Cenozoic Faults Research Articles

Cenozoic faulting of the Ganzi-Yushu (Xianshuihe) fault from apatite (U-Th)/He ages and its implications for the tectonic reorganization in the southeastern Tibetan plateau

The Ganzi-Yushu-Xianshuihe fault that lies along the northeastern boundary of the Chuan-Dian crustal fragment provides the opportunity to study the tectonic evolution and geodynamic mechanisms of the southeastern Tibetan Plateau. Apatite (U-Th)/He data from an elevation transect provide robust evidence for the initiation of the Ganzi-Yushu fault. The consistent AHe ages of the lower samples constrain the onset of fault activity to 9.4 ± 1.5 Ma. Moreover, the zircon U-Pb dating and rare earth element (REE) analysis confirm that the Queer Shan and Gaogong granitic plutons were emplaced as a whole and then displaced by the Ganzi-Yushu fault. Combining the total offset of these two plutons and the onset timing of the fault activity yields a long-term average left-lateral strike-slip rate of 7.3–10.8 mm/yr for the Ganzi-Yushu fault. Based on the summarized synchronous deformation in the southeastern Tibetan Plateau, including the initiation of fault activity along the whole Ganzi-Yushu-Xianshuihe fault, the slip reversal of the Red River fault, and the fault activity along a series of left-slip faults in the Indochina block, we suggest that the southward extrusion of the Chuan-Dian crustal fragment and clockwise rotation around the Eastern Himalayan Syntaxis initiated at the middle-late Miocene (15-10 Ma).

Large non-karst caves of the Altai-Sayan mountain region: morphology and genesis

In the Altai-Sayan mountain region, located in southern Siberia, there are a number of caves developed in rocks in which karst processes are impossible to occur. In East Sayan, these are the Big Oreshnaya and Dudinskaya caves, the total length of which is more than 50 km and 35 km, respectively. Within the Altai Mountains, these are the Altaiskaya and Kek-Tash caves with a total length of 4.7 and 3.2 km, respectively. Mapping of the listed caves revealed that the morphology of their passages and the general structure differ significantly from those of caves in carbonate rocks. The passages have a flattened shape in cross section. Their width is usually meters and tens of meters, vertical extension is tens and hundreds of meters, and lateral extension is hundreds of meters. In general, the pattern of the passages is arranged in a box-like structure, where the pasages fit into a system of disjoint extended subvertical planes with rare short subvertical planes connecting them. The structure of the passages of the studied caves resembles the structure of karst caves, rotated vertically by 90°. The main directions of the passages there are not aligned in subhorizontal planes, but in subvertical ones. The revealed structure corresponds to the geometry of the structural pattern of Late Cenozoic fault systems formed as a result of subhorizontal compression. Signs of abundant argillization (alteration of the initial substance by hydrothermal processes and its replacement by newly formed clay minerals) were found in the studied caves. The formation mechanism of the studied caves is offered: removal of the substrate argillized by hydrothermal processes along the fault zones, by groundwater without significant participation of karst processes.

Cenozoic faulting leading to petroleum escape in SW Ordos Basin, China: Evidence from fault-related calcite in situ U-Pb dating, rare earth elements and fluid inclusions

Understanding the link between fault activity and movement to petroleum escape is crucial for assessing the petroleum exploration potential in sedimentary basins. As a significant petroliferous basin in China, the Ordos Basin hosts the world-class uncompartmentalized Jingbian natural gas field within the Ordovician marine carbonate reservoirs. However, the role of the unique exhumation history and the Cenozoic faulting in the formation of such large-scale oil-gas fields remain unclear. Our study combines fault-related calcite U-Pb dating with fluid inclusions analysis offers a unique opportunity to trace petroleum leakage along the the carbonate strata brittle fault zones in the SW Ordos Basin. Calcite samples collected from the carbonate fault zone and across the Ordovician carbonate strata in the SW Ordos Basin reveal clear positive Eu anomaly, slight positive Y anomaly, the lack of positive La and Gd anomalies, and the absence of a negative Ce anomaly. The Y/Ho ratios range from 29 to 36, with an average value of 32, indicating calcite formation in a hydrothermal environment during fault activation. U-Pb dating of these fault-related calcites yields ages of 32.8 ± 3.3 Ma and 23.7 ± 7.4 Ma. Raman spectroscopy of fluid inclusions reveals the presence of CH4 gas, coeval with the fault-related calcite. The homogenization temperatures (Th) of aqueous inclusions coeval with CH4 inclusion from two calcite veins range from 140.0 to 172.4 °C (average Th = 157.8 °C, n = 16) and 127.7–154.3 °C (average Th = 142.2 °C, n = 18). Low temperature thermochronology suggest rapid uplift since 40 Ma, potentially linked to fault activity. The Cenozoic erosion rate was 0.06 mm/y during the ∼9 Myr period from 32.8 to 23.7 Ma in the SW Ordos Basin, suggesting that Cenozoic faulting may have created permeable pathways for petroleum escape. This study provides a temporal link between Cenozoic uplift, faulting, and petroleum loss in SW Ordos Basin.

MIDDLE PLEISTOCENE NEOTECTONIC ACTIVATION OF THE MOUNTAIN BORDERING THE MUYA-KUANDA RIFT VALLEY (BAIKAL RIFT ZONE)

Geological and geomorphological studies of the northeastern branch of the Baikal rift zone have revealed structural features of sedimentary strata, as well as the features of lithology and interaction of heterochronous loose sedimentary complexes, block structure of rift valley bottoms and their mountain border, fault network, and activated Cenozoic faults. The Middle Pleistocene neotectonic uplift was identified on the southern slopes of the North Muya and the Kodar ranges and in the mountains bordering the Muya-Kuanda and Parama rift valleys. The authors have studied the parameters of this uplift, determined neotectonic movement amplitudes in the uplift areas, traced the marginal disjunctives and the kinematics of their movements, and identified homochromous sedimentary strata and determined their formation age.The activation of tectonic processes, during which the neotectonic uplift was formed, occurred in the early Middle Pleistocene, before the onset of glaciation. The formation of a dammed lake in the system of Muya-Kuanda rift valleys is associated with the tectonic damming of the Vitim River. During the Middle Pleistocene glaciation, the Kodar Range glaciers have twice formed the ice dams in the area of Lake Oron, which led to the emergence of dammed lakes in the Vitim valley connected with lakes in the Muya-Kuanda troughs. The shoreline of these lakes is preserved as a high rock terrace with an absolute height of 860±10 m along the perimeter of the rift valleys.In the Late Pleistocene, the terrace complex in the Muya-Kuanda rift valleys was mainly formed under the influence of climatic factor.

Time Constraints on the Late Cenozoic Fault Evolution Along the Northern Margin of the Iranian Plateau in the Arabia‐Eurasia Collision Zone

AbstractThe collisional Iranian Plateau and its recent kinematic evolution represent a natural example to study the intraplate response to the transferred deformation from an active convergent plate margin. The late Cenozoic deformation and structural evolution of the Plateau is not well understood. Here, we integrate structural, tectonostratigraphic, and morphotectonic field observations with low‐temperature thermochronometric data along the NW‐SE trending Kushk‐e‐Nosrat (KN) Fault to unravel the exhumation history and the kinematic change at the northwestern boundary of the Iranian Plateau. We found different sets of strike‐slip related structures along the KN Fault zone, which are classified into four categories based on their cross‐cutting relations and the superimposition of kinematic indicators. These include dextral transtension, dextral, dextral transpression, and sinistral kinematics. The unreset zircon (U‐Th)/He and apatite fission track results and the reset apatite (U‐Th)/He data from the restraining area along the KN Fault suggest 80–60°C of cooling during the early Miocene (∼20–18 Ma) and late Miocene–early Pliocene (∼7–5 Ma) due to dextral and dextral transpressional kinematics along the KN Fault zone, respectively. The dextral transtentional faulting was recorded as deposition of the Qom Formation within the releasing overlap areas along the KN Fault at >20–18 Ma. The kinematics of the KN Fault changed to sinistral during Pliocene–Quaternary times presumably triggered by the simultaneous clockwise rotation of central Iran, Alborz Mountains, and the South Caspian block. Our study proposes that the morphological and tectonostratigraphic evolution of the northern margin of the Iranian Plateau has mainly been controlled through local uplift and exhumation in restraining areas and local thick deposition in releasing areas of the major strike‐slip faults during the late Cenozoic time.

Limited Evidence of Late Quaternary Tectonic Surface Deformation in the Eastern Tennessee Seismic Zone, United States

ABSTRACT The ∼300-km-long eastern Tennessee seismic zone, United States, is the secondmost seismically active region east of the Rocky Mountains. Seismicity generally occurs below the Paleozoic fold-and-thrust belt within the Mesoproterozoic basement, at depths of 5–26 km, and earthquake magnitudes during the instrumental record have been moment magnitude (Mw) ≤4.8. Evidence of surface deformation may not exist or be difficult to detect because of the vegetated and soil-mantled landscape, landslides, locally steep topography, anthropogenic landscape modification, or long, irregular recurrence intervals between surface-rupturing earthquakes. Despite the deep seismicity, analog models indicate that accumulation of strike-slip or oblique-slip displacement at depth could be expected to propagate upward through the Paleozoic section, producing a detectable surficial signal of distributed faulting. To identify potential surface deformation, we interrogated the landscape at different spatial scales. We evaluated morphotectonic and channel metrics, such as channel sinuosity and catchment-scale hypsometry. In addition, we mapped possible fault-related topographic features on 1-m lidar data. Finally, we integrated our observations with available bedrock and Quaternary surficial mapping and subsurface geophysical data. At a regional scale, most morphotectonic and channel metrics have a strong lithologic control. Within smaller regions of similar lithology, we observe changes in landscape metrics like channel sinuosity and catchment-scale hypsometry that spatially correlate with new lineaments identified in this study and previously mapped east–west Cenozoic faults. These faults have apparent left-lateral offsets, are optimally oriented to slip in the current stress field, and match kinematics from the recent focal mechanisms, but do not clearly preserve evidence of late Pleistocene or Holocene tectonic surface deformation. Most newly mapped lineaments might be explained by either tectonic or nontectonic origins, such as fluvial or karst processes. We also reevaluated a previously described paleoseismic site and interpret that the exposure does not record evidence of late Pleistocene faulting but instead is explained by fluvial stratigraphy.

New Magnetotelluric Data Reveal Deep Fault Boundaries and Contrasting Late Cenozoic Fault Kinematics Between the Qilian Shan Thrust Wedge and Beishan‐Alxa Block, Western China

AbstractThe structural connectivity and kinematic relationship between the Altyn Tagh sinistral strike‐slip fault (ATF) and Qilian Shan fold‐and‐thrust belt along the north Tibetan margin east of 96°E is an important question for tectonicists interested in the evolving active deformation field of Central Asia and associated earthquake hazards of China's Hexi Corridor region. New results from a detailed 130‐km‐long N‐S magnetotelluric (MT) survey from the Qilian Shan to Beishan elucidates the locations and down‐dip orientations of major faults. Importantly, the results indicate that the Heishan‐Jinta’Nanshan fault system roots steeply into the lower crust, is unconnected to the Qilian Shan thrust wedge, and has reactivated the margin of the North China Craton and an older, regional ductile shear belt. The structurally linked ATF‐Heishan‐Jinta’Nanshan system defines a fundamental kinematic boundary in central Asia between the NE directed Qilian Shan thrust belt to the south and the eastwardly extruding Beishan‐Alxa Block to the north.

The Impact of Pre-Existing Faults on Fault Geometry during Multiphase Rifts: The Jiyang Depression, Eastern China

The combination of multi-phase extension and pre-existing fault reactivation results in a complex fault pattern within hydrocarbon-bearing basins, affecting hydrocarbon exploration at different stages. We used high-resolution 3D seismic data and well data to reveal the impact of multi-phase extension and pre-existing fault reactivation on Cenozoic fault pattern changes over time in the Jiyang Depression of eastern China. The results show that during the Paleocene, a portion of NW-striking pre-existing faults reactivated under NS extension and controlled the basin structure (type 1). Other parts of the NW-striking pre-existing faults stopped activity and served as weak surfaces, and a series of NNE-striking faults were distributed in an en-echelon pattern along the NW direction at shallow depths (type 2). In areas unaffected by pre-existing faults, NE-striking faults formed perpendicular to regional stresses. During the Eocene, the regional stresses shifted clockwise to near-NS extension, and many EW-striking faults developed within the basin. The NE-striking faults and the EW-striking faults were hard-linked, forming the ENE-striking curved faults that controlled the structure in the basin (type 3). The NNE-striking faults were distinctly strike-slip at this time, with the ENE-striking faults forming a horsetail pattern at their tails. Many ENE-striking faults perpendicular to the extension direction were formed in areas where the basement was more stable and pre-existing faults were not developed (type 4). There were also developing NS-striking faults that were small in scale and appeared in positions overlapping different main faults (type 5). Additionally, different fault patterns can guide different phases of hydrocarbon exploration. Type 1, type 2, and type 3 faults are particularly suitable for early-stage exploration. In contrast, type 4 and type 5 faults are more appropriate for mature exploration areas, where they may reveal smaller hydrocarbon reservoirs.

Chemical Characterization and Genesis of Thermal Reservoir Water in the Southern Part of the Jizhong Depression

The Jizhong Depression is a typical Mesozoic and Cenozoic fault basin located in the northwestern part of the Bohai Bay Basin that has abundant hydrothermal and geothermal resources and enormous development potential. In this study, hydrochemical and isotopic analyses were conducted on water samples from the southern region of the Jizhong Depression. The formation and evolution processes of the deep geothermal water were analyzed, the circulation process of the deep geothermal water was determined, and the genetic mechanism of the geothermal systems was elucidated. The hydrochemical types of the geothermal fluids in the sandstone reservoirs in the research area are mainly Cl·HCO3−Na type, while the geothermal fluids in the carbonate reservoirs are mainly Cl-Na type and Cl·HCO3−Na type. The ion components in the geothermal water are mainly controlled by the dissolution of the carbonate rocks and the alternate adsorption of cations. The elevation of the geothermal water supply area is 763–1063 m, and the main source is precipitation from the mountainous areas in the western Taihang Mountains. The Na-K-Ca temperature scale and multi-mineral equilibrium method have relatively small errors and are suitable for the southern region of the Jizhong Depression, with average errors of 21.44 °C and 32.64 °C, respectively. The depth of the Jxw thermal storage cycle in the research area is 3033–5187 m, and the depth of the Ng thermal storage cycle is 1360–2862 m. The content of the main ions (Na+, K+, and Cl−) in the water samples of the study area is greater in the Jxw thermal storage than in the Ng thermal storage; the Jxw thermal storage water samples have lower γNa+/γCl− values than the Ng thermal storage; and the γSO42−/γCl− and γCl−/(γHCO3− + CO32−) values are greater than those of the Ng thermal storage, indicating that the Jxw thermal storage is located in a geological environment with better sealing, longer flow, slower water circulation, more complete leaching, and higher salinity than the Ng thermal storage. Part of the deep thermal storage is transmitted upwards through the rocks via thermal conduction, and part is transmitted upwards along fault channels via thermal convection, forming a convection–conduction-type geothermal system.

The development and origin of the two-stage silicification of Upper Jurassic limestones from the northern part of the Kraków-Częstochowa Upland (Southern Poland)

The Upper Jurassic carbonates representing the microbial-sponge megafacies in the area of the Kraków-Częstochowa Upland (KCU) were locally silicified. In the reclaimed Lipówki Quarry, in Rudniki near Częstochowa (in the northern part of the Upland), macroscopically different silicification products were observed in blocks of Upper Jurassic limestones, deposited as mining waste. Two varieties were distinguished: (i) chert concretions representing the I silicification stage and (ii) light-brown, silicified limestones infilling the fractures in chert concretions or forming the cortices around the concretions or forming irregular bodies, all representing the II silicification stage. The diagnostic features are the following: (i) macroscopic development, (ii) the presence of moganite exclusively in chert concretions and (iii) significant differences in crystallinity index (CI) values, namely: 0.1–0.7 for chert concretions and 6.0–6.6 for silicified limestones. The formation of chert concretions was initiated as early as in unconsolidated sediment, whereas the II silicification stage followed the chemical compaction of the limestones. The results of geochemical analyses of the products of both silicification stages indicated that the probable source of silica were the low-temperature hydrothermal solutions. Two types of fractures were found in the chert concretions, generated during different tectonic events. The older, open fractures were formed during the extension of the Late Jurassic sedimentary basin, which formerly occupied the territory of the more recent KCU. These fractures were infilled with unconsolidated, fine-detrital carbonate sediment, in which the concretions were embedded and finally silicified in the II silicification stage. The younger, closed fractures, transversal to those filled by the products of II silicification stage, along which small displacements are evident, document the later tectonic deformations presumably related to Cenozoic faulting.

RELATIONSHIP BETWEEN THE PALEOZOIC AND CENOSIOIC FAULTING ENSEMBLES IN THE WESTERN PART OF THE ALTAI-SAYAN FOLDED AREA

Fault structures in folded areas are an important element of the geological structure. Their age and history of development affect seismicity, distribution of minerals, and engineering and geological characteristics of the area. The geological structure of the Altai-Sayan folded area was mainly formed during the Paleozoic and transformed during the Cenozoic activation. Geoinformation methods and technologies were used to compare between the Paleozoic and Cenozoic fault networks. It is shown that the degree of reactivation of the Paleozoic faults varies greatly within the territory.Conjugate analysis of the orientation and spatial distribution of faults of different ages in the study area does not confirm that the Cenozoic fault system was formed by reactivation or inherited development of the Paleozoic fault system. These two systems arose at different compression orientations. The left-lateral strike-slip ensemble was formed under sublatitudinal compression in the Paleozoic, and the right-lateral strike-slip ensemble - under submeridional compression in the Cenozoic. A significant coincidence between the directions of the main faults of different ages is due to their dominant strike along the boundaries of the accretionary complexes in the region.

Structural characteristics and genetic mechanism of transfer zones in an extensional rift zone: An example from the Xihu Sag, East China Sea Basin

The Xihu rift zone within the East China Sea Shelf Basin (ECSSB) is governed by NE-striking segmented extensional faults, which were formed by Cenozoic orthogonal NW-SE extension. However, the segmentation of the NE-striking faults has up to now received only limited attention. Here, we employ seismic data, information about pre-existing faults, the Cenozoic fault system, and fault activity rate to analyze the structural characteristics and genetic mechanism of the transfer zones in the Xihu sag. Our results demonstrate that: (1) The Cenozoic structures and evolution of the Xihu sag are fundamentally controlled by the NE-striking extensional faults, while showing influence from the pre-existing NW-striking basement structures. (2) The transfer zones are preliminarily recognized on the fault system map along the bottom of the Pinghu Formation (T40 surface, ∼43 Ma), which is segmented by the NE-striking faults. The cross faults are identified in the transfer zones, which are commonly truncated by the T30 (∼33.9 Ma) surface and above the T100 (∼66 Ma) surface. These faults are generally composed of strike-slip structures. In addition, the transfer zones are primarily developed above the pre-existing NW-striking basement faults. (3) A hybrid genetic model is proposed to interpret the formation of the NW-striking strike-slip transfer zones in the Xihu sag, including the influence of the pre-existing NW-striking basement faults, and the different extensions along the rifts. Finally, six genetic-mechanism-structural models are established for general cases, based on whether the pre-existing faults are developed and the different extensions existed or not. This study may have significant implication for future study on the transfer zones in this area.

Cenozoic Fault Growth Mechanisms in the Outer Apulian Platform

This work focuses on a ca. 55 km-long extensional fault zone buried underneath the foredeep deposits of the southern Apennines, Italy, with the goal of deciphering the Cenozoic fault growth mechanisms in the Outer Apulian Platform. By considering public 2D seismic reflection profiles, well logs, and isochron maps data, the study normal fault zone is interpreted as made up of four individual fault segments crosscutting Top Cretaceous, Top Eocene, Top Miocene, and Top Pliocene chrono-stratigraphic surfaces. The computed cumulative throw profiles form either bell-shaped or flat-shaped geometries along portions of the single fault segments. The computed incremental throw profiles also show an initial fault segmentation not corresponding with the present-day structural configuration. Data are consistent with the initial, post-Cretaceous fault segments coalescing together during Miocene–Pliocene deformation and with fault linkage processes localizing at the stepover/relay zones. Pleistocene faulting determined the evolution of a coherent fault system. The computed n-values obtained for the single time intervals by considering the maximum fault throw–fault length relations indicate that the fault segments formed scale-dependent geometries. Variations of these computed values are interpreted as due to the higher degree of maturity reached by the entire fault system during Miocene to Pleistocene deformation.

Multiphase faults activation in the southwest Huizhou Sag, Pearl River Mouth basin: Insights from 3D seismic data

The southwest Huizhou Sag is located in the Zhu I depression in the northern part of Pearl River Mouth Basin, which is influenced by the pre-existing basement fabrics and multiphase rifting, and has complex fault patterns in the Cenozoic. Using 3D seismic data of the southwest Huizhou Sag, we used seismic interpretation, fault pattern analysis from isochron maps, detailed fault throw analysis and structural evolution section analysis to constrain the initial formation timing, active periods and genesis of different striking normal faults, and the influence of basement faults on Cenozoic faults and the evolution progress of the sag was discussed, which significantly improve our understanding on the tectonic evolution of the northern Pearl River Mouth Basin. There are four groups of faults developed in the southwest Huizhou Sag, consisting of NE-SW, ENE-WSW, E-W and WNW-ESE striking, and the boundary faults of the subsag are mostly curved. Selective reactivation of ENE-WSW and WNW-ESW striking basement faults controlled the evolution of fault system during the Cenozoic. The southwest Huizhou Sag experienced multiple phases of extension, and the extension direction rotated clockwise from NW-SE to NNE-SSW. During the Early Eocene (Rift Ia), a large number of NE-SW striking faults were formed, accompanied by reactivation of ENE-WSW and WNW-ESW striking basement faults. These group of faults continued to be active during the Middle Eocene (Rift Ib) and some ENE-WSW striking faults were newly formed. The Late Eocene to Early Oligocene (Rift II) was dominated by E-W striking faults, and the depocenter shifted to the northwestern part of the study area. The Middle-Late Oligocene to Quaternary (Post-rift) was dominated by WNW-ESE striking faults, and the depocenter was not obvious.

АНАЛИЗ ЭФФЕКТИВНОСТИ ПРОГРАММНЫХ КОМПЛЕКСОВ ЭЛЕКТРОТОМОГРАФИИ ДЛЯ ИНТЕРПРЕТАЦИИ ПОЛЕВЫХ ДАННЫХ В СЕЙСМОАКТИВНЫХ РАЙОНАХ (НА ПРИМЕРЕ ГОРНОГО АЛТАЯ)

Since 2004, regular investigations with the use of electrical exploration methods have been conducting by researchers of Institute of Petroleum Geology and Geophysics SB RAS on the territory of the Gorny Altai. The electrotomography method is used to construct geoelectric models of the upper section part to depths of several tens of meters. One of the important tasks of this method is to determine characters of fault zones. Large regional Cenozoic faults are distinguished by significant shifts and are usually well manifested in relief. Intradepression interblock faults overlaid by sedimentary deposits are hard to identify by geological methods, but they are reflected mainly by zones with a reduced value of electrical resistance in sections according to electrotomography data. The paper considers practical examples of the ET method use for studying fault structures of the Gorny Altai. Analysis of the accumulated volume of electrotomography field data allowed researchers to compile typical models simulating the fault structures of this territory. The results of simulated data inversion obtained by numerical modeling of fault zones of the Gorny Altai using well-known third-party programs and proprietary developments are compared. The capabilities of different software systems are analyzed for interpretation of electrotomography data.

New 3D fault model for eastern Flanders (Belgium) providing insights on the major deformation phases in the region since the late Paleozoic

A new 3D fault model was created for the Upper Paleozoic to Cenozoic subsurface in eastern Flanders (Belgium). The model was based on the integration of 2D seismic interpretations, borehole and gravimetric data, as well as coal mining and topographic maps. Four major tectonic phases, taking place during the latest Paleozoic, Jurassic, Late Cretaceous and Cenozoic, shaped the fault network. The latest Paleozoic phase was transpressional and expressed by local folding of the Carboniferous strata underneath the base Permian unconformity. The largest anticlines were asymmetric, with amplitudes of up to 500 m and SSW-NNE oriented axal planes. The subsequent Jurassic phase caused normal faulting across the area, resulting in the development of the northeast-dipping, western border fault systems of the Campine Basin and Roer Valley Graben. Fault strikes were predominantly WNW-ESE to NNW-SSE. Both fault directions were most likely inherited from early Carboniferous and older tectonic phases. Jurassic fault reactivation explains the activity along fault populations with different orientations as well as the linkage of these faults into long (>10 km) systems, despite displaying generally relatively small vertical throws (<500 m). Soft-linked boundaries (accommodation zones) between Jurassic fault domains are located on top of the largest latest Paleozoic transpressional anticlines.The Late Cretaceous major tectonic phase was compressional and involved inversion of the Roer Valley Graben with subsequent subsidence and carbonate deposition in the flanking Campine Block.During the Cenozoic extensional phase, most normal faults that developed were rooted in Jurassic faults and therefore displayed similar WNW-ESE to NNW-SSE strikes. Cenozoic extension was, however, weaker than Jurassic extension; Cenozoic fault numbers, lengths and vertical throws were smaller than during the Jurassic phase. Also during the Cenozoic phase, faulting was more localized onto the pre-existing Roer Valley Graben border fault system compared to the more diffuse Jurassic faulting. The Cenozoic faults were generally planar, whereas some of its Jurassic roots near and in the border fault system of the Roer Valley Graben were listric.

Late Cretaceous–Early Cenozoic exhumation across the Yalong thrust belt in eastern Tibet and its implications for outward plateau growth

Rapid denudation and uplift of eastern Tibet have accelerated during the Late Miocene due to lateral lower crustal flow, without a significant contribution from upper crustal shortening. However, growing lines of evidence have revealed that Early Cenozoic faulting controlled enhanced denudation and shortening. Here, we report 51 new zircon and apatite (U Th)/He and apatite fission-track ages from seven granite samples along one primary branch fault (the Yunongxi fault) of the Yalong thrust belt in eastern Tibet. Cooling ages and inverse thermal modeling revealed two pulses of accelerated exhumation during the Late Cretaceous (70–65 Ma) and the Late Eocene–Early Oligocene (40–30 Ma). We suspect that the surface uplift of eastern Tibet, due to the convergence rate acceleration between India and Eurasia, triggered the first cooling stage. A synchronous out-of-pace Early Cenozoic cooling pattern across the Yunongxi fault was further identified and could be due to fault initiation at ca. 40–30 Ma. We argue that the Late Eocene–Early Oligocene rapid cooling and exhumation and the associated outward plateau growth were primarily accommodated through upper-crust faulting along the Yalong–Longmen Shan thrust belt. This deformation pulse was the first-stage response of fault activity to the India–Eurasia collision in eastern Tibet. More extensive Late Miocene deformation driven by lateral lower crustal flow consequently bypassed these early-stage fault systems and overwhelmed the Late Cretaceous and Late Eocene–Early Oligocene deformation in eastern Tibet. • The footwall of Yunongxi fault underwent accelerated exhumation during the Late Cretaceous and Late Eocene–Early Oligocene. • The striking differential cooling across the Yunongxi fault was most likely due to fault initiation ca. 40–30 Ma. • The second exhumation pulse was the first-stage response of fault activity to the India–Eurasia collision in eastern Tibet.

The structure and role of faulting and fracturing system in spatial oil saturation of rocks and in occurrence of oil reservoirs within Chezhen sag of Jiyang depression in the Bohai Bay Basin in East China

The article reports the integrated analysis of the history, geodynamics, modern faulting system, internal structure and spatial occurrence of Paleozoic and Paleogene (Eocene) accumulations of oil in the promising Chezhen block of the Chezhen sag of the Jiyang depression in the Bohai Bay Basin in East China. After review of the new geological, geophysical and field studies, the authors find out that in this structurally complex system of faults and fractures of different age, orientation and types, the present-day spatial occurrence of oil reservoirs is governed by the neofaults which blanket the whole geological section, including the Paleozoic period. The studies (analysis of polished sections) into internal structure (micro fracturing) and oil saturation of rocks produce some new data of interest for the theory and practice. The studies of samples from the reservoir and non-reservoir rocks in exploration drilling in the Shahejie pay horizon show that oil saturation is connected with the presence of the younger age system of micro fractures (permeable) of horizontal and vertical (faults) orientation. The further exploration in the promising Chezhen block of the Shenli oil field is recommended to continue in the zones of the Cenozoic faults as any rocks (irrespective of their lithology, including low-porosity rocks) can be saturated with oil in these zones which contain the best-type reservoirs (fractured) and feature active fluid neodynamics.

Further evidence for the East Coast fault system and faults associated with the Summerville restraining bend and their possible relationship to the 1886 Charleston, South Carolina, earthquake, USA

The integration of aeromagnetic, LiDAR, and previously acquired seismic-reflection data and surficial geologic maps supports the existence of the East Coast fault system ( and faults associated with its 12⁰ Summerville restraining bend beneath the South Carolina Coastal Plain. Aeromagnetic data revealed a 10- to 15-km-wide zone of subtle, 22- to 35-km-long linear magnetic anomalies trending ~N10°E across the southern meizoseismal area of the 1886 Charleston earthquake that we postulate are associated with Cenozoic low-displacement brittle faults in the crystalline basement west of Charleston. We hypothesize that lineaments ML4 and ML5 represent the principal displacement zone along the southern end of the ECFS because they coincide with steeply dipping, west-side-up buried faults interpreted from previously acquired seismic-reflection profiles and a ~320-m dextral offset in the Brownsville Pleistocene beach ridge deposit. The alignment of the NNE-SSW-oriented Edisto dome, uplift along releveling line 9, gently upwarped longitudinal profiles along the Caw Caw and Horse Savanna swamps, local incision along the Ashley River, and exposures of the early Oligocene Ashley Formation near the incised part of the Ashley River support Quaternary uplift along the southern ECFS. The 12⁰ change in trend formed by lineaments ML4 and ML5 supports the existence of the Summerville restraining bend in the ECFS, east of which are numerous ENE-WSW- to NW-SE-oriented LiDAR lineaments that we postulate are surface expressions of faults that formed to compensate for the increased compression produced by dextral motion along the bend. Sinistral displacement along one of these proposed faults associated with the ~40-km-long, east-west-oriented Deer Park lineament may have produced the main shock of the 1886 Charleston earthquake.&#x0D; &#x0D;

The Influence of Basement Terranes on Tectonic Deformation: Joint Earthquake Travel‐Time and Ambient Noise Tomography of the Southern South Island, New Zealand

AbstractDetermining how the crustal structure developed in previous tectonic regimes influences current deformation is important for understanding seismogenic behavior. Paleozoic‐Mesozoic convergent‐margin tectonics produced the southeastern South Island crust, which is currently involved in late Cenozoic transpressional collision. We examine crustal velocity structure through joint inversion of earthquake travel times and ambient noise derived group velocities to increase the resolution of Vp (P‐wave velocity) and Vp/Vs across the region. This method improves the details of the shallow velocity structure and highlights lithological properties, uplifted regions, and distributed fracture zones. The Otago schist shows thick lower crust while contrasting higher Vp below 15 km depth characterizes the Matai terrane and Median batholith, both backstops during accretion and deformation. The complex velocity structure, integrated with late Cenozoic faults, structural domains, seismicity patterns, and geodynamic modeling, shows how Cenozoic structures relate to deeper properties. Seismicity within the schist is distributed within transition regions rather than along specific faults, and these zones contain low Vp and low Qp (1/attenuation). The most prominent seismicity zone is along the transition from northern Otago ranges to the Southern Alps, where faulting and brittle deformation corresponds to the eastern edge of ductile crustal thickening above the bending of the strong oceanic lower crust. The thick weak crust rheology of Otago, relative to Canterbury, enables broad deformation, with numerous late Cenozoic faults that may not persist to great depth. Along the southern stronger plutonic terranes, there is a band of sparse deeper (15–35 km) seismicity, consistent with strong elastic brittle crust.