The effect of extractable organic matter and solid organic matter on the pore structure of shale from Yangchang Formation in the Ordos Basin, China is investigated in this study. The shale samples ...were successively crushed, extracted by dichloromethane to remove extractable organic matter, treated by hydrogen peroxide to remove solid organic matter. The porosity, organic and mineralogical characteristic of original, extracted and H2O2 treated shale samples were analyzed via low pressure gas adsorption measurement, X-ray diffraction (XRD) and Rock-Eval pyrolysis. Results show that pores in the studied shale were occupied and blocked by extractable organic matter with varying degrees which seriously affect porosity. Pores with small diameter will be preferential occupied and blocked. The plentiful generation of hydrocarbon in organic-rich shale will lead to high fluid pressure in pore which protect pore from compaction during evolution and lead to a higher porosity. This protection mainly act on macropores. Pores in the studied shale were dominated by quartz-related and clay-related pores, and organic matter hosted pore is rare. Solid organic matter content act as a harmful factor to total porosity of studied shale. Firstly, high content of solid organic matter reduce the relative content of quartz and clay minerals then lead to a low total porosity. Secondly, solid organic matter occupied and blocked pores related to quartz and clay minerals.
Abstract
Exploring features of wood anatomy associated with fire scars found on fossil tree trunks is likely to increase our knowledge of the environmental and ecological processes that occurred in ...ancient forests and of the role of fire as an evolutionary force. In Petrified Forest National Park, Arizona, where Late Triassic fossil trees are exposed, we found 13 examples of fossil logs with external features resembling modern fire scars. One specimen with the unambiguous external features of a fire scar was collected for analysis of its fossilized wood. A light-colored band composed of compressed and distorted tracheids was associated with the scarring event. Cell lumen diameter and cell wall thickness in the pre-scarring fossilized wood show a response similar to that described in modern trees experiencing drought conditions. Tracheids in the post-scarring wood are initially smaller, and then become larger than average following a recovery period, as is often observed in modern conifers following fire. The responses in external morphology and wood anatomy to drought and fire were similar to those of some modern trees and support the view that some forests may have experienced conditions favoring the evolution of fire-adapted traits for more than 200 million years.
A rich assemblage of various types of bromalites from the lower Carnian "Konservat-Lagerstätte" from the Reingraben Shales in Polzberg (Northern Calcareous Alps, Lower Austria) is described for the ...first time in detail. They comprise large regurgitalites consisting of numerous entire shells of ammonoid Austrotrachyceras or their fragments and rare teuthid arm hooks, and buccal cartilage of Phragmoteuthis. Small coprolites composed mainly of fish remains were also found. The size, shape and co-occurrence with vertebrate skeletal remains imply that regurgitalites were likely produced by large durophagous fish (most likely by cartilaginous fish Acrodus). Coprolites, in turn, were likely produced by medium-sized piscivorous actinopterygians. Our findings are consistent with other lines of evidence suggesting that durophagous predation has been intense during the Triassic and that the so-called Mesozoic marine revolution has already started in the early Mesozoic.
The Middle Triassic was a time of major changes in tetrapod faunas worldwide, but the fossil record for this interval is largely obscure for terrestrial faunas. This poses a severe limitation to our ...understanding on the earliest stages of diversification of lineages representing some of the most diverse faunas in the world today, such as lepidosauromorphs (e.g., lizards and tuataras). Here, we report a tiny new lepidosauromorph from the Middle Triassic from Vellberg (Germany), which combines a mosaic of features from both early evolving squamates and rhynchocephalians, such as the simultaneous occurrence of a splenial bone and partial development of acrodonty. Phylogenetic analyses applying different optimality criteria, and combined morphological and molecular data, consistently recover the new taxon as a stem-lepidosauromorph, implying stem-lepidosauromorph species coinhabited areas comprising today's central Europe at the same time as the earliest known rhynchocephalians and squamates. It further demonstrates a more complex evolutionary scenario for dental evolution in early lepidosauromorphs, with independent acquisitions of acrodonty early in their evolutionary history. The small size of most terrestrial vertebrates from Vellberg is conspicuous, contrasting to younger Triassic deposits worldwide, but comparable to Early Triassic faunas, suggesting a potential long-lasting Lilliput effect in this fauna.
The Geologic Time Scale 2012, winner of a 2012 PROSE Award Honorable Mention for Best Multi-volume Reference in Science from the Association of American Publishers, is the framework for deciphering ...the history of our planet Earth. The authors have been at the forefront of chronostratigraphic research and initiatives to create an international geologic time scale for many years, and the charts in this book present the most up-to-date, international standard, as ratified by the International Commission on Stratigraphy and the International Union of Geological Sciences. This 2012 geologic time scale is an enhanced, improved and expanded version of the GTS2004, including chapters on planetary scales, the Cryogenian-Ediacaran periods/systems, a prehistory scale of human development, a survey of sequence stratigraphy, and an extensive compilation of stable-isotope chemostratigraphy. This book is an essential reference for all geoscientists, including researchers, students, and petroleum and mining professionals. The presentation is non-technical and illustrated with numerous colour charts, maps and photographs. The book also includes a detachable wall chart of the complete time scale for use as a handy reference in the office, laboratory or field.
The most detailed international geologic time scale available that contextualizes information in one single reference for quick desktop access. Gives insights in the construction, strengths, and limitations of the geological time scale that greatly enhances its function and its utility. Aids understanding by combining with the mathematical and statistical methods to scaled composites of global succession of events. Meets the needs of a range of users at various points in the workflow (researchers extracting linear time from rock records, students recognizing the geologic stage by their content).
Understanding water distribution behaviors plays an essential role in shale gas development due to the hydraulic fracturing technology. In this study, water vapor adsorption isotherms were measured ...for Upper Triassic Yanchang and Lower Silurian Longmaxi samples at 288.15 K, 298.15 K and 308.15 K to investigate the adsorption behaviors of water on shale. For a description of adsorption process, a Dent’s model provides an estimate of primary and secondary adsorption sites of water adsorption. The effects of temperature, shale mineralogy, and water distribution were discussed. The results show that temperature has a negative effect on water vapor adsorption. Adsorption capacities of primary and secondary sites decrease with increasing temperature. Water vapor adsorption capacity is tightly associated with clay content, whereas water vapor adsorption has no significant relationship with total organic carbon (TOC). Normalized water vapor adsorption content also has no significant relationship with TOC, which indicates no obvious correlation between water vapor adsorption and TOC content. The inter-crystal pores of clay minerals provide significant specific surface for gas adsorption in shale. At low relative pressure, a large number of water molecules adsorb on the primary sites. At high relative vapor pressure, most of the primary sites have been occupied, so that the secondary adsorption sites will be utilized. Therefore, due to relative weak binding energies in secondary adsorption sites, water cluster are formed in micro-pores of shale. As relative vapor pressure increases, capillary condensation gradually predominates over the adsorption. The study will reveal mechanism of water adsorption and distribution characteristics on shale and provide some foundation for geological reserve estimation and shale gas recovery prediction.
This study quantified the anisotropy of element composition in Upper Triassic “Chang 8” shale in Jiyuan district of Ordos Basin, China and provided the microscopic evidence for the existence of ...dominant fracture zone.
Element quantification was carried out ensuring both observational resolution and sample representativeness. Results show that for shale slices in two directions which are 45° (225°) and 0° (180°/360°), the distribution of elements is significantly different from that in other directions. The minimum of element contents often occurs in 45° (225°) and the maximum of element contents often occurs in 0° (180°/360°). The brittleness parameter value stays at a high level from 0° (180°/360°) to 22.5° (202.5°). The maximum value occurs in 0° (180°/360°), and the minimum value occurs in 45° (225°) which has obvious significance in shale stimulation.
The conclusion proved that the existence of predominant fracture zone in shale has the microscopic evidence in micro-scale brittle minerals.
While temnospondyl fossils have been relatively well documented in the Western world and Africa; research on temnospondyl fossils in South-East Asia and India has received less attention. ...Nonetheless, they add a substantial amount to the record of palaeobiogeographic distribution of the Triassic temnospondyl amphibians. During the Triassic, almost every temnospondyl family (aside from dissorophoids) was present in India. According to the findings, the assemblage and species diversity of Triassic temnospondyl amphibians peaked in the Early Triassic. With climatic stability and ecological saturation in the Middle and Late Triassic, diversification slowed down or gradually decreased. The Jaccard Similarity coefficient of the Triassic temnospondyl contents in South-East Asia and India shows an agreement in palaeobiogeography; the coefficients reflect the geography of Pangea. According to the Euler diagram, the junction of the Triassic temnospondyls in South-East Asia and India indicates that these regions of India did not have endemic Triassic temnospondyl populations.
Alors que les fossiles de temnospondyles ont été relativement bien documentés en occident et en Afrique, les recherches sur les fossiles de temnospondyles en Asie du Sud-Est et en Inde ont reçu moins d’attention. Néanmoins, ils apportent une contribution substantielle à la compréhension de la répartition paléobiogéographique des amphibiens temnospondyles du Trias. Au cours du Trias, presque toutes les familles de temnospondyles (à l’exception des dissorophoïdes) sont documentées en Inde. D’après les résultats, les diversités des espèces et des assemblages d’amphibiens temnospondyles du Trias ont atteint leur apogée au début du Trias. Avec la stabilité climatique et la saturation écologique au Trias moyen et tardif, la diversification s’est ralentie ou a progressivement diminué. Le coefficient de similarité de Jaccard des contenus temnospondyles du Trias en Asie du Sud-Est et en Inde montre une concordance avec la paléobiogéographie ; les coefficients reflètent la géographie de la Pangée. Selon le diagramme d’Euler, la jonction des temnospondyles triasiques de l’Asie du Sud-Est et de l’Inde indique que ces régions de l’Inde n’avaient pas de populations endémiques de temnospondyles au Trias.
Significant petroleum resources occur in the Ordovician carbonate reservoirs of the Tazhong area (Tarim Basin, China) in accumulations of black oil, volatile oil and condensate. However, the factors ...controlling the distribution of pools with different fluid phases remain poorly understood. Here, we integrate geological and conventional oil/gas geochemical data with an extensive dataset on diamondoids and propose a model for the occurrence of petroleum fluids in the area. Oils in the study area contain low variety and concentration of diamondoids and organic-sulfur compounds (OSCs) and have oil-dissolved wet gas mostly co-generated with oil. In contrast, liquids in the condensate reservoirs are significantly enriched in various types of diamondoids and OSCs, and have dry associated gas with methane enriched in 13C and relatively high content of H2S. We interpret that mature gas from deeper Cambrian strata, likely generated from thermally cracked oils and affected by thermochemical sulfate reduction (TSR), invaded the condensate reservoirs. Black oil reservoirs did not receive this late gas charge and this preserved their oil phase. The 1D burial history models and data on fluid inclusions suggest that oil charged all studied Ordovician reservoirs in the Late Permian – Triassic time, while the late gas charge occurred in selected reservoirs in the Late Himalayan time (∼10 Ma). Diamondoids proved to be useful indicators of the late gas charge as their variety and concentrations in liquids from the study area show good correlation with the extent of gas invasion.
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