The 3D facies architecture and petrophysical properties of hyaloclastite delta deposits: An integrated photogrammetry and petrophysical study from southern Iceland     

Lois Greenfield  John M. Millett  John Howell  Dougal A. Jerram  Timothy Watton  David Healy  Malcolm J. Hole  Sverre Planke 《Basin Research》2020,32(5):1081-1104

Hyaloclastites develop where lava interacts with water resulting in deposits that have a unique and often complex range of petrophysical properties. A combination of eruptive style and emplacement environment dictates the size, geometry and distribution of different hyaloclastite facies and their associated primary physical properties such as porosity, permeability and velocity. To date, links between the 3D facies variability within these systems and their petrophysical properties remain poorly understood. Hjörleifshöfði in southern Iceland presents an exceptional outcrop exposure of an emergent hyaloclastite sequence >1 km wide by >200 m high and enables an investigation of the distribution of the hyaloclastite deposits at seismic scale. Within this study we present a photogrammetry-based 3D model from part of this recent hyaloclastite delta and incorporate previous work by Watton et al. (Journal of Volcanology and Geothermal Research, 2013, 250, 19) to undertake detailed facies interpretation and quantification. Laboratory petrophysical analyses were performed on 34 core plugs cut from key field facies samples, including P- and S-wave velocity, density, porosity and permeability at both ambient and confining pressure. Integration of the 3D model with the petrophysical data has enabled the production of pseudo-wireline logs and property distribution maps which demonstrate the variability of physical properties within hyaloclastite sequences at outcrop to seismic scale. Through comparison of our data with examples of older buried hyaloclastite sequences we demonstrate that the wide-ranging properties of young hyaloclastites become highly uniform in older sequences making their identification by remote geophysical methods for similar facies variations more challenging. Our study provides an improved understanding of the petrophysical property distribution within hyaloclastite sequences and forms a valuable step towards improving the understanding of similar subsurface sequences and their implications for imaging and fluid flow.  相似文献   

Axial and transverse deep-water sediment supply to syn-rift fault terraces: Insights from the West Xylokastro Fault Block,Gulf of Corinth,Greece     

Timothy M. Cullen  Richard E. Ll. Collier  Robert L. Gawthorpe  David M. Hodgson  Bonita J. Barrett 《Basin Research》2020,32(5):1105-1139

Deep-water syn-rift systems develop in partially- or transiently-linked depocentres to form complicated depositional architectures, which are characterised by short transport distances, coarse grain sizes and a wide range of sedimentary processes. Exhumed systems that can help to constrain the tectono-stratigraphic evolution of such systems are rare or complicated by inversion tectonics. Here, we document a mid-Pleistocene deep-water syn-rift system fed by Gilbert-type fan deltas in the hangingwall of a rift margin fault bounding the West Xylokastro Horst block, on the southern margin of the Gulf of Corinth, Greece. Structural and stratigraphic mapping combined with digital outcrop models permit observations along this syn-rift depositional system from hinterland source to deep-water sink. The West Xylokastro Fault hangingwall is filled by two distinct sediment systems; an axial system fed by coarse-grained sediment gravity flows derived from fault-tip Gilbert-type fan deltas and a lateral system dominated by mass transport deposits fed from an evolving fault-scarp apron. Abrupt changes in stratigraphic architecture across the axial system are interpreted to record changes in relative base level, sediment supply and tectonics. Locally, depositional topography and intra-basinal structures controlled sediment dispersal patterns, from bed-scale infilling of local rugose topography above mass transport complexes, to basin-scale confinement from the fault scarp apron. These acted to generate a temporally and spatially variable, heterogeneous stratigraphic architecture throughout the basin-fill. The transition of the locus of sedimentation from a rift margin to a fault terrace through the syn-sedimentary growth of a basinward fault produced regressive surfaces updip, which manifest themselves as channels in the deep-water realm and acted to prograde the system. We present a new conceptual model that recognises coeval axial and transverse systems based on the stratigraphic architecture around the West Xylokastro fault block that emphasizes the lateral and vertical heterogeneity of rift basin-fills with multiple entry points.  相似文献   

Characteristics of migrating submarine canyons from the middle Miocene to present: Implications for paleoceanographic circulation,northern South China Sea   总被引：1，自引：0，他引：1  

Mangzheng Zhu  Stephan Graham  Xiong Pang  Timothy McHargue 《Marine and Petroleum Geology》2010

Previously undocumented, migrating submarine canyons have developed in the Pearl River Mouth Basin along the northern continental margin of the South China Sea from the middle Miocene to present. A grid of high-resolution, 2-D multi-channel seismic profiles calibrated by borehole information permits documentation of these northeastward migrating submarine canyons, as the result of the interplay of gravity flows and bottom currents. The modern canyons have lengths of 30–60 km, widths of 1–5.7 km, and relief of 50–300 m in water depths of 450–1500 m. Buried ancient submarine canyon successions were originally eroded by basal erosional discontinuities and partially filled by canyon thalweg deposits. These are overlain by lateral inclined packages and hemipelagic drape deposits. Basal erosional discontinuities and thalweg deposits are probably created principally by turbidity currents and filled with turbidites. Lateral inclined packages likely were formed by along-slope bottom currents. The evolution of these migrating submarine canyons reveals that northeastward bottom currents have consistently occurred at least from the middle Miocene to present in the study area. It might further imply that thermohaline intermediate water circulation of the South China Sea has been anti-cyclonic from the middle Miocene to present. The initiation of migrating submarine canyons possibly signals commencement of strong bottom currents after the middle Miocene in the South China Sea. The intensification of bottom currents also possibly may reflect shoaling of the major ocean seaways and increased vigor in oceanic circulation forced by global cooling after the middle Miocene.  相似文献   

Grain‐scale dependency of metamorphic reaction on crystal plastic strain     

Timothy Chapman  Geoffrey L. Clarke  Sandra Piazolo  Victoria A. Robbins  Patrick W. Trimby 《Journal of Metamorphic Geology》2019,37(7):1021-1036

The Breaksea Orthogneiss in Fiordland, New Zealand preserves water‐poor intermediate and mafic igneous rocks that were partially recrystallized to omphacite granulite and eclogite, respectively, at P ≈ 1.8 GPa and T ≈ 850°C. Metamorphic reaction consumed plagioclase and produced grossular‐rich garnet, jadeite‐rich omphacite, clinozoisite and kyanite. The extent of metamorphic reaction, identified by major and trace element composition and microstructural features, is patchy on the grain and outcrop scale. Domains of re‐equilibration coincide with areas that exhibit higher strain suggesting a causal link between crystal plastic strain and metamorphic reaction. Quantitative orientation analysis (EBSD) identifies gradual and stepped changes in crystal lattice orientations of igneous phenocrysts that are surrounded by homophase areas of neoblasts, characterized by high grain boundary to volume ratios and little to no internal lattice distortion. The narrow, peripheral compositional modification of less deformed garnet and omphacite phenocrysts reflects limited lattice diffusion in areas that lacked three‐dimensional networks of interconnected low‐angle boundaries. Low‐angle boundaries acted as elemental pathways (pipe diffusion) that enhanced in‐grain element diffusion. The scale of pipe diffusion is pronounced in garnet relatively to clinopyroxene. Strain‐induced mineral transformation largely controlled the extent of high‐T metamorphic reaction under relatively fluid‐poor conditions.  相似文献   

Map Men: Transnational Lives and Deaths of Geographers in the Making of East Central Europe     

Timothy Barney 《The Cartographic journal》2019,56(1):92-93

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Continuous human presence without extensive reductions in forest cover over the past 2500 years in an aseasonal Amazonian rainforest          下载免费PDF全文

Thomas J. Kelly  Ian T. Lawson  Katherine H. Roucoux  Timothy R. Baker  Euridice N. Honorio‐Coronado  Timothy D. Jones  Santiago Rivas Panduro 《第四纪科学杂志》2018,33(4):369-379

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Seasonal dynamics and exports of elements from a first‐order stream to a large inland lake in Michigan     

Kathryn L. Hofmeister  Lucas E. Nave  Paul Drevnick  Timothy Veverica  Renee Knudstrup  Katherine A. Heckman  Susan J. Riha  Rebecca L. Schneider  M. Todd Walter 《水文研究》2019,33(10):1476-1491

Headwater streams are critical components of drainage systems, directly connecting terrestrial and downstream aquatic ecosystems. The amount of water in a stream can alter hydrologic connectivity between the stream and surrounding landscape and is ultimately an important driver of what constituents headwater streams transport. There is a shortage of studies that explore concentration–discharge (C‐Q) relationships in headwater systems, especially forested watersheds, where the hydrological and ecological processes that control the processing and export of solutes can be directly investigated. We sought to identify the temporal dynamics and spatial patterns of stream chemistry at three points along a forested headwater stream in Northern Michigan and utilize C‐Q relationships to explore transport dynamics and potential sources of solutes in the stream. Along the stream, surface flow was seasonal in the main stem, and perennial flow was spatially discontinuous for all but the lowest reaches. Spring snowmelt was the dominant hydrological event in the year with peak flows an order of magnitude larger at the mouth and upper reaches than annual mean discharge. All three C‐Q shapes (positive, negative, and flat) were observed at all locations along the stream, with a higher proportion of the analytes showing significant relationships at the mouth than at the mid or upper flumes. At the mouth, positive (flushing) C‐Q shapes were observed for dissolved organic carbon and total suspended solids, whereas negative (dilution) C‐Q shapes were observed for most cations (Na⁺, Mg²⁺, Ca²⁺) and biologically cycled anions (NO₃^?, PO₄^3?, SO₄^2?). Most analytes displayed significant C‐Q relationships at the mouth, indicating that discharge is a significant driving factor controlling stream chemistry. However, the importance of discharge appeared to decrease moving upstream to the headwaters where more localized or temporally dynamic factors may become more important controls on stream solute patterns.  相似文献   

Relationships between riparian evapotranspiration and groundwater depth along a semiarid irrigated river valley     

Matthew R. Lurtz  Ryan R. Morrison  Timothy K. Gates  Gabriel B. Senay  Aditi S. Bhaskar  David G. Ketchum 《水文研究》2020,34(8):1714-1727

Evapotranspiration (ET) from riparian vegetation can be difficult to estimate due to relatively abundant water supply, spatial vegetation heterogeneity, and interactions with anthropogenic influences such as shallower groundwater tables, increased salinity, and nonpoint source pollution induced by irrigation. In semiarid south-eastern Colorado, reliable ET estimates are scarce for the riparian corridor that borders the Arkansas River. This work investigates relationships between the riparian ecosystem along the Arkansas River and an underlying alluvial aquifer using ET estimates from remotely sensed data and modelled water table depths. Results from a calibrated, finite-difference groundwater model are used to estimate weekly water table fluctuations in the riparian ecosystem from 1999 to 2009, and estimates of ET are calculated using the Operational Simplified Surface Energy Balance (SSEBop) model with over 200 Landsat scenes covering over 30 km² of riparian ecosystem along a 70-km stretch of the river. Comparison of calculated monthly SSEBop ET to estimated alfalfa reference ET from local micrometeorological station data indicated statistically significant high linear correspondence (R² = .87). Daily calculated SSEBop ET showed statistically significant moderate linear correspondence with data from a local weighing lysimeter (R² = .59). Simulated monthly SSEBop ET values were larger in drier years compared with wetter years, and ET variability was also larger in drier years. Peak ET most commonly occurred during the month of June for all 11 years of analysis. Relationships between ET and water table depth showed that peak monthly ET was highest when groundwater depths were less than about 3 m, and ET values were significantly lower for groundwater depths greater than 3 m. Negative sample Spearman correlation highlighted riparian corridor locations where ET increased as a result of decreased groundwater depths across years with different hydroclimatic conditions. This study shows how a combination of remotely sensed riparian ET estimates and a regional groundwater model can improve our understanding of linkages between riparian consumptive use and near-river groundwater conditions influenced by irrigation return flow and different climatic drivers.  相似文献   

The importance of and need for rapid hydrologic assessments in Latin America          下载免费PDF全文

Diego A. Riveros‐Iregui  Timothy P. Covino  Ricardo González-Pinzón 《水文研究》2018,32(15):2441-2451

Long‐term observations are critical in hydrology to understand the dynamics of biological and physicochemical processes involved in and affected by the flux of water. Long‐term observations have been employed to provide basic understanding of the water cycle (e.g., infiltration, evaporation, run‐off generation, and groundwater–surface water interactions), but they are lacking in hydrologically relevant regions such as the Andes Mountains, including alpine watersheds. Although the call for long‐term data acquisition in Latin America has been made, the establishment of long‐term data collection centres remains logistically challenging. This ever‐growing scientific gap hinders our understanding of differences and similarities in hydrological processes of tropical and temperate regions. Furthermore, technological advances such as in situ optical sensors for water quantity and quality remain cost‐prohibitive for both short and long deployment at most existing research sites in Latin America, restricting researchers pursuing research funding or developing meaningful, intersite comparisons and syntheses. Here, we emphasize the importance of and need for rapid assessments (i.e., field campaigns conducted over a few days) for improved hypothesis development and mechanistic understanding of hydrological dynamics in Latin America. We report on rapid assessments conducted in the high‐elevation mountains (>3,000 m) of Colombia. Our results highlight rapidly changing dynamics in nutrient retention potential and dissolved CO₂ (pCO₂), as well as highly variable spatial distribution of water quality parameters (N, C, P, Cl) in areas with varying land use. We present an initial examination of the effects of land‐use change on stream nutrient dynamics in one of the most biodiverse and threatened ecosystems on Earth. We conclude that rapid assessments not only are necessary but also represent a cost‐effective way to develop clear, testable hypotheses to advance a hydrologic research agenda in Latin America and work towards long‐term hydrological knowledge and information for use by other scientists.  相似文献   

Examining the geometry,age and genesis of buried Quaternary valley systems in the Midland Valley of Scotland,UK     

Timothy I. Kearsey  Jonathan R. Lee  Andrew Finlayson  Marieta Garcia‐Bajo  Anthony A. M. Irving 《Boreas: An International Journal of Quaternary Research》2019,48(3):658-677

Buried palaeo‐valley systems have been identified widely beneath lowland parts of the UK including eastern England, central England, south Wales and the North Sea. In the Midland Valley of Scotland palaeo‐valleys have been identified yet the age and genesis of these enigmatic features remain poorly understood. This study utilizes a digital data set of over 100 000 boreholes that penetrate the full thickness of deposits in the Midland Valley of Scotland. It identified 18 buried palaeo‐valleys, which range from 4 to 36 km in length and 24 to 162 m in depth. Geometric analysis has revealed four distinct valley morphologies, which were formed by different subglacial and subaerial processes. Some palaeo‐valleys cross‐cut each other with the deepest features aligning east–west. These east–west features align with the reconstructed ice‐flow direction under maximum conditions of the Main Late Devensian glaciation. The shallower features appear more aligned to ice‐flow direction during ice‐sheet retreat, and were therefore probably incised under more restricted ice‐sheet configurations. The bedrock lithology influences and enhances the position and depth of palaeo‐valleys in this lowland glacial terrain. Faults have juxtaposed Palaeozoic sedimentary and igneous rocks and the deepest palaeo‐valleys occur immediately down‐ice of knick‐points in the more resistant igneous bedrock. The features are regularly reused and the fills are dominated by glacial fluvial and glacial marine deposits. This suggests that the majority of infilling of the features happened during deglaciation and may be unrelated to the processes that cut them.  相似文献