A phase of transient subsidence, sediment bypass and deposition of regressive-transgressive cycles during the breakup of Iberia and Newfoundland

Seismic, outcrop and well data from West Iberia and Newfoundland are used to investigate sediment stacking patterns during continental breakup as a function of tectonic subsidence. In West Iberia, two breakup sequences are revealed on seismic data by marked strata offlap oceanwards from the present-day continental shelf. This character is similar to Newfoundland, where correlative strata comprise Lower Cretaceous–Cenomanian coarse-grained siliciclastics accumulated around local sediment-source areas. The interpreted data reveal that the two breakup sequences: 1) materialise sediment bypass onto continental-slope depocentres that experienced important tectonic subsidence during continental breakup, but without showing typical syn-rift growth packages; 2) generate specific forced-regressive stratigraphic intervals that relate to uplift and exhumation of the proximal margin. Subsidence and sediment stacking patterns in both West Iberia and Newfoundland reflect similar continental breakup processes as they evolved from the upper lithosphere- to their mantle-breakup stages. On both margins, coarse-grained siliciclastic units on the proximal margin give rise to thick shaley successions in deep-water basins. This work also confirms that in a setting dominated by a significant sediment influx, yet lacking the burial rates of continental slope basins in Newfoundland, West Iberia comprised accommodation-driven basins during continental breakup, not necessarily sediment starved. As a corollary of our analysis, we classify breakup sequences around the world based on the characteristic lithologies of their regressive–transgressive depositional cycles

Bi-modal deformation styles in confined mass-transport deposits: examples from a salt minibasin in SE Brazil

High-quality 3D seismic data reveal bi-modal deformation styles in mass-transport deposits filling a salt minibasin in SE Brazil (Espírito Santo Basin). We analyse three mass-transport deposits within the same Miocene stratigraphic interval, and four others in Holocene strata. Our interpretation reveals that deformation in the mass-transport deposits relates to their long-axis orientation. As a result, they are divided into two types: a) Type 1 have long axes parallel to the direction of movement and show significant internal deformation; b) Type 2 have long axes perpendicular to the direction of movement, are highly heterogeneous and include large undeformed slabs. The long axes of Type 2 mass-transport deposits are parallel to the strike of bounding faults and salt structures. The majority of mass-transport deposits show intense deformation at their headwalls, and relative short remobilisation distances are inferred for both Types 1 and 2. In the study area, the timing of emplacement of mass-transport deposits was controlled by the growth of adjacent salt ridges. Earlier halokinesis in the northern axial areas of the minibasin shifted southwards in a second stage. Holocene mass-transport deposits suggest alternating growth of the eastern and western salt ridges. Our results show that detailed seismic-stratigraphic analyses are a key to understanding the timings and magnitude of deformation of mass-transport deposits in salt minibasins. The classification proposed can be applied to MTDs on continental margins and in lacustrine settings

Pinnacle features at the base of isolated carbonate buildups marking point sources of fluid offshore Northwest Australia

We investigated pinnacle features at the base of late Oligocene–Miocene isolated carbonate buildups using three-dimensional seismic and borehole data from the Browse Basin, Northwest Australia. Brightened seismic reflections, dim spots, and other evidence of fluid accumulation occur below most pinnacle features. An important observation is that all pinnacles generated topography on successive late Oligocene–Miocene paleoseafloors, therefore forming preferential zones for the settlement of reef-building organisms by raising the paleo-seafloor into the photic zone. Their height ranges from 31 m to 174 m, for a volume varying from 33 km3 to 11,105 km3. Most of the pinnacles, however, are less than 2000 km3 in volume and present heights of 61–80 m. As a result of this work, pinnacles are explained as the first patch reefs formed in association with mud volcanoes or methanogenic carbonates, and they are considered as precluding the growth of the larger isolated carbonate buildups. We postulate that pinnacle features above fluidflow conduits demonstrate a valid seep-reef relationship, and we propose them to be refined diagnostic features for understanding fluid flow through geological time

Performance evaluation of wavelength division multiplexing photonic analogue-to-digital converters for high-resolution radar systems

The performance of the wavelength division multiplexing (WDM) photonic analogue-to-digital converter (ADC) used for digitization of high-resolution radar systems is evaluated numerically by using the peak signal-to-noise ratio (SNR) metric. Two different WDM photonic ADC architectures are considered for the digitization of radar signals with 5 GHz of bandwidth (spatial resolution of 3 cm), in order to provide a comprehensive study of the compromises present when deploying radar signals with high-resolution: 1) a four-channel architecture with each channel employing an ADC with 5 GSamples/s, and 2) an eight-channel architecture with each channel employing an ADC with 2.5 GSamples/s. For peak powers of the pulsed source between 10 and 20 dBm and a distance between the radar antenna and the sensing object of 2.4 meters, peak SNR levels between 29 and 39 dB are achieved with the eight-channel architecture, which shows higher peak SNR levels when compared with the four-channel architecture. For the eight-channel architecture and for the same peak powers of the pulsed source, peak SNR levels between 11 and 16 dB are obtained when the distance increases to 13.5 meters. With this evaluation using the peak SNR, it is possible to assess the performance limits when choosing a specific radar range, while keeping the same resolution.info:eu-repo/semantics/publishedVersio

Effects of sand-shale anisotropy on amplitude variation with angle (AVA) modelling: The Sawan Gas Field (Pakistan) as a key case-study for South Asia's sedimentary basins

Amplitude variation with angle (AVA) is a technique widely used in the characterisation of hydrocarbon reservoirs and assumes the Earth’s crust to be an isotropic medium. Yet, anisotropy is ubiquitous in stratigraphic sequences and has first-order effects on seismic AVA responses when investigating subsurface prospects. This work analyses the effects of anisotropic strata on AVA responses using the Lower Goru Formation, middle Indus basin (Pakistan) as a case study. In the study area, shale intervals are interbedded with reservoir sands of the Sawan gas field. Shales in this field form laminae or are dispersed within reservoir sands, making the Lower Goru Formation an example of a vertically transversely isotropic (VTI) medium. In this work, we calculate the effective (saturated) mechanical properties of the Lower Goru Formation based on rock physics templates; the Backus (1962) average typically designed for layered media, combined with the empirical relations of Brown and Korringa (1975) and Wood (1955). The input data used in our rock physics modelling is based on detailed petrophysical analyses of well data. Using the saturated effective mechanical properties of the Lower Goru Formation, we generate angle-dependent reflection coefficient curves (and seismic AVA responses) based on exact and approximate solutions, for both isotropic and anisotropic reservoir scenarios. Our results suggest that the effects of lithological anisotropy are more pronounced in places with thick shale beds within reservoir sands. Conversely, angle-dependent reflection curves, and seismic AVA responses based on isotropic or anisotropic cases, give similar solutions in the presence of thin shale beds. As a corollary of this work, we present a Bayesian inversion method for the estimation of porosity in VTI media

Quantitative seismic geomorphology of a submarine channel system in SE Brazil (Espírito Santo Basin): scale comparison with other submarine channel systems

Detailed morphological analyses of a Pleistocene-Holocene submarine channel system in terms of its hierarchical framework, were carried out using a 3D seismic volume from offshore Espírito Santo, SE Brazil. The channel morphology shows marked variations, with five segments (Segments a to e) being identified along its full length. For example, the cross-sectional area of the channel decreases by a factor of 70 from Segment a to Segment c, and is then followed by a nearly four-fold increase from Segment c to Segment d. The significant changes in channel morphology relate to temporal and spatial variations in flow volume within the channel. In the same channel system, the valley reveals three distinct segments (Segments A to C), with similar aspect ratios but marked variations in morphology along the valley distance. Valley morphological changes are chiefly affected by erosional processes. Segment B is characterised by the largest valley-base width, valley width, and cross-sectional area compared to the other two segments. Valley enlargement in Segment B results from relatively high degrees of lateral channel migration and associated cut bank erosion, leading to the widening of the valley, especially the valley base. In Segment C, the valley is characterised by inner bank erosion in the form of shallow-seated mass failures, which only enlarged the upper part of the valley wall. The spatial variations in both channel and valley morphology documented here suggest an important role of local factors (e.g. salt diapirs, tributaries, overbank collapse) in the development of channel systems. Hence, the morphological analyses developed in this work provide an effective tool for studying channels and valleys on continental slopes around the world

Distribution and growth styles of isolated carbonate platforms as a function of fault propagation

Fault control on the position and distribution of isolated carbonate platforms is investigated in Northwest Australia using high-quality 3D seismic and borehole data from the Bonaparte Basin. Specifically, we address the relationship between carbonate productivity and fault growth so as to understand what are the primary controls on the growth of isolated carbonate platforms. Throw-depth (T-Z) and throw-distance (T-D) profiles for normal faults suggest they formed fault segments that were linked at different times in the study area. This caused differential vertical movements; some of the normal faults propagated to the surface, while others have upper tips that are 19–530 ms two-way-time below the sea floor, with the largest throw values comprising faults underneath isolated carbonate platforms. As a result, four distinct zones correlate with variable geometries and sizes of carbonate platforms, which are a function of the topographic relief generated by underlying propagating faults. Some relay ramps form the preferred location for the initiation and development of carbonate platforms, together with adjacent structural highs. Due to the complex effect of fault propagation to the palaeo-seafloor, and soft-linkage through relay ramps, three distinct ICP types are proposed: (1) in the first type, fault throw is larger than carbonate productivity; (2) the second type considers fault throw to be equal or less than carbonate productivity; and (3) in the third type, fault throw post-dates the growth of the carbonate platform(s). The analysis of fault propagation vs. carbonate platform growth shown here is important, as the three ICP types proposed, potentially correlate with variable fracture densities and distributions within the carbonate platforms. Based on our results, types 2 and 3 above enhance fracture- and fault-dominated porosity and permeability to a greater degree, making them favourable targets for hydrocarbon exploration

Composite coatings of chitosan and alginate emulsions with olive oil to enhance postharvest quality and shelf life of fresh figs (Ficus carica L. cv. Pingo De Mel)

Fresh figs are very appreciated and have been associated with health benefits. However, these fruits are highly perishable. In this study, edible coatings were studied envisaging their positive effect in enhancing figs’ shelf-life. Fig fruits cv. ‘Pingo de mel’ were harvested at commercial ripening stage and single emulsion-based coatings, composed of chitosan + olive oil and alginate + olive oil, were applied. After coatings application by dipping each fruit in the emulsion-based solutions at 4 C and drying, the coated fruits were sprayed with crosslinking solutions (6% tripolyphosphate and 1% calcium chloride for chitosan and alginate-based coatings, respectively). Then, were maintained at 4 C and analyzed after 1, 7, 14 and 19 days of storage. After each time interval, fruits were further maintained at 25 C for 2 days. The results have shown that coatings were effective on delaying fungal decay and postharvest ripening indicators (respiration rate, mass loss, softening and total soluble solids/titratable acidity ratio). The results foresee a fruits’ shelf life between 14 and 19 days under refrigeration at 4 C that may be followed up to 2 days at ambient temperature, higher than that estimated for uncoated fruits (less than 14 days at 4 C plus to 2 days at ambient temperature)info:eu-repo/semantics/publishedVersio

Design of chitosan and alginate emulsion-based formulations for the production of monolayer crosslinked edible films and coatings

This study aimed to develop edible monolayer emulsion-based barriers with polysaccharides as film-forming components (chitosan and sodium alginate), soy lecithin as a surfactant and olive oil as a hydrophobic barrier. Monolayer barriers in the form of films were prepared by casting filmogenic emulsions composed of 2% w/v chitosan (dissolved in lactic acid 1% v/v) or 1% w/v sodium alginate, with different lipid contents (25, 50 and 100% w/w biopolymer basis) and different surfactant concentrations (5, 10 and 25% w/w, lipid basis). Glycerol was used as a plasticizer (25 % w/w, biopolymer basis). After the emulsion drying process, the obtained stand-alone films were sprayed with a crosslinking solution, achieving an optimized crosslinker content of 3.2 mgCa2+/cm2 alginate film and 4 mg tripolyphosphate/cm2 chitosan film. The effect of oil and lecithin contents, as well the presence of crosslinking agents, on the film’s water vapour permeability (WVP), water vapour sorption capacity, mechanical properties and colour parameters, was evaluated. The results have shown that the lowest WVP values were obtained with formulations containing 25% lipid and 25% surfactant for chitosan films, and 100% lipid and 25% surfactant for alginate films. The application of the crosslinking agents decreased even further the WVP, especially for chitosan films (by 30%). Crosslinking also increased films’ resistance to deformation under tensile tests. Overall, the films developed present a good potential as polysaccharide-based barriers with increased resistance to water, which envisages the use of the designed formulations to produce either edible/biodegradable films or edible coatingsinfo:eu-repo/semantics/publishedVersio