Mesozoic Rift Basins Research Articles

A Fresh Look at the South Australian Onshore Otway Basin (Insights from Dem's Petroleum Systems Model Project)

The Otway Basin is one of the best known Mesozoic rift basins that span the southern coastline of Australia and has both on and offshore gas production and oil discoveries. 104 petroleum and 6 geothermal wells have drilled since the 1890s. In 1987 Katnook 1 discovered economic gas in the Penola Trough (the most significant hydrocarbon province in the SA part of the basin to date), further drilling led to more discoveries and construction of a processing plant.

Exploring the Geoheritage and Geosites of Jaramara Area, Kachchh, India: a Window into the Mesozoic Rift Basin

Exploring the Geoheritage and Geosites of Jaramara Area, Kachchh, India: a Window into the Mesozoic Rift Basin

Detrital zircon and apatite U-Pb provenance and drainage evolution of the Newark Basin during progressive rifting and continental breakup along the Eastern North American Margin, USA

Abstract Mesozoic rift basins of the Eastern North American Margin (ENAM) span from Florida in the United States to the Grand Banks of Canada and formed during progressive extension prior to continental breakup and the opening of the north-central Atlantic. The syn-rift strata from all the individual basins, lumped along the entire margin into the Newark Supergroup, are dominated by fluvial conglomerate and sandstone, lacustrine siltstone, mudstone, and abundant alluvial conglomerate and sandstone lithofacies. Deposition of these syn-rift sedimentary rocks was accommodated in a series of half grabens and subsidiary full grabens situated within the Permo-Carboniferous Appalachian orogen. The Mesozoic ENAM is commonly depicted as a magma-rich continental rift margin, with magmatism (Central Atlantic magmatic province [CAMP]) driving continental breakup. However, the southern portion of the ENAM shows evidence of magmatic breakup (e.g., seaward-dipping reflectors), and rifting and crustal thinning appeared to start ~30 m.y. prior to CAMP emplacement in the Jurassic. This study provides extensive new detrital zircon and apatite U-Pb provenance data to determine the provenance and reconstruct the paleodrainages of the Newark Basin during progressive rifting and magmatic breakup and the implications for the overall rift configuration and asymmetry during progressive rifting along the ENAM rift margin. Detailed new detrital zircon (N = 21; n = 3093) and apatite (N = 4; n = 559) U-Pb results from sandstone outcrop and core samples from the Newark Basin indicate a distinct provenance shift, with relatively older Carnian syn-rift strata predominately sourced from the hanging wall of the basin bounding fault in the east while relatively younger Norian strata were regionally sourced from both the hanging wall and footwall. The syn-rift strata at the Triassic-Jurassic boundary were sourced from the hanging wall before a transition to local footwall terranes. These results suggest two major provenance changes during progressive rifting—the first occurring during Carnian crustal necking and rift flank uplift as predicted by recent numerical models and the second occurring at the onset of the Jurassic due to regional and local thermal uplift during CAMP magmatism as seen along other magma-rich margins, such as the North Atlantic and the southern portion of the South Atlantic margin.

Controls on hydrocarbon accumulation in the pre-rift paleozoic and late syn-rift cretaceous sandstones in PTAH oil field, north Western Desert, Egypt: Insights from seismic stratigraphy, petrophysical rock-typing and organic geochemistry

North Western Desert (NWD) of Egypt is one of the most petroliferous provinces in North Africa. Mesozoic rift basins in the NWD host several active petroleum systems in their syn- and post-rift sedimentary successions. Also, numerous oil reserves were recently discovered in the pre-rift Paleozoic reservoirs. However, the genetic link between the pre-rift hydrocarbon plays and the syn- and post-rift accumulations is still ambiguous. Additionally, controls on distribution of the optimum rock types in the pre-rift reservoirs need further investigation. Therefore, this study integrates geochemical, seismic-stratigraphic, and petrophysical approaches to better understand these issues based on oil, seismic, and well data retrieved from the Paleozoic pre-rift “Shiffah” and the Cretaceous late syn-rift “Alam El Bueib (AEB)” sandstones in PTAH oil Field in the NWD.Oil retrieved from Shiffah and AEB pay zones displays a similar n-alkane composition dominated by cycloalkanes and nC20+ alkanes. The oil samples retain biomarker signatures of pre-Cretaceous terrestrial organofacies where oleanane is absent, isoprenoid ratio (prestane/phystane) is high (>5) and C29/C27 steranes is greater than 1.5. Shiffah and AEB oils have a common source rock and display compositional characteristics similar to NWD oils derived from the Middle Jurassic Khatatba Formation fluvio-deltaic organofacies. Deep-seated rift-faults cross-cutting the entire syn- and pre-rift successions provide the paths for the upward and downward hydrocarbon migration from Khatatba organofacies to AEB and Shiffah sandstones, respectively. Distribution of the reservoir rock types (RRTs) controlled the thickness of the hydrocarbon column. Reservoir quality decreases from RRTI to RRTIII. RRTI rocks occur in the Shiffah fluvial basin-fill facies, whereas the best RRTs in AEB are classified as RRTII and are exclusively associated with the prograding deltaic facies. Correlation between seismic facies and RRT allows the prediction of their lateral and vertical distribution. Our results highlight existence of excellent reservoir rock types in the pre-rift succession connected with the Jurassic kitchen which charged the entire syn- and post-rift reservoirs.

Stratigraphic architecture and fluvial interpretations of the Upper Cretaceous (Turonian?) Middendorf Formation, Chesterfield County, South Carolina, U.S.A.

ABSTRACT The Upper Cretaceous (Turonian?) Middendorf Formation is a sand-rich stratigraphic unit of fluvial origin that forms a large aquifer in the U.S. Atlantic Coastal Plain. In Chesterfield County (South Carolina), which is the site of the type locality, the formation ranges in thickness from 66.5 to > 119.7 meters. The base of the formation is an unconformity above Paleozoic metasiltstone, and the upper contact is an unconformity above which lies sand of the Quaternary Pinehurst Formation. Outcrops display the following five facies assemblages: 1) sandstone to conglomeratic sandstone (fluvial bar and channel deposits), 2) beds of alternating laminae of sandstone and mudstone (fluvial overbank or floodplain deposits), 3) ≥ 1 m-thick beds of clay (swamp deposits, floodplain deposits, and/or sediment that accumulated in abandoned fluvial channels), 4) 0.2–0.5 m-thick planar to slightly undulatory beds of framework-supported sandstone with a mud matrix (traction-dominated current deposits at the top of fluvial bars, upper-flow-regime bedform deposits in subsidiary fluvial channels, or coarse-grained overbank deposits), and 5) sandstone to conglomeratic sandstone cemented by iron (interpreted as fluvial bar and channel deposits, with the iron cement being a diagenetic “groundwater ferricrete” that formed via the circulation of shallow groundwater and the oxidation of iron-bearing minerals). Kaolinite in various forms is pervasive throughout the formation and is interpreted as an early diagenetic phenomenon that formed by prolonged postdepositional weathering and flushing by meteoric water under a warm and humid paleoclimate. The fluvial system that formed the Middendorf Formation prograded into the area from the west or northwest from uplifted margins of Mesozoic rift basins and/or the Appalachian Mountains. This progradation was a response to a base-level fall and the sediment accumulated during base-level lowstand and subsequent early transgression. In Chesterfield County, the Middendorf Formation can be subdivided into three fining-upward sequences. Each sequence consists predominantly of medium to coarse sand with a greater abundance of gravel in the lower part of the sequence and a greater abundance of clay and silt beds in the upper part. Each sequence is interpreted as either a response to autogenic processes or a response to allogenic sea-level changes, specifically a higher-order (higher-frequency) progression from relative lowstand conditions to early transgression whereby coarse sand and gravel (e.g., fluvial bar and channel deposits) were preserved during initial lowstand conditions and a greater proportion of mud and finer-grained sand (floodplain deposits) were preserved during subsequent early transgression. The Middendorf Formation is correlative with several other kaolinite-rich fluvial sandstones in North America including the Raritan Formation in New Jersey, the Tuscaloosa Formation of the eastern Gulf of Mexico (Alabama, Mississippi, Louisiana), the Woodbine Formation of the central Gulf of Mexico (Texas), and the Frontier Formation of Wyoming. The accumulation and preservation of these formations occurred in response to a Turonian eustatic sea-level fall and subsequent transgression, and the early diagenetic kaolinite in these formations is attributed to similar warm and humid paleoclimate conditions.

Seismic evidence for ductile necking of the mid‐lower crust beneath the Columbrets Basin (Western Mediterranean)

AbstractThe Columbrets Basin is the largest Mesozoic rift basin of the Valencia Trough in the Western Mediterranean. The analysis of a seismic‐reflection survey makes it possible to reconstruct the tectonic fabric underlying the sedimentary basin, including the structure of the top of the lower crust and the Moho. It is proposed that the ductile deformation of the mid‐lower crust was the main mechanism controlling the basin geometry, with the radial flow of mid‐lower crust coeval with the reactivation of two large‐offset SW‐dipping normal faults, inherited from the precursor Permian–Triassic rifting. Mid‐lower crustal necking occurred below the major depocenters, immediately before hyperextension. Our results provide new insight into the formation of circular‐shaped basins and the evolution of depth‐dependent extensional processes during rifting.

The effects of positive tectonic inversion structures on the formation of thrust systems on the western Domeyko Cordillera, northern Chile: Implications for the orogenic development of the outer Andean forearc

This work aims to propose a novel structural setting for the outer Andean forearc. Specifically, we propose a new deformation mechanism related to thrusting belt systems induced by positive tectonic inversion processes in the western flank of the Domeyko Cordillera in northern Chile. Thrust belt systems have been rarely understood for the outer Andean forearc; in fact, the mention of thrusting is scarce and structural interpretations are restricted only to strike-slip faulting and positive tectonic inversion processes. In this study, we have constructed novel balanced cross-sections from new structural fieldwork and combined them with 2-D reflection seismic line re-interpretations, thus offering new ideas about the evolution and development of the forearc of the Central Andes. Based on this, we propose integrated kinematic models that describe the relationships between inherited extensional structures, positive tectonic inversion structures, and the formation of thrust systems. The proposed balanced cross-sections have been restored to a pre-shortening condition. In this way, two structural styles are proposed for the western flank of the Domeyko Cordillera. The first corresponds to west-directed positive tectonic inversion structures, which expose and extrude the Middle Jurassic syn-rift deposit of the ancient Mesozoic rift basin. The second consists of east-directed thin-skinned thrust systems, mainly affecting the Upper Cretaceous to Eocene volcano-sedimentary synorogenic sequences. The interaction between inversion structures and thrust system structural styles would generate a west-directed intracutaneous wedge. Finally, the minimum shortening obtained from our balanced cross-section restorations is ca. 11% for the Río Loa and the San Salvador Canyons segment and ca. 56% for the Quebrada Mala segment. The formation of thrusting structures is controlled by a major detachment fault activated from a regional-scale angular unconformity, which we have named the Quebrada Mala detachment fault. An important part of the shortening was taken up and accommodated by buttressing structures and their associated intraformational detachment-thrust levels.

Evaluation of Hydrocarbon Generation Potential of Laiyang Formation Source Rocks in Ri-Qing-Wei Basin, Eastern Shandong

The Ri-Qing-Wei Basin is a newly discovered Late Mesozoic rift basin on the eastern Shandong coast in recent years. Thick, continuous deposited source rocks are found in the Lingshan Island scientific drilling project. Therefore, it is necessary to evaluate the distribution and hydrocarbon generation potential of source rocks in this area. Organic geochemical experiments were carried out on samples from the core of LK-1 and outcrops in the Lingshan Island, the Laoshan area, and the Jimo Zhougezhuang area to evaluate the maturity, abundance, and type of organic matter in source rocks. The results show that the cumulative thickness of the source rocks in the study area is more than 500 m, and the TOC content is generally greater than 1.0%. The organic matter type is good (mainly type II1 and type II2 kerogen) and the Ro value is more than 2.0. The thermal evolution degree of the organic matter is high with natural gas predominantly generated. We carried out Rock-Eval, PY-GC and gold tube experiments on low-maturity samples of Laikong 2 and established a chemical kinetic model to quantitatively evaluate the study area in combination with sedimentary burial history and thermal history data. The results show that the total resources of the five sags in the study area are about 476 billion cubic meters, and the average resource intensity is about 82.2 million cubic meters/km2. Among them, the resource intensities of the Lingshan Island Sag and Laoshan Sag are 112.6 million cubic meters/km2 and 98.8 million cubic meters/km2, respectively. Studied sites are “small and fertile” and may be used as favorable exploration prospect areas.

Organic geochemistry and oil-source rock correlation of the Cretaceous succession in West Wadi El-Rayan (WWER) concession: Implications for a new Cretaceous petroleum system in the north Western Desert, Egypt

Mesozoic rift basins of the north Western Desert host the majority of proven oil reserves in Egypt. These basins are bounded by poorly-explored structural highs (Kattaniya high, Qattara ridge) with unknown petroleum system. The recently-discovered oil in West Wadi El-Rayan (WWER) concession in the southern part of the Kattaniya high highlighted a need for understanding the petroleum potential of these transit regions. The present study integrates geochemical and basin modelling results to define potential source rocks and decipher the mechanism of oil generation, expulsion and migration. In WWER concession, oil is produced from the Upper Cretaceous (Upper Bahariya) sandstones. Rock-Eval pyrolysis results demonstrate that the Lower Cretaceous Alam El Bueib (AEB) and Upper Cretaceous Lower Bahariya shales below the reservoir contain mature source rocks (S2 up to 28.76, Tmax > 430 °C). WWER oil displays a uniform composition with high pristane/phytane (Pr/Ph > 3), saturates/aromatics (>5.5) and canonical variable values (CV > 6) pointing to a generation from a terrestrial source rock. This is consistent with high contents of C30 hopane, C29 steranes and diasteranes as well as the very low values of dibenzothiophane (DBT)/Phenantherane (<0.1) confirming oil generation from a clay-rich source rock deposited in a fluvio-deltaic environment.Oil-source correlation highlights a robust similarity in compositional biomarkers between the WWER oil and AEB rock extracts. Additionally, the maturity-relevant biomarkers such as Ts/Tm trisnorhopanes and H32 S/(R + S) homohopanes favor an oil expulsion phase during the early stage of oil window in accordance with the basin modelling results and the maturity level of AEB organic-rich facies. These findings shed the light on a new petroleum system in the north Western Desert where the AEB fluvio-deltaic shales are capable of generating early mature oil which migrates through the Cretaceous deep-seated extensional faults into the Bahariya sandstone reservoir.

Main Factors of Mesozoic Tectonic Deformation in the Erlian Basin, Inner Mongolia, China: Insights from Physical Modelling

Erlian Basin is a Mesozoic oil and gas-bearing basin in northeast of China. The extension rate, extension direction, and stratum thickness of this rift basin have a clear control on its shape and extension. In this study, we design three sandbox models of the Erlian Basin to represent the effects of changing these three factors. The extension rate controls the timing of secondary fault formation inside the rift basin; a high extension rate promotes faster deformation inside the rift. The extension direction controls the strike of the fault inside the rift; a greater angle between the extension direction and the normal direction of the strike of the rift favors rapid evolution of internal secondary faults. The stratum thickness represents the control of sedimentation on the rift basin; the thinner the brittle layer, the wider the rift. The simulation results also show that the extension direction is the major factor controlling tectonic deformation in the basin. Stratum thickness and extension rate are secondary controlling factors. Additionally, according to geometric and kinematic similarities between typical Mesozoic rift basins in eastern and adjacent areas of China, we suggest that southeastward extension is a possible kinematic mechanism for basin formation.

A kinematic reconstruction of Iberia using intracontinental strike‐slip corridors

AbstractDespite considerable progress in restoring rifted margins, none of the current kinematic models can restore the Mesozoic motion of the Iberian block in full agreement with the circum‐Iberian geology. This conflict requires a revision of the kinematic description at the onset of divergence. The circum‐Iberian region has a unique geological dataset that allows calibration and testing of kinematic reconstructions and therefore it is an ideal candidate for testing intracontinental restoration approaches. Here we define intracontinental deforming regions, referred to as strike‐slip corridors, based on alignments of Mesozoic rift basins and/or transfer zones bordering rigid continental blocks. We use these strike‐slip corridors and data from the southern N‐Atlantic and Tethys to define the motion path of the Flemish Cap, Ebro and Iberia continental blocks. The resulting Mesozoic kinematic model for the Iberian block is compatible with recently published data and interpretations describing the Mesozoic circum‐Iberian geology. Large‐scale intracontinental strike‐slip corridors may offer a valid boundary condition for reconstructing continental block motion at the onset of divergence in intracontinental settings.

Geology and petroleum prospectivity of the Sea of Hebrides Basin and Minch Basin, offshore NW Scotland

The Sea of Hebrides Basin and Minch Basin are late Paleozoic–Mesozoic rift basins located to the NW of the Scottish mainland. The basins were the target of small-scale petroleum exploration from the late 1960s to the early 1990s, with a total of three wells drilled within the two basins between 1989 and 1991. Although no commercially viable petroleum discoveries were made, numerous petroleum shows were identified within both basins, including a gas show within the Upper Glen 1 well in Lower Jurassic limestones. Organic-rich shales have been identified throughout the Jurassic succession within the Sea of Hebrides Basin, with one Middle Jurassic (Bajocian–Bathonian) shale exhibiting a total organic carbon content of up to 15 wt%. The focus of this study is to review the historical petroleum exploration within these basins, and to evaluate whether the conclusions drawn in the early 1990s of a lack of prospectivity remains the case. This was undertaken by analysis of seismic reflection data, gravity and aeromagnetic data, and sedimentological data from both onshore and offshore wells, boreholes and previously published studies. The key findings from our study suggest that there is a low probability of commercially sized petroleum accumulations within either the Sea of Hebrides Basin or the Minch Basin. Ineffective source rocks, likely to be due to low maturities (due to lack of burial) and the fact that the encountered Jurassic and Permian–Triassic reservoirs are of poor quality (low porosity and permeability), has led to our interpretation of future exploration being high risk, with any potential accumulations being small in size. While petroleum accumulations are unlikely within the basin, applying the knowledge obtained from this study could provide additional datasets and insight into petroleum exploration within other NE Atlantic margin basins, such as the Rockall Trough and the Faroe–Shetland Basin.

Mechanical properties of Mesozoic rift basin formations

Mechanical properties of Mesozoic rift basin formations

Validating far-field deformation styles from the Adjara-Trialeti fold-and-thrust belt to the Greater Caucasus (Georgia) through multi-proxy thermal maturity datasets

Thermal history reconstructions can help to better characterise the geological history of areas that experienced a polyphase tectonic evolution. The integration of published stratigraphic/structural data with new and pre-existing data on thermal maturity (clay mineralogy, Raman spectroscopy, vitrinite reflectance, and pyrolysis) of both surface and subsurface sedimentary successions of a wide region of Georgia including -north to south- the southern Greater Caucasus, the western Kura Basin, and the Adjara-Trialeti fold-and-thrust belt (FTB) provides cogent constraints on its late Mesozoic-Cenozoic tectono-sedimentary evolution.Overall, thermal maturity spans from the low diagenesis (60–80 °C) in the Upper Miocene section of the Kura Basin to anchizone-epizone (about 400 °C) in the central Greater Caucasus axial zone. In more detail, different maturity trends and thermal histories point to the existence of two domains formed by positive tectonic inversion: (i) the Adjara-Trialeti FTB from an Eocene rift basin and (ii) the Greater Caucasus from a Mesozoic rift basin. Multiple thermal indicators, along with stratigraphic/structural evidence, show that the Paleocene section of the Adjara-Trialeti basin fill reached the upper oil window (ca. 115 °C) during maximum sedimentary burial and that the whole basin was then exhumed starting from the late Middle Miocene. A positive correlation between thermal maturity and stratigraphic age points to a limited thermal effect of tectonic loading. In the southern Greater Caucasus, thermal maturity increases progressively with stratigraphic age, from ca. 100 °C (Upper Eocene) to 400 °C (Lower Jurassic), in broad agreement with the reconstructed thickness of the basin-fill succession, thus indicating that most of the thermal maturity was again induced by sedimentary burial.As to the flexural western Kura Basin, its Maikopian (Oligocene-Early Miocene) section reached the oil window (up to ca. 110 °C) whereas the Middle-Late Miocene one is immature. The Kakheti ridge -a highly tectonised portion of the Kura Basin- reached immature to early mature conditions.

Influence of inherited structural domains and their particular strain distributions on the Roer Valley graben evolution from inversion to extension

Abstract. The influence of strain distribution inheritance within fault systems on repeated fault reactivation is far less understood than the process of repeated fault reactivation itself. By evaluating cross sections through a new 3D geological model, we demonstrate contrasts in strain distribution between different fault segments of the same fault system during its reverse reactivation and subsequent normal reactivation. The study object is the Roer Valley graben (RVG), a middle Mesozoic rift basin in western Europe that is bounded by large border fault systems. These border fault systems were reversely reactivated under Late Cretaceous compression (inversion) and reactivated as normal faults under Cenozoic extension. A careful evaluation of the new geological model of the western RVG border fault system – the Feldbiss fault system (FFS) – reveals the presence of two structural domains in the FFS with distinctly different strain distributions during both Late Cretaceous compression and Cenozoic extension. A southern domain is characterized by narrow (&lt;3 km) localized faulting, while the northern is characterized by wide (&gt;10 km) distributed faulting. The total normal and reverse throws in the two domains of the FFS were estimated to be similar during both tectonic phases. This shows that each domain accommodated a similar amount of compressional and extensional deformation but persistently distributed it differently. The faults in both structural domains of the FFS strike NW–SE, but the change in geometry between them takes place across the oblique WNW–ESE striking Grote Brogel fault. Also in other parts of the Roer Valley graben, WNW–ESE-striking faults are associated with major geometrical changes (left-stepping patterns) in its border fault system. At the contact between both structural domains, a major NNE–SSW-striking latest Carboniferous strike-slip fault is present, referred to as the Gruitrode Lineament. Across another latest Carboniferous strike-slip fault zone (Donderslag Lineament) nearby, changes in the geometry of Mesozoic fault populations were also noted. These observations demonstrate that Late Cretaceous and Cenozoic inherited changes in fault geometries as well as strain distributions were likely caused by the presence of pre-existing lineaments in the basement.

Characteristics and controlling factors of lacustrine source rocks in the Lower Cretaceous, Suhongtu depression, Yin-E basin, Northern China

Lacustrine source rocks are widely distributed in the Mesozoic rift basins of northern China. Two lacustrine rift sub-depressions in the Suhongtu depression, Yin-E Basin, have been subjected to a comprehensive analysis of their source rock potential to further reveal the controlling factors and enrichment mechanisms by constructing models for lacustrine source rocks in different tectonic settings. The Hari sag in the Suhongtu depression has significantly greater sedimentary cover and better hydrocarbon generation conditions when compared to the Babei sag by comprehensive analyses of total organic carbon (TOC), chloroform bitumen “A”, Rock-Eval pyrolysis and δ13CPDB. The results show that source rock deposition was affected by organic productivity, organic matter preservation and sedimentation rates. The TOC and δ13CPDB values indicate that there was higher productivity in the lakes of the Hari sag, and productivity reached a maximum during the deposition of the Yingen Formation. The total reduced sulphur (TRS), Pr/Ph, and gammacerane index values indicate that a relative reducing environment was present in the Hari sag. During deposition of the Bayingebi Formation in the Hari sag, the water was suboxic-anoxic, gradually turning anoxic and finally formed a strongly reducing, high-salinity, stratified water environment during deposition of the Yingen Formation. The Babei sag was suboxic-oxidizing throughout the deposition of the Lower Cretaceous lacustrine mudstones. With more active boundary faults and higher sedimentation rates, the terrigenous organic matter inputs to the Hari sub-depression were higher than those in the Babei sub-depression. These observations permitted the development of a model for the formation mechanism for the effective lacustrine source rocks in the Cretaceous fault basin of the Suhongtu depression. In the Hari sag, during source rock deposition of the K1b and K1s formations, intense and more active faults resulted in high terrigenous organic matter being carried into the lake. However, rapid sedimentation rates caused organic matter dispersed. During source rock deposition of the K1y Formation, the sag entered a transition stage from synrift to post-rift with an intermediate sedimentation rate. More organic matter was continuously transported into the basin with high salinity and a strongly reducing sedimentary environment, which caused enrichment of organic matter. In the Babei sag, due to small-scale rifting structures and shallow water conditions, a relatively low influx of terrigenous organic matter and suboxic to oxidizing conditions were developed. This study have important implications for source rock prediction in other lacustrine rift basins.

Peneplains and tectonics in North-East Greenland after opening of the North-East Atlantic

Elevated plateaus with deeply incised valleys characterise elevated, passive continental margins (EPCMs) in all climate zones. These features are, however, a topic of debate regarding when and how the large-scale landscapes formed. We have investigated and mapped the partly glaciated landscape of North-East Greenland (70–78°N). The area consists of crystalline basement and Palaeozoic–Mesozoic rift basins, capped by Palaeogene basalts that erupted during the northeast Atlantic break-up. Our stratigraphic landscape analysis reveals a typical EPCM dominated by two elevated erosion surfaces, extending 200 km east–west and 900 km north–south. The low-relief Upper Planation Surface (UPS; c. 2 km above sea level) cuts across basement and Palaeogene basalts, indicating that it was graded to base level defined by the Atlantic Ocean in post-basalt times and subsequently uplifted. The UPS formed prior to the deposition of mid-Miocene lavas that rest on it, south of the study area. In the interior basement terrains, the Lower Planation Surface (LPS) forms fluvial valley benches at c. 1 km above sea level, incised below the UPS. The LPS is thus younger than the UPS, which implies that it formed post mid-Miocene. Towards the coast, the valley benches merge to form a coherent surface that defines flat-topped mountains. This shows that the LPS was graded to near sea level and was subsequently uplifted. Hence, both the UPS and the LPS formed as peneplains – erosion surfaces graded to base level. The fluvial valley benches associated with the LPS further indicates that full glacial conditions were only established after the uplift of the LPS in the early Pliocene (c. 5 Ma). The uplift of the LPS led to re-exposure of a Mesozoic etch surface. We conclude that episodes of late Neogene tectonic uplift shaped the stepped landscape and elevated topography in North-East Greenland.

Reconstruction of the stress regime in the Jiaolai Basin, East Asian margin, as decoded from fault-slip analysis

The East Asian margin has experienced a complex tectonic history since the Mesozoic and has developed a complex basin-mountain system. The Jiaolai Basin, which is located on the East Asian margin, is a typical Mesozoic rift basin that has undergone multiple tectonic episodes. Here, using field geological surveys, effective stress inversions, and accurate chronological data, we recognize six tectonic episodes that have occurred in the Jiaolai Basin since the Cretaceous: E-W extension (135-121 Ma), which controlled the early deposition of the Laiyang Group; NW-SE extension (120-93 Ma), which controlled the late deposition of the Laiyang Group and the eruption of the volcanic rocks in the Qingshan Group; NE-SW compression (92-86 Ma), which produced folding of the Qingshan Group and its underlying strata and the formation of the unconformity surface between the Wangshi and the Qingshan Groups; N-S extension (85-60 Ma), which controlled the deposition of the Wangshi Group; NW-SE compression (60-55 Ma), which produced the unconformity between the Wangshi Group and the Wutu Group; and NE-SW extension (ca. < 55 Ma), which controlled the deposition of the Wutu Group. Considering the subduction history of the Izanagi plate and the Pacific plate, the activities of these plates may have primarily controlled the temporal variation in the intraplate paleostress regime in the East Asian margin.

Reservoir and sealing properties of the Newark rift basin formations: Implications for carbon sequestration

The Newark Basin is one of the major Mesozoic rift basins along the U.S. Atlantic coast evaluated for carbon dioxide (CO2) storage potential. Its geologic setting offers an opportunity to assess both the traditional reservoir targets, e.g., fluvial sandstones, and less traditional options for CO2 storage, e.g., mafic intrusions and lavas. Select samples from the basal, predominantly fluvial, Stockton Formation are characterized by relatively high porosity (8%–18%) and air permeability (0.1–50 mD), but borehole hydraulic tests suggest negligible transmissivity even in the high-porosity intervals, emphasizing the importance of scale in evaluating reservoir properties of heterogeneous formations. A stratigraphic hole drilled by TriCarb Consortium for Carbon Sequestration in the northern basin also intersected numerous sandstone layers in the predominantly lacustrine Passaic Formation, characterized by core porosity and permeability up to 18% and 2000 mD. However, those layers are shallow (predominantly above 1 km in this part of the basin) and lack prominent caprock layers above. The mudstones in all three of the major sedimentary formations (Stockton, Lockatong, and Passaic) are characterized by a high CO2 sealing capacity — evaluated critical CO2 column heights exceed several kilometers. The igneous options are represented by basalt lavas, with porous flow tops and massive flow interiors, and a crystalline but often densely fractured Palisade Sill. The Newark Basin basalts may be too shallow for sequestration over most of the basin's area, but many other basalt flows exist in similar rift basins. Abundant fractures in sedimentary and igneous rocks are predominantly closed and/or sealed by mineralization, but stress indicators suggest high horizontal compressional stresses and strong potential for reactivation. Overall, the basin potential for CO2 storage appears low, but select formation properties are promising and could be investigated in the Newark Basin or other Mesozoic rift basins with similar fill but a different structural architecture.

What is the structure of the forearc region in the Central Andes of northern Chile? An approach from field data and 2-D reflection seismic data

The tectonic evolution of the Andean forearc in the Central Andes is understood by the superimposition of deformational events associated with different tectonic regimes, which control the main morpho-tectonic units of northern Chile. Varied interpretations have opened a great discussion about the deep structure of the Andean forearc and its implications in the evolution of the Central Andes. These ideas are commonly accompanied by the lack of regional tectonic models that explain the geometry and kinematics of first-order structures. The main limitations are due to the unknown origin of the structural styles in the substrate and their relationships with those exposed in the field. In order to solve this problem, we present a new structural model of the forearc region of northern Chile, specifically along the Central Depression (22°-23°S) supported by field observations and the structural interpretations of 2D seismic data. Four major tectono-sequences have been recognized related to (a) a Paleozoic-Triassic basement rocks, (b) a Jurassic-Lower Cretaceous synrift deposits, (c) Upper Cretaceous-Paleocene volcano synorogenic deposits and (d) a Late Cenozoic covered gravel. The first-order structural styles identified correspond to inverted half-graben basement structures related to the Jurassic Tarapacá Basin. The hanging wall blocks of the master faults are usually composed of large inversion anticlines along which, Jurassic and Lower Cretaceous siliciclastic deposits were expelled. Other basement contractional structures consist of short-cut and by-pass faults that modified the previous geometry of extensional systems. The second-order thin-skinned fold and thrust exposed in the region accommodated the shortening experienced by the Mesozoic synrift deposits during the basin inversion. The Upper Cretaceous-Paleocene deposits usually unconformably overlie the folded Mesozoic synrift deposits. This structural feature is first-order evidence of the positive reactivation of the Mesozoic rift basins and therefore is a regional marker of the onset of the Andean uplift in the region.