Sedimentary Conditions of Evaporites in the Late Jurassic Xiali Formation,Qiangtang Basin：Evidence from Geochemistry Records

The Qiangtang Basin（QB）, located in the central Tibetan Plateau, is a Jurassic marine basin and one of the most important prospective salt resource belts in China. In recent decades, many outcrops of gypsiferous bed have been found in the Jurassic marine strata in the basin. Salt springs with abnormally high sodium（Na-＋） contents had been identified in the Late Jurassic Xiali Formation（Fm.） in the basin in the last years. However, to date, no potash or halite deposits have been identified in the QB. Gypsum outcrops and salt springs are very important signs in the investigation of halite and potash deposits. Therefore, the Xiali Fm. is a potentially valuable layer to evaluate for the possible presence of halite and potash deposits in the basin. However, few studies have explored the formation conditions of evaporites in the unit. Here, we present detailed geochemical records from the Yanshiping section related to the study of the formation conditions of evaporites in the Xiali Fm. of the QB. Climate proxies based on the obviously increased anion concentrations of SO4（2-） and Cl-- and the significant correlation coefficients of Ca2＋-SO42-（R = 0.985） and Na-＋-Cl--（R = 0.8974） reveal that the upper member of the Xiali Fm.（the upper Xiali Fm.） formed under an arid climate and evolved into the sulfate phase or early chloride phase. Provenance proxies based on the obviously increased K-＋ and Na-＋ ion concentrations and the significant correlation coefficient of Na-＋-Cl--（R = 0.8974） suggest that the upper Xiali Fm. featured optimal provenance conditions for the possible formation of halite deposits. The regression and the semi-closed tidal flat environment in the upper Xiali Fm. were favorable for the formation of potash and halite deposits. The low Mg-（2＋） /Ca-（2＋） values（mean value = 1.82） and significant Na-＋-Cl-- correlation coefficient（R = 0.8974） also suggest that the upper Xiali Fm. is the layer most likely to contain potential halite deposits. In addition, the macroscopic correlations of tectonism, provenance, paleoclimate, saliferous strata and sedimentary environment between the QB and the adjoining Amu Darya Basin in Central Asia reveal that the two basins shared similar geologic settings that were favorable for the formation of evaporites during the Late Jurassic. Therefore, the upper Xiali Fm. is a valuable layer to explore for halite deposit and may be potentially valuable in the future exploration for potash deposits in the QB.

Sulfur Isotope Composition of Evaporites in Different Strata in the Tarim Basin

Evaporite series is both an important target area looking for high-quality large potash deposits,but also one of the main types of hydrocarbon cap.Outcrops and drilling results indicate that five sets of evaporites were developed

Occurrence and conceptual sedimentary model of Cambrian gypsum-bearing evaporites in the Sichuan Basin, SW China

During the Cambrian, gypsum-bearing evaporites formed in the Sichuan Basin, SW China. These rocks are important for oil and gas sealing, but details of their distribution and origin are not well established. This study examines the regional distribution and origin of the gypsum-bearing evaporites using a comprehensive analysis of drilling data from 34 wells, 5 measured cross-sections in the basin and surrounding area, and 96 maps of area-survey data. Results show that in the stratigraphic succession, the gypsum-bearing evaporites occur mainly in the Lower Cambrian Longwangmiao Formation, the Middle Cambrian Douposi Formation, and the Middle-Upper Cambrian Xixiangchi Group. Geographically, the rocks are found mainly in the southeastern part of the basin, and the distribution of deposits shows an overall SW-NE trend. The sedimentary environments for evaporite formation were evaporative lagoon and inter-platform basin in a platform setting. Gypsum was generated by the underwater concentration of sea water in a strongly evaporative environment. Both an evaporative restricted platform and a mixeddeposition restricted platform model appear to be applicable to the development of gypsum in the Sichuan Basin. The gypsum-bearing evaporites with the best sealing capacity are located mostly in the southeastern part of the basin. These constraints can be applied directly to regional exploration, and have implications for the regional paleogeography and paleoclimate.

Eogenetic Karst in Interbedded Carbonates and Evaporites and Its Impact on Hydrocarbon Reservoir: A New Case from Middle Triassic Leikoupo Formation in Sichuan Basin, Southwest China

Karst in interbedded carbonates and evaporites has been reported to have important and complex impacts on reservoir. It is significant for exploration and karst geology. Here, we report such a new case from Middle Triassic Leikoupo Formation of Sichuan Basin, Southwest China. Stratigraphic incompleteness and the occurrence of unconformity provide evidence for the presence of eogenetic karst. Under the impact of this eogenetic karst, residual weathered and solution-collapse breccia, solution pores and silicification and dedolomitization have been observed. Classic stratigraphic zonation of karst is not readily distinguishable, which is ascribed to the stratigraphic collapse of carbonate rocks resulting from the dissolution of evaporites by lateral subsurface fluid flow. In terms of impact on reservoir quality, karst can generally improve the initial physical property of the porous layers in theory. However, subsurface fluid flow dissolved the evarporitic beds and facilitated the collapse of overlying strata. As a consequence, the lateral continuity of the reservoirs would be destroyed, and relatively high-quality reservoirs can only be developed with little collapse of overlying strata, reflecting reservoir heterogeneities. This may be a general feature of reservoir formation under the impact of karst in interbedded carbonates and evaporites.

He-Ar-S-Pb Isotopic Compositions of Pyrite：Constraints on the Source of Ore-forming Materials of the Chengchao Skarn Iron Deposit,SE Hubei Province,Eastern China

The Chengchao iron deposit,the largest high-grade skarn iron deposit in southeastern Hubei Province,contains considerable amounts of magnetite and by-product anhydrite.To obtain better understanding of the ore-formation process,this study carried out He-Ar-S-Pb multi-isotopic analyses on the pyrites formed during two stages of mineralization.The results indicate that the δ34S values（ranging from 14.0‰ to 17.6‰） of pyrites formed from the two stages have no obvious differences,suggesting that they were not derived from a single magmatic sulfur source.The δ34S values of anhydrite mostly range from 21.9‰ to 28.4‰,similar to that of the Middle Triassic sedimentary anhydrite in the Middle-Lower Yangtze River metallogenic belt（MLYRB）.The Pb isotopic compositions of the pyrites of both stages are homogeneous,with values of 208Pb/204Pb,207Pb/204Pb,and-206Pb/204Pb being 38.006-38.257,15.523-15.556,and 17.806-18.052,respectively,indicating a mixed crust-mantle source.The He-Ar results exhibit different compositions of the two stages：the -3He/-4He（R/Ra） and 40Ar/-36Ar values for the early-stage pyrite are 0.46-0.63 and 311-322,respectively,whereas the values for late-stage pyrite are 0.23-0.34 and 305-361,respectively.Both stages of pyrites indicate the multiple sources of the ore-forming fluids,with decreasing amount of magmatic water and increasing amount of modified meteoric water（MASW） during fluid evolution.The Triassic evaporites played an important role in the mineralization process.

A Rapid Marine Regression in the Southwestern Tarim Basin in the Latest Cretaceous:Comparison of Two Different Evaporitic Sequences in the Yarkand Basin,Xinjiang Province,China

Two different evaporitic sequences occurred in the latest Cretaceous-Early Paleocene in Yarkand Basin,southwestern Tarim Basin,Xinjiang Province,China:one is characterized by poor gypsum and some small,lenticularshaped halite layers in the Tuyiluoke Formation of the latest Cretaceous,the other is characterized by very thick gypsum and halite layers in the Aertashen Formation of the early Paleocene.In the early developmental stage of the Tuyiluoke Formation,the Yarkand ancient saline lake was a long,strip-shaped depression,NW-SE oriented,along the West Kunlun piedmont,with its eastern boundary to the line along bores Ys1-T1-Ks101,the concentrated center located in the area of borehole S1.In the later developmental stage,the depositional scope was shifted inch by inch to the NW of this saline lake,forming a triangular depositional area,with apices at boreholes Wx1,Ak2 and S1,the concentrated center of the saline lake gradually migrating from borehole S1 region to the northwestern area of the lake,developing four small,evaporatedconcentrated sub-depressions,depositing lenticular-shaped halite.In the early Paleocene,the ancient saline lake was stretched from the West Kunlun piedmont in the west,to the Markit slope in the east,from the South Tianshan piedmont in the north,to the Hotan area in the south,accompanied by giant thicknesses of halite and large-scale gypsum layers,mainly interbedded with limestone in the Aertashen Formation.The evaporites in the latest Cretaceous-early Paleocene were controlled by the marine transgression-regression geological background in the Yarkand Basin.Generally,integrated evaporitic depositional sequences,such as clasolite-gypsum-halite-potash,usually occur in the presence of persistent seawater through evaporation,but this is not the case in the Tuyiluoke Formation.In contrast,very thick gypsum layers are common in the early Paleocene.Typically,adequate mineral sources for evaporites are found within seawater,such as in large basins undergoing long-term marine transgression-regression cycles,where adequate seawater remains,even though the basin was going through a marine regression stage.In the latest Cretaceous,thin gypsum layers indicate a lack of mineral sources.In contrast,the early Paleocene has far larger evaporites,both in width and thickness.This suggests a short-term marine regression stage must have occurred during the spatiotemporal evolution of the evaporites in the latest Cretaceous-Early Paleocene in the basin,meaning that a rapid marine regressive episode has been identified at the end of the Cretaceous.

Origin of Halite in the Lanping–Simao Basin,Southeastern Tibetan Plateau,China:Evidence from Sr and Cl Isotopes

The Lanping−Simao Basin is located on the southeastern Tibetan Plateau,China,and contains massive evaporites.The origin of evaporites in the basin has been hotly debated because of the strong transformation by tectonic movement.Forty halite samples from borehole MK-3 in the Mengyejing area of the basin were collected and analyzed using XRD,Cl-Sr isotopes and chemical compositions to trace the origin of the evaporites in the basin.The Br×10^(3)/Cl ratios of the halite samples are between 0 and 0.55,most of which are synchronized with the law of seawater evaporation and at the stage of halite precipitation from seawater,indicating that the evaporites are mainly of marine origin.The^(87)Sr/^(86)Sr ratios range from 0.707489 to 0.711279;after correction,the^(87)Sr/^(86)Sr 145 Ma ratios range from 0.704721 to 0.707611,equivalent with the 87Sr/86Sr ratios of seawater at 145 Ma,indicating a marine origin.The decay of 87Rb in the evaporite during deposition,change of the depositional environment and the unsealed environment at a later period resulted in the present^(87)Sr/^(86)Sr ratios of some samples being high.The δ^(37)Cl value compositions range from−0.38‰to 0.83‰,which is consistent with the δ^(37)Cl value composition of the world marine halite(−0.6‰to 0.4‰),further confirming that seawater is the main origin.In addition,the high δ^(37)Cl value of some samples at the boundary of the upper and lower evaporite layers might be related to the influence of δ^(37)Cl-rich brine and the incomplete dissolution of the halite.

Characteristics, formation and evolution of pre-salt dolomite reservoirs in the fifth member of the Ordovician Majiagou Formation, mid-east Ordos Basin, NW China

The characteristics and formation of the pre-salt dolomite reservoirs in the fifth member of Ordovician Majiagou Formation in the mid-east Ordos Basin are investigated through observation of cores and thin sections,and geochemical analysis.(1)The pre-salt dolomites can be divided into dolomicrite,grain dolomite and dolarenite,in which the main reservoir space consists of intercrystalline pores and various dissolved pores.(2)The diagenesis in the study area is complex and mainly includes dolomitization,dissolution,filling,and recrystallization.(3)Multi-stages of dolomitization,including penecontemporaneous capillary concentration dolomitization,seepagereflux dolomitization during penecontemporaneous and shallow burial stage,and burial dolomitization in later stage,are conducive to the preservation of primary pores and development of secondary pores.(4)Multi-stages of dissolution also have strong influence on the development of secondary pores;the secondary transgression and regression cycles during the contemporaneous-penecontemporaneous stage led to exposure and dissolution of soluble minerals and thus the generation of secondary pores.(5)In the burial stage,reservoir pores were further improved due to organic acid dissolution and the dissolution by hydrosulphuric acid from thermochemical sulfate reduction(TSR)and its product H2S.(6)High H2S concentration area in pre-salt reservoirs can thus be considered as targets for future exploration.

Groundwater hydrochemistry and isotope geochemistry in the Turpan Basin, northwestern China

The Turpan Basin is located in the arid zone of northwestern China and is a typical closed inland basin surrounded by high mountains. It is one of the most arid regions in the world and, as a result, the groundwater in this area is very important for both domestic and agricultural uses. In the present study, the relationships of major elements（K＋, Na＋, Ca2＋, Mg2＋, HCO3-, SO42- and Cl-） and environmental isotopes（δ18O, δ2H and T） in groundwater were analyzed to investigate the evolution of the regional hydrochemistry within the Turpan Basin. The hydrochemistry results demonstrate that groundwater with high total dissolved solids（TDS） concentration is dominated by sodium chloride（Na-Cl） and sodium sulfate（Na-SO4） type water, whereas that with low TDS concentration（typically from near mountain areas） is dominated by calcium bicarbonate（Ca-HCO3） type water. The evolution of groundwater hydrochemistry within the Turpan Basin is a result of calcium carbonate precipitation, evaporation concentration, cation exchange and dissolution of evaporites（i.e. halite, mirabilite and gypsum）. Furthermore, evaporite dissolution associated with irrigation practice plays a key role in the groundwater salinization, especially in the central part of the basin. Environmental isotopes reveal that the groundwater is recharged by precipitation in the mountain areas and fast vertical infiltration of irrigation return flow. In the southern sub-basin the shallow groundwater and the deep groundwater is separated at a depth of about 40 m, with substantial differences in terms of hydrochemical and isotopic characteristics. The results are useful for decision making related to sustainable water resource utilization in the Turpan Basin and other regions in northwestern China.

Interactions of Copper, Evaporite, and Organic Matter and Genesis of Sandstone-Hosted Copper Deposits in the Chuxiong Basin, Yunnan Province

Studies on organic geochemistry indicate that the origin, type and maturity of organic matter are different among coal-bearing, copper-bearing and evaporite formations in the Mesozoic continental Chuxiong Basin, Yunnan, China. A mechanism has been proposed that (1) during the diagenetic mineralization stage the short-chain organic acids dervied from kerogen played an important role in remobilizing copper from source beds, while oils acted as important carrier of copper, and that (2) during the transformation or remolding mineralization stage, meteoric water leached the evaporite layers and formed downward-percolating oxidizing SO42-rich fluids; meanwhile, the copper-bearing fluids migrating upwards along growth faults from the basement was contaminated by the coal-bearing series on the way and formed reducing organic-rich fluids; oxidation-reduction occurred and sulfides formed when the two kinds of fluids met within sandstones.

Connections between Evaporite Deposition and Glacial Periods since the Middle Pleistocene in Salt Lakes in the Western Qaidam Basin, China

The Quaternary was the main evaporite deposition period in the Qaidam Basin(QB), but the correlation between the evaporite deposition period and the glacial period is still unclear. In this study, the research objects are primarily evaporite-bearing strata in a 461.58 m-long drill core in the QB. X-ray powder diffraction(XRD) and scanning electron microscopy(SEM) were applied to study the evaporite minerals, U-Th dating being applied to construct the ~(230)Th geochronological framework. Evaporite deposition from Marine Isotope Stage(MIS) 15 to MIS 4 in the borehole was reconstructed via mineralogical and geochronological data. The evaporite minerals are mainly halite(NaCl), mirabilite(Na_(2)SO_(4)·10H_(2)O), thenardite(Na_(2)SO_(4)) and gypsum(CaSO_(4)·2H_(2)O). A total of 9 effective ~(230)Th data points, ranging from 492.5 ± 43.0 ka to 62.0 ± 11.9 ka, were obtained. The depositional age of the earliest halite layer in the borehole is 592.5–563.0 ka. There were mirabilite deposits in the QB during the cold glacial environment of MIS 6. During MIS 4, the study area desiccated, with mirabilite and halite being deposited. This study suggests that mirabilite is an indicator mineral for the glacial environment in the QB, while halite deposition does not correspond well to glaciation.

Control of paleogeographic pattern on sedimentary differentiation of evaporite-carbonate symbiotic system:A case study of the sixth sub-member of Ordovician Majiagou Formation M5 Member in central-eastern Ordos Basin,NW China

The relationship between paleogeographic pattern and sedimentary differentiation of evaporite-carbonate symbiotic system is examined based on logging,core and thin section data,by taking the sixth sub-member of fifth member of Ordovician Majiagou Formation(M56)in the central-eastern Ordos Basin as an example.(1)Seven sub-geomorphic units(Taolimiao west low,Taolimiao underwater high,Taolimiao east low,Hengshan high,East salt low,North slope and Southwest slope)developed in the study area.(2)The“three lows”from west to east developed dolomitic restricted lagoon,evaporite evaporative lagoon and salt evaporative lagoon sedimentary facies respectively,the"two highs"developed high-energy grain beach and microbial mound,and the north and south slopes developed dolomitic flats around land.(3)The paleogeographic pattern caused natural differentiation of replenishment seawater from the northwest Qilian sea,leading to the eccentric sedimentary differentiation of dolomite,evaporite and salt rock symbiotic system from west to east,which is different from the classic“bull's eye”and“tear drop”distribution patterns.(4)As the Middle Qilian block subducted and collided into the North China Plate,the far-end compression stress transferred,giving rise to the alternate highland and lowland in near north to south direction during the sedimentary period of M56 sub-member.(5)Taolimiao underwater high and Hengshan high developed favorable zones of microbial mounds and grain shoals in south to north strike in M56 sub-member,making them favorable exploration areas with great exploration potential in the future.

Uranium distribution in the lacustrine calcareous clastic-evaporite sequence in the western Qaidam Basin,and implications for U behavior in concentration of closed water

Uranium(U)provides especially useful information for reconstructing paleoredox conditions due to its unique geochemical properties and behavior in supergene environments.The proxy potential under suboxic-oxic

Evaporite Basin Reservoir Formation

1 Introduction Today,Industrial value of oil and gas basin in the world for a total of more than 120,which contain lamellar or lenticular evaporite a total of 66,about 55%of the basin.According to statistics,in the basin of oil,salt,symbiosis,46%of the oil and gas layer in the basin was

Modelling and applications of dissolution of rocks in geoengineering

The subsoil contains many evaporites such as limestone,gypsum,and salt.Such rocks are very sensitive to water.The deposit of evaporites raises questions because of their dissolution with time and the mechanical-geotechnical impact on the neighboring zone.Depending on the configuration of the site and the location of the rocks,the dissolution can lead to surface subsidence and,for instance,the formation of sinkholes and landslides.In this study,we present an approach that describes the dissolution process and its coupling with geotechnical engineering.In the first part we set the physico-mathematical framework,the hypothesis,and the limitations in which the dissolution process is stated.The physical interface between the fluid and the rock(porous)is represented by a diffuse interface of finite thickness.We briefly describe,in the framework of porous media,the steps needed to upscale the microscopic-scale(pore-scale)model to the macroscopic scale(Darcy scale).Although the constructed method has a large range of application,we will restrict it to saline and gypsum rocks.The second part is mainly devoted to the geotechnical consequences of the dissolution of gypsum material.We then analyze the effect of dissolution in the vicinity of a soil dam or slope and the partial dissolution of a gypsum pillar by a thin layer of water.These theoretical examples show the relevance and the potential of the approach in the general framework of geoengineering problems.

A Comparative Analysis of Evaporite Deposition on Earth and Mars

In this paper,the authors give a brief review of recent observations and studies on Martian salts.On the basis of the comparison of salt sediments on Earth and Mars,the authors propose that potassium salts might be widespread on Martian surface and subsurface.Besides,the authors found a positive correlation between the GRS results of the po-

A facies and palaeogeography-based approach for analysis of petroleum systems in United Arab Emirates

The United Arab Emirates(UAE) is the 8 th largest oil producing country and is rich in oil and gas resources. By the end of 2015, 68 oil and 23 gas fields had been discovered. The initial proved and probable(2 P) oil, gas and condensate reserves amount to 81,135.9 MMb(million barrels), 192.09 Tcf(trillion cubic feet),and 6496.58 MMb respectively, which are mostly reservoired in the Jurassic and Cretaceous carbonates. With the latest field data, this study attempts to document the salient features of petroleum systems in UAE. Based on depositional facies of source rock intervals, pods of source rocks were delineated. On the basis of an oiland gas-source correlation, five known petroleum systems were identified and they are Lower Silurian-Upper Permian Khuff gas, northeast foreland Upper Jurassic-Lower Cretaceous gas, Upper Jurassic-Jurassic petroleum, Upper Jurassic/Lower Cretaceous-Lower Cretaceous composite petroleum, and Middle Cretaceous-Middle to Upper Cretaceous/Cenozoic petroleum systems. Of them, the Upper Jurassic/Lower Cretaceous-Lower Cretaceous composite petroleum system contains 73.2% of the total 2 P reserves and thus it is the focus of this study. The Upper Jurassic and Lower Cretaceous source rocks consist of argillaceous limestone, mudstone and shale, which were deposited as intrashelf basin facies. The distribution of oil and gas in this system is controlled by the source kitchens and the regional evaporite seal.

New ideas on the tectonic of the Kurveleshi anticlinal belt in Albania, and the perspective for exploration in its subthrust

The external thrustbelt of Albania consists of some tectonic zones(Ionian,Kruja and Krasta-Cukali zones),that are westward overthrust,with a large amplitude(50e100 km),above the Apulian platform and South Adriatic Basin.The relative movement of the Adriatico-Apulian sub-plate between,the Euro Asiatic and African plates during from the Mesozoic to the Tertiary period,mainly controlled the tectonic evolution of the Albanides.The Ionian zone consists of anticline belts(Berati,Kurveleshi and Cika),that are overthrust toward the west with an amplitude about 20e30 km Their overthrustings was realized through regional sliding evaporitic horizons,which caused the masking of folded structures in the subthrust,with the perspective plays.The Kurveleshi anticlinal belt represents a mega-anticlinal with a length of 210 km and a width of about 20 km,and it is characterized by anticline structures with heterogeneous dimensions,predominantly those of great dimensions and linear type.The overthrusting of the anticline units has a local character,and it is more developed in the Kurveleshi anticlinal belt.Its magnitude is about 8e10 km.As a result of these overthrusts,imbrication and duplex styles are formed,leadind to the masking of the subthrust complex with structures of large interest(e.g.Delvina,Karbunara,etc.)where two oil fields have been dioscovered beneath the Mali Gjere anticline(Delvina oil field)and the Kremenara anticline(Karbunara oil field).Backthrust faults phenomena are secondary and they taken place in the post-collision stage.Generally they are easterward thrust faults of structural units with an amplitude of 5e10 km.The Kurveleshi anticlinal belt,based on tectonic features,is divided into two parts:The southern part,from Qafa Sevaster in the north down to Greece to the south.and northern part,from Qafa Sevaster in the south up to the end of the Patos-Verbas structure.In the southern part these features predominate:The anticline structures are large in size,and overthrust with a large amplitude(8e10 km)westward.The evaporitic diapirs have erupted through local faults of the anticline structures of the Kurveleshi anticlinal belt(Mali Gjere,Kurveleshi and Fterra anticlines).These eruptions(Delvina,Picar-Kapariel-Bashaj,etc.)have helped in the overthrusting of these structural units.It must be mentioned that the backthrusting is also affected by the diapir action.Moreover,vertical diapir occur,in the center of the structures like Navarica.In the northern part,the anticline structures are generally small to medium in size.Only the Patos-Verbas anticline is larger in size.In the Kurveleshi anticlinal belt the Ballsh and Visoka oilfields have developed.The eastern flank of the Shushica synclinal belt apears folded,and the carbonate anticline structures have developed.Existing oil fields include the Gorisht-Kocul,Cakran-Moallaj-Kreshpan and Amonica.These oil fields shoud continue towards the north(under the overthrust of the Patos-Verbas antcline)and in the south(under the regional ovethrust of the Kuervelesh anticlinal belt).

DESICCATION OF THE MIDDLE ORDOVICIAN EPEIRIC SEA IN NORTH CHINA

Ⅰ. INTRODUCTION The Middle Ordovician evaporites in North China have been commonly considered as distributing only in the central part of the epeiric sea. Their genesis has raised much controversy among sedimentologists. The purpose of this study is to simulate the distribution

Marine transgression(s) to evaporite basin:The case of middle Miocene (Badenian) gypsum in the Central Paratethys, SE Poland

The middle Miocene Badenian evaporite basin of the Carpathian Foredeep Basin was a saline lake, separated by a barrier from the sea and supplied with seawater seeping through the barrier or overflowing it occasionally in the form of short-lived marine transgressions. Such transgressions could leave behind marine microfossils in marly clay intercalations. One of them(2.3 m thick) occurs in the uppermost part of the sulphate sequence, in the unit ‘o’, in the Babczyn 2 borehole section. It contains marine palynomorphs(dinoflagellate cysts) and foraminiferal assemblages indicating a marine environment. The low-diversity benthic foraminiferal assemblages are dominated by opportunistic, shallow infaunally living species, preferring muddy or clayey substrate for thriving, brackish to normal marine salinity, and inner shelf environment. Dinoflagellate cyst assemblages, although taxonomically impoverished, consist of marine species;euryhaline forms that tolerate increased salinity are missing. Relatively common microfossils found in clay intercalations within gypsum have important palaeogeographical implications:they strongly suggest that there existed an additional inflow channel supplying the Polish Carpathian Basin from the south during the evaporite deposition and afterwards.