Geomagnetic field paleointensity in the cretaceous from Upper Cretaceous rocks of Georgia

A representative collection of Upper Cretaceous rocks of Georgia (530 samples from 24 sites) is used for the study of magnetic properties of the rocks and the determination of the paleodirection and paleointensity (H _an) of the geomagnetic field. Titanomagnetites with Curie points of 200–350°C are shown to be carriers of natural remanent magnetization (NRM) preserving primary paleomagnetic information during heatings to 300–350°C. The characteristic NRM component of the samples is identified in the interval 120–350°C. The Thellier and Thellier-Coe methods are used for the determination of H _an meeting modern requirements on the reliability of such results. New paleointensity determinations are obtained and virtual dipole magnetic moment (VDM) values are calculated for four sites whose stratigraphic age is the Upper Cretaceous (Cenomanian-Campanian). It is shown that, in the interval 99.6–70.6 Ma, the VDM value was two or more times smaller than the present value, which agrees with the majority of H _an data available for this time period. According to our results, the H _an value did not change at the boundary of the Cretaceous normal superchron.     

Iron distribution in surface waters in the Middle and Lower Amur basin

New data on iron concentration and distribution in solution and suspension in the water of the Amur and its major tributaries (the rivers of Bureya, Sungary, etc.) collected in 2006?C2009 are given. The distribution of iron over river gauges and along the Amur was found to be uneven. The correlation between iron and humic acids was for the first time assessed in rivers and lakes of the Middle and Lower Amur basin.     

Basic physicochemical characteristics of the state of Upper Amur surface water

The present-day ecological state of the Upper Amur is assessed. Specific features of water quality formation are demonstrated. Local sources of aquatic environment pollution are identified. The distributions of metals in dissolved and suspended forms in the river reach are examined.     

洛伊地区侏罗纪原型盆地形成与演化

以洛伊地区石油地震、钻井及地化资料为基础,利用镜质体反射率（Ro）进行单井剥蚀厚度恢复,应用平衡剖面恢复的早-中侏罗世古地貌呈"三凹三凸"特征,其中,中条山、熊耳山、嵩山由于隆升无早-中侏罗世沉积,在洛阳-济源、义马-宜阳、伊川形成3个沉降中心。依据盆地充填序列及沉积相带进行分析,认为研究区早-中侏罗世为山间坳陷盆地,其形成与演化受控于印支末期-燕山早期的秦岭-大别造山带陆内造山作用。     

Heat flow and ground water movement in the Bohemian cretaceous basin (Czechoslovakia)

Sub-surface temperature fields may be considerably affected by active ground water systems, thereby seriously hampering the interpretation of heat flow data. Quantitative evaluation of the convective component of heat transfer is thus very important in cases such as large sedimentary basins with vast underground water circulation. We propose in this study a simple model of horizontal aquifer. This model was used to examine the effect of the lateral convection on the surface heat flow near the recharge zone of basinal margins. The perturbation of the heat flow field above the aquifer was calculated for various aquifer geometry and various flow velocities and the regional scale dependence of the perturbation on the hydraulic properties of the aquifer was demonstrated. The model was applied to the Bohemian Cretaceous Basin and it was shown that within a few kilometres from the recharge zones the observed surface heat flow may be underestimated by up to several tens of percent. The procedure was tested in two locations in this area, in an attempt to make hydrogeological corrections to the measured heat flow values in several boreholes.     

Hydroclimatology of the Upper Madeira River basin: spatio-temporal variability and trends

Rising in the Andes, the Madeira River drains the southwestern part of the Amazon basin, which is characterized by high geographical, biological and climatic diversity. This study uses daily records to assess the spatio-temporal runoff variability in the Madeira sub-basins. Results show that inter-annual variability of both discharge and rainfall differs between Andean and lowland tributaries. High-flow discharge variability in the Andean tributaries and the Guaporé River is mostly related to sea surface temperature (SST) in the equatorial Pacific in austral summer, while tropical North Atlantic (TNA) SST modulates rainfall and discharge variability in the lowlands. There also is a downward trend in the low-flow discharge of the lowland tributaries which is not observed in the Andes. Because low-flow discharge values at most lowland stations are negatively related to the SST in the tropical North Atlantic, these trends could be explained by the warming of this ocean since the 1970s.

EDITOR A. Castellarin

ASSOCIATE EDITOR A. Viglione     

The structure of ice and ice cover in lower Amur reaches with branched channel

The study is focused on the specific features of ice regime in Amur lower reaches and the structure of ice surface in branches of different size and dynamic state. The main features of ice stratigraphy in different parts of the river have been identified, and ice cover characteristics have been found to show considerable heterogeneity across the channel. Quantitative data on the concentration of terrigenous material in the ice and its distribution within the ice mass have been collected. The amount of terrigenous material was estimated in the ice in Amur lower reaches, from where it is largely exported into the Sea of Okhotsk during spring ice drift.     

The thermal regime of the San Juan basin since late cretaceous times and its relationship to San Juan mountains thermal sources

Heat-flow and coal-maturation data suggest that the thermal history of the San Juan Basin has been influenced by magmatic and volcanic activity in the San Juan Mountains-San Juan volcanic field located to the north of the Basin. Time-dependent isothermal step models indicate that the observed heat flow may be modelled by a (near) steadystate isothermal step extending from 30–98 km depth whose edge underlies the northern San Juan Basin. The observed maturation levels of the Fruitland formation coals in the northern and central Basin, however, require more heat than can be associated with conduction from a deep thermal source (steady-state step) and from the shallow crustal batholith which underlies the San Juan volcanic field. Magmatic activity within the Basin does not appear to be a reasonable source of additional heat. Increased burial depths of the coals may explain some of the elevated maturation levels observed in the central and northern Basin, but it seems likely that an additional source of heat is still required. Heat advection by groundwater movement may have influenced the coal maturation levels in the Basin as well. Both magmatic activity associated with the emplacement of the San Juan batholith and elevated geothermal gradients associated with the steady-state thermal source at depth may have contributed to heating of the groundwater. An appreciation of heat advection by groundwater flow may therefore be most important to understanding regional patterns of heat flow and hydrocarbon maturation.     

Age estimation of the deposition of the cretaceous Upper Sandstones and a later remagnetization event,from Hirna area,SE Ethiopia

Outcrops of the Cretaceous Upper sandstone formation some 375 km to the East of Addis Ababa on the motor Highway to Harar was paleomagnetically investigated. About seventy core samples were collected at various stratigraphic levels from 250–300 meters thick sedimentary formation. After standard sample preparations in the laboratory the resulting specimens were subjected to routine paleomagnetic demagnetization protocol. In the first steps of demagnetizations process the recent and viscous magnetizations were removed by heating until a temperature of level of 300 °C. Further demagnetization of the samples resulted in the isolation of the final magnetization with stable line segments that is directed towards the origin, which is interpreted as Characteristic Remanent Magnetization (ChRM). Rock – magnetic experiments have identified goethite (αFeOOH), hematite (αFe₂O₃), detritial hematite, and magnetite as the magnetic mineral phases carrying the remanence. The ChRM identified resulted in an average value of (D_s = 0.5°, I_s = ?0.7°, α₉₅ = 4.3°, N = 34) for the red sandstones while an average value of (D_s = 335.8°, I_s = ?31.8°, α₉₅ = 4.7°, N = 14) for the limestone intercalations. The former ChRM in the red sandstone is determined to be secondary while the latter ChRM is known to be primary. Comparison of these directional results and their pole equivalents with the African plate Apparent Polar Wander Path curve established by Besse and Courtillot (2003) give ages of between 115–130 Million years for the limestone intercalation and ages of 30 million years for red sandstone unit. These are interpreted respectively as estimates of the age of deposition and a later remagnetization respectively.     

Depositional ages and characteristics of Middle–Upper Jurassic and Lower Cretaceous lacustrine deposits in southeastern Mongolia

Lower Cretaceous lacustrine oil shales are widely distributed in southeastern Mongolia. Due to the high organic carbon content of oil shale, many geochemical studies and petroleum exploration have been conducted. Although most of the oil shales are considered to be Early Cretaceous in age, a recent study reveals that some were deposited in the Middle Jurassic. The present study aims at establishing depositional ages and characteristics of the Jurassic and Cretaceous lacustrine deposits in Mongolia. The Lower Cretaceous Shinekhudag Formation is about 250 m thick and composed of alternating beds of shale and dolomite. The Middle Jurassic Eedemt Formation is about 150 m thick and composed of alternating beds of shale, dolomitic marl, and siltstone. The alternations of shale and dolomite in both formations were formed by lake level changes, reflecting precipitation changes. Shales were deposited in the center of a deep lake during highstand, while dolomites were formed by primary precipitation during lowstand. Based on the radiometric age dating, the Shinekhudag Formation was deposited between 123.8 ±2.0 Ma and 118.5 ±0.9 Ma of the early Aptian. The Eedemt Formation was deposited at around 165–158 Ma of Callovian–Oxfordian. The calculated sedimentation rate of the Shinekhudag Formation is between 4.7 ±2.6 cm/ky and 10.0 ±7.6 cm/ky. Shales in the Shinekhudag Formation show micrometer‐scale lamination, consisting of algal organic matter and detrital clay mineral couplets. Given the average thickness of micro‐laminae and calculated sedimentation rate, the micro‐lamination is most likely of varve origin. Both Middle–Upper Jurassic and Lower Cretaceous lacustrine oil shales were deposited in intracontinental basins in the paleo‐Asian continent. Tectonic processes and basin evolution basically controlled the deposition of these oil shales. In addition, enhanced precipitation under humid climate during the early Aptian and the Callovian–Oxfordian was another key factor inducing the widespread oil shale deposition in Mongolia.     

Thermal maturity assessment of the Upper Triassic to Lower Jurassic Nampo Group, mid-west Korea: Reconstruction of thermal history

Abstract   Thermal maturity of the Upper Triassic to Lower Jurassic Nampo Group, a sediment-fill of the Chungnam Basin located in the central western part of South Korea, was assessed by illite crystallinity measurement and sandstone microtexture analysis. The Nampo Group consists of a fluvio-lacustrine deposit bearing meta-anthracitic coals and was over-thrusted by the basement rocks. Sandstones are characterized by down sequence increasing illite crystallinity, from anchizone to epizone, which is strongly suggestive of burial heating. Deep-burial diagenesis and deformation are evidenced by well-developed pressure solution textures, whose intensity tends to increase down sequence, and by ductile deformation in the lowermost strata. On the basis of the result of illite crystallinity measurement, the maximum paleo-temperature and total burial depth of the Nampo Group are estimated to be ca 340°C and 10 km, respectively; these conditions are in good agreement with the observed ductile deformation features. The absence of strata younger than the Nampo Group in and around the Chungnam Basin suggests that deep burial of the Nampo Group was caused by tectonic crustal loading. The tectonic overload was because of basement over-thrusting that occurred during the Jurassic Daebo orogeny, which is closely related to the orthogonal subduction of the Izanagi Plate beneath the East Asian continent. Subsequent hydrothermal alteration disturbed the thermal maturity pattern, resulting in anomalously high illite crystallinity and meta-anthracitization.     

Recharge and mineralization of groundwater of the Upper Cretaceous aquifer in Orontes basin,Syria

Abstract

Chemical and isotopic data of groundwater of the Upper Cretaceous aquifer in the Orontes basin, Syria, have been used to assess the groundwater geochemistry, the origin of groundwater recharge and groundwater residence time. The chemical data indicate that dissolution of evaporite minerals is the main process controlling groundwater mineralization. The composition of stable isotopes δ¹⁸O and δ²H, together with ¹⁴C activity, reflect the existence of three different groups: (a) groundwater in the Coastal Mountains with δ¹⁸O of –6.65‰, quite similar to modern-day precipitation, and high ¹⁴C (>50 pmC); (b) groundwater in the unconfined aquifer of the Hama Uplift, which has δ¹⁸O of –5.52‰ and ¹⁴C near 20 pmC, and is recharged locally; and (c) groundwater from the confined aquifer of the Homs Depression, which is characterized by more depleted δ¹⁸O,, –8.01‰, and low ¹⁴C (<7 pmC), and might be recharged in the northern piedmont of the Anti-Lebanon Mountains. The distinctive isotope signatures of the latter two groups indicate different recharge elevations and palaeoclimatic effects. The low recharge rate of the groundwater in the Hama Uplift aquifer, and the even slower recharge rate in the Homs Depression aquifer, are reflected by groundwater ¹⁴C residence times of 5 and over 22 Ka BP, respectively.

Editor D. Koutsoyiannis

Citation Al-Charideh, A., 2013. Recharge and mineralization of groundwater of the Upper Cretaceous aquifer in Orontes basin (Syria). Hydrological Sciences Journal, 58 (2), 452–467.     

Late Mesozoic tectonostratigraphic division and correlation of the Bohai Bay basin: Implications for the Yanshanian Orogeny

We present the results of Mesozoic sequences of the Bohai Bay basin in North China, based mainly on geochronology and interpretations of seismic profiles and logging data. Five tectono-stratigraphic sequences are defined: Lower-Middle Triassic, Lower-Middle Jurassic, Upper Jurassic, Lower Cretaceous and Upper Cretaceous. Based on an analysis of detrital zircons, the clastic rocks recorded two intervals of Jurassic magmatic activity, during 180–175 and 160–152 Ma, which can be correlated to the Nandaling and Tiaojishan Formations in the Yanshan area, respectively. However, since Jurassic volcanic rocks have not yet been found in the Bohai Bay basin, we speculate that these two stages of activity were mainly concentrated around the periphery of the North China Craton(NCC) rather than within. Based on an analysis of zircons from volcanic rocks and pyroclastics, the early Cretaceous magmatism in the Bohai Bay basin can be divided into two stages, 125–120 and 110–100 Ma,which can be correlated to magmatism in the eastern part of the NCC. The zircon ages indicate an absence of volcanic activity during the late Tuchengzi and Zhangjiakou periods which may correlate to the uplift of the Bohai Bay basin in the late Late Jurassic. Comparison of the development of Mesozoic basins and sedimentary strata in the central-eastern part of Yanshan tectonic belt and the the Bohai Bay basin indicates that the two areas are generally comparable, but with substantial differences.The central-eastern part of the Yanshan structural belt lacks Early-Middle Triassic strata, and the Bohai Bay basin lacks late Jurassic-early Cretaceous strata. Based on research results from late Mesozoic sedimentary structures in the central and eastern parts of the Yanshan tectonic belt, we infer that episode A of the Yanshanian Orogeny was weak in the Bohai Bay basin and its periphery, while episode B of the Yanshanian Orogeny had a strong influence on the Bohai Bay basin and its periphery. The available data reveal differences in the expression of these episodes: the Bohai Bay basin is characterized by vertical uplift, and the northern margin of NCC is characterized by horizontal compression uplift.     

Trend and long-range correlation characteristics analysis of runoff in upper Fenhe River basin

In order to explore long-term evolution rule and future trend of runoff time series, and exactly detect its tendency and long-range correlation characteristics, runoff data covering 1952–2012 from 3 stations across the upper Fenhe River basin were analyzed. The moving average method, Empirical Mode Decomposition (EMD) method and Mann-Kendall (M-K) trend test method were simultaneously applied to analyze the trend characteristics firstly. Then Rescaled Range analysis (R/S) and Detrended Fluctuation Analysis (DFA) methods were employed to research the long-range correlation characteristics and length of non-periodic cycle of hydrological time series, they can systematically detect and overcome non-stationarity at all time scales. Finally, predict the future trend by combining the trend characteristics with the long-range correlation characteristics and length of non-periodic cycle. The results illustrate the annual runoff series is non-linear, non-normal time series, and have 10 years non-periodic cycle length and noticeable descending trend. This descending trend will continue in a period time of future.     

南黄海盆地基底及海相中、古生界地层分布特征

南黄海盆地是大型海相中、古生界和陆相中、新生界两期叠合型盆地,本文根据最新地震资料结合钻井资料及与海陆地质资料的对比研究对盆地内地震层序进行了划分,得到了陆相中、新生界盆地基底即中、古生界海相盆地的顶界埋深、三叠系和上二叠统的残留厚度,推断了陆相层基底地层分布,并根据磁力异常资料推测了海相中、古生界盆地结晶基底埋深,推断了海相中、古生界整体残留情况.下三叠统青龙组和上二叠大隆及龙潭组在南黄海盆地南部坳陷及勿南沙隆起广泛存在,而在北部坳陷的分布则狭窄,中部隆起则由于隆起和剥蚀作用导致这两套地层几乎没有残余.对中-古生界海相盆地和中-新生界陆相盆地的基底特征进行了比较,认为海相中、古生界在南黄海地区区域性存在,海相层厚度分布特征受基底起伏控制,同时受到印支板块运动的影响,中部隆起区是海相中、古生界比较稳定的地区.下古生界可能在南黄海盆地广泛分布,但受资料限制,还难以获知其残余地层的特征.     

Compositions of Jurassic detrital garnets in Hefei Basin and its implication to provenance reconstruction and stratigraphic correlation

The compositions of Jurassic detrital garnets in Hefei Basin are complicated. Contents of the end member are from zero to 43% for pyrope, from less than 1% to 50% for grossular, from 2% to 92% for almandine, and from zero to 88% for spessartine. Part of relatively pyrope-rich detrital garnets might be originated from high pressure-ultrahigh pressure metamorphic rocks. Contents of spessartine in garnets from the present metamorphic rocks of the Dabie Mountains, including the greenschists of Foziling Group, are lower than 30%. Therefore, they would not be the source of the spessartine-rich detrital garnets in the Jurassic sedimentary rocks of the Hefei Basin. Chemical compositions of the Jurassic detrital garnets in the Hefei Basin have some characteristics in the distribution with strata, which can be applied to study of the sedimentary filling sequence and stratigraphic correlation.