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This study documents the first record of seven-, Quaternary (<27.4 - >1.1 ka) lapilli fall layers at Sumbing volcano, Central Java, Indonesia. These lapilli layers (from lower towards upper stratigraphic height) are named orange–red lapilli, dark brown lapilli, orange lapilli, red–brown lapilli, blackish brown lapilli, pale red lapilli, and red lapilli. All deposits were dominated by juvenile scoria ( C scoria = 54–96%) with various portions of volcanic lithics ( C lithics = 4–44%). The products were dispersed across a wide area (400–2149 km2 for 1 cm isopach), suggesting sub-Plinian to Plinian intensity, with mean eruption plumes reaching 15–28 km and volcano explosivity index (VEI) of 3–4. The deposition of tephra (lapilli) on the roof provides load pressure, thus threatening buildings from collapse. No significant bulk density ( ρ bulk ) variation between each lapilli deposit (690–813 kg/m3 for dry tephra, 856–1007 kg/m3 for wet tephra, and 1208–1422 kg/m3 for saturated tephra). Thus, tephra thickness (h ) is believed to play the most significant role in controlling load pressure ( P = ρ bulk × h ), as it varies over three orders of magnitude (< 1–100 cm). Finally, under the assumption that all-nearby settlements followed the national standard for maximum load capacity (MLC; 487 kg/m2), we proposed three susceptible zones (SZs). The estimated radius for SZ I (representing dry tephra condition) is ~7.7 km and ~14.6 km for VEI 3 and 4 eruptions, respectively. If tephra becomes wet and/or even saturated with water due to heavy rain (which is likely to occur in tropical regions such as the present case), the estimated radius increases to ~12.7 km and ~15.3 km (VEI 3), and ~17.7 km and ~22.1 km (VEI 4) for SZ II and SZ III, respectively. These areas must be evacuated immediately if VEI 3–4 eruptions were to occur at Sumbing volcano. [ABSTRACT FROM AUTHOR]

ABSTRACTThis study produced a drift thickness model for the southwestern Great Slave Lake area of northern Canada, using 12,692 lithostratigraphic records (seismic shothole drillers’ logs, diamond drill holes, petroleum wells), and field observations. Numerous algorithms and modelling parameters were tested using 6122 records of absolute drift thickness, and based on a cross-validation analysis, an empirical Bayesian kriging K-Bessel detrended algorithm was found to produce the best fit. The final model, incorporating selected maximum and minimum thickness estimate data, produced a root mean square error of 4.98 m, with 94.8% of the data points within ±2 m of the modelled drift thicknesses. The model identifies widespread areas of drift >10 m thick, and prominent southeast-northwest aligned bedrock ramps. Karst structures buried by ≤73 m of drift were identified southwest of Great Slave Lake and appear to be aligned with regional fault systems like ore-associated karst at Pine Point. These may be the source of anomalous glacial sediment-derived base metal indicators collected proximally to the west. The most striking drift anomaly is in Cameron Hills where the eastern and northern margins are comprised of shale and siltstone bedrock overlain by 20–40 m of glacial sediments, but the central and western uplands have petroleum well logs identifying glacial sediments up to 400 m thick. In addition to mineral exploration, results of this study provide baseline data that can be used predictively by the petroleum industry in designing future seismic and drilling (casing depth) operations, and by those modelling groundwater sources and flow.

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This study produced a drift thickness model for the southwestern Great Slave Lake area of northern Canada, using 12,692 lithostratigraphic records (seismic shothole drillers’ logs, diamond drill holes, petroleum wells), and field observations. Numerous algorithms and modelling parameters were tested using 6122 records of absolute drift thickness, and based on a cross-validation analysis, an empirical Bayesian kriging K-Bessel detrended algorithm was found to produce the best fit. The final model, incorporating selected maximum and minimum thickness estimate data, produced a root mean square error of 4.98 m, with 94.8% of the data points within ±2 m of the modelled drift thicknesses. The model identifies widespread areas of drift >10 m thick, and prominent southeast-northwest aligned bedrock ramps. Karst structures buried by ≤73 m of drift were identified southwest of Great Slave Lake and appear to be aligned with regional fault systems like ore-associated karst at Pine Point. These may be the source of anomalous glacial sediment-derived base metal indicators collected proximally to the west. The most striking drift anomaly is in Cameron Hills where the eastern and northern margins are comprised of shale and siltstone bedrock overlain by 20–40 m of glacial sediments, but the central and western uplands have petroleum well logs identifying glacial sediments up to 400 m thick. In addition to mineral exploration, results of this study provide baseline data that can be used predictively by the petroleum industry in designing future seismic and drilling (casing depth) operations, and by those modelling groundwater sources and flow. [ABSTRACT FROM AUTHOR]

The Paleogene lava flows of the Faroe Islands Basalt Group are divided into three relatively thick formations. The oldest, the Beinisvørð Formation is separated from the second lava flow succession, the Malinstindur Formation, by two formations composed primarily of volcaniclastic rocks. The oldest of these, the Prestfjall Formation has been interpreted as a period of eruptive quiescence and linked to changes in mantle melting. It is characterised in the south by the occurrence of coals, while the overlying Hvannhagi Formation is a sequence of primary and remobilised volcaniclastic strata. Field, laboratory, palynology, and photogrammetry studies have been used to investigate variations in facies and architecture within these volcaniclastic formations. The data reveal significantly different depositional systems in the Prestfjall and Hvannhagi formations over the ~40 km from the island of Vágar in the north to the island of Suðuroy in the south. Facies distribution in both the Prestfjall and Hvannhagi formations was found to have been controlled by a complex interaction of regional paleoslope, pre-existing topography, the eruption and local collapse of low-angle shield volcanoes, and minor brittle deformation. Lithological data and photogrammetry have enabled the identification of a > 180 m thick succession of volcaniclastic conglomerates deposited by lahars reworking a low-angle shield sector collapse. Co-occurrence of facies characteristic of the Prestfjall, Hvannhagi and Malinstindur formations indicate that volcanic eruption continued at a lower tempo throughout the Prestfjall Formation interval. Identification of a Beinisvørð Formation low-angle volcano shield northwest of the Faroe Islands alters the previous eruption model for this extensive lava field. [ABSTRACT FROM AUTHOR]

Meyal Field is considered as one of the chief hydrocarbon producing fields in the Potwar Basin, Pakistan. The present research emphasize on the subsurface structures affecting the Mesozoic-Cenozoic successions exclusively foremost reservoir units comprising the Eocene Chor Gali and Sakesar formations. Data from six seismic lines and three wells (aligned with those lines) have been deliberated comprehensively with remarkable and tremendous calibration. Five prominent and imperative reflectors specifically the Permian, Triassic, Jurassic, Paleocene and Eocene successions were interpreted through seismic tactics. Time structure maps were equipped on the basis of two-way travel time (TWT) of the seismic line. Likewise, four isopach maps portrayed the thickness discrepancy of prospective hydrocarbon strata. Structurally, analytical section reveals that the Meyal anticline is a plunging and faulted anticline. The pop-up structure is constrained by back-thrust from the north and fore-thrust from the south, on the dip lines. These maps depicted potential reservoir, demarcate promising site for future hydrocarbon exploration.

In this paper, we attempt to predict the depositional environments with associated lithofacies of the main reservoir of the late Cretaceous Mishrif carbonate Formation, depending on the analysis of the created seismic isopach map by integrating seismic and well data. The isopach map was created from a 3D-seismic reflection survey carried out at the Dujaila oil field in southeastern Iraq, which is of an area of 602.26 Km2, and integrated with the data of the two explored wells. Based on the interpretation of the seismic isopach map, the diagram of the 3D-depositional environment model of Mishrif Formation was constructed. It showed three distinguished depositional environments, which were graduated from a back reef lithofacies of a shallow open marine (shelf) environment in the west and NW, to a shoal environment of isolated Rudist reefal buildup in the middle, and a fore reef lithofacies of the deep open marine basin environment in the SE of the field. A 3D-instantaneous frequency model was generated to verify the capability of the seismic isopach map of predicting the depositional environments, which in turn showed that the low frequency was restricted in the region of the high thickness of Rudist reefal buildups (porous reservoir facies) in the vicinity of the productive well Dujaila-1. [ABSTRACT FROM AUTHOR]

Copyright of DYNA - Ingeniería e Industria is the property of Publicaciones Dyna SL and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Camden Syncline and the Lapstone Structual Complex are two major geological features of the central Sydney Basin. We have interpreted over 500 km (45 lines) of an unpublished recenty reprocessed seismic dataset as a means to elucidating the evolution of both features. Major horizons observed in the seismic data have been described and correlated with significant tectonic events that shaped the formation of the greater Sydney-Gunnedah-Bowen Basin; namely Early Permian extension, mid-Permian passive thermal subsidence and Late Permian to mid-Triassic foreland loading. Horizon mapping shows that the Camden Syncline is a broad north-northeast plunging structure whose western limb is truncated by the north-south trending faults and folds of the Lapstone Structural Complex. Furthermore, isochron maps reveal that the Late Permian to mid-Triassic sedimentary succession thickens towards the axis of the Camden Syncline, thus confirming it's role as a depocentre during this period of basin evolution. No abrupt thickening is observed in the Late Permian to mid-Triassic sedimentary succession in the vicinity of the Lapstone Structural Complex indicating that the Lapstone Structural Complex was formed subsequent to the deposition of the Permian-Triassic Sydney Basin sedimentary succession. Furthermore, our interpretation of the reprocessed seismic data confirms that the major structural style of the Lapstone Structural Complex is that of west dipping reverse faults and east facing monoclines. [ABSTRACT FROM AUTHOR]

Structural maps of horizons in four wells containing hydrocarbon bearing zones with tops and bases at subsea depth range of -9,491 to -11,053 ft were produced, showing the trapping mechanism to be mainly fault-assisted anticlinal closures. Petrophysical parameters, time-depth structure, and isopach maps were obtained. The result indicated that the total net volume of the reservoirs yielded oil-in-place of 41.54 MMbbl and gas-in-place of 121.9 tcf. Potential prospects were identified from seismic attributes and reservoir models generated. The results from this study will contribute immensely to a greater understanding of the Niger Delta basin if integrated with geochemical and biostratigraphic studies. [ABSTRACT FROM AUTHOR]