Evaluation of soluble benzene migration in the Uinta Basin

Field sampling and mathematical modeling are used to study the long‐distance transport and attenuation of petroleum‐derived benzene in the Uinta Basin, Utah. Benzene concentration was measured from oil and oil field formation waters of the Altamont‐Bluebell and Pariette Bench oil fields in the basin. It was also measured from springs located in the regional groundwater discharge areas, hydraulically down‐gradient from the oil fields sampled. The average benzene concentration in oils and co‐produced waters is 1946 and 4.9 ppm at the Altamont‐Bluebell field and 1533 and 0.6 ppm at the Pariette Bench field, respectively. Benzene concentration is below the detection limit in all springs sampled. Mathematical models are constructed along a north–south trending transect across the basin through both fields. The models represent groundwater flow, heat transfer and advective/dispersive benzene transport in the basin, as well as benzene diffusion within the oil reservoirs. The coupled groundwater flow and heat transfer model is calibrated using available thermal and hydrologic data. We were able to reproduce the observed excess fluid pressure within the lower Green River Formation and the observed convective temperature anomalies across the northern basin. Using the computed best‐fit flow and temperature, the coupled transport model simulates water washing of benzene from the oil reservoirs. Without the effect of benzene attenuation, dissolved benzene reaches the regional groundwater discharge areas in measurable concentration (>0.01 ppm); with attenuation, benzene concentration diminishes to below the detection limit within 1–4 km from the reservoirs. Attenuation also controls the amount of water washing over time. In general, models that represent benzene attenuation in the basin produce results more consistent with field observations.     

Rocks are heavy: transport costs and Paleoarchaic quarry behavior in the Great Basin

Central place foraging models are used to investigate assemblage variability at two Paleoarchaic (terminal Pleistocene/early Holocene) dacite quarries in the central and eastern Great Basin. Our analyses focus specifically on biface reduction and how varying degrees of reduction relate to the costs of transporting the resulting products upon departing the quarry. Our results suggest that when the distance to be traveled to a residential base is great, reduction will proceed further at the quarry than if the residential base is fairly close. Further, a residential site assemblage will consist of bifaces at later stages of reduction than its associated quarry.     

Approaches to Prehistoric Diet Breadth, Demography, and Prey Ranking Systems in Time and Space

Zooarchaeological data on small game use hold much potential for identifying and dating Paleolithic demographic pulses in time and space, such as those associated with modern human origins and the evolution of food-producing economies. Although small animals were important to human diets throughout the Middle, Upper, and Epi-Paleolithic periods in the Mediterranean Basin, the types of small prey emphasized by foragers shifted dramatically over the last 200,000 years. Slow-growing, slow-moving tortoises, and marine mollusks dominate the Middle Paleolithic record of small game exploitation. Later, agile, fast-maturing animals became increasingly important in human diets, first birds in the early Upper Paleolithic, and soon thereafter hares and rabbits. While the findings of this study are consistent with the main premise of Flannery's Broad Spectrum Revolution (BSR) hypothesis (Flannery, K. V. (1969). In Ucko, P. J., and Dimbleby, G. W. (eds.), The Domestication and Exploitation of Plants and Animals, Aldine Publishing Company, Chicago, pp. 73–100), it is now clear that human diet breadth began to expand much earlier than the Pleistocene/Holocene transition. Ranking small prey in terms of work of capture (in the absence of special harvesting tools) proves far more effective in this investigation of human diet breadth than taxonomy-based diversity analyses published previously. Our analyses expose a major shift in human predator–prey dynamics involving small game animals by 50–40 KYA in the Mediterranean Basin, with earliest population growth pulses occurring in the Levant. In a separate application to the Natufian period (13–10 KYA), just prior to the rise of Neolithic societies in the Levant, great intensification is apparent from small game use. This effect is most pronounced at the onset of this short culture period, and is followed by an episode of local depopulation during the Younger Dryas, without further changes in the nature of Natufian hunting adaptations. An essential feature of the diachronic and synchronic approaches outlined here is controlling the potentially conflating effects of spatial (biogeographic) and temporal variation in the faunal data sets.     

Source water protection in a landscape of 'New Era' deregulation

The concept of source water protection (SWP) has gained prominence in the water resource literature. SWP consists of watershed and groundwater management for the protection of drinking water supplies. The logic behind SWP is that it is easier, cheaper and safer to protect a drinking water source from contamination than it is to remediate after contamination. SWP is largely a regulatory activity, requiring provincial government policy commitments. This research investigates the degree to which recent provincial deregulation plays a role in constraining SWP implementation at the local water utility level. The research was undertaken in British Columbia (BC) where, after 2001, the provincial government advanced widespread 'New Era' deregulation of social and environmental legislation. The apparent contradiction between government deregulation and government commitment to safe drinking water is interrogated. Data were collected using semi-structured interviews and document review in the Okanagan Basin. This article reveals that New Era deregulation initiatives have constrained local efforts to implement SWP on the ground. This article recommends that a single provincial agency should oversee drinking water in BC and that greater attention be given to regional governance for drinking water management in the Okanagan Basin.     

青海民和县寺沟峡岩画调查简报

2019年,丝绸之路南亚廊道调查队在青海省民和县寺沟峡内发现了4幅6组个体102个岩画,并对岩画进行了详细的调查、测绘和数字化扫描。从整个岩面的制作技法来看,有直接磨刻法和敲凿法。岩画主要以抽象图案为主,有少量人像、持物人物、鸟等具象形象。其形象与新石器晚期至青铜时代彩陶图案纹饰相似度较高,与中原地区岩画有着密切关系,为研究官亭盆地早期文化提供了新的突破口。     

The Terminal Pleistocene/Early Holocene archaeology of the Great Basin

The archaeological record of the Terminal Pleistocene and Early Holocene in the Great Basin consists largely of surface lithic artifacts, and consequently research has concentrated on typological and technological studies. The small suite of radiocarbon dates available suggests human presence in the Great Basin by at least 11,500 B.P., but evidence of subsistence is scanty. Technological analyses as well as artifact distributions suggest that the earliest occupants of this region subsisted primarily by hunting, possibly large terrestrial game. As elsewhere in North America, the earliest occupants of the Great Basin faced a rapidly changing environment, with the drying of shallow pluvial lake remnants and the creation of new habitats. Paralleling these changes, significant subsistence resource diversification coupled with expansion into new environments is evident by the close of the Pleistocene.     

Quantitative estimation of overpressure caused by gas generation and application to the Baiyun Depression in the Pearl River Mouth Basin,South China Sea

Hydrocarbon generation can yield high fluid pressures in sedimentary basins as the conversion of solid kerogen to hydrocarbons can result in an increase in fluid volume. To quantify the relationship between gas generation and overpressure in source rocks, a set of equations for computing the pressure change due to gas generation has been derived. Those equations can be used to quantitatively estimate overpressure generated by type III kerogen in source rocks by considering gas generation and leakage, gas dissolution in formation water and residual oil, thermal cracking of oil to gas, and hydrocarbon episodic expulsion from source rocks. The equations also take consideration of other factors including source rock porosity, transformation ratio, total organic carbon (TOC), hydrogen index, and compressibility of kerogen, oil, and water. As both oil and gas are taken into account in the equations, they can also be used to estimate the evolution of overpressure caused by hydrocarbon generation of type I and type II kerogen source rocks. Sensitivity analyses on the type III kerogen source rock indicate that hydrogen index is the most influential parameter for overpressure generation, while TOC and residual gas coefficient (β: ratio of residual gas over the total gas generated) have a moderate effect. Overpressure can be generated even if the gas leakage/loss in the source rock is up to 80% of the total gas generated. This suggests that the internal pressure seal of the source rock is not a critical factor on the pressure change as long as the source rocks are capable of sealing liquid oil. The equations were applied to evaluate the overpressure in the Eocene–Oligocene Enping Formation source rocks due to hydrocarbon generation in the Baiyun Depression, the Pearl River Mouth Basin by considering the source rock properties, hydrocarbon generation history, and hydrocarbon expulsion timing. Two episodes of overpressure development due to gas generation and release were modeled to have occurred in the Enping Formation source rock since 16 Ma. The overpressure release at 10.2–5.3 Ma via hydrocarbon expulsion was apparently related to the Dongsha phase of tectonic deformation, whereas the pressure release at 2–0 Ma was due to pressure generation that was exceeded the fracture‐sealing pressure in the source rocks.     

Pyrophyllite formation in the thermal aureole of a hydrothermal system in the Lower Saxony Basin,Germany

A combined clay mineralogical, fluid inclusion, and K‐Ar study of Upper Jurassic metasediments at the Gehn (Lower Saxony Basin, Germany) provides evidence for a transient hydrothermal event during Upper Cretaceous basin inversion centered on a prominent gravimetric anomaly. Kaolinite and smectite in Oxfordian pelitic parent rocks that cap a deltaic sandstone unit were locally transformed into pyrophyllite, 2M₁ illite, R3 illite–smectite, chlorite, and berthierine at the Ueffeln quarry. The pyrophyllite‐bearing metapelites lack bedding‐parallel preferred orientation of sheet silicates and experienced peak temperatures of about 260–270°C consistent with microthermometric data on quartz veins in the underlying silicified sandstones. The presence of expandable layers in illite–smectite and high Kübler Index values indicate that the thermal event was rather short‐lived. K‐Ar dating of the <0.2 μm fraction of the pyrophyllite‐bearing Ueffeln metapelite yields a maximum illitization age of 117 ± 2 Ma. Lower trapping temperatures of aqueous fluid inclusions in quartz veins and the absence of pyrophyllite in metapelites of the Frettberg quarry in a distance of about 2.5 km from the Ueffeln quarry infer maximum paleotemperatures of only 220°C. The highly localized thermal anomaly at Ueffeln suggests fault‐controlled fluid migration and heat transfer that provided a thermal aureole for pyrophyllite formation in the metapelites rather than metamorphism due to deep burial. A pH neutral hydrothermal fluid that formed by devolatilization reactions or less likely by mixing of meteoric and marine waters that interacted at depth with shales is indicated by the low salinity (3–5 wt. % NaCl equiv.) of aqueous inclusions, their coexistence with methane–carbon dioxide‐dominated gas inclusions as well as carbon, hydrogen, and oxygen isotope data. The upwelling zone of hydrothermal fluids and the thermal maximum is centered on a gravimetric anomaly interpreted as an igneous intrusion (‘Bramsche Massif’) providing the heat source for the intrabasinal hydrothermal system.     

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.