Preliminary results of lithological and palynological study of Svobodny,ancient man’s parking relic in Amur region,Russia

A single-layer monument Svobodny,ancient man's parking lot-1,discovered in 2021 as part of archaeological work to study the zone of economic development of the Amur region was investigated lithologically and palynologically.Based on the results of geomorphological analysis of the territory,the study of artifacts,palynological data,as well as analogy with previously identified and sufficiently studied relics in the region,the existence of the Osinoozersk late Neolithic culture in this territory is assumed.The time of its expansion in the Amur region is determined within the framework of the second half of theⅣmillennium BC to the first half of theⅡmillennium BC.The preliminary results of palynological analysis suggest the existence of a temperate climate here,was close to the modern one,which does not contradict the reconstructed paleoclimate and environments of the region during the Holocene period.

Organic geochemical,petrographic and palynological characterization of claystones of the Palaeogene Toraja Formation,and oil seeps in the Enrekang Sub-basin,south Sulawesi,Indonesia:Implications for hydrocarbon source rock potential

An organic geochemical,petrographical,and palynological evaluation was conducted on 30 claystone outcrop samples of the Toraja Formation,along with a geochemical analysis of an oil seep in the Enrekang Sub-basin.The aim of the study was to determine the correlation between oil and source rock in terms of age,depositional environment,organic material sources,and maturity level.The total organic carbon content of the claystone samples varies from 0.03 to 4.52 wt%,which are classified as poor to excellent.The claystones are immature to post-mature with a mixture of TypeⅡandⅢkerogen.Their vitrinite reflectance values range from 0.47 to 4.52%Ro.The samples of Toraja Formation rock and the oil seep source rock might have a similar depositional environment,a deltaic marine depositional setting with high oxidizing conditions.Organic material sources for rock and oil samples are dominated by terrestrial input.The oil is inferred to have originated from the Paleogene source rocks,which correlates in age with the Toraja Formation.The recovered palynomorphs from the studied rock samples suggest a late Eocene to Oligocene age with a strong terrestrial influence of shallow marine depositional setting.The biomarker analysis shows that the rock samples have a more substantial contribution from the terrigenous higher plants,while the oil sample indicates a higher degree of marine influence.The maturity levels are also different between the oil(peak mature)and the analyzed rock samples(immature).It is inferred that the oil seep source rock is equivalent to the analyzed rock sample but more mature,having been deposited under more marine conditions.The oil seep source rock is not exposed and is located in the deeper part of the basin.A deeper marine facies(i.e.distal delta front and prodelta facies)in front of the distributary mouth bar within a delta is interpreted as the source rock of the oil seep sample.

Palynological Evidence of Late Pleistocene Soft-sediment Deformation Event in the Northeastern Margin of the Tibetan Plateau

The northeastern margin of the Tibetan Plateau is the youngest part of the Tibetan Plateau where tectonic activity is intense and climate change is complex.In this study,combined with field investigations,we explored accelerator mass spectrometry 14C and optically stimulated luminescence dating and palynological analysis of the sedimentary sequence in the Qingshuihe Basin to explain the origin of soft-sediment deformation layer.Dating and palynological results from the Sanchahe section in the basin revealed a detailed history of vegetation variation and associated climate change from~18 to~5 ka BP.The results indicate that the permafrost developed at~18–11.7 ka BP,and the soft-sediment deformation structures formed at~11.7–5 ka BP.Together with the characteristics of the deformation(meter-scale,continuous symmetrical wave)and paleoclimate,we suggest that the soft-sediment deformation layer in the late Pleistocene was cryoturbated under climatic conditions.The discovery of a series of cryoturbations in the Qingshuihe Basin has further enriched the regional distribution of periglacial phenomena in the west of the Ordos Plateau,expanded the distribution range of periglacial phenomena,and provided evidence for exploring the temporal and spatial changes in permafrost in northern China at the end of the late Pleistocene.

A New Palynological Assemblage from the Nenjiang Formation of Dayangshu Basin, and its Geological Implication

Objective The Dayangshu Basin located in eastern Inner Mongolia,is one of the key areas for oil and gas exploration in the periphery of Songliao Basin.So far,this basin has been poorly explored,and the basic geological research is still weak,due to the lack of high-quality paleontologic and stratigraphic data.The previous oil and gas investigations were mainly focused on the Early Cretaceous strata.However,the Late Cretaceous Nenjiang Formation in the basin also has hydrocarbon potential according to the latest research.In recent oil and gas geological survey,palynological fossils have been discovered from the Nenjiang Formation in the Dayangshu Basin,providing new evidence for biostratigraphic division and correlation.

Climate characteristics of the eastern Mongolian Plateau,China during the early Early Cretaceous(145-132 Ma):Palynological evidence from the Tongbomiao Formation in Well Hong-6,Hailar Basin

This study identified two palynological assemblages,namely Bayanhuasporites-Cycadopites-Protoconiferus and Cicatricosisporites-Cedripites-Perinopollenites,in the Tongbomiao Formation in the Hongqi Sag in the Hailar Basin,Inner Mongolia,China for the first time.The former is distributed in the lower part of the Tongbomiao Formation and is characterized by abundant gymnosperm pollen and diverse fern spores.Among them,the gymnosperm pollen is dominated by Paleoconifer(4.98%-31.62%)and Cycadopite(8.55%-25.23%)pollen grains and also includes other pollen grains such as Classopollis,Parcisporites,Erlianpollis,Callialasporites,and Jiaohepollis.The fern spores in the former palynological assemblage contain Bayanhuasporite(0-8.96%),Granulatisporites(0.93%-6.97%),and some important Cretaceous genera,such as Cicatricosisporites,Concavissimisporites,Densoisporites,Hsuisporites,Foraminisporis,and Leptolepidites.The Cicatricosisporites-Cedripites-Perinopollenites palynological assemblage is distributed in the upper part of the Tongbomiao Formation.Gymnosperm(77.30%),Pinaceae(31.9%),and Paleoconiferus(19.02%)pollen predominate this palynological assemblage,and Quadraeculina,Erlianpollis,and Jiaohepollis pollen are also common in this assemblage.The fern spores in this palynological assemblage include abundant Cicatricosisporites(4.29%).Besides,Concavissimisporites,Aequitriradites,and Leptolepidites are also common in this palynological assemblage.No angiosperm pollen has been found in both palynological assemblages.The identification of both palynological assemblages provides important evidence for the biostratigraphic correlation between the Hailar Basin and its adjacent areas.It also enables the reconstructions of the Berriasian-Valanginian(Early Cretaceous)vegetation and the paleoclimate on the eastern Mongolian Plateau during 141-132 Ma.The vegetation reconstructed on the palynological data of the represented by Hailar Basin in eastern Mongolian Plateau(141.6-141.4 Ma),form conifer forest or conifer broad-leaved mixed forest to conifer forest with shrubs and grassland,the climate belongs to warm temperate and warm-subtropicalt,the highest temperature is estimated to reach 35-38℃.Form 132.3 Ma,the vegetation type is conifer forest,and its paleoclimate is sub-humid warm temperate,the highest temperature is estimated to reach 24-29℃.

Palynological and Physicochemical Characterization of Honey in the Sudano-Guinean Zone of Cameroon

The palynological and physico-chemical characterization of honey was investigated in the Sudano- Guinean zone of Cameroon through the melissopalynology analysis. Results showed that honey with the dark amber color was the most represented. Sweet honey with less odour considered as pleasant highly predominate. The pH of honey is low and varies from 3.95 to 5.00;this ranking confirms the hypothesis that honey is from plant through visit of honeybees. The sugar content is very high ranging from 77.93% to 83.13%;the mean value is 78.90% and this value confirms that the honey is floral honey. The density value ranges from 1.39 to 1.43 and does not exceed the average standard (1.39 to 1.44 at 20℃). Water contents correspond to the standards norms. For free acidity, the highest value is 48.68 ± 0.28. There is a low positive correlation (r = 0.2) between free acidity and the pH of honey. Pollen analysis of honeys led to the identification of 41 pollen species belonging to 25 families. The highly represented families are Asteraceae and Myrtaceae. Two thirds of honey is monofloral and characteristics of three dominant species: Nymphaea maculata, Terminalia avicennioides and Syzygium guineense. The pollens of Syzygium guineense are present in all honey samples analysed.

Palynological Assemblage Age and Palaeoenvironment of the Cretaceous Salt-bearing Strata in Laos and Yunnan,China

The study of Cretaceous-Palaeogene salt-bearing strata of the Khorat Basin Laos and the Lanping-Simao Basin in Yunnan,China has an great significance not only in explaining the basin evolution and the genesis of potash

Palynological Analysis of Amber-Bearing Clay from the Lower Cretaceous of Central Lebanon

An amber-bearing lignitic layer of sandy clay from the Lower Cretaceous of Central Lebanon （Mderej-Hammana）yielded a well-preserved,moderately variegated palynoflora,which origin is mixed between land plants and marine microflora.Its detailed analysis led to fulfill its inventory,to propose a paleoenvironmental reconstruction,and to draw the paleoclimate which prevailed over the region：an estuarian area under a rather humid,temperate climate;a variety of ferns grew near the shore-side and in the inward land.A tiny piece of amber containing angiospermous pollen grains of stratigraphical interest allows a precise dating.The marine microflora,poorly diversified,includes chitinous foraminifer linings and dinoflagellate cysts,among which Early Aptian guide taxa are present;their occurrence slightly narrows the stratigraphical range indicated by some palynological taxa which are related to land plants.

Environment and Age of the Upper Devonian‒Carboniferous Zhulumute and Hongguleleng Formations,Junggar Basin,NW China:Ichnological and Palynological Aspects

Two Upper Devonian to Lower Carboniferous sections,namely the Bulongguoer and Haer(Gennaren area)in the Junggar Basin,Central Asian Orogenic Belt,in northwestern China were examined with regard to ichnology and palynology.The deposits of the Hongguleleng Formation and Namu Member of the Heishantou Formation,respectively,are mostly unbioturbated or poorly bioturbated,with poorly diversified trace fossils,which indicate unfavourable conditions for the burrowing benthic community during the Late Devonian and Early Carboniferous.The main factor governing the growth of the bioturbating population was the rapid sedimentation of fine-grained,volcanic material documented as tempestites,which buried the benthic fauna.In the Bulongguoer section,the presence of miospores Teichertospora torquata and Grandispora gracilis enabled identification of the broad Teichertospora torquata–Grandispora gracilis Miospore Zone from the transitional Frasnian/Famennian interval.More accurate identification of palynostratigraphical levels(DE and CZ Miospore zones)is only tentative.On the basis of palynofacies analysis,samples from the lower Bulongguoer section indicate deposition in more proximal conditions,whereas samples from the top of the section indicate deposition in a more distal environment.In the Haer section,only a general biostratigraphic indication for the Tournaisian was possible,owing to poor preservation of organic matter.

Reconstruction of Natural Climatic Conditions for the Last 10000 Years in the Komi Republic,NW Russia(From Palynological Data)

Investigation included palynological analysis and radiocarbon dating of the Holocene lake,alluvial (Oxbow lake)and swamp sediments in middle and northern Taiga subzones of the Komi Republic.On the basis of cores from three boreholes and fourteen outcrops,synchronous spectra correlation and Holocene separation were accomplished.Mean annual and July temperatures were estimated by

Palynological assemblage in the late Early Cretaceous from Sikouzi Section, Liupanshan Group, Central China and its implication to paleoenvironment change

The Cretaceous(ca.145 Ma^65 Ma)was characterized by remarkable greenhouse conditions which was more server than present greenhouse gas emissions.However,this special climate condition is mainly documented from marine records.The information derived from continental sediments including terrestrial vegetation is relatively scarce.Here,we report on a palynological study of 17 samples from the Lower Cretaceous Liupanshan Group of the Sikouzi Section(spanning116 Ma^103 Ma),Liupanshan Basin and analyzed for paleoclimate implications.The palynoflora is diverse,dominated by Classopollis(Cheirolepidiaceae),with abundant ferns and rare angiosperms.The dominant ferns are from Lygodiaceae and Schizaeaceae.The palynological data shows that the Early Cretaceous floras are derived from various settings,i.e.,the Coniferales on high elevation mountains,Cheirolepidiaceae along low hills near lakes,ferns in marsh wetlands,and algae in fresh water lakes.The palynoflora indicates that the climate in the Liupanshan area is hot and dry,and the palaeogeography is characterized by complex and various outlook during the Early Cretaceous,furthermore,climate evolution revealed by the vegetation can be divided into two stages during this period.From 116 Ma to 112 Ma,the concentration of thermophilic and xerophilous species such as Cheirolepidiaceae and Schizaeaceae were relatively low,conifers increased significantly,and fern concentration remained steady.This ecosystem suggests a humid and cold climate during this period.From 112 Ma to 103 Ma,the concentration of Cheirolepidiaceae and Schizaeaceae was relatively high,and conifers decreased significantly.Compared to the upper stage,the total percentage of Lygodiaceae spores were relatively low.Vegetation change during this period may indicate an increased trend of a dry and hot environment in this region.The trend of climate change recorded by the pollen assemblages during this period coincide with global sea surface temperature fluctuation.Thus,climate change recorded by the palynological assemblage in the Sikouzi section correlates well with global climate change during the Early Cretaceous.

Palynological Studies of Some Species of Aspleniaceae-Pteridophyta

Palynology of six fern species belonging to the family Aspleniaceae from Saudi Arabia are investigated by light microscope (LM). These are: Asplenium aethiopicum, Asplenium trichomanes, Asplenium adiantum-nigrum, Asplenium sp.1, Asplenium sp.2 and Ceterach officinarum. All studied spores are oblate-spheroidal in shape class, with 11 - 50 μm in equatorial diameter and with 12 - 49 μm in polar diameter. Two types of spores are recognized: monolete spores in Asplenium aethiopicum, Asplenium trichomanes, Asplenium adiantum-nigrum, Asplenium sp.2 and trilete spores in Asplenium sp.1 and Ceterach officinarum. The exospore (perine) is homogeneous and apparently double-layered in all the studied spores. The perispore is single or double-layered with a microlacunouse structure. The perispore layers can be distinguished by their different contrast, structure and thickness. The exospore sculpture varies from cristates-ridged (Asplenium aethiopicum), cristates granulate (Asplenium adiantum-nigrum), cristates scabrate (Asplenium trichomanes), regulate-scabrates (Asplenium sp.1 and Ceterach officinarum) to papillate or tuberculate sculpture (Asplenium sp.2). Comparison between the earlier studies of some species from Saudi Arabia is given. General characteristics like spore type, ornamentation and laesurae features as well as the number of exospore layers could be useful for taxonomy of Aspleniaceae.

A Systematic Revision of the Genus Plectranthus L. (Lamiaceae) in Saudi Arabia Based on Morphological, Palynological, and Micromorphological Characters of Trichomes

This study aims to investigate the morphology and ultrastructure characters of pollen grains and trichomes in order to evaluate their systematic value of these characters in specific and intraspecific separation of the Saudi Arabian Plectranthus species. A critical systematic revision of 7 species of Plectranthus (Lamiaceae) in Saudi Arabia was conducted by means of numerical analyses based on thirty-one morphological characters, including vegetative parts, seeds, pollen grains, and trichomes. Macro- and micro-morphological characters, including seed and pollen shape, size, coat sculpture, trichome structure, were studied. It reveals the presence of seven species, including two endemic species. The pollen grains were zonocolpate, hexacolpate, prolate to subprolate. Three types of exine ornamentation were recognized. Also, two trichome types could be distinguished and classified into glandular and non-glandular. The glandular trichomes could be distinguished as peltate, capitate and digitiform. The eglandular trichomes were single, uniseriate, multicellular. Pollen and trichome characters were found to be valuable, while seed characters presented only minor taxonomic value. On the basis of UPGMA clustering analysis four branches and clusters were distinguished. The results offer useful data for evaluating the taxonomy of Plectranthus both at subgeneric and sectional levels. Our results indicated some degree of similarity among the species of subgenus Burnatastrum. Plectranthus arabicus is considered as a separate group and may be treated as separate subgenus. Furthermore, the endemic species Plectranthus asirensis and Plectranthus hijazensis constitute a monophyletic group and there are close relationships between this group and Plectranthus tenuiflorus. A key for the identification of the investigated taxa based on studied characters is provided.

Organic Matter Characterization and Palynological Evidence of Mid-Ordovician to Pennsylvanian Age of the Tabenken Coal,Northwest Cameroon

In this work,we intend to investigate the kerogen composition of the Tabenken coal hence,its palaeo-depositional environment and age.Tabenken is one of the three areas in the continental sectors of the CVL(Cameroon Volcanic Line)where coal occurs in between a granitic basement and volcanic outpours.Samples of coal from this seam were studied to determine the organic matter richness,maturity,depositional environment and its age through organic geochemical techniques such as Rock-Eval pyrolysis and palynological studies.HI(Hydrogen Index)obtained is less than 200 mgHC/gTOC for most of the samples indicating Type III kerogen for these samples(gas prone)and terrestrial source of the original peat-forming organic matter.One sample presents a HI of 462 mgHC/gTOC indicating organic matter type II,prone to producing oil.Palynological studies reveal the presence of hydrogen-rich AOM(Amorphous Organic Matter)indicating preservation under dysoxic-anoxic conditions.High values of TOC ranging from 0.29 to 1.98 are suggestive of AOM of terrestrial origin.The remarkable absence of pollen suggestive of deposition before the Pennsylvanian during which the earliest forms of flowering plants first appeared displays a relative abundance of spores in the organic residue suggestive of deposition from the mid-Ordovician.Careful interpretation of palynological data suggests the coal was laid down from the mid-Ordovician to the Pennsylvanian age.

Palaeoenvironmental Evolution During the Holocene in Itapeva Lake,RS,Brazil:Palynological and Geochemical Records

Based on palynological and geochemical data(Organic Carbon-C_(org)and Sulphur-S)of sedimentary samples from a vibrocore,considerations about the palaeoenvironmental evolution of Itapeva Lake region during the Holocene are made.The analysed core(BOXVI)consists in its lowermost part of a fine to medium sand packet,rich in glauconitic minerals,whose upper limit is considered to be the Holocene-Pleistocene contact.Using Cluster analysis on palynomorphs combined with C_(org)and S data,it was possible to distinguish four zones related to the Holocene transgression-regression cycle.Variations in C_(org)and S data permitted the recognition of changes in palaeosalinity.Zone 1 represents the beginning of the Holocene sedimentation;palynomorphs composition reveals a marsh environment under predominating freshwater conditions.In Zone 2,the occurrence of dinoflagellate cysts and high S values,indicating brackish water,reflects Holocene sea level highstand around 5100yrs.B.P.High concentration of Cyperaceae associated with a significant increase in C_(org)in Zone 3 indicates a typical marsh environment influenced at least sometimes by higher saline water,reflecting a regression phase.Salvinia natans(L)All.and Cyperaceae grains are considered to be the most significant palynomorpha in Zone 4,characterising a freshwater marsh.Based on the occurrence of dinoflagellates sample 2,Operculodinium sp.,related to marine to estuarine environments,a question arises regarding about the time at which BarrierⅣbecame completely closed.

Does palynological diversity reflect floristic diversity?A case study from Northeast China

Fossil pollen data can provide important information of past vegetation diversity,on the basis of established relationship between modern palynological and floristic diversity.However,current studies on modern pollen assemblages in China have not examined this relationship yet.Herein,we report a case study from Northeast China,aiming to investigate the representation of modern palynological diversity to regional floristic diversity.A total of 87 sets of modern pollen and vegetation data from various vegetation types were applied to assess modern palynological diversity and floristic diversity in Northeast China,and the relationship between palynological and floristic diversity was studied using spatial pattern comparison and correlation analysis.Moreover,to reduce representation bias related to pollen production and dispersal,we calibrated pollen data using the Regional Estimates of Vegetation Abundance from Large Sites(REVEALS)model with Pollen Productivity Estimates(PPEs)and Fall Speeds of Pollen(FSP).The results show that the spatial variations of palynological and floristic richness among vegetation types are similar,and have a good positive correlation(r=0.41,p<0.01).However,palynological evenness presents a different spatial pattern from floristic evenness,with a weaker positive correlation(r=0.21,p>0.05).The calibration on pollen data using REVEALS model minimized the differences in spatial patterns between palynological and floristic diversity,and improved the correlations between them(richness,r=0.50,p<0.01;evenness,r=0.33,p<0.01).Our study indicates that palynological richness in Northeast China could reflect regional floristic richness in general,and the calibration with REVEALS model is recommended for reconstructing past floristic diversity from pollen data.

Discovery of Paleogene palynological assemblages from the Wanbaogou Group-complex in western part of the Eastern Kunlun orogenic belt and its geological significance

Wanbaogou Group-complex is a suit of melange aggregation of the EasternKunlun orogenic belt, which is divided into two parts, i.e. the exotic blocks and the matrix strata.Based on stromatolite fossils yielded in the exotic blocks, the age of this group-complex was oncedefined to the Precambrian. Recently, two Paleogene palynological assemblages have been found insamples from the matrix strata of the Upper Part in this group-complex by the authors: in ascendingorder, the Al-nipollenites-Quercoidites assemblage of Late Eocene and theCaryapollenites-Pinuspollenites assemblage of Early Oligocene. Those results show that the matrixstrata of this melange were mainly formed in Paleogene, and the event causing mixture should be aHimalayan Movement Phase. This paper is designed to provide some detailed evidence for determiningthe age of the matrix strata in this group-complex based upon study at the Kunlunqiao Section, whichwould be of important geological significance for further understanding this group-complex as asuit of melange aggregation and establishing or improving the stratigraphic framework of the studiedregion. The new finding will certainly benefit from now on the investigation on geotectonic andsedimentary evolution of Eastern Kunlun.

Palynological evidence sheds new light on the age of the Liuqu Conglomerates in Tibet and its geological significance

The Liuqu Conglomerates consist of a suit of terrestrial molasse deposits formed in a foreland basin of the Himalaya-Tibet orogenic belt before the collision of India and Eurasia.These deposits record considerable geological information regarding the late tectonic evolution of the Neotethyan ocean.The palynological study of interlayers of mudstone and mud-sandstones indicates an Oligocene age.The palynological assemblage consists mainly of deciduous broad-leaved angiosperms,with some coniferous gymnosperms and evergreen broad-leaved angiosperms.The deposits reflect a broad-leaved deciduous forest or mixed with conifer-broad-leaved forest ecotypes,showing a warm-temperate or temperate zone climatic environment.This work provides significant new information about the tectonic evolution,paleogeography,and paleoenvironment of southern Tibet during the Cenozoic.

The influence of organic sources and environments on source rock deposition during the periods of Cretaceous–Eocene and Oligocene–Miocene,northern Kalimantan

The sedimentary system of Kalimantan has undergone significant development since the Oligocene.Previous research have largely ignored the capacity of the Cretaceous–Eocene sediments to produce hydrocarbons,focusing instead primarily on the Oligocene–Miocene coal as the principal source rocks.Shales and coals from the outcrops in the northern margin of Kalimantan were analyzed with palynological and geochemical methods to characterize the palaeoenvironmental and palaeoecological differences between the Cretaceous–Eocene and the Oligocene–Miocene samples.The high proportion of Cheirolepidoaceae,Schizaeoisporites and Ephedripites in the pollen assemblage from the Cretaceous–Eocene outcrops reflects an arid tropical/subtropical climate.The relatively low abundances of gymnosperm-derived biomarkers including isopimarane,β-phyllocladane,β-kaurane,suggest the gymnosperm features in flora.High C_(27)/C_(29)ααα20R sterane ratios,(C_(19)–C_(29))tricyclic terpanes/C_(30)αβhopane and extremely low oleanane/C_(30)αβhopane,bicadinane T/C_(30)αβhopane,and diterpenoid abundance indicate that there was a dominance of algae relative to higher plants in the organic matter.The gymnosperm-derived biomarkers,including isopimarane,β-phyllocladane,β-kaurane,suggest that palaeovegetation during this period was dominated by gymnosperms.The saline and reducing conditions in the bathyal and abysmal sea,evidenced by rather low Pr/Ph and high Gammarerane index,are beneficial for the preservation of hydrogen-rich organic matter.It is presumed that the Cretaceous–Eocene shales had great hydrocarbon generation potential in the southern South China Sea.During the period of Oligocene to Miocene in the Zengmu Basin and the Baram-Sabah Basin,the climate changed to a dominant humid and warm condition,which is corroborated by abundant pollen of Florschuetzia and Magnastriatites hawardi.Low C_(27)/C_(29)ααα20R sterane ratios,(C_(19)–C_(29))tricyclic terpanes/C_(30)αβhopane,and high oleanane/C_(30)αβhopane,bicadinane T/C_(30)αβhopane suggest that the palaeovegetation was dominated by angiosperms including the mangrove plants.The extremely abundant higher plants provide ample terrigenous organic matter for the formation of coal-measures in delta facies.The low gammacerane index and high Pr/Ph indicate the fresh and sub-oxic water in delta-neriticabysmal faces,which is not beneficial for the accumulation of hydrogen-rich organic matter.Thus,the Oligocene–Miocene marine argillaceous rocks can be potential sources of natural gas.