Uplift Events Research Articles

Unfolding impacts of freaky tectonics on sedimentary sequences along passive margins: Pioneer findings from western Indian continental margin (Offshore Indus Basin)

The Western Passive Continental Margin of the Indian Plate (WCMI) serves as an elegant laboratory for understanding the syn-sedimentary rift-drift tectonics preserving a variety of episodic structural deformations and complex sedimentary infill. Here we present a multidisciplinary study on Offshore Indus Basin (OIB) that is less investigated compared to adjacent marginal basins along WCMI. Reflection seismic, gravity, borehole, and biostratigraphic data have been used to reconstruct the tectono-sedimentary history of the Meso-Cenozoic succession in OIB. Seismic based dynamic stratigraphy helped in mapping seven different depositional sequences grounded on morpho-tectonic considerations. The seismic expression of these sequences provided an idea of the depositional styles with different tectonic episodes since rifting in Jurassic to basin inversion in Miocene continued to present time. The OIB initially filled from the north with the sediments rapidly prograding southwards. In general, the basin deepens in the central and northwestern part where the formations achieve maximum depths. The analysis of 3D structural models revealed that the region experienced poly-phase deformation from the Late Cretaceous to recent times that include steeply dipping normal faults, horst, and graben, half-graben, half-graben with growth faulting, flower structures, anticline, syncline, and uplift with an angular unconformity. The most remarkable tectonic activity happened at the Early Miocene and resulted in the reactivation of extensional faults into strike-slip faults giving rise to a spectacular structural inversion due to transform movement between Indian and Arabian Plates that continues to present day. The most predominant faults are oriented in S20°-50°E with azimuth as 120°–160° and the maximum dip angles are >80° in the southwest flank of the basin. The main fault trend is S20°E-N20°W and dip angles ranging between 40° and 80° and above. A thick crust and the Ocean-Continent Transition (OCT) is imaged with massive felsic, mafic, and ultramafic intrusions by the help of forward gravity modeling. An initial onset of syn-rift tectonic subsidence between 90 and 68 Ma with a post-rift general increase between 68 and 54 Ma is comprehended while two uplift events at ~40 Ma and ~18 Ma are documented through backstripping analysis. It is inferred that the region is rapidly under complex structural inversion with growing folding, faulting, and flowering structures. This study could help in explaining the unanswered reasons of structural complexities, depositional styles, and basin inversion along worldwide passive margins.

Thermal evolution of the intracratonic Paris Basin: Insights from 3D basin modelling

The thermal evolution of the Paris Basin (PB) has been widely studied using 1D, 2D and, more rarely, 3D thermal models. It is well documented that the PB experienced higher temperatures in the past compared to what is currently observed. However, a quantitative analysis of the main processes and parameters that affect the temperature distribution, at the basin scale and over time, is still not available. In this study, through basin modeling which accounts for the main processes of the thermal evolution of sedimentary basins, we analyze and quantify the role of the different geological mechanisms by discriminating the causes of abnormal temperatures during the Late Mesozoic. This is done with a 3D basin model built from base Moho to present-day topography using the TemisFlow® basin modelling software. The model includes thermal processes within an evolving upper crust defined by three main structural domains. Each crustal sector presents radiogenic heat production, conductivity and thickness values which are used as input parameters to reproduce the paleo- and present-day basal heat flow variations observed in the basin. The model calculates heat flow through time in both, crust and sedimentary column where the crust is coupled with the geological evolution of the basin. This approach allows estimating the eroded thickness during the main Tertiary uplift event and therefore the maximum temperature in the Late Cretaceous. The model is constrained by different types of paleo-thermo-chronometers and by 52 wells that are regionally distributed over the entire basin, resulting in a new regional thermal history of the PB. The amount of missing section in the Cretaceous chalk which mainly affected the eastern part of the basin is increased by up to 500m compared with previous studies and constitutes the key controlling factor of the temperature evolution. This new regional thermal history of the Paris Basin may be important for further analysis of the HC generation from the Lower Jurassic Toarcian source-rock and bring new insights into the geothermal potential of the basin.

A geometric model to estimate slip rates from terrace rotation above an offshore, listric thrust fault, Kaikōura, New Zealand

The Kaikōura Peninsula lies at the transition from subduction to continental collision at the southern end of the Hikurangi subduction system. This study uses a 2012 lidar survey over the Kaikōura Peninsula to re-map a flight of four uplifted Late Pleistocene marine terraces at high resolution. The lidar shows that the terraces are being progressively tilted landwards in a manner consistent with listric thrust faulting offshore. The fault, known as the Kaikōura Peninsula Fault, dips shallowly at c.30° to the northwest at depth and probably truncates the Seaward segment of the Hope Fault in the footwall of the Jordan Thrust. Geometric analysis of the tilt, using ages based on previous dating and a regional sea level curve, suggests that slip rates on the Kaikōura Peninsula Fault have ranged between 2.3 ± 1.5 mm/yr and 4.1 ± 1.3 mm/yr over the Late Pleistocene. The elevations of Late Holocene fringing beaches track regional sea level changes, apart from a departure indicating a single uplift event (penultimate earthquake) in the late 18th to earliest 19th century (1702–1838 CE), followed by uplift in the 2016 Kaikōura earthquake. The slip rate calculated from beach uplift, including the Kaikōura earthquake, is consistent with longer term rates. The accumulation of the slip over only c.220 years following >2000 years of quiescence suggests that the offshore thrust and associated faults exhibit clustered behavior, possibly as a result of keystone faulting.

New hypothesis to explain Quaternary forearc deformation and the variety of plate boundary earthquakes along the Suruga\u2013Nankai Trough by oblique subduction of undulations on the Philippine Sea Plate

Plate-boundary earthquakes of magnitude 8 or greater along the Suruga–Nankai Trough subduction zone have repeated at intervals of 90–150 years, but with widely varying magnitudes and rupture areas. We propose, based on geologic data on crustal movements of the forearc wedge, that these earthquake variations are controlled by two separate locked zones in the deeper part of the plate boundary. Long-wavelength topographic undulations, composed of alternating zones of uplift and subsidence along the forearc wedge, are associated with 2000 to 3000 m of vertical relief that has accumulated during Quaternary time. We suggest that this crustal deformation in the forearc wedge is caused not by stress loading and release during earthquake cycles, but rather by vertical displacements of the plate boundary caused by the westward movement of undulations in the obliquely subducting slab of the Philippine Sea Plate as it subducts beneath Southwest Japan. Dating of emergent marine shell fossil assemblages shows that the Kii Mountains, an uplift zone at the midpoint of the trough, has undergone uplift events at intervals of 400–600 year, and the latest event of those occurred when the 1707 Hoei earthquake ruptured the entire plate boundary along the trough. We infer that the plate boundary under the Kii Mountains is a locked zone and that slips of this zone, which accompanied ruptures of the entire plate boundary, caused uplift of the mountains by decreasing the plate boundary depth. A similar locked zone is inferred under the uplift zone of the Akaishi Mountains, along the eastern margin of the trough, and the 1854 Ansei earthquake pair was presumably caused by the slip of this zone. During the two 1854 events, the locked zone under the Kii Mountains presumably restricted the rupture propagation to the eastern half of the trough, then a rupture of the western half of the trough followed within 32 h. These locked zones are inferred to slip independently every few hundred years and determine the major patterns of characteristic ruptures along the Suruga–Nankai Trough.

Sedimentary sequence and evolutionary history of the Proterozoic basin at the southern margin of the North China Craton

Aulacogen/Rift system deposits and tectonic-magmatic activities can be linked to the breakup of the Columbia supercontinent and have developed in the North China Craton (NCC). The Xiong'er Basin at the southern margin of the NCC consists of late Palaeoproterozoic-Neoproterozoic sedimentary strata and can be divided into three sedimentary sequences. Sedimentary Sequence I (1.83–1.75 Ga) consists of bimodal volcanic-sedimentary rocks of the Xiong'er Group with continental-marine facies and alluvial fan deposits of the Bingmagou Formation with local development. It represents the evolution of the intracontinental fault from initiation to decline. Sedimentary Sequence II (1.75–1.6 Ga) developed after the southern margin of the NCC entered a stable continental margin stage, is dominated by clastic rocks interbedded with local carbonate deposits, and fills the interior of the basin. As continuous transgression led to a transition in the sedimentary environment, sedimentary Sequence III (1.6–1.4 Ga) is dominated by carbonate strata that began to develop afterwards. This sequence is the caprock deposit in the Xiong'er Basin. Subsequently, tectonic uplift events occurred at the southern margin of the NCC, along with the start of exposure and denudation, which lasted for hundreds of millions of years. Moreover, abundant microbially induced sedimentary structures (MISS) with different morphological characteristics developed in clastic strata across different areas of the Xiong'er Basin. These structures effectively indicate sedimentary facies and their evolution, which facilitates the establishment of regional stratigraphic isochronous correlation and connection. For example, based on the time limit for the development of molar-tooth structures (MTS), the Hejiazhai Formation belongs to the Neoproterozoic strata, with a deposition time of 1.0–0.72 Ga. In conclusion, the study of the Precambrian sedimentary succession in the Xiong'er Basin, in response to the supercontinental breakup, can be useful in exploring the coupling mechanisms between various geological events.

Taxonomy and phylogenetic relationship of zokors

Zokor (Myospalacinae) is one of the subterranean rodents, endemic to east Asia. Due to the convergent and parallel evolution induced by its special lifestyles, the controversies in morphological classification of zokor appeared at the level of family and genus. To resolve these controversies about taxonomy and phylogeny, the phylogenetic relationships of 20 species of Muroidea and six species of zokors were studied based on complete mitochondrial genome and mitochondrial Cytb gene, respectively. Phylogeny analysis of 20 species of Muroidea indicated that the zokor belonged to the family Spalacidae, and it was closer to mole rat rather than bamboo rat. Besides, by investigating the phylogenetic relationships of six species of zokors, the status of two genera of Eospalax and Myospalax was affirmed because the two clades differentiated in phylogenetic tree represented two types of zokors, convex occiput type and flat occiput type, respectively. In addition, the two origins in Eospalax were found diverged at 3.71 million years ago (Ma) based on estimation of divergence time. It is suggested that the climate and ecology changes caused by the Qinghai-Tibet Plateau uplift event in 3.6 Ma led to the inner divergence of Eospalax. The intraspecific phylogenetic relationships of partial zokors were well resolved, the two clades of Eospalax cansus represented two geographical populations, respectively, and the divergent pattern of Eospalax baileyi was characterized by allopatric divergence spatially. In this study, we explored the taxonomic status and phylogenetic relationships of Myospalacinae at the molecular level. These works would be significant to understanding the evolutionary process and to clarify the mechanism of differentiation of Myospalacinae.

Significant differences in invertebrate assemblages between low- and high-uplifted intertidal shores in the Simeulue Island, Indonesia, after a megathrust earthquake of 2004 and 2005

Co-seismic uplift provides significant effects on rocky intertidal assemblages. However, previous studies mainly focused on analysing invertebrate assemblages before and after the uplift event and are conducted in the Pacific Ocean region. The present study evaluated differences in invertebrate assemblages (i.e. species richness, species density, abundance, and composition) between low-uplifted (the uplift of ≤ 75 cm) and high-uplifted (the uplift of > 75 cm) intertidal shores in the Simeulue Island, Indonesia, after a megathrust earthquake of Indian Ocean in 2004 and 2005. The proportion of sediment types (i.e. clay, silt, sand, and gravel) was also analysed to determine their relationships to these assemblages. Invertebrate assemblages on high-uplifted intertidal shores showed lower species richness, higher abundance, and different compositions compared to those on low-uplifted intertidal shores. High-uplifted intertidal shores were dominated by Clypeomorus bifasciata (G.B. Sowerby II, 1855) (a cerithiid gastropod), while low-uplifted intertidal shores were dominated by Calcinus sp. (a hermit crab). Invertebrate assemblages were not significantly influenced by the proportion of most sediment types. These results indicate that co-seismic uplift should be considered in the management of rocky intertidal shores, especially those in the geologically active area.

The Ediacaran–Cambrian boundary: Evaluating stratigraphic completeness and the Great Unconformity

The Ediacaran–Cambrian transition was a time of marked biological and sedimentary changes, representing a significant evolutionary breakthrough in Earth’s history. Numerous explanations have been posited for these dramatic changes. One view emphasizes an extensive period of widespread continental denudation during the Neoproterozoic followed by extensive reworking of the basement during the early Cambrian, resulting in the formation of what is known as the “Great Unconformity”. Geologic events leading to the formation of this unconformity have been hypothesized as an environmental trigger for the Cambrian explosion. Here we review seventeen key Ediacaran-Cambrian successions around the globe with a focus on their sedimentary facies and sequence-stratigraphic architecture. Based on this information, we explore the relationship of the Ediacaran–Cambrian boundary to this unconformity, underscoring a more nuanced scenario. We consider each section in a chemostratigraphic and chronostratigraphic framework, and consider the hypothesized origin of this unconformity at each locale—for example, whether it was eustatic in origin and therefore of global stratigraphic significance or whether it resulted from local tectonics, implying marked inter-basin diachronism. Our systematic review shows that significant diachronism was involved in the generation of the Great Unconformity, suggesting that the sea-level fall reflects overprint of local tectonics on pure eustasy. In most places, the Great Unconformity is actually a composite sequence boundary resulting from successive eustatic episodes of sea-level rise and fall overprinted by multiple tectonic events of subsidence and uplift. Thus this surface should not be used for inter-basin correlations. Although the general proximity and common co-occurrence of the Ediacaran–Cambrian boundary with a sequence boundary (SB) in places resulting in fluvial valley incision, has proved challenging for biostratigraphic sampling, by mapping this unconformity and its associated facies, there are new opportunities. In particular, paleontological work in terminal Ediacaran deposits located in interfluve positions may be promising because these areas may have preserved thick shallow-marine strata below the SB. Such strata could hold additional clues to help fill in gaps in our understanding of the Ediacaran roots of the Cambrian explosion.

(U\u2013Th)/He thermochronometric mapping across the northeast Japan Arc: towards understanding mountain building in an island-arc setting

Topographic relief in arc-trench systems is thought to be formed by plate subduction; however, few quantitative investigations have so far been reported, with respect to the related mountain building process. This study applies apatite and zircon (U–Th)/He thermochronometry (AHe, ZHe, respectively) to Cretaceous granite rocks in the north part of the northeast (NE) Japan Arc to reveal its cooling/denudation history. Weighted mean AHe ages ranging from 88.6 to 0.9 Ma and ZHe ages from 83.9 to 7.4 Ma were determined for 10 rock samples. Using the AHe data, denudation rates were obtained for each sample. On the fore-arc side, denudation rates of < 0.05 mm/year were calculated, indicating a slow denudation process since the Paleogene. However, in the Ou Backbone Range and on the back-arc side, denudation rates at > 0.1–1.0 mm/year were computed, probably reflecting a recent uplift event since ~ 3–2 Ma. These data indicate a clear contrast in thermal and denudation histories between the tectonic units in this study area, similar to that previously reported from the southern part of NE Japan Arc. A comparison of the thermal/denudation histories between the N- and S- traverses, revealed the arc-parallel trend, the uplift model of the volcanic arc, and some minor variations of thermal/denudation histories in each tectonic unit. This study offers some further insights into the understanding of tectonic processes in an island-arc setting.

Geology and petroleum prospectivity of the Larne and Portpatrick basins, North Channel, offshore SW Scotland and Northern Ireland

The Larne and Portpatrick basins, located in the North Channel between SW Scotland and Northern Ireland, have been the target of a small programme of petroleum exploration activities since 1971. A total of five hydrocarbon exploration wells have been drilled within the two basins, although as of yet no commercial discoveries have been made. The presence of hydrocarbon shows alongside the discovery of two good-quality reservoir–seal couplets within Triassic and underlying Permian strata has encouraged exploration within the region. The focus of this study is to evaluate the geology and hydrocarbon prospectivity of the Portpatrick Basin and the offshore section of the Larne Basin. This is achieved through the use of seismic reflection data, and gravity and aeromagnetic data, alongside sedimentological, petrophysical and additional available datasets from both onshore and offshore wells, boreholes and previously published studies. The primary reservoir interval, the Lower–Middle Triassic Sherwood Sandstone Group ( c . 600–900 m gross thickness), is distributed across both basins and shows good to excellent porosity (10–25%) and permeability (10–1000 mD) within the Larne Basin. The Middle–Late Triassic Mercia Mudstone Group should provide an excellent top seal where present due to the presence of thick regionally extensive halite deposits, although differential erosion has removed this seal from the margins of the Larne and Portpatrick basins. The Carboniferous, which has been postulated to contain organic-rich source-rock horizons, as inferred from their presence in adjacent basins, has not yet been penetrated within the depocentre of either basin. There is, therefore, some degree of uncertainty regarding the quality and distribution of a potential source rock. The interpretation of seismic reflection profiles presented here, alongside the occurrence of hydrocarbon shows, indicates the presence of organic-rich pre-Permian sedimentary rocks within both basins. 1D petroleum system modelling of the Larne-2 borehole shows that the timing of hydrocarbon generation and migration within the basins is a significant risk, with many traps post-dating the primary hydrocarbon charge. Well-failure analysis has revealed that trap breach associated with kilometre-scale uplift events, and the drilling of wells off-structure due to a lack of good-quality subsurface data, have contributed to the lack of discoveries. While the Larne and Portpatrick basins have many elements required for a working petroleum system, along with supporting hydrocarbon shows, the high risks coupled with the small scale of potential discoveries makes the Portpatrick Basin and offshore section of the Larne Basin poorly prospective for oil and gas discovery. Thematic collection: This article is part of the Under-explored plays and frontier basins of the UK continental shelf collection available at: http://www.lyellcollection.org/cc/under-explored-plays-and-frontier-basins-of-the-uk-continental-shelf

Late Cenozoic tectono-geomorphologic evolution of the northern Tian Shan mountain range: Insight from U-Pb ages of detrital zircon grains from the Upper Oligocene-Quaternary sediments of the southern Junggar basin

Being one of the largest intra-continental orogens of the world, the Tian Shan orogenic belt was uplifted to its present elevation due to the far-field effect of the India-Asia convergence. In this study, we performed a systematic study on the Upper Oligocene-Quaternary sedimentary rocks from the southern Junggar basin, including conglomerate clast counting and detrital zircon U-Pb dating, to reconstruct the Late Cenozoic uplift history of the northern Tian Shan mountain range. The new detrital zircon U-Pb data provide new constrains on the Late Cenozoic intra-continental deformation of the Borohoro range. The Yili-Central Tian Shan and North Tian Shan were the major sources for the Junggar basin during the Latest Cretaceous-Paleogene period. At that time, the Borohoro range was characterized by low topography and wide drainage pattern. As the uplift of the North Tian Shan commenced at ~25–23 Ma, the high topography of the northern Borohoro range blocked the transport of sediments from the Yili-Central Tian Shan to the north. The North Tian Shan became the primary provenance area of the southern Junggar basin. According to sedimentary provenance analysis and geomorphologic survey, we infer that the Yili-Central Tian Shan started to uplift at 12–9 Ma. Combined with previously published data, our results suggest that the Middle Miocene uplift event most likely occurred in both the hinterland and foreland regions along the whole Tian Shan mountain range.

Chromitite genesis based on chrome-spinels and their inclusions in the Sartohay podiform chromitites in west Junggar of northwest China

Primary high-Al [Cr# = 100 × Cr/(Cr + Al) of 48.2–54.7] chromitites coupled with high-Cr (Cr# = 70.9–80.7) chromitite fragments are identified in the podiform chromitites hosted by the Sartohay ophiolitic mélange in west Junggar, northwest China. New petrographic and mineralogical data for chrome-spinels in both types of chromitites and their host harzburgites, as well as inclusions within chrome-spinels, are reported here to reveal the genesis of the Sartohay chromitites. Abundant primary monomineralic and polymineralic mineral inclusions including Na-phlogopite, enstatite, diopside, pargasite, olivine, rutile, ilmenite, sulphide, and occasionally zircon are found in the high-Al chromitites. Chemical compositions of these mineral inclusions indicate that the trapped melts are rich in H2O, Na2O, and TiO2. Temperatures and pressures estimated based on the equilibrium of mineral phases within inclusions are 812–992 ℃ and ~10.6 kbar, respectively. The calculated parental melt compositions (Al2O3 = 15.0–16.1 wt%; TiO2 = 0.30–0.96 wt%; Co = 37.0–48.2 ppm; Ga = 11.2–13.3 ppm) in equilibrium with high-Al chromitites suggest that these chromitites probably formed by the interaction between MORB-like melts and intermediate depleted harzburgites. In contrast, the high-Cr chromitite fragments with needle-shaped clinopyroxene lamellaes are entirely free of globular hydrous silicate inclusions. The parental melt compositions (Al2O3 = 10.3–12.2 wt%; TiO2 = 0.11–0.26 wt%; Co = 55.8–60.4 ppm; Ga = 13.4–17.2 ppm) in equilibrium with high-Cr chromitites show boninitic affinity. We propose that the high-Cr chromitites initially formed at an arc-related environment, then the deep recycling and uplift events occurred and resulted in high-Cr chromitites occurring as residual fragments in a back-arc basin spreading ridge. Subsequently, high-Al chromitites were formed and mechanically juxtaposed with the pre-existing high-Cr ones in the Sartohay ophiolitic mélange.

Depositional style changes during the Permo‐Carboniferous–Early Jurassic evolution of the Central Kalahari Karoo Sub‐basin, Botswana

The Permo‐Carboniferous–Lower Jurassic Karoo succession in the Central Kalahari Karoo Sub‐basin of Botswana is largely confined to the subsurface, and contains coal, coalbed methane and groundwater resources, similar to other Karoo strata throughout southern Africa. Characterization of the stratigraphic architecture (i.e., spatiotemporal stacking character of sedimentary facies) is essential for various aspects of subsurface resource prediction (e.g., resource parameters; reservoir architecture; mining feasibility). This study uses sedimentary facies analysis on borehole cores from central Botswana and sequence stratigraphic principles to resolve large‐scale depositional style changes during the evolution of the greater Kalahari Karoo Basin in southwestern Gondwana. The results show that changes in the Karoo stratigraphic architecture define two, large‐scale overall fining‐upward depositional sequences (i.e., Lower and Upper Karoo) that are marked by regional subaerial unconformities. These regionally mappable depositional sequences contain pairs of high‐ to low‐amalgamation units, which are typified by stacked, multistorey sandstone bodies, succeeded by finer grained units that are sometimes rich in coal (e.g., the Dukwi‐Makoro‐Kamotaka vs. the Morupule‐Serowe‐Tlhabala formations in the Lower Karoo; the lower versus upper Mosolotsane‐Ntane formations in the Upper Karoo). The large‐scale depositional style changes, reflecting base‐level fluctuations and variation in the balance between accommodation and sediment supply, resulted from climatic changes (e.g., Permo‐Carboniferous deglaciation), tectonic events (e.g., regional pre‐Mosolotsane uplift event), and marine incursions. The latter is documented, for the first time, via the marine‐influenced ichnofauna in the uppermost Ecca Group. Further refining this initial sequence stratigraphic framework for the Botswanan Karoo will require acquisition of radioisotopic dates (e.g., U–Pb zircon ages) and modern seismic reflection data.

Reversible subsidence on the North West Shelf of Australia

The Northwest Shelf (NWS) of Australia is characterized by offshore basins associated with Permian and Jurassic rifting and was only slowly subsiding by the Neogene. International Ocean Discovery Program (IODP) Expedition 356 targeted this region by coring four sites in the Northern Carnarvon and Roebuck Basins and two sites in the Perth Basin to the south on the Australian western margin. We use detailed lithological, physical property and age data with paleobathymetric interpretations, to infer tectonic subsidence apparently confined to the NWS that reverses (uplifts) with about the same amplitude and rate as an earlier subsidence event. About 300 m of tectonic subsidence occurred over one million years from 6 to 5 million years ago and then reverses when 300 m of tectonic uplift occurred from 2 to 1 Ma. The along strike extent of this subsidence pattern is ∼ 400 km. The similarity of magnitude and duration of the subsidence and uplift phases suggest that the subsidence is reversible. The results cannot be explained by glacial eustatic variability nor can the uplift event be attributed to sediments filling the accommodation space generated earlier. Reversible subsidence is a key fingerprint of dynamic topography. Although the rates of subsidence and uplift are roughly ∼ 300 m/Myr, a substantial portion of the changes occur over less than 1 Myr and the rates inferred from a detailed least squares analysis can reach up to about 500 m/Myr. These rates are incompatible with dynamic topography associated with motion of Australia over large-scale convection (10 to 40 m/Myr) or that associated with instability of the base of the lithosphere (<15 m/Myr). The vertical motions are too large to be associated with simple flexure of a plate and plate buckling in that the required amplitudes would lead to permanent deformation of the plate. A new geodynamic mechanism is required to fit the observations.

Uplift and exhumation events and thermochronological constraints at the end of Triassic in southwestern Ordos Basin

Uplift and exhumation events and thermochronological constraints at the end of Triassic in southwestern Ordos Basin

Along-strike variations in recent tectonic activity in the Santander Massif: New insights on landscape evolution in the Northern Andes

The integration of drainage analysis and topographic metrics provides excellent tools to assess the Quaternary tectonic activity modeling landscape evolution in evolving orogens. Furthermore, detecting active structures through the geomorphological analysis of landscapes helps to identify potentially seismogenic structures that could impact the socio-economic conditions in developing countries. Therefore, this paper presents a tectonic geomorphology study conducted on the Santander Massif (SM, Colombian Eastern Cordillera) and surrounding areas. The SM has structures with reported Quaternary activity such as the Bucaramanga, Morro Negro-Las Mercedes, and Chitagá faults, which summed to a poorly-constrained paleosismological history with significant shallow events is the prime incentive of this work. Our study is based on the acquisition of topographic data through swath profiles, local relief, slope variability, filtered topography, minimum bulk erosion, which along with geomorphic indices like the normalized concavity steepness (ksn), the hypsometric integral (HI), the ratio valley floor width to valley height (Vf) and normalized river profiles provided new insights on the recent landscape evolution in this part of the Northern Andes.We compared published apatite fission tracks (AFT) data for the study area with the uplift pattern deciphered from the geomorphic indices to detect the consistency in exhumation and denudation processes both in the long and short-term. Consequently, the central SM, as well as the faulted block between the Bucaramanga and Guamalito faults, evidence a highly-incised landscape with local relief values exceeding the 1500 m, then, responding with a sharp incision to recent surface uplift. Interestingly, this uplift pattern in central SM matches with published AFT data and is related to Neogene exhumation events controlled by secondary structures like the Suratá Fault. We attribute this exhumation event, and accelerated denudation rates within the SM, to the influence exerted by the “collision” between the SM and the Pamplona Indenter, leading to the unroofing of basement rocks at the deformation front (e.g., the Vetas High) and the topographic building of the range.For the upthrown block (hanging wall) of the Bucaramanga Fault, the occurrence of poorly-graded river profiles with an average concavity factor of 12.01, as well as irregular hypsometric curves with convex lower reaches, reinforce the hypothesis that late Cenozoic topographic rejuvenation in the SM was also forced by the tectonic activity of the Bucaramanga Fault. We expect empirical uplift rates >0.08 mm/yr (very high to high tectonic activity) for the mountain front encompassed between La Esperanza and Bucaramanga localities. We state this assumption since the mountain front delimited by the structure mentioned above is quite straight, it preserves remarkable morphostructural features and displays V-shaped valleys with an average Vf index of 0.38. This uplift rate is in good agreement with recent thermochronological exhumation rates (0.1 to > 0.3 mm/yr) published by Siravo et al. (2019).Higher uplift rates associated with the Bucaramanga Fault were also constrained with the erosion proxy index, i.e., the ksn index. High ksn values (above 128) were observed following a linear pattern, which in turn seems controlled by the main trace of the Bucaramanga Fault. For instance, the river system draining the western piedmont of the SM, near Aguachica, records slope-break knickpoints that we interpret as evidence of an incisional wave migrating upstream and adjusting a late Neogene uplift event associated with the Bucaramanga Fault. Conversely, the northern SM presents variable tectonic activity with the inner part, east of the Guamalito Fault, presenting low tectonic activity with little surface uplift and dominant strike-slip kinematics. We recognize the Ocaña-Ábrego zone as a relict landscape with well-preserved non-consolidated deposits that may record the initial exhumation and denudational pulses of the SM during the Andean Orogeny.

Reativação Tectônica Quaternária no Domínio Sul da Província Borborema, NE do Brasil: Integração de Dados Morfométricos, Geológicos e Geofísicos da Bacia do Rio Una

An integration of data in different scales was built aiming to identify possible effects of tectonic reactivations of Cenozoic origin (post-rift), related to the continental basement adjacent to the coastal zone of Pernambuco marginal basin, over which was formed the hydrographic basin of the Una River. The study was based in the integration of morphometric parameters of the Una River channel modeled with satellite radar imagery, geological data, and 2D multichannel shallow seismic data acquired over the river channel in the proximities of Barreiros and Palmares cities. Morphometric analysis comprised the calculation of the length-gradient index along the longitudinal profile of the Una River. Geological data were collected from basement outcrops near the cities of Barreiros and Palmares. Barreiras Formation outcrops located in the coastal basin, near the city of Sao Jose da Coroa Grande were also investigated. Analysis of longitudinal profile showed that the Una River channel was established over three planed surfaces, created by successive events of uplift and erosion of Borborema Plateau which controlled the compartmentation of this hydrographic basin. The calculation of length-gradient index showed the occurrence of first order anomalies in the middle course, and second order anomalies in the middle and low course of the river profile. Anomalies of first and second order are located over the main shear zones of the Pre-Cambrian basement, trending NE-SW. These anomalies are also related to younger fractures and faults trending NW-SE. Interpretation of seismic sections showed a series of high angle faults within the basement which affected Quaternary and holocenic deposits. The investigation also found faults in deposits of Barreiras Formation (Miocene) located in the coastal zone near the border of the Pernambuco Basin. Faults in basement rocks and in sedimentary deposits formed flower-like structures, which indicates the actuation of a transcurrent regime in the continental margin, with a maximum compression trending E-W and extension trending N-S. This regime affected the morphology of the Una River profile and the sedimentary deposits formed in its drainage basin.

A modeling and numerical simulation study of enhanced CO2 sequestration into deep saline formation: a strategy towards climate change mitigation

The net increase in anthropogenic carbon dioxide (CO2) emissions from fossil fuel combustion contributes significantly to the global warming and climate change. CO2 capture and storage (CCS) in geological formations, specifically in deep saline aquifers, is among the very promising strategies to control and mitigate emissions into the atmosphere. Injection of CO2 into a reservoir may result in the formation of pore pressure which can initiate cracks and trigger fault activities. CO2 may leak into the atmosphere and invade shallow groundwater sources. Release of CO2 into the atmosphere has enormous effects on the environment and significantly contributes to global climate change. Therefore, storage safety, injection efficiency, and monitoring remain crucially important considerations in CO2 injection. This study attempts to establish an optimal CO2 injection strategy that aims at enhancing CO2 storage with an increased safety at Ordos basin. Furthermore, it establishes the safety limits of CO2 plume migration from the central axis of the injection well. In the investigation, injection parameters such as injection rate and bottom hole pressure were analyzed. The CO2 plume migration analysis was performed, and migration limits were determined. Simulation results revealed that different formation layers have varying storage capacities and pressure withstanding ability. The site maximum storage rate goal of storing 100,000 t of CO2 per year was attained. It is advised to perform injection at the Majiagou layer due to sufficient storage capacity and greater depth of over 2400 m from the surface. This study recommends that an optimum CO2 sequestration strategy which does not result into excessive migration of injected CO2 plume and limit formation pressure buildup should be adopted. Therefore, deep underground storage at an average depth of above 2400 m is optimum, because it has an adequate storage space to accommodate the desired rate of 100,000 t/year. Besides, its geological settings favor storage safety in the event of significant uplift that may cause induced seismicity. Furthermore, it will also limit CO2 plume that may come into contact with shallow groundwater sources. Likewise, investing in low carbon and carbon-free energy technologies and enhancement of energy efficiency systems around the site is also recommended.

Fold-and-thrust deformation of the hinterland of Qilian Shan, northeastern Tibetan Plateau since Mesozoic with implications for the plateau growth

The northeastern margin of the Tibetan Plateau (NETP) represents an ideal site to probe the far-field effects and plateau growth in response to the collisions of Eurasia Continent with India Plate and intervening terranes. Here, we investigate the fold-and-thrust deformation of the Shule River region in the hinterland of Qilian Shan, NETP since Mesozoic, based on geological mapping and structural analysis to evaluate the role of multiple-phase deformation in plateau rise and growth. The structural style of the Shule River region is dominated by the foreland-verging Liuhuang Shan fold-and-thrust belt (LHTB) to the southwest and the hinterland-verging Tuolai Nan Shan fold-and-thrust belt (TLTB) to the northeast, separated by the Cenozoic Shule River intermontane basin. Integrated with published thermochronological, sedimentological and structural data, our study reveals four significant deformation phases in the NETP since the Mesozoic. During the Late Triassic to Early Jurassic time, the regional deformation spread in the NETP and produced the Jura-type folds and related thrusts of the LHTB in the study area under the NE-SW-directed compression, and was likely driven by the collision between the Qiangtang and Kunlun terranes. During the late Early Cretaceous, the continuous Lhasa-Qiangtang collision induced reactivation of the LHTB and an extensive exhumation event in the NETP. Since the Early Eocene, the upper crustal shortening and initial uplift of the NETP have accommodated the far-field stress of India-Eurasian collision. Given the widespread Miocene uplift event in the NETP, revealed by previous studies, we attribute the southwestward thrusting of the TLTB and tight-isoclinal syncline of the Oligocene-Miocene Baiyanghe Formation to the significant crustal shortening and topographical growth of NETP during the Early-Middle Miocene. The reactivation of TLTB and newly generated low-angle reverse faults represent gently tilted deformation and plateau growth in response to surface uplift of NETP as a whole since the Late Miocene. Our results imply that the multiple-phase deformation in the NETP since the Late Triassic should have been a first-order control on plateau growth.

Nucleotide diversity and demographic history of Pinus bungeana, an endangered conifer species endemic in China

AbstractOrographic and climatic oscillations have played crucial roles in shaping the nucleotide diversity and evolutionary history of many species across the Northern Hemisphere. In this study, based on 10 nuclear loci and a chloroplast DNA marker, we analyzed the nucleotide polymorphisms and demographic history of the endangered conifer species Pinus bungeana in Northwest China and investigated the phylogenetic relationships between P. bungeana and two related species, that is, Pinus gerardiana and Pinus squamata. We found that P. bungeana exhibited an extremely low level of nucleotide diversity (πsil = 0.00159). Demographic simulations based on DIYABC analysis showed that P. bungeana underwent demographic expansion and contraction during the Miocene. According to ecological niche modeling, we found that this species survived in situ during the glacial period and was not restricted to southern refugia. We speculate that P. bungeana may have experienced widespread population shrinkage from the Last Interglacial to the Last Glacial Maximum due to geological or climatic events. Isolation‐with‐migration analysis revealed that the divergence (~2.4–4.2 Ma) among P. bungeana and its related species was significantly associated with the Qinghai–Tibetan Plateau uplift events in the mid‐to‐late Tertiary period. Species tree analyses suggested that these three related Pinus species formed a monophyletic clade with high bootstrap support. These results suggest that the Miocene–Pliocene and Pleistocene geological and climatic fluctuations might have profoundly affected the nucleotide diversity and demography of this psychrotolerant conifer species in western China.