Diagenesis and elemental geochemistry under varying reservoir oil saturation in the Junggar Basin of NW China: implication for differentiating hydrocarbon‐bearing horizons

In this paper, we attempt to differentiate hydrocarbon‐bearing reservoir horizons of the Junggar Basin of NW China based on the characteristics of diagenesis and associated elemental geochemistry. Reservoirs at this site have varying levels of oil saturation that correlate with the degree of dissolution in minerals (e.g., calcite and feldspar). Four different horizons with varying diagenetic mineral assemblages were observed, including (i) kaolinite‐rich, oil‐dominated horizons, (ii) kaolinite–pyrite–hematite‐rich, oil–water‐dominated horizons, (iii) siderite–chlorite‐rich, water‐dominated horizons, and (iv) chlorite‐rich horizons with negligible hydrocarbon production. The mean MnO content of the representative diagenetic mineral (e.g., calcite) in each of the above horizons is >2.5, 2.0–2.5, 1.5–2.0, and <1.0 wt%, respectively. We propose that the above methodology can be used for the identification of reservoir hydrocarbon‐bearing horizons. We argue that the indicators presented here can be applied in oil exploration across the Junggar Basin.     

Chiefdoms and states in the Yuncheng Basin and the Chifeng region: A comparative analysis of settlement systems in North China

Regional settlement datasets for the Yuncheng Basin and the Chifeng region are re-analyzed for comparison so as to reconstruct differing patterns of community development at local and supra-local scales. A methodological implication of this reanalysis is that comparing settlement areas and surface artifact densities between projects requires special attention to how the data were recorded so as to put them on the same measurement scale. The analytical approaches originally taken to reconstructing community organization in the two regions, while differing in several respects, are shown to produce highly compatible results, permitting a comparison of the two trajectories with a sound empirical foundation. Neolithic settlement began much earlier in Chifeng, but rates of demographic and community growth were extremely slow. In Yuncheng, early village growth was much more dramatic. Multiple chiefly districts of modest size emerged in both regions, but those of Yuncheng, despite their shorter developmental trajectory, had substantially larger populations. Their central settlements, in particular, grew to be much larger than those in Chifeng and the special activities carried out at these centers differed between the two regions. A poorly understood, but not contemporaneous, demographic disruption punctuated both sequences. It was followed by the emergence of political integration on a much larger scale in the Yuncheng Basin, focused on a single settlement an order of magnitude larger than its predecessors. In Chifeng, regional population soared far beyond previous levels, but political integration remained persistently small in scale.     

The Fremont Complex: A Behavioral Perspective

The Fremont complex is composed of farmers and foragers who occupied the Colorado Plateau and Great Basin region of western North America from about 2100 to 500 years ago. These people included both immigrants and indigenes who shared some material culture and symbolic attributes, but also varied in ways not captured by definitions of the Fremont as a shared cultural tradition. The complex reflects a mosaic of behaviors including full-time farmers, full-time foragers, part-time farmer/foragers who seasonally switched modes of production, farmers who switched to full-time foraging, and foragers who switched to full-time farming. Farming defines the Fremont, but only in the sense that it altered the matrix in which both farmers and foragers lived, a matrix which provided a variety of behavioral options to people pursuing an array of adaptive strategies. The mix of symbiotic and competitive relationships among farmers and between farmers and foragers presents challenges to detection in the archaeological record. Greater clarity results from use of a behavioral model which recognizes differing contexts of selection favoring one adaptive strategy over another. The Fremont is a case where the transition from foraging to farming is followed by a millennium of adaptive diversity and terminates with the abandonment of farming. As such, it serves as a potential comparison to other cases in the world during the early phases of the food producing transition.     

史前太湖流域社会复杂化进程初步研究

通过对太湖流域不同文化时期社会经济、社会关系以及宗教信仰三个方面考古资料的分析,将太湖流域社会发展分为均质、平等社会,初步分化社会和复杂分层社会三个阶段。     

Impacts of Pleistocene glacial loading on abnormal pore‐water pressure in the eastern Michigan Basin

The hydromechanical effects of Pleistocene glacial loading on the Michigan Basin are assessed using numerical analysis based on coupled stress and pore‐water pressure. The two‐dimensional model domain included the Basin cross section and extended 10 km into the Precambrian. In the analysis, we considered the effects of the number of glacial loading cycles, the presence and connectedness of a deep Cambrian aquifer, the direction of glacial advance, the effect of a wet versus dry glacier/soil interface, topographic effects, density‐driven flow effects, and lithosphere flexure on the development of anomalous pressures. The modeling results were compared with data collected from highly instrumented wells completed in the eastern margin of the Basin. The present‐day results define regions of significant underpressure in the upper Ordovician and lower Silurian formations characterized by very low hydraulic conductivity and regions of overpressure where hydraulic conductivity is higher. To achieve the degree of underpressure observed in the instrumented wells using the model, a specific loading cycle applied over 100 000 years was repeated four times. As the number of loading cycles increased, the Paleozoic formations reached a state where the underpressures remain constant. Our results also illustrate the difference in poroelastic modeling between the application of mechanical loads on the land surface and the application of an equivalent hydraulic head, where the latter developed overpressures rather than the observed underpressures. The modeling also shows that the overpressures observed in the Cambrian formations are most likely to be the result of density‐driven flow. Finally, the simulations show that the effects of lithosphere flexure in the hydromechanical models results in the development of lateral stresses that generate overpressures rather than underpressures in the southern half of the domain. As there are no suitable observation points, these results remain unconfirmed, and further study is warranted.     

四川会理县李家坪遗址新石器时代遗存发掘简报

2018年3月至6月,为配合金沙江下游河段的乌东德水电站建设,四川省文物考古研究院等对位于四川会理县新安傣族乡新开田村的李家坪遗址进行了考古发掘,发掘面积1000平方米。发现新石器时代晚期的房址、灰坑等数十座遗迹,出土百余件遗物及大量陶片标本,为研究城河流域乃至金沙江中下游地区新石器时代晚期考古学文化谱系提供了重要实物资料。     

New radiometric dates for precolumbian (2000–700 b.p.) earthworks in western Amazonia,Brazil

Abstract

In this paper we present new data on the precolumbian geometric ditched enclosures identified in Acre State, western Amazonia, Brazil. Remote sensing and ground survey have revealed 281 earthworks, located mainly on the edges of high plateaus overlooking the river valleys drained by the southeastern tributaries of the Upper Purus River. Excavations have shown that the few existing cultural materials are concentrated on the slopes and in the bottoms of the ditches, as well as on small mounds that were likely remains of houses, whereas the central, flat enclosed areas lack major archaeological features. New radiocarbon dates place the initial stage of earthwork construction as early as ca. 2000 b.p. We suggest that the building of these geometric earthworks may have been a regionally shared phenomenon, especially among the Arawak and the Tacana peoples, who used them for special gatherings, religious activities, and, in some cases, as village sites.     

LA-ICP-MS analysis of quartzite from the Upper Gunnison Basin,Colorado

We report the results of LA-ICP-MS analysis of 402 quartzite samples representing 48 collection loci in the Upper Gunnison Basin (UGB), Colorado and determine the extent to which the sources can be geochemically discriminated from one another using this non-destructive technique. The ability to differentiate among the sources would open the door to provenance studies of the quartzite chipped-stone tools and debitage that constitute 95% or more of most of the 3000-plus prehistoric site assemblages documented in the UGB. Our samples represent prehistorically quarried and non-quarried quartzite sources, including outcrop (primary) and gravel (secondary) deposits. The results reveal spatial and chronological trends in quartzite elemental composition that can be exploited for provenance determinations of quartzite artifacts from UGB sites, albeit using an assemblage-based sourcing strategy that differs from the familiar approach of “matching” obsidian artifacts to their statistically likeliest geological source. We offer a preliminary version of a sourcing protocol for UGB quartzite.     

Cainozoic euphorbiacean wood from the Canning Basin,Western Australia

A new species of fossil wood is described, Bridelioxylon canningense Bamford & McLoughlin, belonging to the Phyllanthoideae group of the Euphorbiaceae. The woods occur in indurated sandstones and conglomerates preserved in palaeochannels incised into the Upper Permian Condren Sandstone in the Landrigan Cliffs, northern Canning Basin, Western Australia. Based on the presence of the dicotyledonous woods and the geomorphological setting of the palaeochannel, a Palaeogene age is suggested for the host rocks. This is the first record of fossil euphorbiacean wood in Australia; pollen has been previously recorded. The fossil wood is most closely comparable to extant members of Bridelia that currently occupy the warmer and wetter parts of Australia.