Shallow sediment deformation styles in north-western Campeche Knolls,Gulf of Mexico and their controls on the occurrence of hydrocarbon seepage     

Feng Ding  Volkhard Spiess  Ian R. MacDonald  Markus Brüning  Noemi Fekete  Gerhard Bohrmann 《Marine and Petroleum Geology》2010,27(4):959-972

During German R/V Meteor M67/2 expedition to Campeche Knolls, southern Gulf of Mexico, a set of 2D high resolution seismic data was acquired to study the near-surface sediment structure and its relationship with hydrocarbon seepages in this salt province. The comprehensive survey covered 20 individual bathymetric highs or ridges and identified three principle structural types: Passive Type, Chaopopte Type, and Asymmetric Flap Type. The first type is the result of passive diapirism, whereas the latter two were initialized by a regional compressional event in the Miocene, but are later differently modified by salt tectonism. Chapopote Type structures appear as symmetrical domes, with uplifted coarse-grained Miocene sediments in their cores and rather thin syn-kinematic sediments covering the crests. Asymmetric Flap Type structures are also first folded as domes or ridges, but one flap later subsided together with salt evacuation, resulting in single uplifted monoclines. With the coarse-grained pre-kinematic sediments as reservoir units, both structural types can focus and accumulate hydrocarbons. The geometries of the structures suggest that hydrocarbons are accumulated in the center of the Chapopote Type structures and in the subsided flaps of the Asymmetric Flap Type structures. Hydrocarbon leakage from these thinly sealed reservoirs is regarded as the principle mechanism for the seepage in the study area, and accordingly the most seepage-prone positions are above these reservoirs. The seep locations suggested by analysis of sea-surface oil slick images of SAR satellite data are also examined in this study. These independently derived seep locations confirm the seepage-prone positions to be above the shallow buried reservoirs. This study suggest that the shallow sediment structures control the distribution of the hydrocarbon seeps of the north-western Campeche Knolls, although the hydrocarbons are sourced from the greater depth.  相似文献   

Paleogene of the Huanghekou Sag in the Bohai Bay Basin,NE China: deposition–erosion response to a slope break system of rift lacustrine basins     

Hao Liu  Qinglong Xia  Ian D. Somerville  Yuan Wang  Xinhuai Zhou  Chengmin Niu  Xiaofeng Du  Xintao Zhang 《Geological Journal》2015,50(1):71-92

The sequence architecture and depositional systems of the Paleogene lacustrine rift succession in the Huanghekou Sag, Bohai Bay Basin, NE China were investigated based on seismic profiles, combined with well log and core data. Four second‐order or composite sequences and seven third‐order sequences were identified. The depositional systems identified in the basin include: fan delta, braid delta, meander fluvial delta, lacustrine and sublacustrine fan. Identification of the slope break was conducted combining the interpretation of faults of each sequence and the identification of syndepositional faults, based on the subdivision of sequence stratigraphy and analysis of depositional systems. Multiple geomorphologic units were recognized in the Paleogene of the Huanghekou Sag including faults, flexures, depositional slope break belts, ditch‐valleys and sub‐uplifts in the central sag. Using genetic division principles and taking into consideration tectonic features of the Paleogene of the Huanghekou Sag, the study area was divided into the Northern Steep Slope/Fault Slope Break System, the Southern Gentle Slope Break System and T10 Tectonic Slope Break System/T10 Tectonic Belt. Responses of slope break systems to deposition–erosion are shown as: (1) basin marginal slope break is the boundary of the eroded area and provenance area; (2) ditch‐valley formed by different kinds of slope break belts is a good transport bypass for source materials; (3) shape of the slope break belt of the slope break system controls sediments types; (4) the ditch‐valley and sub‐sag of a slope break system is an unloading area for sediments; and (5) due to their different origins, association characteristics and developing patterns, the Paleogene slope break belt systems in the Huanghekou Sag show different controls on depositional systems. The Northern Fault Slope Break system controls the deposition of a fan delta‐lacustrine‐subaqueous fan, the Southern Gentle Slope Break system controls the deposition of a fluvial–deltaic–shallow lacustrine and sublacustrine fan, and the T10 Tectonic Slope Break System controls the deposition of shallow lacustrine beach bar sandbodies. The existence of a slope break system is a necessary but not a sufficient condition for studying sandbody development. The formation of effective sandbodies along the slope break depends on the reasonable coupling of effective provenance, necessary association patterns of slope break belt, adequate unloading space and creation of definite accommodation space. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Cloud Forest Conservation in the Central Highlands of Guatemala Hinges on Soil Conservation and Intensifying Food Production     

Ian Pope  Jon Harbor  Laura Zanotti  Guofan Shao  Dawn Bowen  Gary R. Burniske 《The Professional geographer》2016,68(1):1-13

Soil erosion threatens long-term soil fertility and food production in Q’eqchi’ communities native to the Sierra Yalijux and Sierra Sacranix mountain ranges in the central highlands of Guatemala. Environmental factors such as steep topography, erodible soils, and intense precipitation events, combined with land subdivision and reduced fallow periods as a consequence of population growth, contribute to severe erosion and strain soil resources. The preservation of the region's cloud forests hinges on enhancing production of staple crops through agricultural intensification while maintaining soil fertility through implementation of soil conservation measures.  相似文献   

Development and Extension of An Aggregated Scale Model: Part 1 – Background to ASMITA     

Ian TOWNEND  Zheng Bing WANG  Marcel STIVE  Zeng ZHOU 《海洋工程》2016,(4):483-504

Whilst much attention has been given to models that describe wave, tide and sediment transport processes in sufficient detail to determine the local changes in bed level over a relatively detailed representation of the bathymetry, far less attention has been given to models that consider the problem at a much larger scale (e.g. that of geomorphological elements such as a tidal flat and tidal channel). Such aggregated or lumped models tend not to represent the processes in detail but rather capture the behaviour at the scale of interest. One such model developed using the concept of an equilibrium concentration is the Aggregated Scale Morphological Interaction between Tidal basin and Adjacent coast (ASMITA). In this paper we provide some new insights into the concepts of equilibrium, and horizontal and vertical exchange that are key components of this modelling approach. In a companion paper, we summarise a range of developments that have been undertaken to extend the original model concept, to illustrate the flexibility and power of the conceptual framework. However, adding detail progressively moves the model in the direction of the more detailed process-based models and we give some consideration to the boundary between the two.  相似文献   

Government-Funded Deep Geophysical Surveys to Encourage Mineral Exploration: Results from the Western Australian “Exploration Incentives Scheme”     

Michael Dentith  Klaus Gessner  Simon Johnson  Ruth Murdie  Perla Pina-Varas  Jessica Spratt  Ian Tyler  Huaiyu Yuan 《《地质学报》英文版》2018,92(Z1):16-17

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Characterising the vertical separation of shale-gas source rocks and aquifers across England and Wales (UK)     

Sian E. Loveless  John P. Bloomfield  Robert S. Ward  Alwyn J. Hart  Ian R. Davey  Melinda A. Lewis 《Hydrogeology Journal》2018,26(6):1975-1987

Shale gas is considered by many to have the potential to provide the UK with greater energy security, economic growth and jobs. However, development of a shale gas industry is highly contentious due to environmental concerns including the risk of groundwater pollution. Evidence suggests that the vertical separation between exploited shale units and aquifers is an important factor in the risk to groundwater from shale gas exploitation. A methodology is presented to assess the vertical separation between different pairs of aquifers and shales that are present across England and Wales. The application of the method is then demonstrated for two of these pairs—the Cretaceous Chalk Group aquifer and the Upper Jurassic Kimmeridge Clay Formation, and the Triassic sandstone aquifer and the Carboniferous Bowland Shale Formation. Challenges in defining what might be considered criteria for ‘safe separation’ between a shale gas formation and an overlying aquifer are discussed, in particular with respect to uncertainties in geological properties, aquifer extents and determination of socially acceptable risk levels. Modelled vertical separations suggest that the risk of aquifer contamination from shale exploration will vary greatly between shale–aquifer pairs and between regions and this will need to be considered carefully as part of the risk assessment and management for any shale gas development.  相似文献   

A New Reference Material for Tritium Organic Molecules in Sediment: Results of an International Intercomparison Exercise          下载免费PDF全文

Phillip E. Warwick  Ian W. Croudace  Richard M. Marsh  Nicolas Baglan  Sang Bog Kim 《Geostandards and Geoanalytical Research》2018,42(2):253-262

Solid matrix ³H reference materials are challenging to prepare given the volatile nature of ³H and are often unrepresentative of the range of ³H forms that may be encountered during routine analysis. As a result, few ³H reference materials are currently available, undermining verification of analytical techniques for environmental ³H measurement. To address this, an International Working Group on Organically‐Bound Tritium Analysis determined to produce a tritium natural matrix reference material (NMRM). The reference material comprises marine sediment blended with sewage sludge contaminated with ³H‐organic species arising from authorised discharges from a radiopharmaceutical manufacturing site. Previous studies have demonstrated that the ³H species have persisted in the environment over three decades providing valuable supporting data to underpin the characterisation of the NMRM. The preparation and characterisation of the NMRM are described along with the subsequent application of the reference material in an international intercomparison exercise involving nineteen laboratories from nine countries. A reference value of 168 ± 22 Bq kg^?1 was derived from the data arising from the proficiency test.  相似文献   

Textural and micro-analytical insights into mafic–felsic interactions during the Oruanui eruption,Taupo     

Shane?M.?RooyakkersEmail authorView author&#;s OrcID profile  Colin?J.?N.?Wilson  C.?Ian?Schipper  Simon?J.?Barker  Aidan?S.?R.?Allan 《Contributions to Mineralogy and Petrology》2018,173(5):35

Quenched juvenile mafic inclusions (enclaves) are an occasional but informative component in the deposits of large felsic eruptions. Typically, the groundmasses of these inclusions rapidly crystallize as the mafic magma is chilled against a more voluminous, cooler felsic host, providing a physical and chemical record of the nature and timing of mafic–felsic interactions. We examine mafic inclusions of two compositional lineages (tholeiitic and calc-alkaline) from deposits of the 25.4 ka Oruanui eruption (Taupo, New Zealand). 2-D quantitative textural data from analysis of back-scattered electron images reveal a marked diversity in the groundmass textures of the inclusions, including median crystal sizes (amphibole: 14–45 µm; plagioclase: 21–75 µm) and aspect ratios (amphibole: 1.7–4.2; plagioclase: 2.1–4.0), area number densities (amphibole: 122–2660 mm^?2; plagioclase: 117–2990 mm^?2), area fractions (?) of minerals (?_plag?=?23–45%, ?_amph?=?0–28%, ?_cpx?=?0–6%, ?_oxides?=?0.6–5.5%), and the relative abundance of plagioclase and amphibole (?_plag/?_amph?=?1.0–4.6). Textural parameters vary more significantly within, rather than between, the two compositional lineages, and in some cases show marked variations across individual clasts, implying that each inclusion’s cooling history, rather than bulk composition, was the dominant control on textural development. Groundmass mineral compositions are also diverse both within and between inclusions (e.g. plagioclase from An_34–92, with typical intra-clast variability of ~?20 mol%), and do not correlate with bulk chemistry. Diverse groundmass textures and mineral and glass chemistries are inferred to reflect complex interplay of a range of factors including the degree and rate of undercooling, bulk composition, water content and, possibly, intensive variables. Our data are inconsistent with breakup of a crystallizing ponded mafic layer at the base of the Oruanui melt-dominant body, instead implying that each inclusion partially crystallized as a discrete body with a unique cooling history. Extensive ingestion of mush-derived macro-crystals suggests that mechanical breakup of mafic feeder dikes occurred within a transition zone between the mush and melt-dominant magma body. In this zone, the mush lacked yield strength, as has been inferred from field studies of narrow (meters to few tens of meters) mush-melt transition zones preserved in composite intrusions. Evidence for plastic deformation of inclusions during eruption and the abundance of fresh residual glass in inclusions from all eruptive phases suggest that the inclusions formed syn-eruptively, and must have been formed recurrently at multiple stages throughout the eruption.  相似文献   

The Neogene and Quaternary of England: landscape evolution,tectonics, climate change and their expression in the geological record     

Jonathan R. Lee  Ian Candy  Richard Haslam 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(3):452-481

During the Neogene and Quaternary, tectonic and climatic processes have had a profound impact upon landscape evolution in England and, perhaps as far back as 0.9 Ma, patterns of early human occupation. Until the Late Miocene, large-scale plate tectonic processes were the principal drivers of landscape evolution causing localised basin inversion and widespread exhumation. This drove, in places, the erosion of several kilometres of Mesozoic cover rocks and the development of a regional unconformity across England and the North Sea Basin. By the Pliocene, the relative influence of tectonics on landscape evolution waned as the background tectonic stress regime evolved and climatic influences became more prominent. Global-scale climate-forcing increased step-wise during the Plio-Pleistocene amplifying erosional and depositional processes that operated within the landscape. These processes caused differential unloading (uplift) and loading (subsidence) of the crust (‘denudational isostasy’) in areas undergoing net erosion (upland areas and slopes) and deposition (basins). Denudational isostasy amplified during the Mid-Pleistocene Transition (c.0.9 Ma) as landscapes become progressively synchronised to large-scale 100 ka ‘eccentricity’ climate forcing. Over the past 0.5 Ma, this has led to the establishment of a robust climate record of individual glacial/interglacial cycles enabling comparison to other regional and global records. During the Last Glacial-Interglacial Transition and early Holocene (c.16–7 ka), evidence for more abrupt (millennial/centennial) scale climatic events has been discovered. This indicates that superimposed upon the longer-term pattern of landscape evolution is a more dynamic response of the landscape to local and regional drivers.  相似文献   

The stratigraphical signature of the Anthropocene in England and its wider context     

Jan Zalasiewicz  Colin Waters  Mark Williams  David C. Aldridge  Ian P. Wilkinson 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(3):482-491

The Anthropocene deposits of England, here regarded as those formed after ～1950 CE, are now extensive, take various forms, and may be characterized and recognized by a number of stratigraphic signals, such as artificial radionuclides, pesticide residues, microplastics, enhanced fly ash levels, concrete fragments and a novel variety of ‘technofossils’ and neobiotic species. They include the uppermost parts of both ‘natural’ deposits such as the sediment layers formed in lakes and estuaries, and more directly human-made or human-influenced ones such as landfill deposits and the ‘artificial ground’ beneath urban areas and around major constructions. ‘Negative deposits’ include the worked areas of quarries and regions such as the English Fenland, where thick peat deposits have ablated to leave a strongly modified underlying landscape, and extend beneath into the subterranean realm as mine workings, metro systems and boreholes. The production of these is still rapidly increasing and evolving in character, while the early signs of global change, such as warming, sea level rise, and modifications to biotic assemblages, are beginning to further modify the emerging geology of this new phase of Earth history.  相似文献