most updated synthesis of the Capiru Group, and provides the basis for recognition and individualization of lithostratigraphic units. The lithostratigraphic units reflect depositional/tectonic events, which involved: a) passive continental margin deposition on the Curitiba microplate, b) compressional episodes during the Brasiliano - Pan African Orogeny (Late Neoproterozoic), c) extensional processes that followed the collision stage (Cambrian), and finally, the d) extensional tectonics related to the Gondwana break-up during the Lower Cretaceous, that culminated to the Proto-Atlantic Ocean opening.

The Intergenerational Effects of a Large Wealth Shock: White Southerners after the Civil War

The nullification of slave wealth after the US Civil War (1861–1865) was one of the largest episodes of wealth compression in history. We document that White Southern households that owned more slaves in 1860 lost substantially more wealth by 1870, relative to Southern households that had been equally wealthy before the war. Yet, their sons almost entirely recovered from this wealth shock by 1900, and their grandsons completely converged by 1940. Marriage networks and connections to other elite families may have aided in recovery, whereas transmission of entrepreneurship and skills appear less central. (JEL D31, G51, J15, J24, N31, N32)

Magnetotelluric evidence for a Rhyacian suture zone hidden underneath the Seridó belt, Borborema Province, Northeastern Brazil

The Borborema Province is a complex orogenic system in northeast Brazil, whose current structural configuration is associated with the late Neoproterozoic-early Phanerozoic Brasiliano/Pan-African Orogeny. Magnetotelluric (MT) data were collected along four linear profiles across the northeastern corner of the province to assess the regional deep electrical resistivity structure. The site distribution is non-ideal for 3-D modeling, but dimensionality analysis showed that the data are dominated by 3-D effects. The model resulting from the 3-D inversion was critically evaluated for robustness and was found to provide a coherent view of the regional structure. A major crustal conductivity anomaly was modeled beneath Neoproterozoic supracrustal rocks of the Seridó belt and this anomaly deepens to upper mantle depths in the northwest direction. Considering independent geophysical information and the geometry and location of the conductor, it likely reflects remnants of a northwest-directed subduction zone with enhanced conductivity associated with interconnected magnetite along the suture/shear zone. Constrained by geochemical data, it is proposed that subduction occurred during the Rhyacian orogenic event and since then became a key pre-existing intra-basement mechanical weakness, prone to concentrate tectonomagmatic events. Its reactivation during several episodes of extension and compression in the Borborema Province was linked to the nucleation of the original Seridó rift basin (pre-Brasiliano), emplacement of mineralized bodies and crustal deformation in the Seridó belt (Brasiliano), and tectonic control for volcanics erupted during the Cenozoic (post-Brasiliano). All these processes after the Rhyacian collision in this sector of the province took place in an intracontinental setting.

Hereditary neuropathy with liability to pressure palsies: a case report

Hereditary neuropathy with liability to pressure palsies (HNPP) is a rare hereditary disorder characterized by recurrent episodes of nerve compression. The first attack usually occurs in the second or third decade of life. In the majority of cases, HNPP is associated with a mutation at chromosome 17 p11.2-12 comprising the gene encoding peripheral myelin protein 22 (PMP22). Here we present a case report of a 43-year-old male with HNPP confirmed by DNA testing. The patient complained of recurrent episodes of bilateral foot extensor muscles weakness and/or hyperesthesia on the outer surface of the hands and forearms, which started after a prolonged posture maintaining and without evident precipitating factors. We also describe typical clinical, electrophysiological, and nerve ultrasound characteristics of the disease.

Lithospheric evolution, thermo-tectonic history and source-rock maturation in the Gippsland Basin, Victoria, southeastern Australia

A fully integrated 3D basin model was built to study the lithospheric structural evolution and the thermal history of the offshore part of the Gippsland Basin to investigate the type, timing and magnitude of its initial opening mechanism and their effects on source rocks. The applied workflow included seismic interpretation of major faults and magmatic features, seismic reinterpretation of existing main stratigraphic boundaries and adjustment of the basement topography. Different scenarios for a McKenzie-type basal heat flow evolution were tested based on a two-step inversion approach, which translates the thickness changes of lithospheric layers into basal heat flow. Finally, a crustal layer model was assigned to the existing 3D numerical basin model and the effects on thermal maturation of petroleum source rocks were investigated. The results of the calibrated inversion model suggest intense lithospheric stretching and mantle upwelling during the Early Cretaceous caused initial breakup and subsidence of the Gippsland Basin. This syn-rift phase was accompanied by increasing basal heat flow from initially ∼50 mW/m2 to a maximum of 80–90 mW/m2. The resulting upwelled Moho with an associated crustal thickness of locally only 8 km agrees with geophysical observations. Elevated paleogeothermal gradients between 50 and 60 °C/km prevailed from ca 120 to 80 Ma. Episodes of compression, uplift, erosion, and thermal subsidence resulted in fast and continuous cooling during the early post-rift and a constant basal heat flow of 45–50 mW/m2 since the Eocene. Two main pulses of petroleum generation were identified in the Paleocene and in the Miocene–Pliocene. This novel two-step crustal layer inversion method allows a detailed reconstruction of the thermal history of rift basins and can provide useful information about the maturation of petroleum source rocks. KEY POINTS A temperature history reconstruction of the Gippsland Basin is given based on a large-scale numerical 3D model. Tectonically induced strong variability in paleoheat flows is recognised. Strong maturation and petroleum generation developed during the Paleogene and Neogene.

STRUCTURE AND EVOLUTION OF THE TEREK‐CASPIAN FOLD‐AND‐THRUST BELT: NEW INSIGHTS FROM REGIONAL SEISMIC DATA

The Terek‐Caspian fold‐and‐thrust belt along the northern flank of the Greater Caucasus Mountain Range together with the adjacent foreland basin is one of the oldest oil‐producing regions in Russia. Despite the long history of exploration, recently acquired seismic data has provided new insights about the structural architecture and evolution of this area. Its structural development during the Neogene was constrained by a syn‐extensional tectonic fabric inherited from Jurassic rifting and extension of the Great Caucasus Basin. The structural framework of this basin controlled the distribution of syn‐extensional deposits, and the Cenozoic reactivation of lateral ramps resulted in along‐strike variations in structural style. Thus western, central and SE segments of the Terek‐Caspian foldbelt are recognised and are referred to here as the Terek‐Sunzha fold zone, the Dagestan Promontory, and the Maritime Zone in southern Dagestan.Three principal episodes of Cenozoic compression in the Terek‐Caspian fold‐and‐thrust belt took place. The first episode in the Oligocene resulted in the inversion of pre‐existing normal faults with the coeval development of a foreland basin to the north of the thrust belt. The dominance of sediments of northerly provenance in the foreland basin suggests there was only moderate uplift of the Greater Caucasus at this time. However, significant uplift of the orogenic belt took place during later phases of Sarmatian (Late Miocene) and Akchagylian (Late Pliocene) compression. Erosion of the uplifting Greater Caucasus gave rise to the development of large‐scale, northerly prograding clinoforms which are clearly observed on seismic profiles in the foreland basin. Shortening was largely accommodated by wedge‐shaped thrusting facilitated by the presence of mechanically weak stratigraphic units.Structural development of the Terek‐Sunzha fold zone in the west of the Terek‐Caspian fold‐and‐thrust belt was largely controlled by a Tithonian salt layer which provided an efficient basal detachment surface and which also supplied material to squeezed diapirs in front of the belt. To the east, the plan‐view shape and internal architecture of the Dagestan Promontory were influenced by the areal extent of the Lower‐Middle Jurassic depocentre of the palaeo‐Volga delta which is up to 10 km thick. In the Maritime Zone, the style of shortening was mostly controlled by the presence of a pre‐existing structural high composed of folded Palaeozoic‐Triassic strata in front of the fold‐thrust belt.

Lower Jurassic deformation in the eastern Huincul High, Argentina

Subsurface characterization of the structure and sedimentary sequences in the Agua del Cajón area was performed to understand the Lower Jurassic deformation across the eastern Huincul High. Integration of seismic, well data, and fossil fauna allowed establishing the Late Triassic rifting and Jurassic compressional evolution underwent for this area. Four Late Triassic - Early Jurassic extensional depocenters were recognized, being the most significant the Agua del Cajón and El Salitral depocenters. In general, all of them present an E-W to WNW-ESE orientation and are flanked by NNE to NE-trend transfer zones. The contractional structural style of the Agua del Cajón area consists of south-vergence reverse faults and folds with two primary trends: (i) E-W to WNW-ESE and (ii) NE-SW to NNE-SSW. According to the slip and uplift amount, the first-order structural feature in the study area corresponds to the S-verging, E-W Huincul fault. Geometries and patterns in the seismic reflectors evidence two compressional episodes from late early Toarcian to Callovian time. The first one is associated with the inversion of the previous master normal fault of the El Salitral and Agua del Cajón depocenters during the late early Toarcian. The inversion of the NE-SW synthetic normal fault associated with the El Salitral depocenter also occurred during the first deformation pulses favored by its perpendicular orientation to NW-SE Jurassic σ1. NE-SW fault associated with the Agua del Cajon inversion shows no evidence of inversion-related deformation mechanisms. Instead, the formation of this structure is related to the previous NE-SW transfer zone. After a tectonic quiescence period in late Toarcian – late Aalenian, the compressional activity continued during the late Aalenian and Bajocian evidenced by progressive unconformities into Jurassic sequences. This activity would have continued until Callovian times. These results are in agreement with previously reported evolution in the eastern-central Huincul High region. However, they indicate that the contractional intraplate deformation in the southern Neuquén basin would have begun during the late early Toarcian; this is older than previously proposed.