Water balance and water quality in the Çürüksu basin, western Turkey

The purpose of this study is to determine the hydrological properties, groundwater potential, and water quality of the Çürüksu basin, western Turkey, and to contribute to the efforts of providing an adequate water supply for the city of Denizli. To achieve these objectives, the study consisted of mapping the geology and hydrogeology, determining the water balance, and defining the water quality. The basement rock units in the study area include several impervious metamorphic rock types and Mesozoic karstic limestone, which are overlain by Oligocene fluvial and lacustrine strata, Pliocene travertine and limestone, and Quaternary alluvium. The karstic limestone and the travertine and limestone strata constitute potential aquifers in the Çürüksu basin. The discharge regimes of the 22 springs in the two basins show little change through the year. The flow systems of the springs also have a large storage capacity and drainage occurs very slowly. The discharge of the springs does not appear to be affected immediately by monthly variations in precipitation. According to the water balance, the precipitation in the Çürüksu basin cannot provide all of the measured surface runoff. Excess runoff is 2?m3?s–1 in the Çürüksu basin, and in the adjacent Gökp?nar basin the deficit in surface runoff is also 2?m3?s–1. Thus, the underground catchment area of the springs extends beyond the surface drainage area of the Çürüksu basin. Although the P?narba??, Kazanp?nar, and Böceli springs emerge from the karstic limestone aquifer in the Çürüksu basin, these springs are fed from the adjacent Gökp?nar basin. The spring waters emerging from karstic limestone are fresh, of the calcium bicarbonate type, soft, and potable. The spring waters emerging from the travertine and limestone aquifer are low-temperature, brackish, of the calcium sulfate type, very hard, and not potable but useful for the irrigation. The occurrences of coal strata and hydrothermal activity have caused some deterioration of groundwater quality.     

Provenance analyses of early Mesozoic sediments in the Ningwu basin: Implications for the tectonic–palaeogeographic evolution of the northcentral North China Craton

This paper reports results from detrital zircon U–Pb geochronology, Hf isotopic geochemistry, sandstone modal analysis, and palaeocurrent analysis of the early Mesozoic strata within the Ningwu basin, China, with the aims of constraining the depositional ages and sedimentary provenances and shedding new light on the Mesozoic tectonic evolution of the northcentral North China Craton (NCC). The zircons from early Mesozoic sandstones are characterized by three major populations: Phanerozoic (late Palaeozoic and early Mesozoic), late Palaeoproterozoic (with a peak at approximately 1.8 Ga), and Neoarchaean (with a peak at approximately 2.5 Ga). Notably, three Phanerozoic zircons in the Early Triassic Liujiagou Formation were found to have positive ε_Hf(t) values and characteristics typical of zircons from the Central Asian Orogenic Belt (CAOB). Therefore, the CAOB began to represent the provenance of sediment in the sedimentary basins in the northern NCC no later than the Early Triassic (261 Ma), implying that the final amalgamation of the NCC and CAOB occurred before the Early Triassic. The U–Pb geochronologic and Hf isotopic results show that the Lower Middle Triassic sediments were mainly sourced from the Yinshan–Yanshan Orogenic Belt (YYOB), and that a sudden change in provenances occurred, shifting from a mixed YYOB and CAOB source in the Middle Jurassic to a primarily YYOB source in the Late Jurassic. The results of the sandstone modal analysis suggest that the majority of the samples from the Lower Middle Jurassic rocks were derived from either Continental Block or Recycled Orogen sources, whereas all the samples from the Upper Jurassic rocks were derived from Mixed sources. The change in source might be ascribed to the southward subduction and closure of the Okhotsk Ocean and the resulting intense uplift of the YYOB during the Late Jurassic. This uplift likely represents the start of the Yanshan Orogeny.     

Early–Middle Jurassic evolution of the northern Yangtze foreland basin: a record of uplift following Triassic continent–continent collision to form the Qinling–Dabieshan orogenic belt

The northern Yangtze foreland basin system was formed during the Mesozoic continental collision between the North and South China plates along the Mianlue suture. In response to the later phase of intra-continental thrust deformation, an extensive E–W-trending molasse basin with river, deltaic, and lake deposits was produced in front of the southern Qinling–Dabieshan foreland fold-and-thrust belt during the Early–Middle Jurassic (201–163 Ma). The basin originated during the Early Jurassic (201–174 Ma) and substantially subsided during the Middle Jurassic (174–163 Ma). A gravelly alluvial fan depositional system developed in the lower part of the Baitianba Formation (Lower Jurassic) and progressively evolved into a meandering river fluvial plain and lake systems to the south. The alluvial fan conglomerates responded to the initial uplift of the southern Qinling–Dabieshan foreland fold-and-thrust belt after the oblique collision between the Yangtze and North China plates during the Late Triassic. The Qianfoya Formation (lower Middle Jurassic) mainly developed from shore-shallow lacustrine depositional systems. The Shaximiao Formation (upper Middle Jurassic) predominantly consists of thick-bedded braided river delta successions that serve as the main body of the basin-filling sequences. The upward-coarsening succession of the Shaximiao Formation was controlled by intense thrusting in the southern Qinling–Dabieshan fold-and-thrust belt. Palaeogeographic reconstructions indicated an extensive E–W foredeep depozone along the fold-and-thrust belt during the Middle Jurassic (174–163 Ma) that was nearly 150 km wide. The depozone extended westward to the Longmenshan and further east to the northern middle Yangtze plate. The northern Yangtze foreland basin was almost completely buried or modified by the subsequent differential thrusting of Dabashan and its eastern regions (Late Jurassic to Cenozoic).     

Impact of rock-water interactions and recharge on water resources quality of the Agadir-Essaouira basin,southwestern Morocco

The Agadir-Essaouira area in the occidental High Atlas Mountains of Morocco is characterized by a semi-arid climate. The scarcity and quality of water resources, exacerbated by long drought periods, constitute a major problem for a sustainable development of this region. Groundwater resources of carbonate units within Jurassic and Cretaceous aquifers are requested for drinking and irrigation purposes. In this study, we collected 84 samples from wells, boreholes, springs, and rivers. Hydrochemical and isotopic data were used to examine the mineralization and origin of water, which control groundwater quality. The chemical composition of water seems to be controlled by water-rock interactions, such as dissolution of carbonates (calcite and dolomite), weathering of gypsum, as well as ion exchange processes, which explain the observed variability. Stable isotopes results show that groundwater from the mainly marly Cretaceous aquifer are submitted to an evaporation effect, while samples from the chiefly calcareous Jurassic aquifer indicate a meteoric origin, due to a rapid infiltration of recharge runoff through the karstic outcrops. The low values of δ¹⁸O and δ²H suggest a local recharge from areas with elevations ranging from 400 to 1200 m for the Cretaceous aquifer and from 800 to 1500 m for the Jurassic units.     

The Jurassic structural evolution of the western Daqingshan area,eastern Yinshan belt,North China

The western Daqingshan area, located in the eastern Yinshan belt, is dominated by the southern Daqingshan fold-and-thrust system and the northern Shiguai basin. Based on detailed structural investigations, stratigraphic controls, and geochronology, a three-stage tectonic evolution is proposed for the western Daqingshan area during the Jurassic. The discovery of syndepositional normal faults in the Early–Middle Jurassic sequences suggests that an N–S extensional regime (ca. 200–170 Ma) characterized the first deformational stage, which controlled the initial formation of the Shiguai basin. Subsequently, the relatively expansive rift basin was dissected by the initial development of the Daqingshan fold-and-thrust system that was associated with a N–S compressional regime (ca. 170–160 Ma). This phase of deformation involved the Lower–Middle Jurassic synrift sediments into a series of E–W-trending compressional structures, and controlled the deposition of Late–Middle Jurassic Changhangou growth strata ahead of the deformation front. Finally, the progression of Daqingshan fold-and-thrust system was dominated by NW–SE compression (ca. 160–145 Ma), which converted the previous E–W-trending compressional structures into a stepped geometry marked by several NE-trending oblique footwall ramps, and resulted in the depocentre of the Late Jurassic Daqingshan synorogenic conglomerate migrating markedly northeastwards. The driving mechanisms for these three palaeostress fields are considered as asthenosphere upwelling following Permian–Triassic collisional orogenesis, closure of the Mongol–Okhotsk Ocean, and NW-directed subduction of the Palaeo-Pacific plate, respectively.     

库车坳陷的地质结构及其对大油气田的控制作用

库车坳陷是在晚二叠世之前的古生代褶皱基底上历经晚二叠世-三叠纪的前陆盆地、侏罗-古近纪的伸展坳陷盆地和新近纪-第四纪陆内前陆盆地的演化而形成的。基底中的软弱层、侏罗系煤层和古近系库姆格列木组与新近系吉迪克组膏盐(泥)岩构成了自山前向盆地内部逐渐抬升的滑脱面,与自山前向盆地内部逐渐趋缓的地表面构成楔形体。该楔形冲断体的内部结构具有"垂向分层、横向分带与纵向分段"特点,NW向的阿瓦特-喀拉玉尔滚和NE向的库车横向构造转换带将其分割为乌什、拜城与阳霞3个构造区段。构造层发育特点决定了库车坳陷发育三叠-侏罗系的区域展布的有效烃源岩和(侏罗系、)白垩系-第三系储盖组合;分层变形特点导致盐下层形成叠瓦冲断构造组合,冲断层成为油源断层;叠瓦式的冲断层相关褶皱背斜组合导致了复式天然气聚集区带的形成,即在大北-克拉苏式的构造带上每一冲断层相关褶皱背斜带独立成藏,复合连片形成复式油气聚集(区)带,目前拜城北、克深、克拉苏背斜带已呈现这种趋势;撕裂断层则决定着构造带上具体的油气富集区段。库车坳陷油气资源丰富,地质结构特点决定了不同类型油气田分布的分区性。     

秦岭——大别造山带与江南造山带的差异隆升过程:来自江汉盆地中新生代沉积记录的证据

江汉叠合盆地地处扬子地区中部,夹持于秦岭--大别造山带与江南造山带中段之间,是中生代中期以来在扬子浅海台地基础上发育起来的典型海陆交互相-陆相叠合盆地,其中充填了厚逾10000m的中三叠世-新近纪陆源碎屑岩系。据印支期以来的造山活动历程与成盆演化特点,将盆山耦合过程划分为造山前期、主造山期、造山后期与非造山期4个阶段,将盆地充填层序划分为陆架边缘、前陆、断陷和坳陷4个(盆地世代)超层序。依据盆内沉积物碎屑组份分析,发现中三叠世江南造山带进入强造山活动期,白垩纪末进入造山带坍塌后的活动平静期;秦岭--大别造山带的主造山活动阶段为晚三叠-早侏罗世,古近纪末处于非造山活动相对平静阶段。盆区整体呈现东部造山活动早,山带隆升早,持续时间长,剥露地层较快较早进入变质岩层段;西部造山活动时间晚,隆升时间相对较晚,剥露地层在早侏罗世初期才依次切入变质岩层段;盆地南、北缘山带总体呈现多幕式差异隆升过程。     

Hydrologic and hydrogeologic analyses of an alluvial aquifer underlying Kushabhadra-Bhargavi River basin,Odisha, India

This paper deals with the analysis of groundwater condition in an alluvial aquifer system underlying Kushabhadra-Bhargavi River basin of Odisha, India. The rainfall data and river-stage data of the Kushabhadra River were analyzed for the periods of 1995–2009 and 1991–2010, respectively. Using the available lithologic data, geologic profiles along North-South and East-West sections were prepared and stratigraphy analysis was performed to characterize aquifers and confining layers present in the river basin. The results of stratigraphic analyses indicated that a two-layered aquifer system consisting of an unconfined aquifer and a confined aquifer exists in the study area. The thickness of unconfined aquifer varies from 3.4 to 46.5 m, whereas that of confined aquifer varies from 3.1 to 80.3 m over the basin with an interconnecting confining layer of thickness ranging from 2.1 to 60.0 m. The rainfall-groundwater dynamics and hydraulic connectivity were also investigated for gaining insights into groundwater characteristics. The analysis of groundwater levels indicated that the correlation among the 14 sites is better for most pairs of the sites (r = 0.50 to 0.96) in case of pre-monsoon season’s data and annual data as compared to monsoon and post-monsoon season’s data. This indicates good hydraulic connectivity among the observed sites in the study area. The significant seasonal groundwater fluctuations in the study area indicate appreciable recharge to the aquifer during the monsoon season. The findings obtained and insights gained from this study can be helpful for the water managers and decision makers to understand groundwater dynamics for the efficient planning and management of vital groundwater resources in the region. It is recommended that groundwater monitoring should be continued at more sites to understand long-term spatio-temporal characteristics of groundwater in the study area.     

贵州省大方县五凤井田水文地质特征初探

五风井田位于贵州省大方县城东侧,面积89.22km^2,含煤地层为二叠系上统龙潭组,主要可采煤层为6中、26、33号煤层,煤炭总资源量26 130万t。井田内主要含水层为三叠系茅草铺组岩溶溶洞含水层（T1m）,夜郎组玉龙山灰岩岩溶裂隙含水层T1y2）,二叠系中统长兴组岩溶裂隙含水层（P3c）、茅口组岩溶溶洞-暗河含水层（P2m）。矿床属于以岩溶充水为主,水文地质条件中等的矿床。井田的充水水源为地表水、地下水和小煤矿、采空区的老窑积水,充水通道为断裂破碎带及采矿冒落裂隙带。     

Groundwater flow in an ‘underfit’ carbonate aquifer in a semiarid climate: application of environmental tracers to the Salt Basin,New Mexico (USA)

The Salt Basin is a semiarid hydrologically closed drainage basin in southern New Mexico, USA. The aquifers in the basin consist largely of Permian limestone and dolomite. Groundwater flows from the high elevations (～2,500 m) of the Sacramento Mountains south into the Salt Lakes, which are saline playas. The aquifer is ‘underfit’ in the sense that depths to groundwater are great (～300 m), implying that the aquifer could transmit much more water than it does. In this study, it is speculated that this characteristic is a result of a geologically recent reduction in recharge due to warming and drying at the end of the last glacial period. Water use is currently limited, but the basin has been proposed for large-scale groundwater extraction and export projects. Wells in the basin are of limited utility for hydraulic testing; therefore, the study focused on environmental tracers (major-ion geochemistry, stable isotopes of O, H, and C, and ¹⁴C dating) for basin analysis. The groundwater evolves from a Ca–HCO₃ type water into a Ca–Mg (Na) – HCO₃–Mg (Cl) water as it flows toward the center of the basin due to dedolomitization driven by gypsum dissolution. Carbon-14 ages corrected for dedolomitization ranged from less than 1,000 years in the recharge area to 19,000 years near the basin center. Stable isotopes are consistent with the presence of glacial-period recharge that is much less evaporated than modern. This supports the hypothesis that the underfit nature of the aquifer is a result of a geologically recent reduction in recharge.     

Detrital zircon U–Pb ages of Late Triassic–Late Jurassic deposits in the western and northern Sichuan Basin margin: constraints on the foreland basin provenance and tectonic implications

Upper Triassic to Upper Jurassic strata in the western and northern Sichuan Basin were deposited in a synorogenic foreland basin. Ion–microprobe U–Pb analysis of 364 detrital zircon grains from five Late Triassic to Late Jurassic sandstone samples in the northern Sichuan Basin and several published Middle Triassic to Middle Jurassic samples in the eastern Songpan–Ganzi Complex and western and inner Sichuan Basin provide an initial framework for understanding the Late Triassic to Late Jurassic provenance of western and northern Sichuan Basin. For further understanding, the paleogeographic setting of these areas and neighboring hinterlands was constructed. Combined with analysis of depocenter migration, thermochronology and detrital zircon provenance, the western and northern Sichuan Basin is displayed as a transferred foreland basin from Late Triassic to Late Jurassic. The Upper Triassic Xujiahe depocenter was located at the front of the Longmen Shan belt, and sediments in the western Sichuan Basin shared the same provenances with the Middle–Upper Triassic in the Songpan–Ganzi Complex, whereas the South Qinling fed the northern Sichuan Basin. The synorogenic depocenter transferred to the front of Micang Shan during the early Middle Jurassic and at the front of the Daba Shan during the middle–late Middle Jurassic. Zircons of the Middle Jurassic were sourced from the North Qinling, South Qinling and northern Yangtze Craton. The depocenter returned to the front of the Micang Shan again during the Late Jurassic, and the South Qinling and northern Yangtze Craton was the main provenance. The detrital zircon U–Pb ages imply that the South and North China collision was probably not finished at the Late Jurassic.     

Major types and time–space distribution of Mesozoic ore deposits in South China and their geodynamic settings

The ore deposits of the Mesozoic age in South China can be divided into three groups, each with different metal associations and spatial distributions and each related to major magmatic events. The first event occurred in the Late Triassic (230–210 Ma), the second in the Mid–Late Jurassic (170–150 Ma), and the third in the Early–Mid Cretaceous (120–80 Ma). The Late Triassic magmatic event and associated mineralization is characterized by peraluminous granite-related W–Sn–Nb–Ta mineral deposits. The Triassic ore deposits are considerably disturbed or overprinted by the later Jurassic and Cretaceous tectono-thermal episodes. The Mid–Late Jurassic magmatic and mineralization events consist of 170–160 Ma porphyry–skarn Cu and Pb–Zn–Ag vein deposits associated with I-type granites and 160–150 Ma metaluminous granite-related polymetallic W–Sn deposits. The Late Jurassic metaluminous granite-related W–Sn deposits occur in a NE-trending cluster in the interior of South China, such as in the Nanling area. In the Early–Mid Cretaceous, from about 120 to 80 Ma, but peaking at 100–90 Ma, subvolcanic-related Fe deposits developed and I-type calc-alkaline granitic intrusions formed porphyry Cu–Mo and porphyry-epithermal Cu–Au–Ag mineral systems, whereas S-type peraluminous and/or metaluminous granitic intrusions formed polymetallic Sn deposits. These Cretaceous mineral deposits cluster in distinct areas and are controlled by pull-apart basins along the South China continental margin. Based on mineral assemblage, age, and space–time distribution of these mineral systems, integrated with regional geological data and field observations, we suggest that the three magmatic–mineralization episodes are the result of distinct geodynamic regimes. The Triassic peraluminous granites and associated W–Sn–Nb–Ta mineralization formed during post-collisional processes involving the South China Block, the North China Craton, and the Indo-China Block, mostly along the Dabie-Sulu and Songma sutures. Jurassic events were initially related to the shallow oblique subduction of the Izanagi plate beneath the Eurasian continent at about 175 Ma, but I-type granitoids with porphyry Cu and vein-type Pb–Zn–Ag deposits only began to form as a result of the breakup of the subducted plate at 170–160 Ma, along the NNE-trending Qinzhou-Hangzhou belt (also referred to as Qin-Hang or Shi-Hang belt), which is the Neoproterozoic suture that amalgamates the Yangtze Craton and Cathaysia Block. A large subduction slab window is assumed to have formed in the Nanling and adjacent areas in the interior of South China, triggering the uprise of asthenospheric mantle into the upper crust and leading to the emplacement of metaluminous granitic magma and associated polymetallic W–Sn mineralization. A relatively tectonically quiet period followed between 150 and 135 Ma in South China. From 135 Ma onward, the angle of convergence of the Izanagi plate changed from oblique to parallel to the coastline, resulting in continental extensional tectonics and reactivation of regional-scale NE-trending faults, such as the Tan-Lu fault. This widespread extension also promoted the development of NE-trending pull-apart basins and metamorphic core complexes, accompanied by volcanism and the formation of epithermal Cu–Au deposits, granite-related polymetallic Sn–(W) deposits and hydrothermal U deposits between 120 and 80 Ma (with a peak activity at 100–90 Ma).     

3D modeling and monitoring of karst system as a base for its evaluation and utilization: a case study from eastern Serbia

Beljanica Mountain in eastern Serbia is a part of the Carpathian Balkan arch (northern Alpine branch). It covers an area of about 300 km² and consists mostly of Jurassic and Cretaceous limestones. Numerous surface karst features, long caves and several large karstic springs located in Beljanica’s piedmont along the contact of karstic and non-karstic rocks are all indicators of an intense karstification. Currently, the large karstic water reserves of Beljanica Mountain are not properly utilized because of their distance from main consumers, the objection by national water managers that the springs lack a stable and sufficient discharge particularly during recession periods. Due to its unpolluted and high quality water, the area is a great prospect for future water supply, and provides an opportunity for artificial regulation and for the design and implementation of specific tapping structures. This paper includes an analysis of the created 3D ArcGIS model of karst interior and its correlation with historical and newly collected data of spring discharges and groundwater physico-chemical characteristics. The results of karst aquifer monitoring (both quantitative and qualitative) are linked with the results of extensive field geological and speleological survey of the upper non-saturated part of the karst (such as sinkholes, pits and caves) and with the investigation of the permanently saturated deeper part of the aquifer (including the diving methods). The model of karst interior is based on the data from the 69 caves, 15 sinks and 1,682 dolines (sinkholes) surveyed. The total length of the karst channels network, calculated using the GIS model and presented in a 3D environment, is 647 km. The catchment areas of five major springs that drain the areas are estimated to range from only 7 km² (Malo Vrelo Spring) to 124 km² (Vrelo Mlave Spring). The groundwater exploitable reserves of Beljanica karst aquifer are estimated to be over 4 m³/s. The waters are low mineralized, unpolluted and have a great potential for water supply.     

Evaluation of unconfined aquifer parameters from flow to partially penetrating wells in Tailan River basin, China

Effective evaluation, management and abstraction of groundwater resources of any aquifer require accurate and reliable estimates of its hydraulic parameters. This study, therefore, looks at the determination of hydraulic parameters of an unconfined aquifer using both analytical and numerical approaches. A long-duration pumping test data obtained from an unconfined aquifer system within the Tailan River basin in Xinjiang Autonomous Region in the northwest of China is used, in this study, to investigate the best method for estimating the parameters of the aquifer. The pumping test was conducted by pumping from a radial collector well and measuring the response in nine observation wells; all the wells used in the test were partially penetrating. Using two well-known tools, namely AquiferTest and MODFLOW, as an aid for the analytical and numerical approaches, respectively, the parameters of the aquifer were determined and their outputs compared. The estimated horizontal hydraulic conductivity, vertical hydraulic conductivity, and specific yield for the analytical approach are 38.1–50.30 m/day, 3.02–9.05 m/day and 0.204–0.339, respectively, while the corresponding numerical estimates are 20.50–35.24 m/day, 0.10–3.40 m/day, and 0.27–0.31, respectively. Comparing the two, the numerical estimates were found to be more representative of the aquifer in the study area since it simulated the groundwater flow conditions of the pumping test in the aquifer system better than the analytical solution.     

Jurassic volcaniclastic – basaltic andesite – dolerite sequence in Tasmania: new age constraints for fossil plants from Lune River

Jurassic plants excavated from a 12 × 5 m site, at Lune River, southern Tasmania, include an araucarian tree and numerous pteridophytes, belonging to the orders Osmundales, Filicales and Bennettitales. The fossils occur in 2 – 3 m of immature volcanilithic sandstone beds. The sandstone consists primarily of clasts from granitic basement rocks underlying much of southeast Tasmania and mafic clasts containing feldspathic microliths, and primary, phreatomagmatic quartz crystals. Detrital zircons from the sandstones are mostly Early Jurassic (Toarcian) in age (182 ± 4 Ma) with minor Triassic (226 Ma), Devonian (380 – 360 Ma) and Proterozoic populations. Basaltic andesite, hereafter referred to as andesite, caps the volcanilithic units and displays similar ratios of fluid-immobile trace elements (e.g. Zr/Nb, Ti/V), to the Jurassic dolerite found in Tasmania, indicative of a common source. The andesites are correlated with the Jurassic Kirkpatrick Basalts (Trans-Antarctic Mountains, Antarctica) based on their field relationships with bounding strata, age, and distinctive similarities in major-element composition and fluid-immobile trace-element ratios. The andesite is interpreted as an extrusive equivalent of the Tasmanian dolerite. Importantly, drillcore from Lune River contains stoped clasts of andesite in fine-grained dolerite, indicating that the andesite pre-dates the dolerite. Thermal alteration index of microfossils (3 – 3.3) and reflectance of organic material within the sediments (0.54 – 0.77 Ro) resulted from contact metamorphism associated with the emplacement of this basalt. The sedimentology and stratigraphy of the depositional environment, plus the presence of hydrophilic pteridophytes and gymnosperms, indicates that the Toarcian environment was temperate to warm and humid, with an abundant supply of water.     

Stratigraphic and structural evolution of the Blue Nile Basin,Northwestern Ethiopian Plateau

The Blue Nile Basin, situated in the Northwestern Ethiopian Plateau, contains ∼1400 m thick Mesozoic sedimentary section underlain by Neoproterozoic basement rocks and overlain by Early–Late Oligocene and Quaternary volcanic rocks. This study outlines the stratigraphic and structural evolution of the Blue Nile Basin based on field and remote sensing studies along the Gorge of the Nile. The Blue Nile Basin has evolved in three main phases: (1) pre‐sedimentation phase, include pre‐rift peneplanation of the Neoproterozoic basement rocks, possibly during Palaeozoic time; (2) sedimentation phase from Triassic to Early Cretaceous, including: (a) Triassic–Early Jurassic fluvial sedimentation (Lower Sandstone, ∼300 m thick); (b) Early Jurassic marine transgression (glauconitic sandy mudstone, ∼30 m thick); (c) Early–Middle Jurassic deepening of the basin (Lower Limestone, ∼450 m thick); (d) desiccation of the basin and deposition of Early–Middle Jurassic gypsum; (e) Middle–Late Jurassic marine transgression (Upper Limestone, ∼400 m thick); (f) Late Jurassic–Early Cretaceous basin‐uplift and marine regression (alluvial/fluvial Upper Sandstone, ∼280 m thick); (3) the post‐sedimentation phase, including Early–Late Oligocene eruption of 500–2000 m thick Lower volcanic rocks, related to the Afar Mantle Plume and emplacement of ∼300 m thick Quaternary Upper volcanic rocks. The Mesozoic to Cenozoic units were deposited during extension attributed to Triassic–Cretaceous NE–SW‐directed extension related to the Mesozoic rifting of Gondwana. The Blue Nile Basin was formed as a NW‐trending rift, within which much of the Mesozoic clastic and marine sediments were deposited. This was followed by Late Miocene NW–SE‐directed extension related to the Main Ethiopian Rift that formed NE‐trending faults, affecting Lower volcanic rocks and the upper part of the Mesozoic section. The region was subsequently affected by Quaternary E–W and NNE–SSW‐directed extensions related to oblique opening of the Main Ethiopian Rift and development of E‐trending transverse faults, as well as NE–SW‐directed extension in southern Afar (related to northeastward separation of the Arabian Plate from the African Plate) and E–W‐directed extensions in western Afar (related to the stepping of the Red Sea axis into Afar). These Quaternary stress regimes resulted in the development of N‐, ESE‐ and NW‐trending extensional structures within the Blue Nile Basin. Copyright © 2008 John Wiley & Sons, Ltd.     

Reconstructing the stages of orogeny around the Junggar basin from the lithostratigraphy of Late Paleozoic,Mesozoic, and Cenozoic sediments

The Junggar basin contains an almost continuous section of Late Carboniferous–Quaternary terrigenous sedimentary rocks. The maximum thicknesses of the stratigraphic units constituting the basin cover make up a total of ~ 23 km, and the basement under the deepest part of the basin is localized at a depth of ~ 18 km. Both the folded framing and the basin edges have undergone uplifting and erosion during recent activity. These processes have exposed all the structural stages of the basin cover. Considering the completeness and detailed stratigraphic division of the section, we can determine the exact geologic age of intense mountain growth and erosion periods as well as estimate the age of orogenic periods by interpolating the stratigraphic ages. During the Permian orogeny, which included two stages (255–265 and 275–290 Ma), the Junggar, Zaisan, and Turpan–Hami basins made up a whole. During the Triassic orogeny (210–230 Ma), the Junggar and Turpan–Hami basins became completely isolated from each other. During the Jurassic orogeny (135–145 and 160–200 Ma), the sedimentation took place within similar boundaries but over a smaller area. During the Cretaceous orogeny (65–85 and 125–135 Ma), the mountain structures formed mainly at the southern boundaries of the basin and along the Karamaili–Saur line. The Junggar and Zaisan basins were separated at that time. The Early and Middle Paleogene were characterized by relative tectonic quiescence. The fifth orogenic stage began in the Oligocene. The recent activity consists of two main stages: Oligocene (23–33 Ma) and Neogene–Quaternary (1.2–7.6 Ma to the present).     

Late Ordovician to early Silurian calc-alkaline magmatism in the Xiemisitai Mountains,northern West Junggar: a response to the subduction of the Junggar-Balkhash Ocean

Basement exposed in the Placer de Guadalupe–Plomosas uplift in northern Mexico provides important clues for the geologic evolution of the region. The stratigraphic units form stacked thrust sheets of psammitic and calcareous formations, interlayered with magmatic rock. The eastern calcareous and quartzite formations exhibit structures associated with ductile deformation, whereas the upper stratigraphic units only contain structures formed via younger brittle deformation. Porphyry interlayered in the upper Plomosas Formation has a U-Pb zircon age of 171 ± 1 Ma. This age is consistent with its stratigraphic position, interbedded quartzarenites with a maximum depositional age of ~168 Ma. Granite flakes within the Horquilla Formation are dated at 209 ± 3 Ma, and the La Viñata quartzite exhibits a maximum age of ~193 Ma. The Upper Plomosas Formation correlates well with the arc-related Middle Jurassic Nazas Formation of northeastern Mexico, constituting the first report of a Jurassic continental margin arc outcrop in the ‘Central Mexican Gap zone’. We document Late Norian to Bajocian ages for the stratigraphic units cropping out in the Placer de Guadalupe area. The Jurassic age cluster indicates that the Nazas Arc magmatism in the region occurred during the Late Triassic and ended in the Middle Jurassic times. Permian ages previously assigned to these rocks and the occurrence of a Permo–Triassic deformation event have to be dismissed.     

Thermal modeling of Carboniferous to Triassic sediments of the Karawanken Range (Southern Alps) as a tool for paleogeographic reconstructions in the Alpine–Dinaridic–Pannonian realm

Vitrinite reflectance was measured in Late Carboniferous to Triassic shales, siltstones and marls of the Karawanken Range. Thermal models of the central South-Karawanken Range were calibrated on the basis of these data. They suggest an eroded overburden of more than 3,200 m of Jurassic to Cretaceous sediments and a heat flow in the range of 42 to 60 mW m^?2 during the time of maximum subsidence. Because the reconstructed thermal history of the South-Karawanken Range is very similar to the thermal history of the Generoso basin (western Southern Alps), these data provide strong evidence for a deep basinal position of the Southern Karawanken Range during Jurassic to Cretaceous times. A vitrinite reflectance anomaly at the northern margin of the South-Karawanken Range is explained by advective heat transport during the Oligocene. The heat source for the anomalies at the western margin of the Seeberg Rise and in the area between the Periadriatic Lineament and the Donat Fault Zone is unknown. Vitrinite reflectance in Late Triassic sediments indicates the South-Karawanken Range and the South-Zala Unit of the Pannonian basement as exotic blocks in the Sava Composite Unit. This is explained by Miocene displacement of structural units, which were derived from different paleogeographical segments of the Permo-Mesozoic western Tethyan margin.     

Post-drilling destabilization of temperature profile in borehole Yaxcopoil-1, Mexico

As part of the International Continental Scientific Drilling Program (ICDP), the 1.5-km-deep borehole Yaxcopoil-1, located in the Chixculub meteor impact structure in Mexico, has undergone further study after drilling operations ceased. Temperature logs were repeated ten times at intervals 0.3–0.8, 15, 24 and 34 months after borehole shut-in. The logs bear a distinct signature of transient heat transfer by groundwater flow manifested by a gradual distortion of the linear temperature profile when a cold wave of 0.8–1.6°C amplitude was detected propagating downward from 145 to 312 m at a rate of 4–6 m/month. To understand the nature of this moving anomaly, a 20-day monitoring of the cold wave was carried out at a depth of 307 m that showed further cooling of 0.6°C during the first 16 days of the passage followed by temperature stabilisation. As an explanation of this unusual phenomenon, a theory is proposed, whereby the drilling mud has accumulated within the overlying and cooler highly porous and permeable karstic rocks during the drilling and migrates downward. The observed migration rate suggests a permeability higher than 10^?11 m². This indicates a high vulnerability to contamination of the only freshwater aquifer in the Yucatan region.