Yanji Basin Research Articles

Experimental Study on Mechanical Properties of Highly Swelling Soft Rocks in the Yanji Basin, Northern China

Experimental Study on Mechanical Properties of Highly Swelling Soft Rocks in the Yanji Basin, Northern China

A new paralligatorid (Crocodyliformes, Neosuchia) from the mid-Cretaceous of Jilin Province, northeastern China

Numerous dinosaurian, crocodyliform, and testudine fossils have been recently recovered from the mid-Cretaceous of the Yanji Basin, Jilin Province, China. Among the crocodyliform remains, the specimen (YJDM 00009) described here represents a new genus and new species, Yanjisuchus longshanensis gen. et sp. nov. It is the third Cretaceous crocodyliform found in Jilin Province after Paralligator sungaricus and Rugosuchus nonganensis. Y. longshanensis is a medium-to-large neosuchian characterized mainly by the frontal with a wedge-shaped elevation anteriorly, a transversely oriented, grooved preorbital ridge, the fused dentaries, and the dentary dentition with a diastema. Y. longshanensis was situated phylogenetically within the Paralligatoridae, with Rugosuchus nonganensis and many other species of Paralligator from Central Asia. The discovery of Y. longshanensis not only adds a new group to the local reptilian fauna but also is important to our understanding of the biogeography and diversity of Paralligatoridae in Asia.

A possible brachiosaurid (Dinosauria, Sauropoda) from the mid-Cretaceous of northeastern China.

Brachiosauridae is a lineage of titanosauriform sauropods that includes some of the most iconic non-avian dinosaurs. Undisputed brachiosaurid fossils are known from the Late Jurassic through the Early Cretaceous of North America, Africa, and Europe, but proposed occurrences outside this range have proven controversial. Despite occasional suggestions that brachiosaurids dispersed into Asia, to date no fossils have provided convincing evidence for a pan-Laurasian distribution for the clade, and the failure to discover brachiosaurid fossils in the well-sampled sauropod-bearing horizons of the Early Cretaceous of Asia has been taken to evidence their genuine absence from the continent. Here we report on an isolated sauropod maxilla from the middle Cretaceous (Albian–Cenomanian) Longjing Formation of the Yanji basin of northeast China. Although the specimen preserves limited morphological information, it exhibits axially twisted dentition, a shared derived trait otherwise known only in brachiosaurids. Referral of the specimen to the Brachiosauridae receives support from phylogenetic analysis under both equal and implied weights parsimony, providing the most convincing evidence to date that brachiosaurids dispersed into Asia at some point in their evolutionary history. Inclusion in our phylogenetic analyses of an isolated sauropod dentary from the same site, for which an association with the maxilla is possible but uncertain, does not substantively alter these results. We consider several paleobiogeographic scenarios that could account for the occurrence of a middle Cretaceous Asian brachiosaurid, including dispersal from either North America or Europe during the Early Cretaceous. The identification of a brachiosaurid in the Longshan fauna, and the paleobiogeographic histories that could account for its presence there, are hypotheses that can be tested with continued study and excavation of fossils from the Longjing Formation.

Taxonomy, biostratigraphic and paleoecological aspects of non-marine ostracod fauna from the Jinju Formation (Albian) of the Gyeongsang Basin, South Korea

A total of seven species belonging to six genera of cypridoidean ostracods were recovered from three sections (Jeongchon, Hotan, and Tapri) of the Albian Jinju Formation from the Gyeongsang Basin, South Korea: Scabriculocypris yanbianensis, Cypridea khandae sp. nov., Cypridea samesi, Mongolocypris kohi, Lycopterocypris? cf. celsa, Candona sp., and Djungarica sp. Based on its morphology, C. khandae sp. nov. is considered to be the first record of the Cypridea alta-group in Korea. Although many species are endemic to the Jinju Formation, the occurrence of Scabriculocypris yanbianensis indicates that this fauna was linked with the contemporaneous fauna of the Tongfosi Formation of the Yanji Basin, northeast China. Based on previous studies and newly collected specimens, the taphonomic features of the sections indicate the presence of two distinct thanatocoenoses: a low-energy autochthonous thanatocoenosis (Jeongchon and Tapri sections) and a slightly higher energy thanatocoenosis (Hotan section). Finally, the absence of cytheroidean and darwinuloidean ostracods could be explained by the presence of unstable lake/temporal waterbodies and their low competitiveness.

Geochronological and Paleomagnetic Constraints on the Lower Cretaceous Dalazi Formation from the Yanji Basin, NE China, and its Tectonic Implication

The Lower Cretaceous Dalazi Formation in the Yanji Basin, eastern Jilin Province is of particular interest because it contains key fresh water fossil taxa, oil and gas resources, a potential terrestrial Albian–Cenomanian boundary, and regional unconformities. However, the lack of a precise chronology for the non-marine strata has precluded a better understanding of the regional stratigraphic correlation and terrestrial processes. Here, we report magnetostratigraphic and U–Pb geochronologic results of a sedimentary sequence from the Xing’antun section in the Yanji Basin. Thirty-two zircons from the tuff sample were analyzed by secondary ion mass spectrometry (SIMS); the U–Pb zircon dating method yielded a weighted mean of 206Pb/238U age of 105.7 ± 0.8 Ma (2σ, internal error). Paleomagnetic results show that the Dalazi Formation is of normal polarity, which was correlated to the early chron C34n constrained by the SIMS U–Pb zircon geochronologic data, further demonstrating that the terrestrial sedimentary sequence of the upper Dalazi Formation is of late Albian age. The established geochronologic framework allows the regional correlation of the Dalazi Formation in the Yanji Basin to the strata from other terrestrial sequences in northeastern China. The similar geodynamic and geologic background between the Yanji Basin and other terrestrial rift basins in northeastern China suggests that the unconformity between the Dalazi and Longjing formations may represent syn-rift and post-rift stages in the Yanji Basin, and thus the switch from extension to contraction during the mid-Cretaceous, precisely constrained to ~106–101 Ma based on our new chronology and previously published high-precision U–Pb dating of the lower Longjing Formation. It is most likely attributable to the docking of the west Pacific plate along the East Asian continental margin.

A potential terrestrial Albian–Cenomanian boundary in the Yanji Basin, Northeast China

The terrestrial Albian–Cenomanian (A–C) transition was an important time interval for the co-evolution of animals and flowering plants, as well as for the diversification of dinosaurs and mammals on continents. Due to a worldwide lack of terrestrial sedimentation at that time, and the difficulty of direct correlation between marine and non-marine stratigraphy, only a few studies have discussed the terrestrial A–C boundary; therefore, it remains poorly understood compared with other stratigraphic boundaries. Northeast China is an ideal place to study the terrestrial A–C boundary because the area contains the most complete and continuous terrestrial Cretaceous succession in the world. Here, we report a SIMS U-Pb zircon age of 105.14 ± 0.37 Ma for the uppermost part of the Dalazi Formation in the Yanji Basin. Additional ostracod-based biostratigraphic data indicate an Albian to Cenomanian age for the conformably overlying Longjing Formation. Alignment of the new comprehensive geochronological and biostratigraphic data with previously published chronological data suggests that a potential terrestrial A–C boundary occurs within the Longjing Formation of the Yanji Basin. This study provides an updated, precise chronostratigraphic framework for the evolution of the major terrestrial faunas and flora in the Yanji Basin, and represents a new contribution to the terrestrial Cretaceous timescale recorded in northeast China.

The deformation and permeability of Yanji mudstone under cyclic loading and unloading

During the constructions of motorways and high-speed railway lines in the Yanji Basin, large amounts of excess mudstones due to the enormous tunnel excavations and slope cuts would be deposited as landfills. Assessing the deformation and permeability of Yanji mudstone became important for the design, construction and operation of the landfills. This paper presents an experimental study on the deformation and permeability of Yanji mudstone by carrying out a series of oedometer tests with loading/unloading cycles. The results show that the sample with a lower initial water content exhibited greater swelling deformation after inundation, a lower yield stress, greater deformation and a higher hydraulic conductivity during the loading/unloading cycles. As the number of loading/unloading cycles increased, the yield stress and accumulated plastic deformation increased, while the compression index, rebound index and hydraulic conductivity decreased. The samples became stiffer and their hydromechanical behaviour tended to be stable after three cycles. The compression curves could be divided into pre-yield and post-yield zones. The post-yield zones of compression curves and the rebound curves could be normalized into a unique line, and the pre-yield zones of the compression curves could be described as lines. Basic equations were developed to predict mudstone deformation under cyclic loading and unloading. Additionally, an empirical relationship between the hydraulic conductivity and void ratio was also proposed. The ability of the proposed methods was verified by the overall good agreement between the experimental results and predicted values.

Ostracod faunas from the Dalazi and Tongfosi formations (Yanji Basin, northeast China): Biostratigraphic, palaeogeographic and palaeoecological implications

This work provides a detailed taxonomic study of ostracod species from the Dalazi and Tongfosi formations of the Yanji Basin (Jilin Province, NE China). Fourteen species including one new species belonging to nine genera have been recovered: Scabriculocypris tonfosiensis, Scabriculocypris yanbianensis, Cypridea concinaformis, Mongolocypris yanjiensis, Mongolianella kyranbeki sp. nov., Lycopterocypris infantilis, Lycopterocypris sp., Yumenella toorojensis, Candona spp., Cyprois sp., Vlakomia ustinovskii and Vlakomia jilinensis. With the recovery of well-preserved specimens, the sieve pore, ontogeny and sexual dimorphism of Vlakomia jilinensis and Vlakomia ustinovskii are recognized for the first time. The ostracod biostratigraphic correlations suggest that the age of the Tongfosi Formation is Albian and may extend upwards into the Upper Cretaceous, and the Dalazi Formation is not older than the Albian, probably of early Late Cretaceous age. The ostracod faunas of the Tongfosi and Dalazi formations show affinities to faunas of Eastern Mongolia and South Korea, providing evidence of potential faunal exchanges between Northeastern China, Eastern Mongolia and South Korea during the Albian to early Late Cretaceous time. On the basis of their ostracod faunas, the Tongfosi and Dalazi formations represent a shallow-littoral lacustrine depositional environment that potentially included small ephemeral water bodies.

The relationship between the swelling pressure and shear strength of unsaturated soil: the Yanji Basin as a case study

The swelling pressure is a unique and important parameter for reflecting the engineering characteristics of expansive soil, providing a method to study the shear strength of expansive soil. The results of previous studies indicate that the shear strength of unsaturated soil is composed of three parts, and the swelling pressure contributes to the matric suction. Unsaturated direct shear tests and swelling tests of undisturbed expansive soils in the Yanji Basin were performed in this study, and the relationship between the swelling pressure and water content, as well as between the total cohesion and initial water content, were analyzed. According to a data regression analysis, a variety of fitting functions were used for comparisons and a linear relationship between the swelling pressure and the matric suction was established. The study indicate that the exponential fitting function, power function, and linear function should be used and compared with one another to find the best fit. This research is significant for the study of the relationship between shear strength and the swelling pressure of unsaturated soil.

Mid-Cretaceous dinosaur track assemblage from the Tongfosi Formation of China: Comparison with the track assemblage of South Korea

A Yanji Basin tracksite in the Cretaceous Tongfosi Formation in the Yanbian Korean Autonomous Prefecture, Jilin Province was reinvestigated twenty years after the original study.The re-examination confirms the presence of tracks tentatively referred to ornithopods and theropod tracks including several not previously reported. In addition to the main track-bearing level, a second footprint horizon was identified from which a probable ornithopod track was collected. Some of the formerly identified tracks were documented using photogrammetry, whereas others that had been collected, eroded, buried or obscured by dense vegetation. The age of the track-bearing beds is inferred to be late Albian to early Cenomanian. Comparison with track-bearing units of the same age in Shandong, China, and Korea indicated quite different compositions of track assemblages. In the case of the Korean sites the differences may be facies related. While the Korean ichnofauna is characterized by the co-occurrence of ornithopod, sauropod and tridactyl theropod tracks with didactyl dromaeosaurid, Minisauripus (small theropod), pterosaur and avian tracks, the latter four are absent in the Tongfosi assemblage. This could reflect a restricted environment being not favourable for activities of these trackmakers or simply a preservational bias.

Morphology and phylogenetic origin of the spinicaudatan Neodiestheria from the Lower Cretaceous Dalazi Formation, Yanji Basin, north-eastern China

The spinicaudatan Neodiestheria Chen is an important component of the diverse Early Cretaceous Yanjiestheria fauna in eastern Asia. Examination under a scanning electron microscope of newly collected and well-preserved specimens of Neodiestheria dalaziensis Chen from the Albian Dalazi Formation of Zhixin, Jilin Province, north-eastern China, has revealed morphological features of the carapace not recognized previously, namely that puncta are not only evenly distributed on growth bands near the umbo and gradually merge into a punctate fine reticulation and dense radial lirae on each growth band in the upper-middle part of the carapace, but also occur on growth lines and within the lumina of a fine reticulum, and between radial lirae on growth bands in the middle and lower parts of the carapace. Growth bands in anteroventral, ventral and posteroventral parts of the carapace are also ornamented with transversely elongate large pits (depressions) surrounded by swellings, appearing as a large reticulum superimposed over fine reticulation and radial lirae. These ontogenetically developing morphological patterns on the growth bands of the juvenile stage of the carapace indicate that Neodiestheria is closely related phylogenetically to Triglypta Wang.

Difficulties and Solutions on Tight Sandstone Reservoir Hydraulic Fracture in Yanji Basin

Hydraulic fracture, as a stimulation treatment, has been widely used in process of oil exploring in oil well. But in tight sandstone reservoir, it still exist many problem due to compactness, low-permeability, hardness and brittleness characters of the sandstone. To resolve the problem above-mentioned,this text considering the low natural productivity status of tight sandstone reservoir in Yanji Basin, to analyze the reservoir characters of tight sandstone reservoir base on density testing and mechanic parameters testing of the stone. The results shown that the special reservoir characters of tight sandstone sand lead to high fracture pressure of formation, poor connectivity of fracture, filtration and backflow problems of fracturing fluid. So we put forward reasonable recommendations for fracturing to resolve the problem above-mentioned. Through the application of oriented perforating technology, improvement of fracture fluid system and fracturing technology, provide a new effective technological measure for fracturing in tight sandstone, and promoting the development of fracturing technology in tight sandstone reservoir.

A male cone of Pseudofrenelopsis dalatzensis with in situ pollen grains from the Lower Cretaceous of Northeast China

A Classopollis-containing male cone found in close association with Pseudofrenelopsis dalatzensis from the Lower Cretaceous Dalazi Formation of Yanji Basin, eastern Jilin, China was studied using scanning electron microscopy and described as Classostrobus dalatzensis sp. nov. The small oval cone, borne on the top of a stalk (fertile short shoot), consists of helically arranged microsporophylls, each with a rhomboid and expanded distal head. The short shoot is divided into indistinct nodes and internodes with fine longitudinal striations. Cuticles of the microsporophyll and the internode of the short shoot are generally similar to Pseudofrenelopsis dalatzensis internode cuticles, all of them having papillate outer surfaces. Stomata are similar in structure and arrangement, with papillae of subsidiary cells overhanging the stomatal pit. Epidermal cells are rectangular or isodiametrical, each with a robust papilla on the periclinal wall. Hypodermal cells are present between the stomatal files. The internal structure of the in situ Classopollis pollen grains was studied in detail. Pollen grain is small, with thin sexine, poorly developed nexine and may be immature. This is the first record of in situ pollen grains Classopollis in China of which the internal structure is known in detail.

Late Mesozoic transgressions of eastern Heilongjiang and their significance in tectonics, and coal and oil accumulation in northeast China

The spatial and temporal distribution of Late Mesozoic marine and brackish-water sediments in eastern Heilongjiang records three main transgressive interludes: The late Middle Callovian–Valanginian, Barremian–Aptian and Albian marine invasion phases. The Callovian–Valanginian transgressions were limited to the northeastern corner of eastern Heilongjiang, but the others intermittently extended northwest-, southwest- and westwards along the Yunshan shallow embayment, which opened into and deepened towards the northwestern Palaeo-Pacific. They not only flooded almost all of the subsiding basins surrounding the embayment, but during peak transgressions also widely flooded areas outside eastern Heilongjiang, such as the Yanji, Beipiao–Fuxin and Songliao basins along the Tan–Lu fault system of northeast China. All the transgressions came from the northwestern Palaeo-Pacific Ocean, and probably the Arctic Sea as well. In addition to the eustatic sea level changes, the late Early Cretaceous transgressions of northeast China were closely related to the tectonic movements within the Tan–Lu fault system and the circum-Paleo-Pacific, which were very pronounced and went hand in hand with a strong volcanic activity and ongoing subsidence. During the late Early Cretaceous, the long-term existence of a marine embayment in eastern Heilongjiang, successive marine transgressions, and flooding along the Tan–Lu fault system in northeast China ensured a humid climate across all of northeast China. These transgression and climatic conditions produced a number of extensive and long-lasting swamps and marsh lands in both paralic and limnic environments. Luxuriant plant and thriving animal growth led to the accumulation of abundant organic matter in the deposits. As a result, a number of late Early Cretaceous coal basins and oil fields formed in eastern Heilongjiang, the Yanji basin of eastern Jilin, Beipiao–Fuxin basin of western Liaoning, and the Songliao basin, northeast China.

Water-salt balance and water environment forecast of Lake Bosten in Xinjiang

Comprehensively sorting out, sifting and analyzing multi-year monthly data of hydrographical, meteorological, water and land uses, social economy, remote sensing from Yanji Basin, this paper simulated and analysed conditions of water-salt balance of Lake Bosten from 1960 to 2003 using Water-Salt Balance Model. Based on these studies, two projects were provided for development planning of Yanji Basin in the near future. And then, it forecasted and analysed water environments of Lake Bosten in future 40 years. According to the simulation results, some conclusion was following: Though there was exporting salt in an accumulation of average 306000t/a that made desalination in the lake, it might increase freshwater and decrease input-salt to reduce the degree of mineralization of Lake Bosten. After the construction projects in recent years were implemented in Yanji Basin, the degree of mineralization of Dahu would be limited between 0.84g/L and 1.38g/L according to scenarios of Project B. Under such circumstances, the degree of mineralization of Dahu could be adjusted and controlled under 1.00g/L. The degree of mineralization of Dahu could decrease to 1.00g/L in 2040 according to the simulation. Water quality of Kongque River was difficult to restore to original state, but its degree of mineralization could be controlled under 0.60g/L because of the improved water environments of Lake Bosten. Forecast analysis of Project B showed that it was beneficial to water environments of Lake Bosten when the construction project in the near future was completed in Yanji Basin. And water environments of Lake Bosten would tend to a well-ordered circle.

Discovery of Pseudofrenelopsis gansuensis from the Lower Cretaceous of Wangqing, Jilin Province, and Its Significance in Correlation of Cretaceous Red Beds in China

Abstract: New data from abundant vegetative shoots and cuticular analysis are provided for the Cretaceous cheirolepidiaceous conifer Pseudofrenelopsis gansuensis Deng, Yang et Lu. The material was found from a new locality of the Lower Cretaceous strata in the Luozigou Basin, Wangqing, Jilin Province, northeastern China. Pseudofrenelopsis is a common plant in the Dalazi Formation of the Yanji Basin about 150 km from Wangqing, but there exists different species, Pseudofrenelopsis dalatzensis only. Both P. dalatzensis and P. gansuensis have been recorded from the Lower Cretaceous of Jiuquan, Gansu Province, but they are in different stratigraphic horizons. The Lower Cretaceous plant‐bearing strata in Luozigou have used to correlate with the Dalazi Formation of the Yanji Basin. The discovery of P. gansuensis, which is lower in horizon than P. dalatzensis in Jiuquan, may indicate that they are also different in horizon in Jilin. Cheirolepidiaceous conifers are among the few fossils of red beds of the Early Cretaceous in China. The present discovery of Pseudofrenelopsis gansuensis provides important evidence for classification, correlation and determination of geological ages of the Early Cretaceous non‐marine red deposits of the two separate basins in remote areas of North China.

Paleomagnetism of Cretaceous rocks in the Jiaodong Peninsula, eastern China: Insight into block rotations and neotectonic deformation in eastern Asia

Although first‐order agreement of paleomagnetic directions between south China and Siberia shows that terranes between them were sutured by Cretaceous times, deformation by ongoing tectonism has continued and been especially focused near the continental margin of eastern Asia. To help evaluate differential rotations and relate them to regional strike‐slip and extensional tectonic regimes, we have conducted paleomagnetic study on Cretaceous sediments and volcanic rocks from the Jiaodong Peninsula south of the Bohai Sea in eastern China bordering the Tan‐Lu Fold Zone (TLFZ). Paleomagnetic results from 73 sites in the (Early Cretaceous) Laiyang and Qingshan groups and (Late Cretaceous) Wangshi Group yield magnetizations of primary or synfolding (mid‐Cretaceous) origins. Large differential block rotations of Early Cretaceous age are identified near the Muping‐Jimo Fracture Zone (MJFZ) dissecting the peninsula although Late Cretaceous declinations are regionally systematic and show post‐Late Cretaceous counterclockwise rotation of ∼14° in the Jiaolai Basin relative to the reference North and South China blocks. Block boundaries are identified as the TLFZ to the west and the MJFZ in the southeast. The eastern Jiaodong Peninsula is rotated clockwise relative to the North and South China blocks by a comparable amount (∼20°) to the southern Korean Peninsula to the east and to the Liaodong Peninsula and Yanji Basin to the north. Although these blocks are unlikely to be tightly coupled, their collective clockwise rotation mirrors counterclockwise rotations north of the Japan Sea and probably resulted from regional extension focused above uprise of asthenosphere beneath eastern Asia during Cretaceous times.

Palynology and age of some Cretaceous nonmarine deposits in Mongolia and China

To provide biostratigraphic and paleoecologic data for a major international project studying dinosaur trackways in eastern Asia, samples were collected for palynological analysis from the Choyr Basin of southeastern Mongolia and the Yanji Basin, Jilin Province, northeastern China. Palynologically productive samples from the Choyr Basin are from strata previously identified as either the Shinekhudag Formation or the Zuunbayan Formation but recently renamed the Khuren Dukh Formation; productive samples from the Yanji Basin are from the Tongfosi Formation. The biostratigraphically most important palynomorphs from both units are angiosperm pollen. The Khuren Dukh Formation is determined to be middle to late Albian in age. The Tongfosi Formation is determined to be early Cenomanian in age. These results conflict with some previously published interpretations of the ages of these units. Lacustrine depositional environments are indicated for both units by the presence of freshwater algae in both deposits.

On the Water-Salt Change of Bosten Lake in Xinjiang

在博斯腾湖水文和水化学实测资料的基础上,研究了博斯腾湖水盐的年际和年内变化.近 40年来,水质年际变化经历了好→中→差→中的过程;年内变化与区内最大补给源开都河不同季节河流来水量变化以及湖周农田排盐水等因素直接相关,而湖水的矿化度与水位变化呈负相关.对湖水主要离子含量变化特点和湖区矿化度变化规律的研究表明,湖水补给源及湖水循环状况是影响湖水水质变化的主要因素.;Bosten Lake isone of the biggest freshwater lakes in China.On the basis of in situ hy drological and hy dro-chemical data of Bosten Lake, this paper discusses the annual and seasonal change of water saltof Bosten Lake in detail.During the past 40 years or so, The lake water has undergone an annual changing process and the seasonal change is closely related to the water discharge coming from Kaidu River thatis the largest water source supplying for the Bosten Lake.The farmland drainage contains salt around the Lake.The change of mineralized deg ree in the lake is negatively correlated with the water levelin the pasr 40 years, i.e.when the water levelis lower, the lake mineralized deg ree is higher.With the increase of ion content, Ca²⁺ and Mg²⁺ increase slow ly, while the contents of SO₄^2-, Cl^-and K⁺+Na⁺ show markable increase.The descending ion contentorder is SO₄^2->Cl^->HCO₃->K⁺+Na⁺ >Mg²⁺ > Ca²⁺ >CO₃^2-, and its proportion may differ with the sampling positions in the lake.The hydro-chemical ty pe is SO₄^Na.The lake water sources and lake water circulation are the main factors that have impacts on the change of lake water quality.The measurement for improving Bosten lake water eco-environment are suggested as follows:farmland irrigation quota should be reduced, river water amount flowing into Bosten Lake be promised, the groundwater resources utilization in the Yanji Basin be sped-up, and the lake water circulation intensity streng thened.