Northern Tianshan Mountains Research Articles

Provenance Characteristics from the Mesozoic to Cenozoic Era and Their Implications for Basin-Mountain System Evolution in the Southwestern Junggar Basin: Insights from Field Outcrop Observations in the Tostai Area

The Mesozoic-Cenozoic formations in the southwestern Junggar Basin are a key target for oil and gas exploration. However, complex provenance conditions hinder comprehensive understanding of sedimentary reservoirs. Based on petrology and elemental geochemistry analysis of field outcrops in the Tostai area. Research was conducted on the tectonic background, sediment transport distances, compositions of parent rocks and evolutionary Characteristics of Provenance Conditions in the provenance areas. It is generally believed that there have been three notable shifts in basin-mountain relationships during this period. Initially, from the Triassic to Jurassic, the Northern Tianshan magmatic rock area predominated as the primary provenance, with decreasing basin-mountain proximity and predominantly magmatic rock sediment composition indicating near provenance. Subsequently, heightened Cretaceous tectonic activity in the Tianshan Mountains led to significant uplift of metamorphic rock regions in the Middle Tianshan Mountains, gradually becoming the provenance for the study area. This increased distance between provenance and sedimentary areas, marked by a substantial presence of metamorphic rocks in sediments indicating far provenance. Lastly, the Cenozoic Himalayan movement resulted in vigorous uplift of the magmatic rock area in the northern Tianshan Mountains, reestablishing it as the primary provenance. This minimized basin-mountain distance, leading to deposition of near-provenance transported alluvial fans, braided rivers, and predominantly magmatic rock sediments.

Environmental and Climatic Drivers of Phytoplankton Communities in Central Asia.

Artificial water bodies in Central Asia offer unique environments in which to study plankton diversity influenced by topographic barriers. However, the complexity of these ecosystems and limited comprehensive studies in the region challenge our understanding. In this study, we systematically investigated the water environment parameters and phytoplankton community structure by surveying 14 artificial waters on the southern side of the Altai Mountains and the northern and southern sides of the Tianshan Mountains in the Xinjiang region. The survey covered physical and nutrient indicators, and the results showed noticeable spatial differences between waters in different regions. The temperature, dissolved oxygen, total nitrogen, and total phosphorus of artificial water in the southern Altai Mountains vary greatly. In contrast, the waters in the northern Tianshan Mountains have more consistent physical indicators. The results of phytoplankton identification showed that the phytoplankton communities in different regions are somewhat different, with diatom species being the dominant taxon. The cluster analysis and the non-metric multidimensional scaling (NMDS) results also confirmed the variability of the phytoplankton communities in the areas. The variance partitioning analysis (VPA) results showed that climatic and environmental factors can explain some of the variability of the observed data. Nevertheless, the residual values indicated the presence of other unmeasured factors or the influence of stochasticity. This study provides a scientific basis for regional water resource management and environmental protection.

Spatial and temporal changes of glaciers and glacial lakes in the Northern Tianshan Mountains over the past 30 years

Spatial and temporal changes of glaciers and glacial lakes in the Northern Tianshan Mountains over the past 30 years

Effect of plant roots on the radiocarbon age of loess deposits in arid central Asia

Radiocarbon and OSL dating are the two main approaches used to date aeolian deposits in arid central Asia (ACA). Previous results showed that, compared with OSL dating, the 14C ages of loess deposits in ACA are underestimated when the loess age is beyond ∼25 ka. However, the cause of this radiocarbon age underestimation has not been adequately addressed. In this study, we measured the 14C ages of different dating materials, including pyrolysis volatile (Py-V), pyrolysis residue (Py-R), humin, and total organic carbon fractions from two loess sections in ACA (the Hoalin section in the western Pamir Mountains, and the TLD16 section in the northern Tianshan Mountains). The results show that different dating material yielded different 14C ages for all the loess samples, and all the radiocarbon ages obtained are younger than their corresponding OSL ages. Based on these results, together with a regional comparison of 78 14C ages from ACA with their corresponding OSL ages, we propose that the 14C age underestimation is mainly due to the contamination by the deep penetration of the extended root systems of the plants that grow in arid areas, whereas this effect is less significant in the summer monsoon–dominated Chinese Loess Plateau.

Responses of radial growth and stable carbon isotopes to climate in the northern Tianshan Mountains

Climate change has profound effects on forest ecosystems. Schrenk spruce (P. schrenkiana) is a natural conifer species endemic to the arid inland areas of Asia. In this study, the relationship between tree-ring parameters of P. schrenkiana and major meteorological factors were analyzed, and the main limiting factors for tree radial growth and stable carbon isotope fractionation were explored. Our results indicate that moisture stress before and during the growing season have an important influence on radial growth of P. schrenkiana, especially, the correlation coefficient between tree-ring width and vapor pressure deficit (VPD) from previous August to current July is as high as −0.622 (n = 51, p < 0.01). Collinearity analysis further supports the conclusion that the limiting factor for the radial growth of P. schrenkiana is moisture. Although the correlation analysis results show that the tree-ring δ13Ccorr is significantly positively correlated with sunshine duration (SD), additional analysis based on first order difference variables suggests that the climate factor may not be the only limiting factor for the stable carbon isotope fractionation of tree rings in the Sayram Lake Basin. This lays the foundation for the assessment of forest management practices and carbon sink capacity in light of future climate change.

Origin and evolution of the genera Lonsdaleia and Actinocyathus: Insights for the Mississippian palaeogeography from the western Palaeotethys

Representatives of the subfamily Lonsdaleiinae Chapman, 1893 are common in the Mississippian of the western Palaeotethys. A general analysis of the origin, distribution and evolution of that subfamily has been undertaken. The most probable hypothesis for the origin of the genus Lonsdaleia McCoy, 1849 is to acquire colonialism via the genus Axophyllum Milne Edwards and Haime, 1851. Actinocyathus d’Orbigny, 1849 would be a descendant of Lonsdaleia by increasing integration in the colonies. The first occurrences of Lonsdaleia have been recorded in the lower Visean from northern Britain and northern Tianshan Mountains of northwestern China, but the diversification and migration to the whole Palaeotethys only happened in the late Visean. Three hypotheses are proposed on that matter. The Serpukhovian was also a period of migrations and diversification for these genera. Both Lonsdaleia and Actinocyathus have been recorded in Bashkirian refuges, the Sverdrup Basin in northern Laurasia and the Tindouf Basin in northern Africa, respectively. The division of the western Palaeotethys into six subprovinces based on the distribution of corals is proposed.

Spatial Variation in Desert Spring Vegetation Biomass, Richness and Their Environmental Controls in the Arid Region of Central Asia

A precise evaluation of spatial patterns in desert vegetation biomass, species richness and their environmental controls is essential for a deeper comprehension of the potential carbon preservation and sustainability of grassland ecosystems. There are widespread reports suggesting robust associations among biomass, species richness and mean annual precipitation (MAP) or temperature (MAT) at different scales. However, these reports were inconsistent, and knowledge on the desert grasslands of Central Asia remains limited. In this study, we showed that spatial patterns of biomass and species richness along the zonal climate of the northern Tianshan Mountains exhibited substantial regional differences and the relationship among biomass, richness and elevation exhibited a substantial exponential decline. We discovered that functional groups of biomass, total biomass and species richness in the desert exhibited exponential growth along the MAP gradient and a quadratic relationship with MAT. Furthermore, the biomass–species richness relationships were bell-shaped in the desert zone. Accordingly, the biomass and species richness had spatial differences. At a regional scale, the spatial variation in the desert biomass and species richness was primarily dependent on climate. Our results demonstrated the specificity between the desert vegetation and climate in arid regions of Central Asia and revealed the regularity between biomass and species richness in desert areas. The research results emphasized the impact of precipitation on desert vegetation in arid regions of Central Asia and the relationship between biomass and plant species richness, which is of great significance for understanding desert ecosystems and protecting the ecological environment.

Burial and exhumation history of Jurassic sedimentary rocks in the southern margin of the Junggar Basin: Implications for the growth of the northern Tianshan Mountains

• Apatite fission-track dating yields 147–50 Ma for the Jurassic sedimentary rocks in the southern margin of Junggar Basin. • The Jurassic sedimentary rocks experienced two cooling stages at 150–110 Ma and the Late Miocene (20–10 Ma). • The exhumation of Jurassic sedimentary rocks was associated with the northward expansion of the Tianshan Mountains. • The two cooling stages had a wide range of regional dynamic responses in northwestern China. Constraining the burial and exhumation evolution of sedimentary basins is crucial for understanding the deformation histories of basin–mountain transition zones. The thick Jurassic sedimentary successions on the southern margin of the Junggar Basin are an essential archive of the uplift and deformation of the Tianshan Mountains. Apatite fission-track and vitrinite reflectance analyses were performed on the Jurassic sedimentary rocks bordering the northern Tianshan Mountains, providing direct insight into the burial and exhumation of the southern margin of the Junggar Basin. Our apatite fission-track data indicate four main cooling stages during 150–125 Ma; 120–105 Ma; 100–80 Ma; and 75–45 Ma. Thermal-history modeling results demonstrate that the Jurassic sedimentary rocks were exhumed in the northern Tianshan Mountains, indicating a history of probable Early to Middle Jurassic sedimentary burial followed by slow cooling commencing at approximately 150–110 Ma. Then, this region undergone gradual deplanation between the Late Jurassic–Cretaceous and the Miocene and rapid cooling since the Late Miocene (20–10 Ma). These two stages of cooling and exhumation are interpreted to reflect the accretion of the Lhasa Block and the India-Eurasia collision, respectively. Furthermore, the thermal history of the Jurassic sedimentary rocks is consistent with the sedimentation pattern and depositional environments in the southern margin of the Junggar Basin, providing complementary evidence for the time of exhumation and implying that denudation migrated into the Junggar Basin concurrent with uplift of the northern Tianshan Mountains.

Radial Growth of Picea schrenkiana Influenced by Increasing Temperature in the Tianshan Mountains

There is a tendency of warming and wetting in northwestern China in recent decades. However, less is known about whether or not tree growth shows an increasing trend. In this study, we developed three tree-ring width chronologies of Picea schrenkiana in the northern Tianshan Mountains to assess changes in the radial growth of P. schrenkiana and to discuss the stability of the relationships between tree growth and climate. Three chronologies all showed that the tree-ring index has declined significantly since the 1960s. At two western sites, the growth of P. schrenkiana was negatively affected by the summer temperature of the previous year. At the eastern site, early summer temperature-induced drought of the current year was the key factor affecting tree growth. The result of moving-window correlations was consistent with correlation analyses. Spatial correlation analyses revealed that variations in tree-ring width could respond to a wide range of temperature changes in northwestern China, especially in the past half century. We expect that climate warming hinders the radial growth of P. schrenkiana in the northern Tianshan Mountains. Our study also helps to clarify the characteristics of tree growth in northwestern China under the influence of westerlies.

Spatiotemporal Distribution Patterns and Exposure Risks of PM2.5 Pollution in China

The serious pollution of PM2.5 caused by rapid urbanization in recent years has become an urgent problem to be solved in China. Annual and daily satellite-derived PM2.5 datasets from 2001 to 2020 were used to analyze the temporal and spatial patterns of PM2.5 in China. The regional and population exposure risks of the nation and of urban agglomerations were evaluated by exceedance frequency and population weight. The results indicated that the PM2.5 concentrations of urban agglomerations decreased sharply from 2014 to 2020. The region with PM2.5 concentrations less than 35 μg·m−3 accounted for 80.27% in China, and the average PM2.5 concentrations in 8 urban agglomerations were less than 35 μg·m−3 in 2020. The spatial distribution pattern of PM2.5 concentrations in China revealed higher concentrations to the east of the Hu Line and lower concentrations to the west. The annual regional exposure risk (RER) in China was at a high level, with a national average of 0.75, while the average of 14 urban agglomerations was as high as 0.86. Among the 14 urban agglomerations, the average annual RER was the highest in the Shandong Peninsula (0.99) and lowest in the Northern Tianshan Mountains (0.76). The RER in China has obvious seasonality; the most serious was in winter, and the least serious was in summer. The population exposure risk (PER) east of the Hu Line was significantly higher than that west of the Hu Line. The average PER was the highest in Beijing-Tianjin-Hebei (4.09) and lowest in the Northern Tianshan Mountains (0.71). The analysis of air pollution patterns and exposure risks in China and urban agglomerations in this study could provide scientific guidance for cities seeking to alleviate air pollution and prevent residents’ exposure risks.

Effects and contributions of meteorological drought on agricultural drought under different climatic zones and vegetation types in Northwest China

Meteorological drought is one of the driving forces behind agricultural drought. The response of agricultural drought to meteorological drought remains poorly understood under different climatic zones and vegetation types in Northwest China (NWC). Furthermore, the contribution of climate factors and human activities to agricultural drought in NWC remains unclear. We combined the Standardized Precipitation Evapotranspiration Index (SPEI) and the satellite Vegetation Condition Index (VCI) to characterize meteorological and agricultural drought, respectively. Based on the trend analysis, Spearman's correlation coefficient and residual trend analysis, we studied the variation characteristics and response relationships of meteorological and agricultural drought under different climatic zones and vegetation types in NWC from 2000 to 2019 and evaluated the contributions of climate factors (SPEI and precipitation) and human activities on the agricultural drought. The results showed that under different climatic zones and vegetation types, the SPEI and VCI all showed an upward trend in NWC, indicating that meteorological and agricultural drought slowed down. It was further pointed out that the climate was humidified and the soil moisture increased in NWC. Meteorological drought has a definite effect on agricultural drought, and the effect varied non-linearly along the drought gradient with the strongest responses in the semiarid ecosystems. Drought resistance of different climatic zones and vegetation types was different, caused by the specific sensitivity and uniqueness of local arid environment. Among them, grasslands dominated the regional SPEI–VCI changes in NWC. The combined effects of climatic factors (SPEI and precipitation) and human activities promoted the variation of agricultural drought in NWC. Climatic factors were the main drivers of agricultural drought change in grasslands, with the contribution rate reaching 76.71%. However, human activities all contributed significantly to agricultural drought than climatic factors, especially in the Loess Plateau, Junggar Basin and northern Tianshan Mountains, where the positive contribution of human activities exceeded 80%. Thus, the SPEI and VCI can effectively reveal the change law of meteorological drought and agricultural drought in NWC. This study provides a theoretical basis for drought disaster relationship assessment.

Dynamics of Vegetation Greenness and Its Response to Climate Change in Xinjiang over the Past Two Decades

Climate change has proven to have a profound impact on the growth of vegetation from various points of view. Understanding how vegetation changes and its response to climatic shift is of vital importance for describing their mutual relationships and projecting future land–climate interactions. Arid areas are considered to be regions that respond most strongly to climate change. Xinjiang, as a typical dryland in China, has received great attention lately for its unique ecological environment. However, comprehensive studies examining vegetation change and its driving factors across Xinjiang are rare. Here, we used the remote sensing datasets (MOD13A2 and TerraClimate) and data of meteorological stations to investigate the trends in the dynamic change in the Normalized Difference Vegetation Index (NDVI) and its response to climate change from 2000 to 2019 across Xinjiang based on the Google Earth platform. We found that the increment rates of growth-season mean and maximum NDVI were 0.0011 per year and 0.0013 per year, respectively, by averaging all of the pixels from the region. The results also showed that, compared with other land use types, cropland had the fastest greening rate, which was mainly distributed among the northern Tianshan Mountains and Southern Junggar Basin and the northern margin of the Tarim Basin. The vegetation browning areas primarily spread over the Ili River Valley where most grasslands were distributed. Moreover, there was a trend of warming and wetting across Xinjiang over the past 20 years; this was determined by analyzing the climate data. Through correlation analysis, we found that the contribution of precipitation to NDVI (R2 = 0.48) was greater than that of temperature to NDVI (R2 = 0.42) throughout Xinjiang. The Standardized Precipitation and Evapotranspiration Index (SPEI) was also computed to better investigate the correlation between climate change and vegetation growth in arid areas. Our results could improve the local management of dryland ecosystems and provide insights into the complex interaction between vegetation and climate change.

The constraint of deep rock stresses in H underground gas storage based on a modified stress polygon and focal mechanism solution

H underground gas storage (H-UGS), located in the junction of the southern margin of the Junggar Basin and the eastern part of the northern Tianshan Mountains, is one of the large natural gas storage in China. It is of significance to study the deep rock stresses in H-UGS for fault slip tendency, safe storage of energy and other research. Most of the regional stress information in H-UGS data from in-suit measurements lacks deep in-suit stress data in this region. This research proposes a hybrid constrain stress magnitudes present in deep rock masses. First, the fault friction strength, an essential parameter of lateral pressure coefficient polygon, is established by the stress accumulation index method and apparent friction strength evaluation method. Second, we inverse the stress factor R from the focal mechanism solutions in this area, and the lateral pressure coefficient polygon is qualified quadratic to narrow down the range of results by this parameter. Finally, the complete stress profile of H-UGS is obtained by using the simple transition relationship between lateral pressure coefficient and in-situ stress. The result shows that the principal compressive stress of the H-UGS region is determined by the N22°E, the maximum lateral pressure coefficient K max (or S H) at three depths (3.0km, 6.5km, and 12.0km ) are 1.2 (80.22 MPa), 1.22 (202.72 MPa), 1.28 (421.34 MPa) respectively, and the minimum lateral pressure coefficient K min (or S h) are 0.87 (58.21 MPa), 0.86 (142.12 MPa), 0.86 (282.61 MPa) respectively. The result is primarily consistent with in-situ measurement from the depth of 3.0km to 3.7km. The maximum horizontal principal stress and the minimum coincidence ratio are 54% and 69%. The result of estimating deep rock stresses established in this research provides sufficient regional stress field data in H-UGS.

Paleo-environmental implications of the micro-botanical remains recovered from a military garrison of Han Dynasty in Xinjiang

According to the dynastic chronicles of the Han dynasty, City of Shule (疏勒城) was a large fortress located at in the farthest northwest of the Han Empire. The Shichengzi site was a settlement occupied by Han armies, which was considered as matching the location of City of Shule on the ancient Silk Road in Xinjiang, directly dating to about the first century AD. In the present study, we provide a preliminary investigation on palaeobotanical and palynological evidence recovered from a depositing soil profile at Shichengzi site in northern Tianshan Mountains. Although it shows that natural vegetations around Shichengzi was dominated by desert steppe during the late Holocene period, it can be seen that there was a relatively warm and humid environment when Han armies firstly relocated in the region. This suggests that such an improved climate conditions might have played an important role in supporting the development of Han culture in eastern Central Asia at approximately 2000 BP.

Quantifying the contribution of climate change and human activities to biophysical parameters in an arid region

Quantifying the variation of biophysical parameters and their driving mechanisms is essential for monitoring land surface environmental changes and for understanding the land–atmosphere interaction in the arid region. Due to the complexity of human activities, most researches are limited to climate change, whereas the response analysis of human activities to changes in biophysical parameters are still lacking or not comprehensively considered. Therefore, large biases and uncertainties still exist in the estimates of regional responses to global change. Firstly, we specifically quantified the main human activities related to land use/land cover change (LULCC) in the northern Tianshan Mountains (NTM), and identified the spatiotemporal changes of primary biophysical parameters, including Albedo, leaf area index (LAI), land surface temperature (LST), and Normalized Difference Vegetation Index (NDVI). Then, we tested the performance of the five models used, including multiple linear regression (MLR), random forest (RF), support vector regression (SVR), multi-layer perceptron (MLP), and K-nearest neighbor (KNN). RF outperformed others and was used to quantify and disaggregate the contribution of climate change and human activities to land surface parameters in the NTM. We found a strong spatial heterogeneity in the spatial variation of all biophysical parameters. Except for LST, the annual maximum Albedo, LAI, and NDVI showed a significant increasing trend in the NTM from 2000 to 2019 (p < 0.05). Generally, climate change contributed more to the biophysical parameters than human activities. However, the contribution of human activities to NDVI was 0.51, which was greater than that of climate change during 2000–2015. This study provides new insight on the impact of climate change and human activities on biophysical parameters and a scientific basis for model parameterization in the arid region.

Estimation of mountain block recharge on the northern Tianshan Mountains using numerical modeling

Estimation of mountain block recharge on the northern Tianshan Mountains using numerical modeling

Impacts of topographic factors on regional snow cover characteristics

At a local scale, snow cover is influenced by terrain properties, and it affects water availability across some arid and semiarid regions. This study aimed to quantify the spatial heterogeneity of snow cover due to topographic effects based on moderate-resolution image spectroradiometer (MODIS) daily snow cover products, processed with spatial and backward temporal filters. A snow-dominant region in the middle section of the northern Tianshan Mountains in China was selected, and the snow cover ratio (SCR) and the number of snow cover days (SCD) were investigated. The results suggest that MODIS images are biased toward underestimation of the snow cover in the study region, and the error is primarily manifested within the elevation band of 1 500–2 500 m. The snow cover is mainly affected by elevation, and snow mostly accumulates above 3 800 m. In addition, the differences in SCR and SCD between the south- and north-facing slopes are more significant than those between the east- and west-facing slopes. Notably, the north-facing slopes have the maximum values of SCR and SCD, whereas the south-facing slopes have the minimum values of SCR and SCD. Furthermore, the impact of slope gradients on snow cover varies across seasons. Snow cover on a sloped surface decreases with the slope gradient during winter, while it tends to increase with the slope gradient during the other seasons. Overall, this study presents a useful perspective on the variance in regional snow cover and provides guidance for the water resources management of snow meltwater with different terrain features.

Assessment of Inter-Sectoral Virtual Water Reallocation and Linkages in the Northern Tianshan Mountains, China

Quantitative analysis of the reallocation and linkages of virtual water in the economic sector was important for the integrated water resources management in inland arid regions. Taking the northern Tianshan Mountains (NTM) as an example, we applied the environmental input-output model to design the accounting framework for the reallocation of blue and green virtual water (VW) in the economic sector and analyzed the correlation effect of VW reallocation among various sectors by backward and forward linkages in economic analysis. The results showed that the direct blue and green water consumption of primary industry respectively accounted for 99.2% and 100% of the total water consumption in NTM. Planting sector had the largest amount of VW outflow among all sectors. Animal husbandry, forestry and construction had a large pulling effect on VW outflow of planting sector, while planting sector and animal husbandry were the main sectors for VW export of blue and green water. We suggest that the government can increase the import of blue-green VW for agricultural raw materials through VW trade and develop industries such as service and electricity that have less pulling effect on the primary industry VW, so as to improve the economic added value of VW in the primary industry and reduce the loss of VW in primary industry production and trade flows in future water management.

Mg, C and O isotopic compositions of Late Cretaceous lacustrine dolomite and travertine in the northern Tianshan Mountains, Northwest China

The Junggar Basin was characterized by high temperature and strong tectonic activities during the Late Cretaceous, in which a dolomite-forming lacustrine depositional system associated with travertine was deposited in its southern sector adjoining the northern Tianshan Mountains. Two broad types of dolomite are identified in terms of mineralogy, including the homogeneous and anhedral dolomite-A and high order degree and euhedral dolomite-B, which are also largely varied in mineral size (10–20 μm and 30–50 μm in size, respectively). The dolomites display a low degrees of dolomite order (mean = 0.48) and Ca-rich (mean = 55.8). Compared with δ18O values (PDB) of limestones in the shore to shallow facies (−7.0 to −11.1‰), the apparent positive δ18O values of dolomites (−4.2 to −5.9‰) indicate a stronger evaporation environment, while the values of −6.8 to −8.1‰ in the salt marsh facies dolomitic limestone may reflect transitional conditions. Moreover, the more positive δ26Mg values of dolomites (ranging from −1.52 to −2.91‰) than those of limestone and travertine (−3.58‰ and −4.31‰, respectively) also indicate an origin related fractionation effect. In addition, based the occurrence of low-temperature hydrothermal minerals, including chlorite, barite, siderite and silver in the dolostone and travertine, we interpret a new travertine-related origin for the lacustrine dolomite. Thermal water entering saline and alkaline lake environments subject to strong evaporation promoted dolomitization. From the simulation of the Rayleigh and seepage reflux models, we speculate that the lacustrine dolomites formed in a near-surface environment (25–50 °C). Moreover, the results contain abundant information on palaeoenvironmental and palaeoclimatic changes, which are very important for reconstructing and deciphering palaeoenvironments and expanding the dolomitization model under thermal water influenced evaporative lacustrine conditions.

Origin and palaeoenvironmental indications of Eocene to Oligocene primary lacustrine dolomite, Northern Tianshan Mountains, NW China

During the Eocene to Oligocene, lacustrine dolostone developed in the Anjihaihe Formation on the northern margin of the Tianshan Mountains in the southern Junggar Basin. Dolostone formation is usually restricted to specific environmental and geochemical conditions; therefore, dolostone contains considerable information on palaeoenvironment and palaeoclimate changes. Furthermore, this dolostone provides more information on the formation process and formation mechanisms of dolostone. The studied dolostone is white to greyish white and consists of dolomite crystals that are 3–10 µm in size, homogeneous, subhedral to euhedral and nearly stoichiometric (with average Mg/Ca molar ratios of 0.97). The high Sr content (average 1996 ppm), relatively high δ18O values (average −1.8‰) and co-occurrence with halite and gypsum reflect evaporative and saline conditions. The δ26Mg values of the dolostone range from −0.81 to −2.44‰, with a mean of −1.78‰. Strong positive correlations exist between the δ26Mg values and depth (r = 0.76) and the Mg isotope Rayleigh distillation model results, which indicates that δ26Mg fractionation occurred in conjunction with evaporation and that most of the Anjihaihe lacustrine dolomite developed in a natural environment at 25–50 °C. Moreover, evidence of microbes can be found covering the surface of the dolostone in the presence of a few framboids of pyrite. Additionally, clay layers in the dolostone are primarily composed of bentonite (40–60%) but also contain small amounts of montmorillonite (0.8–3.5%) and zeolite (0.1–0.5%). Detrital zircon ages of 40–44 Ma are presented for the first time for the Anjihaihe Formation. The results show that understanding the primary lacustrine dolostone is significant and essential to reconstructing the evolution of palaeoenvironments and synsedimentary volcanic activity in the northern Tianshan Mountains during the Eocene to Oligocene. This work also provides a possible model that explains the formation of the studied dolostone in an evaporative saline lacustrine environment.