Load structures are known as an important type of soft sediment deformation structure,and are characterized by gravity(density difference)as the main driving force and deformation occurring at the lithologic interface with inverted density. According to whether the deformation structures are separated from the parent body,load structures can be divided into three categories including,non-separated load structures,separated load structures,and composite load structures. The non-separated load structures include heavy load(mold)structures,flame structures,water drop structures and diapir(extrusion)structures,and the separated load structures includes sand ball(false nodule),ball pillow layer and mud ball. A large number of load structures were recognized in the cores and outcrops of the Yanchang Formation of the Late Triassic in the Ordos Basin. Through the analysis of the characteristics,formation conditions and triggering mechanisms of different types of load structures,it is believed that the load structures were the result of the dual mechanisms of earthquakes and gravity. In addition to gravity,seismic disturbance was also the main reason for the formation of various deformation structures. It reflects the characteristics of strong tectonic activity in the Ordos basin during the Middle Indosinian Movement.
A series of tectonic movements during the Late Mesozoic greatly changed the topography and landform in eastern China,forming a geomorphic pattern of “high in the east and low in the west”. There is still a controversial issue on the existence of plateaus or mountains in eastern China during the Cretaceous,and thus the evolutionary processes,paleoaltitude and the extensional range of plateaus or mountains need further studies. In this paper,we collected the palynological data of xerophyte and disaccate pollen from vorious localities of China during the Cretaceous,and further discussed the paleovegetation succession and palaeoclimate evolution,which provides paleontological evidence for the interpretation of the geomorphology in eastern China at that time. The result shows that there were three climate zones in China during the Cretaceous: (i)the northeastern region was a warm and humid subtropical-warm climate zone;(ii)the northern region was a semi-arid tropical-subtropical transitional climate zone;(iii)the Tibet,Xinjiang and southern China were a hot and tropical-subtropical climate zone. The interpretation of the geomorphology shows that there was a high-altitude landform in northeast China during the early Early Cretaceous. Additionally,it is likely that coastal mountains existed in the Fujian and Zhejiang regions during the Early Cretaceous. In early Late Cretaceous,the range of coastal mountains in eastern China reached its maximum. From the late Late Cretaceous to Early Paleocene,the mountains in eastern China gradually collapsed,and by the Early Paleocene,the mountains were probably disappeared.
The newly discovered hyoliths yielded from the Lower Devonian of East Junggar of Xinjiang,China,are documented herein for the first time,including three genera and three species: Fuyunotheca wangi gen. et sp. nov.,Costulatotheca schleigeri Earp,2019,and Ottomarites sp. As a new genus and species,F.wangi gen. et sp. nov. is mainly distinguished by typically oblate oval to subtriangular cross-section,swollen dorsal side with a pronounced median ridge,ventral side weakly convex. Surface sculpture prominent transverse striations and weakly longitudinal streaks on both dorsum and venter,and several sets of remarkable ribs parallel to the aperture in the anterior third of the conch. Palaeoecological analysis shows that F.wangi gen. et sp. nov. is a kind of orthothecids,which could live in a normal,oxygenated shallow-marine environment with certain degree of hydrodynamics. Furthermore,based on the Devonian hyoliths reported so far from all over the world,it has been recognized 14 genera and 66 species as valid from 12 areas in 11 countries(excluding indeterminate genera and species). Palaeogeographic distribution analysis shows that the Devonian hyoliths were mainly distributed in the southern hemisphere,that were positioned near the Laurussia and Gondwana,with a few species sporadically distributed in other plates or blocks. Newly discovered specimens of these early Devonian hyoliths not only expands the palaeogeographic distribution range of hyoliths during the Devonian period,but also provides new evidence for inter-continental biostratigraphic correlation. Phylum uncertain Class Hyolitha Marek, 1963 Order Orthothecida Marek, 1966 Family INDET. Fuyunotheca gen. nov. Type species Fuyunotheca wangi gen. et sp. nov. Etymology Fuyun(Gr.)is derived from the Chinese Pinyin of the word “Fuyun” of Fuyun County,Altay Prefecture,Xinjiang. The theca(Gr.)means the capsule,membrane,sheath,and shell of organisms. Diagnosis Orthothecids having straight and middle-sized conch with oblate oval to subtriangular cross-section;swollen dorsal side with a pronounced median ridge;ventral side flat to weakly convex. Aperture straight or almost straight. Apical part of shell blunt. No apical septa were found. Surface sculpture prominent transverse striations and weakly longitudinal streaks on both dorsum and venter,and several sets of remarkable ribs parallel to the aperture in anterior third of the conch near the apertural side. The separation distances between each set of transverse ribs gradually widen from the aperture to the apical end of the shell. Operculum is unknown. Remarks The main difference between Hyolithida and Orthothecida is that the former has protrusions(lips)on the ventral side of aperture(Malinky and Racheboeuf,2010). The aperture of the new genus Fuyunotheca gen. nov. is straight and without protrusions,so it can be attributed to the order Orthothecida Marek,1966. According to the taxonomy of Orthothecidae Sysoev,1958 revised by Malinky(2009b),its venter is concave to flat,and sculpture of conch consists of longitudinal ridges or lines,without transverse ornamentation. The new genus has the similar conch with that of the family Orthothecidae,but differs from them in having a flat to slightly convex venter and sets of unique transverse ribs on the conch. The new genus is similar to Bolitheca Marek and Isaacson,1992 and Neobactrotheca Marek and Isaacson,1992 from the Middle Devonian Icla Formation of Bolivia. However,specimens of Bolitheca exhibit pronounced longitudinal ridges on the dorsum,the semi-elliptical cross-section,and rounded lateral ridges(Malinky and Racheboeuf,2011). Specimens of Neobactrotheca have many longitudinal ridges and no median ridges on the dorsum. Besides,the conch of Neobactrotheca differs from that of this new species by having elliptical cross-section and smooth transitions to the lateral ridges(Marek and Isaacson,1992). It is for this reason that we establish a new genus,belonging to the indeterminate family. Fuyunotheca wangi gen. et sp. nov. Fig.2 Etymology The species is named in honor of Wang Hongzhen,the famous paleontologist who described hyoliths from China for the first time. Holotypoe One well-preserved dorsum of conch,specimen number: XJLD-001(Fig.2-A). Paratype One well-preserved venter of conch,specimen number: XJLD-003(Fig.2-C). Other materials Specimen registration number: XJLD-002,004—046. Venter or dorsum of 44 conchs with incomplete aperture or initial part. Diagnosis As for the genus. Description The conch is straight and conical,expanding gradually and evenly from the apex to the aperture, and the aperture is thickened(Fig.2-E,ta). The growth angle of the conch is about 9.90°. The length of the shell is about 41 mm,and the diameter of the aperture is about 9 mm. The dorsum passes through the oblate lateral ridge to the venter,and its cross-section has oblate oval to subtriangular shape(Fig.2-B2). There is a median ridge running through the conch(Fig.2-A,B1,dmr)in the middle of dorsum. There are slightly inclined surfaces on both sides of the ridge,and a longitudinal groove on the right slope(Fig.2-A,gr). Sets of remarkable ribs(Fig.2-A,2-C,2-D,tr)parallel to the aperture are distributed in the anterior third of the conch. There are five groups of ridges(Fig.2-A,tr1-tr5)which are made up of 2-5 transverse ridges in each group. The separation distances between each set of transverse ribs gradually widen from the aperture to the apical end of the shell. Surface of shell from the middle to the initial part covered with slight growth lines(Fig.2-F,tl). In addition,the conch is also decorated with weakly longitudinal lines(Fig.2-G,ll),that are most prominent next to aperture but become fainter in direction of apex. But longitudinal lines become thicker near the lateral ridge(Fig.2-G,tll),which may be caused by pressure applied to the shell during diagenes. Ventral side almost flat to very slightly convex,and bears the same ornamentation as the dorsum without a median ridge(Fig.2-C,2-D,tr). The apex is damaged to some extent,but it still can be seen that it is bluntly rounded in form,and no septa are visible. Locality and horizon The first member of the Tuoranggekuduke Formation,Emsian Age,Lower Devonian,Chawukar area,Fuyun County,Altay Prefecture,Xinjiang.
Silicate rocks are factors that influence the global carbon cycle as well as climate change by chemically reacting with carbon dioxide,removing atmospheric carbon dioxide and sequestering it in weathering products or ocean carbonate rocks. Quantifying the total amount of carbon dioxide consumed by weathering of global silicate rocks is key to understanding the Earth’s current and past climate change. This paper systematically investigates the data sources,research methods,calculation formulas,and main influencing factors of five quantitative models of chemical weathering-CO2 consumption of silicate rocks. The CO2 consumption calculated by the latest Celine model serves as a reference standard for comparing the advantages,disadvantages and scope of application of each model. The existing models estimate the global carbon dioxide consumption of chemical weathering of rock silicate rocks to be 69-169 Tg/yr,in which the main parameters of each model include climate(temperature,runoff)and lithology,and the secondary parameters include tectonic uplift,volcanism and plant interaction. Future exploration of the quantitative calculation of carbon dioxide consumed by the chemical weathering of silicate rocks should consider more control effects and the interconnections between factors. In addition,the use of big data analysis methods to generalize these quantitative models to the reconstruction of the palaeoclimate of the deep earth may be a future research trend.
This paper briefly describes the new achievements of oil and gas exploration in carbonates,deeply buried carbonate rocks,especially the genetic theory of dolomites at the 17th National Congress of Palaeogeography and Sedimentology. The relevant theme includes 55 oral presentations and 15 panels,which are related to(1)the genesis and reservoir of dolomite in Tarim,Sichuan,Ordos,Qaidam,Tuha and Bohai Bay basins,(2)formation,characteristics and preservation mechanism of deep and ultra-deep dolomite reservoirs,and(3)quantitative evaluation of bioliths and carbonate formation processes. It is worth recommending the study on the characteristics and genetic mechanism of high-quality,ultra-deep(10 km)dolomite reservoir,Exploration of the ultra-deep dolomite has become a representative result of the genetic theory of dolomite,guiding production practice. It is a supplement to the weak link in the application of basic research of dolomite genesis in the 21st International Sedimentology Congress(2022,Beijing)and in recent years. The summary of the characteristics and genetic mechanism of deep dolomite reservoirs in various parts of the Sichuan Basin comes from graduate students’ summary of the results of different university projects,which is very valuable. The theory of formation of deep dolomite reservoir,evaluation and exploration of high-quality ultra-deep dolomite reservoir is put forward. In particular,the laser ablation plasma mass spectrometry U-Pb dating technique has been widely used,which has realized the qualitative and quantitative analysis of the characteristics and genetic mechanism of dolomitization in geological time. The discussion of biolith is characteristic. They represent the close integration of sedimentology,lithofacies and paleogeography,mineralogy and petrology,new technology and dolomite genetic theory and practical application. The overall innovation depth,research means,system theory and application characteristics in oil and gas exploration deployment are significant,which is the highlight of this conference. Shortcomings are represented by the only one poster on marine reef dolomite. It is expected that the 18th Karamay Conference will further deepen the research in the above fields,and the topic of marine island dolomite research will be paid more attention.
Quartz is an important part of shale,making it crucial to clarify its genetic mechanism for the reconstruction of shale diagenetic process and the formation of shale oil and gas reservoir. The genesis of quartz in shale is complex,with the main types, including terrigenous detrital quartz,biogenic quartz and diagenetic authigenic quartz, identifiable through ordinary thin section observation,scanning electron microscopy,energy spectrum analysis and cathodoluminescence. The main sources of diagenetic authigenic quartz silica are clay mineral transformation,felsic dissolution and biosilicon dissolution,and volcano-hydrothermal activity. Terrigenous detrital quartz is mostly silt-grade and strongly emits light under cathodoluminescence,typically displaying a two-peak spectrum. Micron-sized biogenic quartz does not emit light,and clay mineral-derived quartz is predoninantly found around or embedded within clay minerals, such as illite. In addition to the morphology and occurrence characteristics of different types of quartz,there are also differences in geochemical elements. Quartz affected by hydrothermal activities is rich in Fe and Mn,while terrigenous detrital quartz is rich in Ti and Al elements. Detrital SiO2 and Zr are positive correlation,as does biogenic quartz with TOC content. The biogenic quartz Fe/Ti ranges between 0.4 and 20. Diagenetic authigenic quartz is formed in multiple stages,which is closely related to the burial diagenesis process of shale and affects the properties of shale reservoirs. Diagenetic authigenic quartz is mainly formed in early and middle diagenetic stages. Terrigenous detrital quartz and biogenic quartz are conducive to inhibiting compaction and protecting primary pores. Processes involving diagenetic authigenic quartz, like clay mineral transformation and felsic dissolution create dissolution pores and organic pores,with quartz filling some pores,thereby reducing porosity. Identifying the origin of quartz in shale is of great significance to the analysis of shale sedimentary environment and the prediction of favorable reservoir distribution.
