Strong Tectonic Activity Research Articles

Yilan crater, a newly identified impact structure in northeast China

This study reports the discovery of Yilan crater, a newly identified impact structure in northeast China. The crater has a rim-to-rim diameter of 1.85 km, and is located in Yilan County of Heilongjiang Province. The latitude and longitude coordinates of the crater are 46°23′03″N and 129°18′40″E, respectively. The crater lies in a low mountainous and hilly area of the southwest border of the Xiaoxinganling mountain range. Most of the crater is covered with dense forests. Geotectonically, the area belongs to the eastern Central Asian Orogenic Belt where strong tectonic and magmatic activities have occurred since the late Proterozoic. The crater was entirely formed within the bedrock of Cretaceous granite and appears as a bowl-shaped structure. Approximately one-third of the southern part of the crater rim has been significantly eroded and mostly removed; otherwise, most of the crater rim is well preserved. In a panoramic view, the crater appears as an unclosed ring mountain surrounding a circular depression, and it has steep walls and a relatively flat floor. The crater rim raises approximately 70–120 m above the surrounding terrain. The maximum elevation of the crater rim over the present crater floor is approximately 150 m. Most of the crater rim is composed of granite impact breccia varying from granules to boulders in size. The crater’s interior has been filled by a large amount of granite impact breccia at the bottom and lacustrine deposits at the top. The target rock of granite contains abundant quartz. This study investigated the planar deformation features (PDFs) in the quartz, which is one of the commonest shock metamorphic features in numerous terrestrial impact structures. For the investigation, granite impact breccia was collected from the crater floor. Most of the samples were made into polished thin sections for identifying the PDFs in quartz. Some fine-grained fragments of quartz were also collected from the samples for observation and analysis. The crystallographic orientations of the quartz PDFs were observed on a 4-axis universal stage under an optical microscope. No PDFs in quartz were observed in the quartz of large granite breccia fragments, but many PDFs appeared in the quartz of the fine-grained samples. One to four sets of PDFs in quartz were observed. The forms of the PDFs with Miller indices, such as (0001), { 10 1 ¯ 1 } and { 10 1 ¯ 3 }, were indexed. The observed multiple sets of PDFs in quartz provide unambiguous evidence of shock-metamorphism and confirm an impact origin of the structure. The topographic and structural features of the crater, as well as the occurrences of crater-filled materials (impact breccia and lacustrine deposits), characterize a bolide impact site. Based on 14C dating of the lacustrine deposits from the crater floor, the Crater Lake disappeared approximately 10 ka ago; this disappearance can be related to the loss of crater rim in the southern part of the crater. The large-scale absence of the crater rim cannot be explained by tectonic activity, normal weathering, or erosional process, and must correspond to directional erosion caused by a specific exogenic geological process after the formation of the impact crater. The geologic agent, mechanism, and history of the strong erosion of the crater rim require further investigation. The Yilan crater is the second confirmed impact structure in a large country (China) with an area of 9.6 million square kilometers.

Characteristics and Mechanism of Loess Landslides Induced by Strong Earthquake in The Loess Plateau of China

The Loess Plateau is the main loess distribution area in China with strong tectonic activity and frequent earthquakes. This paper systematically summarizes the characteristics and mechanism of loess landslides induced by strong earthquakes. The geometric characteristics of loess seismic landslide are gentle slope with 10°∼25°. The motion characteristics of earthquake-induced loess landslides are high-speed and long-distance. The distribution characteristics of loess seismic landslides are also basically consistent with the distribution of earthquake active region, and mainly distribute in loess hilly and gully area or the edges of the loess tableland. Based on the mechanism of seismic instability of loess slope, we consider that there are three types of loess landslides: seismic subsidence type, liquefaction type and tension-shear coupling type.

Tectonic uplift of the northern Qinling Mountains (Central China) during the late Cenozoic: Evidence from DEM-based geomorphological analysis

The Qinling Mountains, which stretch from east to west in Central China, represent an important geological and geographical boundary between North China and South China. Because of the northeastward growth of the Tibetan Plateau since the late Cenozoic, the northern Qinling Mountains have been strongly reactivated and uplifted. To investigate the landscape response to the tectonic uplift, the geomorphic indices of the northern Qinling Mountains, including the hypsometry, mathematical function of the longitudinal profile, channel longitudinal profile, and steepness index were analyzed. The topographic analysis reveals that the landscape evolution of the Heihe River Basin is in a transient state. The upstream of the Heihe River Basin has undergone a long period of erosion and represents relict landscape. In contrast, the downstream represents adjusting landscape, which formed by river incision in response to the rapid uplift of the northern Qinling Mountains. This is a result of the extension of the Weihe Graben, which has formed due to the northeastward growth of the Tibetan Plateau during the late Cenozoic. The spatial distribution of the geomorphic indices reveals that the NE striking Taibai Fault has experienced strong tectonic activity since the late Cenozoic and is a secondary fault that accelerated the uplift rate of the northern Qinling Mountains. The tectonic stress due to the northeastward growth of the Tibetan Plateau has been transmitted to the northern Qinling Mountains along the Taibai Fault. Therefore, we proposed that the uplift of the northern Qinling Mountains is due to the combined effects of the Weihe Graben extension and Taibai Fault activity, forming the highest peak (Taibai Mountain) of the northern Qinling Mountains near the intersection of the Qinling Piedmont Fault and Taibai Fault.

Relationships between tectonic activity and sedimentary source‐to‐sink system parameters in a lacustrine rift basin: A quantitative case study of the Huanghekou Depression (Bohai Bay Basin, E China)

AbstractLacustrine rift basins commonly preserve a fairly complete record of the sediment source‐to‐sink (S2S) system, and consequently may form an ideal natural laboratory for establishing quantitative relationships between the various elements within the S2S system. The tectonic‐activity rate in the source (e.g., fault‐growth rate and fault‐activity rate), accommodation space and depositional system in the sink (e.g., areal extent and volume, as well as the depositional dip of the fan‐ and braid‐deltas) are genetically related and their quantitative correlations are explored. The Palaeogene succession on the southwestern margin of the Huanghekou Depressionin the Bohai Bay Basin, one of the largest lacustrine rift basins in eastern China, was chosen to study these relationships, using 3‐D seismic, core and well‐log data. The tectonic activity was strongly related to the sediment supply, accommodation space and morphology of the sink area. Three different rates of tectonic activity are identified; these led to changes in the basic features of the S2S system that influenced each other. In Members 4 and 3 (lower unit) of the Shahejie Fm. (40.44–44.7 Ma), strong tectonic activity led to significant uplift, resulting in the widest exposure of the provenance area to erosion, to a high sediment‐supply rate, to a steep slope and to a large accommodation space which controlled the development of several fan‐deltas with steep progradational angles. In Member 3 (upper unit) of Shahejie Fm. (37.89–40.44 Ma) and Member 3 of Dongying Fm. (30.2–33.28 Ma), decreased tectonic activity led to slower uplifting, resulting in a wider alluvial plain, longer transport distances, a lower sediment‐supply rate and less accommodation space, so that braid‐deltas with larger volumes and a gentler slope developed; In Members 1 and 2 of Shahejie Fm. (33.28–37.89 Ma) and Member 2 of Dongying Fm. (26.71–30.2 Ma), still further decreasing tectonic activity led to a still lower sediment‐supply rate, a more gentle depositional slope, less accommodation space, and the development of several braid‐deltas with a gentle angle. The quantitative relationships established here advance our understanding of the relationships within lacustrine source‐to‐sink systems, especially for tectonically controlled rift basins.

Geomorphic evolution and neotectonics of the Qianhe River Basin on the southwest margin of the Ordos Block, North China

The Qianhe River Basin is located at the convergence zone of the northeastern margin of the Tibetan Plateau (NETP), the Ordos Block and the Qinling Mountains. A tectonic geomorphology study of the Qianhe River is significant for providing a deeper understanding of the tectonic transition between the NETP and the Ordos Block and the dynamic relationship of these three tectonic units. Based on Advanced Spaceborne Thermal Emission and Reflection global digital elevation model (ASTER-GDEM) data and geographic information system (GIS) techniques, four tectonic geomorphic indices, the hypsometric integral (HI), stream length-gradient (SL), drainage basin asymmetry (AF), and drainage basin shape (BS), were calculated and analyzed. Geologic evidence from field surveys, deformation measurements, and fault slip rate estimates was also obtained to further discuss the tectonic activity and tectonic geomorphic evolution model. Through analytical comparisons, we proposed that the variations in the applied geomorphic index values were not significantly affected by climate and lithology but indicated variations in related tectonic activity. The geomorphic index value analysis suggested relatively strong tectonic activity in Liupanshan Mountain and Longshan Mountain and northwestward tectonic tilting of the southwest margin of the Ordos Block. The actual mechanisms responsible for the observed variations in the Qianhe River Basin are the rapid uplift and northeastward extrusion of the Qinghai-Tibetan Plateau and the local tilting uplift of the southwestern Ordos Block.

Geochemical characteristics of the Carboniferous-Permian source rocks in Western Henan, China

55 source rock samples in the Carboniferous-Permian strata, southern Northern China basin were analyzed in this paper to obtain the sedimentary characteristics, organic matter abundance, kerogen type and thermal maturity and the unconventional oil and gas prospects. The results demonstrated that the source rocks were all dominated by the evolution of the sedimentary environment. High thermal evolution resulted in low S1, whereas poor preservation caused by strong tectonic activities resulted in low S2. The units of the southern North China Basin with weak tectonic activity and good preservation conditions may be the main areas for future unconventional gas exploration.

Delineasi Zona Prospek Sistem Panasbumi Daerah ‘P’ Menggunakan Pemodelan Multi Dimensi Data Magnetotelurik Terintegrasi Data Geologi dan Geokimia

A study for delineating geothermal system of prospect area “P” has been done by using multi-dimensional modeling of magnetotelluric data. Physiographycally, geothermal prospect of “P” area is located at non-volcanic Banda inner arc hosted by Malihan Sekis rock complex with Perm-Trias age. The existance of geothermal system in this area is indicated by the presence of thermal manifestations in form of 6 chloride-bicarbonate hot springs with temperature in the the range of 37-67oC, and pH of 6-7. The development of geothermal system is most probably associated with strong tectonic activity caused by the collision between Seram island plate and Australian plate that ignite the occurence of intrussive body as heat source. In order to know the subsurface information of prospect area, magnetotelluric (MT) survey has been done. The processing of MT data was started from time-series data, continued by noise filtering, rotation of strike orientation and static shift correction to obtain better MT curve. The data were then being inversed by means of 1-Dimensional, 2-Dimensional and 3-Dimensional inversion methods. Reservoir temperature is estimated to be around 160-180 oC and classified as moderate temperature. The result of MT data inversions shows the presence of conductive layer ( 300 ?m) with updome shape appears underneath the manifestations occurence (MAP1, MAP2, MAP4, and MAP5), indicating that the heat source is located in northern part and elongate to souteast direction. The conceptual model of geothermal system was built based on integrated interpretation of geological, geochemical and geophysical data. The prospect area and recommendation of drilling location is estimated to be ± 3 km2 around upflow zone. Keywords: Prospect zone, geothermal system, magnetotelluric method, multi-dimension modeling

Source-to-sink analysis of continental rift sedimentation: Triassic Cuyo basin, Precordillera Argentina

The northernmost outcrops of the Triassic extensional Cuyo basin in western Argentina reveal a basal coarse conglomerate overlain by a thinning-fining upward siliciclastic red-bedded section with subordinated tuffs and microbial-rich carbonates (Cerro Puntudo Formation), unconformably covered by a second coarse conglomerate (El Relincho Formation), which were previously interpreted as two rifting events. An integrated analysis of facies associations, stacking patterns, paleocurrent and provenance was carried out in order to reveal the rift sedimentation using a source-to-sink approach. Besides the traditional controls in continental basins (e.g.,sedimentation, tectonics and climate), this study considers possible drainage pattern evolution in order to differentiate isolated versus integrated depocenter stages. U-Pb zircon data corroborate our analysis and reveal a volcanic basement source of 256.8±3.5Ma (Permian/Lopingian) and a sedimentation age of 249.8±2.5Ma (Early Triassic) for a tuff interbedded within the Cerro Puntudo Formation, complementing previous age of 243.8±1.9Ma (Middle Triassic) at the top of this unit. Stratigraphic stacking allows the interpretation of three evolutionary stages. A first stage, represented by thick massive boulder-volcanic-rich conglomerates characterizing alluvial fan deposition, indicates strong tectonic activity of border faults (first rifting event). These features suggest high surface gradient and high available space controlling accommodation and dispersal of gravity and debris-flow deposits. Paleocurrents to the east reveal largely north-south normal faults located to the west and sediment supply from a proximal volcanic source area. A second stage, represented by a notable fining-thinning upward facies, including fluvial and palustrine (stromatolites with pedogenetic features) deposits, indicates a transition to tectonic quiescence. These facies associations developed in a context of low sedimentation rate, limited tectonic relief and low accommodation space. A third stage is represented by greenish well-roundedcoarse-grained polymictic conglomerates of El Relincho Formation that unconformably truncate the Cerro Puntudo Formation. These conglomerates are interpreted as perennial braided fluvial systems (with paleocurrents to the northwest) indicating drainage reorganization primarily influenced by climate change and combined tectonic reactivation, previously considered the second rifting event. Climate change affected sediment delivery and allowed regionally connectivity and overfilling of the depocenters. In this last stage, northwest axial transport from variable sources within the Precordillera (to the southeast) is inferred from provenance analysis indicating open linked-depocenters. This study suggests a new stratigraphic correlation for the northern part of the Cuyo basin, implying that during the first rifting event a semi-arid climate prevailed with development of isolated and independent depocenters (first and second stages), whereas above the unconformity initiating the second rifting event (third stage) depocenters were interconnected. In the light of our source-to-sink analysis, such paleogeographic change allowed overfilling and laterally linkage of separate half-grabens along the Cuyo basin. Whereas tectonic reactivation may better explain renewed conglomerate deposition, climate change toward more humid conditions allowed previously separated depocenters to be connected through axial drainages.

Analyzing successive landslide dam formation by different triggering mechanisms: The case of the Tangjiawan landslide, Sichuan, China

The catastrophic Tangjiawan landslide, triggered by the 2008 Wenchuan earthquake, blocked the Duba River, impounding one of the most dangerous coseismic barrier lakes in Beichuan, China. The lake was drained by an artificial spillway within one month after the earthquake to minimize the potential dam-breach flooding risk. However, on September 5, 2016, this landslide was reactivated and dammed the river again, creating a 20-m high dam at the same location and resulting in the formation of a barrier lake with a volume of 0.6 million m3. The day after the event we carried out a field investigation of the landslide and obtained a high-resolution image and DEM using UAV. The satellite images from 2005, 2008, 2010 and 2015 were also collected to analyze the evolution of the landslide. Together with multi-temporal DEMs, the geometry and volumes of the displaced mass and the landslide dams and barrier lakes were calculated using image interpretation and 3D spatial analysis with GIS. This landslide is of great scientific interest, as it presents a good example of multiple reactivation of a pre-historical giant landslide under different triggering conditions: a reactivation of an older landslide during the Wenchuan earthquake, and a second reactivation during a rainfall event several years later. Meanwhile from the hazard assessment and prevention perspective, it is also representative as it dammed the river twice in 2008 and 2016, posing threats to both upstream and downstream areas. We infer that the successive landslides in this region could be caused by the strong tectonic activities: including earthquakes and high average uplifting rate. The results of landslide volume analysis using multi-temporal DEMs, contribute to the landslide mechanism analysis, and suggest that the landslide volume estimation is effected by the landslide type, landslide rupture surface location, and resolution of DEM. We also compare the performance of different empirical models of landslide stability and dam-breach flood parameters and discuss their application during the quick assessment of the potential hazard of the landslide dams. Generally, the successive landslide dams at the Tangjiawan site are caused by the successive landslide reactivations on an anti-dip slope controlled by strong tectonic activity and river erosion, involve with a mass of loose materials of previous landslide deposition, and possess high flood risk to the downstream area. The experience gained in this work can be used to assist the hazard assessment and the planning of the emergency measures for similar landslide dams in the future.

Restored topography of the Po Plain‐Northern Adriatic region during the Messinian base‐level drop—Implications for the physiography and compartmentalization of the palaeo‐Mediterranean basin

AbstractThe Messinian Salinity Crisis (MSC) involved the progressive isolation of the Mediterranean Sea from the Atlantic between 5.97 and 5.33 Ma, and a sea‐level fall whose timing, modalities, and magnitude remain actively debated. At that time, the central Mediterranean was undergoing strong tectonic activity due to the rollback of the Adria slab and eastward migration of the Apenninic belt. The combined effects of the post‐evaporitic MSC sea‐level drop and morphostructural changes (due to the Intra‐Messinian phase) resulted in a regional unconformity, which shows erosive markers and conformable relationships with the Messinian and Mio–Pliocene boundary in the Po Plain and Northern Adriatic Foreland. Here, we produce a palaeotopographic reconstruction of the Po Plain‐Northern Adriatic region (PPNA) during the Messinian peak desiccation event based on such regional unconformity. We mapped this surface through wells and 2D seismic data form Eni's private dataset. The unconformity shows V‐shaped incisions matching the present‐day southern Alpine valleys and filled with Messinian post‐evaporitic and Pliocene deposits, suggesting that the modern drainage network is at least of late Messinian age. The Messinian unconformity has been restored to its original state through flexural‐backstripping numerical modelling. The resulting landscape suggests a maximum sea‐level drop of 800–900 m during the MSC peak, and is consistent with stratigraphic and sedimentologic data provided by previous works. The modelled shoreline separates the subaerially eroded land from an elongated basin composed by two ca. 400 and 1,000 m deep depocentres during the maximum sea‐level drop. These results suggest that the Mediterranean was split in at least three sub‐basins subject to independent base levels, fresh‐water budgets, and flexural responses during the maximum lowstand.

Electron spin resonance (ESR) dating of pre-Quaternary faults in the Sichuan basin, SW China

The electron spin resonance (ESR) dating method is thought to be limited to the Quaternary period. In this study, we attempt to expand the ESR dating range to the pre-Quaternary using three fault-zone samples collected from faults in the Sichuan basin and its surroundings. We adopt a γ-ray radiation dose of up to 2 × 104 Gy, which is much greater than that typically employed, and find that the ESR intensity of the E1′ center (a type of signal for ESR dating) in quartz continuously increases with the γ-ray dose and is slightly influenced by the radiation dose rate. This indicates the potential of ESR to date pre-Quaternary faults. By simulating environmental radiation under geological burial conditions, we use ESR to date the latest extension event in the western Hubei and Hunan thrust belt to 9.17 ± 0.76 Ma and the thrusting of the Longmenshan fault zone toward the Sichuan basin to approximately 6.14 ± 0.73 Ma. Conversely, the saturated ESR intensity of fault-zone samples from the Daba fault zone suggests a lack of strong tectonic activity in the southern Daba fault zone in the last 10 Ma. Our results are consistent with fission track ages and the regional tectonic evolution history. Therefore, ESR is a practical method for dating pre-Quaternary faults in structural and petroleum geology applications.

Application of observations of recent tectonic activity in the Świebodzice Depression (the Sudetes, SW Poland) in assessing seismic hazard in the Fore-Sudetic Monocline

Tiltmeter observations with application of horizontal pendulums have been carried out for 40 years in the Geodynamic Laboratory in Książ. Long-term observations have not indicated any correlation of these data with meteorological or seasonal phenomena. Following an epoch of fast azimuth changes, a gradual compensation process took place, excluding the effect of gravitational creep of the rock massif. An assumption was made that the observed large changes of the equilibrium azimuths of the horizontal pendulums that result from tectonic tilt of the foundation blocks. Multiannual tiltmeter observations allowed to determine the temporal characteristics and amplitude tectonic effects. Intervals of strong tectonic activity in the rock massif of the Świebodzice Depression last from several days to over ten weeks and are separated by several tens of hours of low activity. Amplitude of the rock massif deformation reaches values from over ten to several tens of amplitudes of the tidal signal, i.e. up to several hundreds of micrometres. Water-tube tiltmeters (WT) launched in 2003 have confirmed the characteristics of tectonic effects and their incidental occurrence. Beside the tilt effects, WT have enabled to confirm vertical movement of the foundation blocks. Geological investigations in the Świebodzice Depression have indicated the presence of a numerous faults separating particular blocks in the rock massif. The presence of this fault system favours the dislocation of foundation blocks, which results in a quake-less relaxation of tectonic stresses and absence lack of seismic activity in the Świebodzice Depression. Foundation blocks separated by faults combined with the multiscale measurement system of WTs form a natural detector of regional tectonic activity, allowing to determine with micrometric resolution the representative function of tectonic activity in the rock massif of the Świebodzice Depression.

Delta-fed turbidites in a lacustrine rift basin: the Eocene Dongying depression, Bohai Bay Basin, East China

ABSTRACTSediment avalanche from delta ramp is one of the significant development mechanisms for a turbidite system in a lacustrine basin. To advance our understanding of deep-water sedimentary processes in a lacustrine delta ramp, delta-fed turbidites in the Eocene Dongying depression of the Bohai Bay Basin were studied using core data, 3-D seismic data and well log data. Sandy debris flows, muddy debris flows, mud flows, turbidity currents, slides, sandy slumps and muddy slumps were interpreted based on the identification of lithofacies. Data indicates that deep-water sedimentary processes in the study area were dominated by debris flows and slumps, which accounted for ∼68% and 25% (in thickness) of total gravity flow deposits, respectively; turbidity-current deposits only accounted for ∼5%. Mapping of turbidites showed that most were deposited after short-distance transportation (<20 km), restricted by the scale of deep-water areas and local topography. Channels, depositional lobes, debris flow tongues, muddy turbiditic sheets, slides and slumps were identified in a delta-fed ramp system. Slides and slumps were dominant at the base of slopes or at the hanging walls of growth faults with strong tectonic activity. Channels and depositional lobes developed in gentle, low-lying areas, where sediments were transported longer distances. Sand-rich sediment supply, short-distance transportation and local topography were crucial factors that controlled sedimentation of this ramp system. Channels generally lacked levees and only produced scattered sandstones because of possible hydroplaning of debris flow and unstable waterways. In addition to lobes, debris flow tongues could also be developed in front of channels. These findings have significant implications for hydrocarbon exploration of deep-water sandstone fed by deltas in a lacustrine basin.

A systematic engineering geological evaluation of diabase dikes exposed at the underground caverns of Dagangshan hydropower station, Southwest China

Dagangshan hydropower station is located in the middle of Dadu River, Southwest China. Many diabase dikes were exposed in the adamellite granite body during excavation of the underground caverns. The dikes are highly directional, have crushed interiors, exhibit strong alteration, and have poor contact relationships with surrounding rocks, all of which is inconsistent with the characteristics of typical diabase. This paper describes systematic research that focused on the dikes’ spatial distribution, macroscopic characteristics, physical and mechanical properties, and common instability modes. Factors influencing their stability and their corresponding control measurements are discussed in the context of the site and its conditions. Results show that most of the dikes located in the underground caverns are the branches of the main dike β9, which produced from a strong basic magma extrusion–overflow event happened in between the Permian and Triassic. Due to multiple strong tectonic activities, the chlorite alignment of these dikes generally tended to be significant and leaded the physical and mechanical properties to be poor. Then, excavation and repetitive blasts resulted in strong disturbances to the original dikes and even caused rock unloading (collapse, rock block fall) and groundwater runoff system (water inflow) change. According to the common instability modes and reasons of diabase dikes, some specific control measures including solidified rubbles, reinforcement methods, pre-grouting, and small ducts are implemented in order to keep the surrounding of diabase safety, and the results show that the control methods perform a proper effect on these engineering problems.

Dissolved gaseous mercury (DGM) in the Mediterranean Sea: Spatial and temporal trends

Abstract Dissolved gaseous mercury (DGM) was studied in surface and deep waters of the Mediterranean Sea over the last 15 years during several oceanographic cruises on board the Italian research vessels Urania and Minerva Uno, covering the Western and Eastern Mediterranean Basins as well as Adriatic Sea as its northernmost part. DGM was measured together with other mercury species (RHg - reactive Hg, THg - total Hg, MeHg - monomethyl Hg and DMeHg - dimethylmercury), and with water quality parameters in coastal and open sea deep water profiles. DGM represents a considerable portion of THg (on average 20%) in Mediterranean waters. Spatial and seasonal variations of measured DGM concentrations were observed in different identified water masses. DGM was the highest in the northern Adriatic, the most polluted part of the Mediterranean Sea as a consequence of Hg mining in Idrija and heavy industry in northern Italy, and near the Gulf of Lion. Generally, average DGM concentration was higher in the West and East Mediterranean Deep Waters (WMDW and EMDW) and Levantine Intermediate Water (LIW) than in overlaying Modified Atlantic Water (MAW); however, it was the highest in N Adriatic Surface waters (NAdSW) and consequently in outflowing Adriatic Deep Waters (AdDW). In deep water profiles the portion of DGM typically increased at depths with oxygen minimum and then towards the bottom, especially in areas with strong tectonic activity (Alboran Sea, Strait of Sicily, Tyrrhenian Sea), indicating its bacterial and/or geotectonic origin. During oceanographic cruises in 2011 and 2015 in the Tyrrhenian Sea, novel methods for continuous DGM determination in surface waters (Wangberg and Gardfeldt, 2011, Begu et al., 2016) were applied and compared to the standard method, and showed good agreement.

Paleogene tectonic evolution controls on sequence stratigraphic patterns in the Fushan sag, northern South China Sea

Tectonism is of extreme importance to sequence stratigraphic patterns in continental sedimentary basins, affecting both the architectures and internal makeup of sequences. Sequence stratigraphic framework of the Paleogene system in the Fushan sag, northern South China Sea, was built using 3D and 2D seismic data, complemented by drilling cores and well logs data. One first-order, three second-order and seven third-order sequences were identified. Analysis of paleotectonic stress field, unconformities and subsidence history showed that the Paleogene tectonic evolution presented significant characteristics of multistage and episode, and can be divided into three stages: rifting stage I (initial rifting period), rifting stage II (rapid subsidence period), rifting stage III (fault-depressed diversionary period). Partition of the west and east in tectonic activity was obvious. The west area showed relatively stronger tectonic activity than the east area, especially during the rifting stage II. Episodic rifting and lateral variations in tectonic activity resulted in a wide variety of structural slope break belts, which controlled both the sequence architectures and interval makeup, and strongly constrained the development of special facies zones or sand bodies that tended to form hydrocarbon accumulation. This paper classifies the genetic types of slope break belts and their relevant sequence stratigraphic patterns within the Fushan sag, and further discusses the tectonic evolution controls on sequence stratigraphic patterns, which suggests that vertical evolution paths of structural slope break belts and relevant sequence stratigraphic patterns as a response to the Paleogene tectonic evolution were strongly controlled by sag margin types and lateral variations of tectonic activity.

Seismites in the Dasheng Group: New evidence of strong tectonic and earthquake activities of the Tanlu Fault Zone

More than 80 layers of seismites were recognized from the Early Cretaceous Dasheng Group in the Mazhan and Tancheng graben basins in the Tanlu Fault Zone, eastern China. The responsible seismic events took place about 110–100 Ma in the Early Cretaceous. The fault zone was affected at the time by strong tectonics, due to tension-related stretching and scattered squeezing by strike-slip faults. These tectonic activities induced a series of strong earthquakes with Richter magnitudes (M) of 5–8.5. The earthquakes affected saturated or semi-consolidated flood and lake sediments, and produced intra-layer deformations by several processes, including liquefaction, thixotropy, drop, faulting, cracking, filling and folding, which resulted in the formation of various soft-sediment deformation structures, such as dikes and veins of liquefied sand, liquefied breccias, liquefied homogeneous layers, load structures, flame structures, ball-and-pillow structures, boudinage, diapirs, fissure infillings, a giant conglomerate wedge, and syn-sedimentary faults. The seismites are new evidence of tectonic and seismic activities in the Tanlu Fault Zone during the Early Cretaceous; the series of strong seismic events that can be deduced from them must be considered as a response to the destruction of the North China Craton.

Palynostratigraphy and palynofacies of the Upper Triassic Streppenosa Formation (SE Sicily, Italy) and inference on the main controlling factors in the organic rich shale deposition

This paper focuses on the Upper Triassic Streppenosa Formation, penetrated by the Pachino 4 on-shore well, (Southern Sicily, Italy) in order to find stratigraphic age constrains and to reconstruct the paleoenvironmental evolution of this basin within the Upper Triassic palaeogeographic scenario of the western Tethys. Pachino 4 is one of the wells drilled by Eni Exploration and Production in the south-eastern Hyblean plateau with the purpose to better define the time and space distribution of reservoirs and source rocks in an area characterized by considerable subsidence and strong tectonic activity, balanced by high sedimentation rate. The Streppenosa Formation depocenter consists of a thick sequence (>2500m) of organic rich shales, turbiditic limestones and marly limestones, grouped into three members (Lower, Middle and Upper). The well diversified microflora assemblages allow the dating of the upper part of the Lower Member and the Middle Member as Norian and the Upper Member as Rhaetian. The palynofacies variations across the Streppenosa Formation show significative changes in the relative abundances of the organic debris that, associated with the lithological and sedimentological features, allowed a reconstruction of the depositional facies successions and a hypothesis for the forcing mechanisms driving the black shale deposition. We considered that the deposition of the Streppenosa Formation occurred in an epeiric basin, under oxygen-depleted bottom waters, with different depth that varied through time in response to the sedimentation rates, eustatic sea level changes, and basin subsidence. The integration of palynofacies and lithofacies data suggests a crucial role for river runoff, responsible for water stratification and for primary productivity increase in the water column. The process was triggered by warmer and wetter climate conditions as documented in many Upper Triassic successions of the western Tethys realm.

Geomorphic indices of rivers and drainage in China’s Longmen Shan Fault zone and their implications for regional tectonic activity

Theoretical models suggest that active tectonic deformation can impose a primary control on the patterns and styles of channels. The Longmen Shan Fault zone, which is located on the eastern margin of the Tibetan Plateau, has experienced strong tectonic activity, including uplift and strike-slip phases of tectonic movements. Here, we adopt ASTER-GDEM2 data and utilise a stream-power incision model to extract information on the spatial characteristics of differential tectonic movements. Analysis of the patterns and styles of 37 channels exhibits systematic differences in the channel steepness indices and the river sinuosity values along the strike of the Longmen Shan Fault zone. Our primary results demonstrate that the normalised channel steepness indices in the southern part of the Longmen Shan Fault zone are much higher than those in the northern part, where the river sinuosity values are much lower. Comparisons between the five drainage basins reveal that the river systems in the middle southern part of the fault zone are mainly controlled by tectonic uplift and thrusting, whereas the river systems in the middle northern part of the fault zone are mostly attributed to right-lateral strike-slip movement.

The final collision of the CAOB: Constraint from the zircon U–Pb dating of the Linxi Formation, Inner Mongolia

The Linxi Formation occupies an extensive area in the eastern Inner Mongolia in the Central Asian Orogenic Belt (CAOB). The Linxi Formation is composed of slate, siltstone, sandstone and plant, lamellibranch microfossils in the associated strata. Major and trace element data (including REE) for sandstones from the formation indicate that these rocks have a greywacke protolith and have been deposited during a strong tectonic activity. LA-ICPMS U–Pb dating of detrital zircons yield ages of 1801 to 238 Ma for four samples from the Linxi Formation. 425–585 Ma, together with the ∼500 Ma age for the metamorphism event previously determined for Northeast China, indicates that their provenance is the metamorphic rocks of Pan-African age that have a tectonic affinity to NE China. A few older zircons with U–Pb ages at 1689–1801 Ma, 1307–1414 Ma, 593–978 Ma are also present, revealing the Neoproterozoic history of NE China. The youngest population shows a peak at ca. 252 Ma, suggesting that the main deposition of the Linxi Formation was at late Permain. Moreover, the ca. 250 Ma zircon grains of all four samples yield weighted mean 206Pb/238U ages of 250 ± 3 Ma, 248 ± 3 Ma, 249 ± 3 Ma, and 250 ± 2 Ma, respectively. These ages, together with the youngest zircon age in the sample ZJB-28 (ca. 238 Ma), suggest that the deposition of the Linxi Formation extended to the early Triassic. Combining with previous results, we suggest that the final collision of the Central Asian Orogenic Belt (CAOB) in the southern of Linxi Formation, which located in the Solonker–Xra Moron–Changchun suture, and the timing for final collision should be at early Triassic.