Bleached mudstone,iron concretions,and calcite veins: a natural analogue for the effects of reducing CO2‐bearing fluids on migration and mineralization of iron,sealing properties,and composition of mudstone cap rocks

This study investigates the Wangfu Depression of the Songliao Basin, China, as a natural analogue site for Fe migration (bleaching) and mineralization (formation of iron concretions) caused by reducing CO₂‐bearing fluids that leak along fractures after carbon capture, utilization, and storage. We also examined the origin of fracture‐filling calcite veins, the properties of self‐sealing fluids, the influence of fluids on the compositions of mudstone and established a bleaching model for the study area. Our results show that iron concretions are the oxidative products of precursor minerals (pyrite and siderite) during uplift and are linked to H₂S and CO₂ present in early stage fluids. The precipitation of calcite veins is the result of CO₂ degassing and is related to CO₂, CH₄, and minor heavy hydrocarbons in the main bleaching fluids. In our model, fluids preferentially enter high‐permeability fracture systems and result in the bleaching of surrounding rocks and precipitation of calcite veins. The infilling of calcite veins significantly decreases the permeability of fractures and forces the fluids to slowly enter and bleach the mudstone rocks. The Fe²⁺ released during bleaching migrates to elsewhere with the solutions or is reprecipitated in the calcite veins and iron concretions. The formation of calcite veins reduces the fracture space and effectively prevents fluid flow. The fluids have an insignificant effect on minerals within the mudstone. In terms of the chemistry of the mudstone, only the contents of Fe₂O₃, U, and Mo change significantly, with the content of U increasing in the mudstone and the contents of Fe₂O₃ and Mo decreasing during bleaching.     

Interpretation of observed fluid potential patterns in a deep sedimentary basin under tectonic compression: Hungarian Great Plain, Pannonian Basin

The ≈ 40 000 km² Hungarian Great Plain portion of the Pannonian Basin consists of a basin fill of 100 m to more than 7000 m thick semi‐ to unconsolidated marine, deltaic, lacustrine and fluviatile clastic sediments of Neogene age, resting on a strongly tectonized Pre‐Neogene basement of horst‐and‐graben topography of a relief in excess of 5000 m. The basement is built of a great variety of brittle rocks, including flysch, carbonates and metamorphics. The relatively continuous Endr?d Aquitard, with a permeability of less than 1 md (10^?15 m²) and a depth varying between 500 and 5000 m, divides the basin's rock framework into upper and lower sequences of highly permeable rock units, whose permeabilities range from a few tens to several thousands of millidarcy. Subsurface fluid potential and flow fields were inferred from 16 192 water level and pore pressure measurements using three methods of representation: pressure–elevation profiles; hydraulic head maps; and hydraulic cross‐sections. Pressure–elevation profiles were constructed for eight areas. Typically, they start from the surface with a straight‐line segment of a hydrostatic gradient (γ_st = 9.8067 MPa km^?1) and extend to depths of 1400–2500 m. At high surface elevations, the gradient is slightly smaller than hydrostatic, while at low elevations it is slightly greater. At greater depths, both the pressures and their vertical gradients are uniformly superhydrostatic. The transition to the overpressured depths may be gradual, with a gradient of γ_dyn = 10–15 MPa km^?1 over a vertical distance of 400–1000 m, or abrupt, with a pressure jump of up to 10 MPa km^?1 over less than 100 m and a gradient of γ_dyn > 20 MPa km^?1. According to the hydraulic head maps for 13 100–500 m thick horizontal slices of the rock framework, the fluid potential in the near‐surface domains declines with depth beneath positive topographic features, but it increases beneath depressions. The approximate boundary between these hydraulically contrasting regions is the 100 m elevation contour line in the Duna–Tisza interfluve, and the 100–110 m contours in the Nyírség uplands. Below depths of ≈ 600 m, islets of superhydrostatic heads develop which grow in number, areal extent and height as the depth increases; hydraulic heads may exceed 3000 m locally. A hydraulic head ‘escarpment’ appears gradually in the elevation range of ? 1000 to ? 2800 m along an arcuate line which tracks a major regional fault zone striking NE–SW: heads drop stepwise by several hundred metres, at places 2000 m, from its north and west sides to the south and east. The escarpment forms a ‘fluid potential bank’ between a ‘fluid potential highland’ (500–2500 m) to the north and west, and a ‘fluid potential basin’ (100–500 m) to the south and east. A ‘potential island’ rises 1000 m high above this basin further south. According to four vertical hydraulic sections, groundwater flow is controlled by the topography in the upper 200–1700 m of the basin; the driving force is orientated downwards beneath the highlands and upwards beneath the lowlands. However, it is directed uniformly upwards at greater depths. The transition between the two regimes may be gradual or abrupt, as indicated by wide or dense spacing of the hydraulic head contours, respectively. Pressure ‘plumes’ or ‘ridges’ may protrude to shallow depths along faults originating in the basement. The basement horsts appear to be overpressured relative to the intervening grabens. The principal thesis of this paper is that the two main driving forces of fluid flow in the basin are gravitation, due to elevation differences of the topographic relief, and tectonic compression. The flow field is unconfined in the gravitational regime, whereas it is confined in the compressional regime. The nature and geometry of the fluid potential field between the two regimes are controlled by the sedimentary and structural features of the rock units in that domain, characterized by highly permeable and localized sedimentary windows, conductive faults and fracture zones. The transition between the two potential fields can be gradual or abrupt in the vertical, and island‐like or ridge‐like in plan view. The depth of the boundary zone can vary between 400 and 2000 m. Recharge to the gravitational regime is inferred to occur from infiltrating precipitation water, whereas that to the confined regime is from pore volume reduction due to the basement's tectonic compression.     

The recognition of multiple spatial patterns: a case study from the French upper paleolithic

A pattern recognition approach to spatial analysis is applied to artifact distributions from the Magdalenian site of Pincevent, Section 36. Patterning is investigated using a κ-means cluster analysis that permits iterative mapping of artifact distributions at several scales of spatial complexity. Multiple scales of patterning are recognized in the Pincevent distributions. These patterns are assessed in terms of those discovered by the excavators through intensive visual inspection of the materials. Basic concordance is seen between these two approaches. Finally, the analysis detects more detailed patterning. A relationship between artifact abundance and location seems to hold constant throughout the site.     

The sources and formation processes of brines from the Lunnan Ordovician paleokarst reservoir,Tarim Basin,northwest China

The most important petroleum exploration target in the Tarim Basin, northwest China, is the paleokarst reservoir. To understand the source and evolution of brine in this type of reservoir, a total of 37 formation‐water samples were collected from the Middle‐Lower Ordovician paleokarst reservoir in the Lunnan oilfield. The δD‐δ¹⁸O correlation and Cl/Br ratios reflect the mixture of two fluids: meteoric water and evaporated seawater. The different degree of mixture divided samples into two groups. Group 1 samples, from deep strata (5150–6667 m.b.s.l.) in the east of the field, with elevated δD (?53.5 to ?38.0‰), δ¹⁸O values (0.66–5.99‰), and lower Cl/Br ratios (336–478 for Cl/Br, except LN634‐1 and LN631‐1) were formed by evaporation of seawater plus a small contribution from meteoric water. Group 2 samples, from shallow strata (5038–6067 m.b.s.l.), in the west of the field, have contrasting features (?59.6 to ?48.5‰ for δD, ?0.47 to 2.17‰ for δ¹⁸O, and 501 to 871 for Cl/Br), which reflect a mixture of evaporated seawater with a high proportion of meteoric water. Both of the fluid types exchanged oxygen isotope with minerals. The investigation into cation composition reveals that, before entering into the current reservoir, waters suffered albitization of plagioclase; moreover, meteoric water dissolved evaporites and seawater experienced dolomitization. A mixing trend showed by strontium isotopes (0.709801–0.711628) gave further evidence for the mixture of two fluid types. Based on the correlation of geological history with our data, two infiltration models of meteoric waters can be constructed. According to the chemical and isotopic compositions of the waters, an east fluid regime (Group 1) and a west fluid regime (Group 2) have thus been defined. Better understanding of the subsurface fluid movement patterns may be helpful for the local exploration.     

Two new cowries (Gastropoda: Cypraeidae) from the middle Miocene of South Australia

Yates, A.M., December, 2008. Two new cowries (Gastropoda: Cypraeidae) from the middle Miocene of South Australia. Alcheringa 32, 353–364. ISSN 0311-5518.

The South Australian specimens of the cypraeids Umbilia leptorhyncha (McCoy, 1877) and Lyncina (Austrocypraea) contusa (McCoy, 1877) are re-examined. Umbilia caepa sp. nov. differs from U. leptorhyncha in its smaller size, more strongly pyriform shape, weaker and less extensive apertural dentition, plate-like columellar margin of the posterior canal and more extensive basal flanges. True U. leptorhyncha is also recorded from the Cadell Formation of South Australia, demonstrating that the two species were sympatric in the Murray Basin. The specimens originally referred to Cypraea contusa var. from the Cadell Formation have had a confusing taxonomic history and they are here named as a new species Lyncina (Austrocypraea) cadella sp. nov. The new species differs from true L. (A.) contusa in its smaller size, less extensive malleations of the dorsal surface, fewer apertural teeth and a projecting internal margin of the fossula. These two new species boost a small but growing list of species that were endemic to the Murray Basin during the middle Miocene.     

铜仁锦江流域先秦时期遗址发掘的主要收获

2010年3～5月,贵州省文物考古研究所等单位对贵州省东部铜仁市锦江流域的磨刀湾、笔架冲、方田坝等遗址进行了发掘和试掘,此次工作是建国以来在贵州省锦江流域首次进行的系统考古发掘工作,获得了一批夏商、西周、两汉和宋明清时期的考古资料,具有重要的学术意义.本文着重介绍此次考古发掘中先秦时期遗存的主要收获,并对其学术意义展开初步讨论.     

土尔扈特蒙古西迁后的经济状况及其对东归的影响

土尔扈特蒙古西迁至伏尔加河流域后,其经济状况可以概括为:传统游牧经济由盛而衰;以互通有无为基础的对俄贸易往来不断;为俄国军事战役出兵助战获得战利品和报酬成为特殊的收入来源;突袭其他民族和控制贸易路线是增加财富的渠道之一;捕鱼成为相当一部分生活贫困的土尔扈特人赖以维持生计的重要方式。作者认为经济状况恶化是促使土尔扈特蒙古东归的原因之一。     

Geophysical signatures associated with fluid flow and gas hydrate occurrence in a tectonically quiescent sequence,Qiongdongnan Basin,South China Sea

Interpretation of high‐resolution two‐dimensional (2D) and three‐dimensional (3D) seismic data collected in the Qiongdongnan Basin, South China Sea reveals the presence of polygonal faults, pockmarks, gas chimneys and slope failure in strata of Pliocene and younger age. The gas chimneys are characterized by low‐amplitude reflections, acoustic turbidity and low P‐wave velocity indicating fluid expulsion pathways. Coherence time slices show that the polygonal faults are restricted to sediments with moderate‐amplitude, continuous reflections. Gas hydrates are identified in seismic data by the presence of bottom simulating reflectors (BSRs), which have high amplitude, reverse polarity and are subparallel to seafloor. Mud diapirism and mounded structures have variable geometry and a great diversity regarding the origin of the fluid and the parent beds. The gas chimneys, mud diapirism, polygonal faults and a seismic facies‐change facilitate the upward migration of thermogenic fluids from underlying sediments. Fluids can be temporarily trapped below the gas hydrate stability zone, but fluid advection may cause gas hydrate dissociation and affect the thickness of gas hydrate zone. The fluid accumulation leads to the generation of excess pore fluids that release along faults, forming pockmarks and mud volcanoes on the seafloor. These features are indicators of fluid flow in a tectonically‐quiescent sequence, Qiongdongnan Basin. Geofluids (2010) 10 , 351–368     

Rare Types of Trephination from Hungary Shed New Light on Possible Cross‐cultural Connections in the Carpathian Basin

Symbolic or incomplete trephinations are very common in Hungary in 9^th–11^thcentury AD skeletal series connected to early Hungarians, although they also occur in the preceding Avar Age (6^th–9^th c. AD) material. During the compilation of a database of regional cranial modification data, the authors found rare almond‐shaped symbolic trephinations in both periods, while these had formerly only been reported in Early Hungarian series. In this study, the new almond‐shaped lesions are described along with other symbolic trephinations of 14 newly found skulls from the 8^th–11^thcenturies AD in the Southern Great Plain of Hungary. The authors review the research of the phenomenon. The new findings may strengthen the theory of direct and very close cultural connections of these two ethnic groups, adding a new aspect to the debate over the origin and relationship of Late Avar (late 7^th–early 9^th c. AD) and Early Hungarian (9^th–11^th c. AD) populations. Copyright © 2013 John Wiley & Sons, Ltd.     

Riparian environment in shaping social and economic behavior during the first phase of the evolution of Late Neolithic tell complexes in SE Hungary (6th/5th millennia BC)

The period corresponding to the initial phase of cultural evolution in the Late Neolithic of SE Hungary (turn of the 6th and 5th millennia) is characterized by a major transformation recorded both in settlement structure and strategy, as well as material culture of the agrarian societies settled in the SE part of the Great Hungarian Plains. According to the available chronological data and archeology from the sites of multi-layered settlement complexes (tells) located on natural highs of the floodplain of the River Tisza, during the initial phase of its evolution representatives of the Tisza Culture were mainly confined to the SE part of the Great Hungarian Plains south of the Körös River. This period was followed by a relatively stable phase lasting about 150 years which hallmarked the greatest northward expansion of the culture. Some studies noticed strange features in connection with the first settlement complexes dated to the first period especially along the northern borderline of the culture’s distribution; i.e. a loose cluster of distinct settlement nuclei instead of concentration of settlements to a confined area characteristic of tells. Furthermore, by the end of the first phase, in the evolution of some settlements a northward shift of the houses away from the water was recorded. Most likely these reflect a socioeconomic response to some transformation in the local and/or regional riparian environment. As shown by our data gained from the paleoecological analysis of freshwater mollusks from a tell site, the referred pre-transitional period was characterized by pronounced floods causing major perturbations in the regional riparian environment. At the same time, the introduction of new subsistence strategies including shellfishing and fishing and the reordering of settlement structure was also recorded at several sites implying a successful adaptation to such most likely climate-induced perturbation, which is contemporary with the 5.1 ky event known in the literature.