Hybrid event beds are texturally and compositionally‐diverse deposits preserved within deepwater settings. They are deposited by flows exhibiting ‘mixed behaviour’, forming complex successions of ...sandstone and mudstone, which are often challenging to predict. Hybrid event beds are documented in deep‐marine settings, where they have been thoroughly characterized, and are well‐known as effective fluid transmissibility barriers and baffles in reservoirs. By comparison, there are far‐fewer studies of hybrid event beds from deep‐lacustrine settings, where their character and distribution remains relatively under‐explored. In order to provide insights into these deposits, this study presents the detailed analysis of three‐dimensional seismic data, wireline logs and core from a series of ancient deep‐lacustrine fan systems in the North Falkland Basin. Results confirm that deep‐lacustrine hybrid event beds comprise the same idealized sequence of the ‘H1–H5’ divisions. However, in this study H3 ‘debrite’ units can be sub‐divided into ‘H3a–H3c’, based on: sharp or erosional intra‐H3 contacts, bulk lithology, mud‐content and discrete sedimentary textures. This study interprets the H3a–H3c sub‐units as the products of multiple flow components formed through significant rearward longitudinal flow transformation processes, during the emplacement of a single hybrid event bed. Hybrid event beds are observed within lobe fringes, where flow types, energies and transport mechanisms diversify as a result of flow transformation. The temporal context of hybrid event bed occurrences is considered in relation to stages of fan evolution, including: the Initiation; Growth (I); Growth (II); By‐pass; Abandonment; and Termination phases. Hybrid event beds are mainly found in either the initiation phase where flow interaction and erosion of initial substrates promoted mixed flow behaviour, or in the abandonment phase as facies belts retreated landward. The results of this study have important implications in terms of flow processes of hybrid event bed emplacement, in particular sub‐division of the H3 unit, as well as the prediction of hybrid event bed occurrence and character within ancient deep‐lacustrine fan settings, in general.
Fault relay ramps are important sediment delivery points along rift margins and often provide persistent flow pathways in deepwater sedimentary basins. They form as tilted rock volumes between ...en‐echelon fault segments, which become modified through progressive deformation, and may develop through‐going faults that ‘breach’ the relay ramp. It is well established that hinterland drainage (fluvial/alluvial systems) is greatly affected by the presence of relay ramps at basin margins. However, the impact on deepwater (deep‐marine/lacustrine) subaqueous sediment gravity flow processes, particularly by breached relay ramps, is less well documented. To better evaluate the complex geology of breached relay settings, this study examines a suite of high‐quality subsurface data from the Early Cretaceous deep‐lacustrine North Falkland Basin (NFB). The Isobel Embayment breached relay‐ramp, an ideal example, formed during the syn‐rift and was later covered by a thick transitional and early post‐rift succession. Major transitional and early post‐rift fan systems are observed to have consistently entered the basin at the breached relay location, directed through a significant palaeo‐bathymetric low associated with the lower, abandoned ramp of the structure. More minor systems also entered the basin across the structure‐bounding fault to the north. Reactivation of basin‐bounding faults is shown by the introduction of new point sources along its extent. This study shows the prolonged influence of margin‐located relay ramps on sedimentary systems from syn‐rift, transitional and into the early post‐rift phase. It suggests that these structures can become reactivated during post‐rift times, providing continued control on deposition and sourcing of overlying sedimentary systems. Importantly, breached relays exert control on fan distribution, characterised by laterally extensive lobes sourced by widespread feeder systems, and hanging walls settings by small‐scale lobes, with small, often line‐sourced feeders. Further characterising the likely sandstone distribution in these structurally complex settings is important as these systems often form attractive hydrocarbon reservoirs.
Early post‐rift deposition associated with the breached relay structure can be divided into two domains: (1) systems which entered the basin at the breached relay structure via the lower abandoned ramp; (2) systems which entered directly across the hangingwall of structure bounding faults. Into the early post‐rift, systems continue to enter at the same locations, however, fan geometries and sources change in response to overall basin subsidence becoming the main accommodation driver.
Geological processes alter pore spaces over time, and their analysis can shed light on the dynamic fractal structure and fluid flow of rocks over time. This study presents experimental evidence to ...illustrate that the pore fractal structure evolves with sedimentation, carbonate cementation, clay growth, and dissolution. It examines, describes and characterizes a suite of core samples from the Gaotaizi oil layer of the second and third members of the Qingshankou Formation, Songliao Basin, China. The effects of mechanical compaction and other diagenesis effects on fractal pore structure on sedimentary rocks are discussed. A schematic diagram is proposed that describes the impacts of these diagenetic processes on fractal pore structure at the microscopic scale in sedimentary rocks. This work links the state of diagenetic alteration and fractal pore structure, which can guide practical applications such as predicting the permeability of sedimentary rocks.
Plain Language Summary
Mechanical compaction or chemical alteration process will change the pore space of the rock, including pore size and grain‐pore interface properties. We present the evidence that geological processes alter the “roughness” amplitude of grain‐pore interface (fractal pore structure) in sedimentary rock, and discuss the evolutionary mechanism of the “roughness” amplitude of grain‐pore interface. This work links the state of diagenetic alteration and fractal properties of rocks, which can guide practical applications such as predicting permeability of sedimentary rocks for any historical period.
Key Points
Evolution of fractal dimension with diagenesis was revealed
Effects of diagenesis on fractal upper and lower limits were discussed
Effect mechanism of fractal pore structure was revealed in sedimentary rocks
Modern, tide‐dominated and tide‐influenced coastlines are characterized by a range of environments, including deltas, estuaries and lagoons. However, some tide‐dominated basins and related ...sedimentary units in the rock record, such as the semi‐enclosed, shallow, Utah–Idaho Trough foreland basin of the Jurassic Curtis Sea, do not correspond to any of these modern systems. Persistent aridity caused the characteristic severe starvation of perennial fluvial input throughout this basin, in which the informal lower, middle and upper Curtis, as well as the underlying Entrada Sandstone, and the overlying Summerville Formation were deposited. Wave energy was efficiently dissipated by the shallow basin's elongated morphology (approximately 800 × 150 km), as its semi‐enclosed morphology further protected the system from significant wave impact. Consequently, the semi‐enclosed, shallow‐marine system was dominated by amplified tidal forces, resulting in a complex distribution of heterolithic deposits. Allocyclic forcing strongly impacted upon the system's intrinsic autocyclic processes as the lower Curtis was deposited. Short‐lived relative sea‐level variations, along with uplift and deformation episodes, resulted in the accumulation of three parasequences, each separated by traceable flooding and ravinement surfaces. The subsequent transgression, which defines the base of the middle Curtis, allowed for the shallow‐marine part of the system to enter into tidal resonance as a consequence of the flooded basin reaching the optimal configuration of approximately 800 km in length, corresponding to an odd multiple of the quarter of the tidal wavelength given an average minimum water depth of 20–25 m. This resonant system overprinted the effects of allocyclic forcing and related traceable stratigraphic surfaces. However, the contemporaneous and neighbouring coastal dune field sedimentary rocks of the Moab Member of the Curtis Formation, characterized by five stacked aeolian sequences, as well as the supratidal deposits of the Summerville Formation, lingered to record allocyclic signals, as the Curtis Sea regressed. This study shows that a tide‐dominated basin can enter into tidal resonance as it reaches its optimal morphological configuration, leading to the overprinting of otherwise dominant allocyclic processes by autocyclic behaviour. It is only by considering the sedimentological relationships of neighbouring and contemporaneous depositional systems that a full understanding of the dynamic stratigraphic history of a basin alternatively dominated by autocyclic and allocyclic processes can be achieved.
This study shows that (a) a tide‐dominated basin can enter into tidal resonance as it reaches its optimal morphological configuration, leading to the overprinting of otherwise dominant allocyclic processes by autocyclic behaviour. (b) It is therefore required to extend the research focus to neighbouring and contemporaneous depositional systems in order to fully understand the dynamic stratigraphic history of a basin alternatively dominated by auto‐ and allocyclic processes.
Male and female Fischer 344 rats were exposed to naphthalene vapors at 0 (controls), 0.1, 1, 10, and 30ppm for 6h/d, 5 d/wk, over a 90-day period. Following exposure, the respiratory epithelium and ...olfactory epithelium from the nasal cavity were dissected separately, RNA was isolated, and gene expression microarray analysis was conducted. Only a few significant gene expression changes were observed in the olfactory or respiratory epithelium of either gender at the lowest concentration (0.1ppm). At the 1.0ppm concentration there was limited evidence of an oxidative stress response in the respiratory epithelium, but not in the olfactory epithelium. In contrast, a large number of significantly enriched cellular pathway responses were observed in both tissues at the two highest concentrations (10 and 30ppm, which correspond to tumorigenic concentrations in the NTP bioassay). The nature of these responses supports a mode of action involving oxidative stress, inflammation and proliferation. These results are consistent with a dose-dependent transition in the mode of action for naphthalene toxicity/carcinogenicity between 1.0 and 10ppm in the rat. In the female olfactory epithelium (the gender/site with the highest incidences of neuroblastomas in the NTP bioassay), the lowest concentration at which any signaling pathway was significantly affected, as characterized by the median pathway benchmark dose (BMD) or its 95% lower bound (BMDL) was 6.0 or 3.7ppm, respectively, while the lowest female olfactory BMD values for pathways related to glutathione homeostasis, inflammation, and proliferation were 16.1, 11.1, and 8.4ppm, respectively. In the male respiratory epithelium (the gender/site with the highest incidences of adenomas in the NTP bioassay), the lowest pathway BMD and BMDL were 0.4 and 0.3ppm, respectively, and the lowest male respiratory BMD values for pathways related to glutathione homeostasis, inflammation, and proliferation were 0.5, 0.7, and 0.9ppm, respectively. Using a published physiologically based pharmacokinetic (PBPK) model to estimate target tissue dose relevant to the proposed mode of action (total naphthalene metabolism per gram nasal tissue), the lowest transcriptional BMDLs from this analysis equate to human continuous naphthalene exposure at approximately 0.3ppm. It is unlikely that significant effects of naphthalene or its metabolites will occur at exposures below this concentration.
•We investigated mode of action for carcinogenicity of inhaled naphthalene in rats.•Gene expression changes were measured in rat nasal tissues after 90day exposures.•Support a non-linear mode of action (oxidative stress, inflammation, and proliferation)•Suggest a dose-dependent transition in the mode of action between 1.0 and 10ppm•Transcriptional benchmark doses could inform point of departure for risk assessment.
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•In the Carboniferous Junggar Basin, 16 deep-water facies were identified, categorized into five depositional element types.•Arc volcanism and submarine volcanism differentially ...influenced different depositional elements.•Volcanism is crucial in determining types, formation, and distribution of deep-water deposits.
The Carboniferous sedimentary successions of the north-western and southern margins of the Junggar Basin in northwest China show a gradual vertical transition from deep- to shallow-marine depositional environments. Stratigraphically, these successions are composed of sedimentary and igneous lithologies (volcaniclastic), which record the closure and subduction of the remnants of the western Junggar and northern Tianshan oceanic basins that formed branches of the Paleo-Asian Ocean. In the current study, 16 facies and 7 facies associations related to sediment gravity flows were identified. These lithofacies associations collectively reflect five depositional elements, which include mass transport deposits, gravity flow channel deposits, lobe complex deposits, submarine volcanic ridge deposits, and submarine volcanic turbidite fans. Submarine and subaerial arc volcanism are shown to have controlled the characteristics of gravity flow sedimentation recorded in these successions. Island–arc volcanic material in the Junggar Basin is divided into three sources: erosion of the arc by fluvial systems, island–arc eruption materials, and submarine volcanism. Volcaniclastic deposits were transported into the deep-marine basin by submarine sediment gravity flows. These flows included turbidity currents, supercritical flows, gravel-rich debris flows, sandy debris flows, and muddy debris flows. Submarine vents generated lava flows that were deposited onto the abyssal plain and triggered subaqueous pyroclastic density flows. This study and its analysis of the characteristics and likely genesis of these gravity flow sediments improve the understanding of the dynamic relationship between volcanic activity and gravity flow sedimentation in near-arc basins. These findings provide a useful case-example of sediment gravity flow systems in island–arcs, which can be compared with and used as a relevant analog for other deposits in similar settings globally.
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