The Structure of Cambrian Deposits of the Vilyui Hemisyneclise, Based on an Integrated Analysis of Drilling and Seismic Data

—We present a model of the stratigraphic and lateral distribution of Cambrian deposits in the Vilyui hemisyneclise, based on an analysis of drilling data and interpretation of seismic data. The study shows a series of formations and sequences penetrated by wells (Syugdzher saddle, Khorgochum monocline, Ygyatta depression, Tyukyan–Chybyda monocline, Arbai–Sinyaya megaswell, etc.). In the areas where the Cambrian was not penetrated by wells, the distribution of Cambrian deposit was inferred based on the available seismic data. The distribution of the Kuonamka Horizon formed by Cambrian organic-rich rocks is characterized in detail. These are the Kumakh and Sinyaya–Kutorgina sequences and the Inikan and Kuonamka formations. It has been found that the Kuonamka Horizon was deposited during two stages, Botomian and Toyonian–early Mayan. The horizon is overlain by younger deposits of the Mayan Stage, with characteristic cross-bedding structures. Schemes of facies zoning of the Cambrian for Botomian, Toyonian–early Mayan, and middle Mayan times were constructed based on the most recent geological and geophysical understanding of the Vilyui hemisyneclise.

Badenian (middle Miocene) continental paleoenvironment in the Novohrad–Nógrád Basin (Central Paratethys): a volcano-sedimentary record from the Páris-patak Valley in Hungary

Two levels of volcaniclastics, comprising conglomerates, sandstones and mudstones, are interbedded with upper middle Miocene (upper Badenian) andesite pyroclastics near the Hungarian-Slovakian border in the distal region of the Central Slovakian Neogene Volcanic Field. Based on the field sedimentological investigations, the facies of the volcaniclastics (e.g., lateral and vertical grain size changes, sedimentary structures, textures, clast composition), their geometry and field relationships are documented herein with the aim of reconstructing the depositional environment. The silica-cemented volcaniclastics are mostly andesite clasts with only ~ 5% being granitoid, quarzitic, and tuff clasts as well as charred fossil wood fragments. The coarse-grained facies association includes crudely stratified, tabular or lenticular, clast-supported pebble-cobble conglomerates with erosive basal surfaces, b-axis imbrication, alternating with sets of cross-bedding. The fine-grained facies association comprises cross-bedded pebbly to medium-grained sandstone and lenses of tuffaceous clayey siltstone with rare horizontal lamination and water-escape structures. Rip-up mudstone clasts, with diametre up to 1 m, are present in both facies associations, revealing the co-existence of abandoned silty palaeo-channel plugs. Facies associations are arranged in several 0.5-4-m-thick, fining-upwards successions that likely formed in shallow channels as downstream- to laterally accreting longitudinal bars, extensive gravel sheets and bars that migrated in peak flow during floods. Palaeocurrent indicators (i.e., clast imbrication, direction of planar cross-bedding, orientation of petrified wood logs) show bedload transport by traction currents, initially towards ~S, and later towards ~W. Intermittently debris flows also occurred. Cross-bedded sandstones formed as in-channel transverse bars during medium/low discharge. Variation of grain size shows frequent discharge fluctuations during permanently wet conditions in the late Badenian. The 4-5-m-deep, low-sinuosity channels were part of a high-energy, gravel-bed braided-river system on the south-eastern foothills of the Lysec palaeo-volcano. Here, pyroclastics were reworked and redeposited as volcaniclastics during inter-eruption, high-discharge episodes.

Cross-Bedding and Structural Mapping for Rockfall Assessment of a Tunnel using Hi-Resolution LiDAR (Fribourg, Switzerland)

<p>Lithology identification and discontinuity mapping are necessary for rockfall hazard assessment in tunnels. However, the restricted exposure and variability of rock face orientation in tunnels ought to be taken into account. Therefore, using Light Detection and Ranging (LiDAR) technique may significantly contribute to this task.</p><p>A historical carved tunnel in the Upper Marine Molasse (a poorly consolidated sandstone) of the City of Fribourg (Switzerland) was then investigated by fieldwork and LiDAR. Interestingly, it appears that in addition to joints and layering, some specific sedimentary structures, i.e. cross-bedding, have an important role in the tunnel roof stability. Cross-bedding is a sedimentary structure that can be identified clearly by the geometry of layer within one or more beds in a series of rock strata that does not run parallel to the plane of stratification.</p><p>In order to detect and analyse these sedimentary structures, the intensity of the backscattered LiDAR signal is analysed using the Oren-Nayar reflectance model, which considers range, incidence angle, scanned surface geometry (i.e. roughness). It provides corrected values of intensities that make possible to distinguish and identify geometry of cross-beddings in the tunnel.</p><p>An analysis of structural discontinuities was also performed using Coltop Software which identified joint sets developed inside the tunnel. Based on this approach, lithology characterizations, orientation of each discontinuity and bedding structures could be identified in point clouds confidently for understanding the mechanisms of potential rockfalls in the tunnel.</p>

The Gröbminger Mitterberg (Austria): A time machine to the pre-LGM?

<p>The Last Glacial Maximum (LGM) is well understood in many parts of the European Alps, but open questions remain concerning glacial phases prior to the LGM as the record is fragmentary. The Gröbminger Mitterberg (GM), located among the Enns Valley in Styria (Austria) is one such location where pre-LGM glacial and paraglacial processes can be studied. The GM emerges roughly 200 m from the Enns Valley floor and is situated between unmetamorphosed Mesozoic carbonates in the north and crystalline basement units in the south. Strata occur below a cover of up to more than 10 m thick basal till attributed to the LGM. The sedimentary record rests on the phyllites and greenschists that crop out at the steep southern flank of the GM. The sediment consists of an assortment of pebble-sand deposits with individual sand lenses, sand bodies with climbing ripples and undulose bedding, and fine-sand/silt laminated strata. In grain-supported intervals, cracked pebbles occur, which are interpreted to record subglacial loading. Cross-bedding orientations, together with the limited amount of unmetamorphosed carbonate pebbles in the sequence, imply that sediment was sourced from the GM and deposited at its margins, rather than from surrounding mountains towards the centre of the Enns Valley. Three depositional regimes have been recognised: deltaic sediment (both distal sands with ripples and proximal, cross-bedded gravel), lake bottom sediment (laminated fine-sand and silt) and fluvial deposits (channels with basal lag deposits and local cross bedding). The delta facies testify to the presence of lacustrine conditions. By analogy to the Unterangerberg in the Inn Valley (Tyrol, Austria; Starnberger et al. 2013), the following sequence of events is proposed. Before the LGM, sediment derived from the wider catchment area accumulated in the Enns Valley in lakes and rivers. Aggradation within the whole Enns valley resulted in deposition on the present day GM. During the LGM, the large Enns Glacier eroded much of the sediment record, especially around the GM. Deposits on top of the GM were then concealed by > 10 m thick diamicts and thereby preserved. Future age dating of the sediments will provide a better-constrained chronology to the sequence of events proposed above.</p>

TWO-COMPONENT FLUID FRONT TRACKING IN FAULT ZONE AND DISCONTINUITY WITH PERMEABILITY HETEROGENEITY

Fluid front tracking is important in two-phase/component fluid flow in porous media with different heterogeneities, especially in the improved recovery of oil. Three different flow patterns of stable, viscous fingering, and capillary fingering exist based on the fluids’ viscosity and capillary number (CA). In addition, fluid front and sweep efficiency are affected by the heterogeneity of the porous medium. In the current study, the heterogeneous porous media are: (1) normal fault zone or cross-bedding with heterogeneity in permeability, and (2) a fracture or discontinuity between two porous media consisting of two homogeneous layers with very low and high permeabilities, in which immiscible water flooding is performed for sweep efficiency and streamlines tracking purposes. By considering the experimental glass micromodel and the simulation results of discontinuity, a crack is the main fluid flow path. After the breakthrough, fluid inclines to penetrate the fine and coarse grains around the crack. Moreover, an increase in flow rate from 1 and 200 (ml/h) in both the experimental and simulation models causes a reduction in the sweep efficiency from 14% to 7.3% and 15.6% to 10% by the moment of breakthrough, respectively. In the fault zone, the sweep efficiency and the streamline of the injected fluid showed a dependency on the interface incident angle, and the layers’ permeability. The presented glass micromodel and Lattice Boltzmann Method were consistent with fluid dynamics, and both of them were suitable for a precise evaluation of sweep efficiency and visualization of preferential pathway of fluid flow through cross-bedding and discontinuity for enhanced oil recovery purposes.

Supplemental Material: Evaluating the Shinumo-Sespe drainage connection: Arguments against the “old” (70–17 Ma) Grand Canyon models for Colorado Plateau drainage evolution

Table S1: Rotations of measured paleomagnetic paleopoles to test the error introduced by measuring inclinations relative to cross bedding of different orientations instead of horizontal bedding. Table S2: Detrital zircon data used in this study. Table S3: Quantitative comparison results from DZstats.

Supplemental Material: Evaluating the Shinumo-Sespe drainage connection: Arguments against the “old” (70–17 Ma) Grand Canyon models for Colorado Plateau drainage evolution

Table S1: Rotations of measured paleomagnetic paleopoles to test the error introduced by measuring inclinations relative to cross bedding of different orientations instead of horizontal bedding. Table S2: Detrital zircon data used in this study. Table S3: Quantitative comparison results from DZstats.

Tidal circulation in an Early Permian epicontinental sea: insights from a mathematical modeling approach

<p>The intracratonic Paraná Basin and its western extension - Chaco-Paraná Basin - are located in the south-central portion of South America and cover an area of about  ~1.8 million km<sup>2</sup>, including portions in Brazil, Argentina, Uruguay, and Paraguay. The Early Permian epicontinental sea was shallow and likely connected with the Panthalassa in the southern portion of Uruguay (Lavina, 1992). The transgressive sedimentary succession of the Guatá Group is composed of coastal plain and shallow marine deposits (Rio Bonito Formation), in complex associations due to base level fluctuations and irregular deglaciation paleotopography, and offshore-transitional deposits (Palermo Formation) (Lavina and Lopes, 1987). The Rio Bonito Formation is mostly preserved within paleovalleys carved by glaciers and tectonic. The tidal-influence in this formation occurs throughout the succession and are mainly characterized by medium- to coarse-grained arkosic and quartz sandstones with uni- and bidirectional cross-bedding, herring-bone cross-bedding, tidal bundles, reactivation surfaces, mud drapes, and double mud drapes (Fritzen et al., 2019; Lopes and Lavina, 2001). Besides the tidal sedimentological aspects, the conditions that governed tide in this epicontinental sea are poorly understood. In this work, we present a theoretical perspective on the behavior of tides in the Paraná Basin epicontinental sea during the Early Permian. Mathematical models were applied to test the existence of amphidromic points in the basin, to verify the possibility of resonance, as well as to test the tidal amplification inside two paleovalleys. The obtained results were compared to Hudson Bay, considered here a modern analog. According to the paleogeography, paleolatitude (Southern Hemisphere), depositional records and insights from the modern analog, the studied Early Permian epicontinental sea likely had bear more than one clockwise-rotation amphidromic system. Resonant effects may also have affected circulation, especially at sea depth below 100 m. In the simulated scenarios, tidal amplification in both valleys was variable but concentrated between micro to mesotidal amplitudes. This is the first contribution to the understanding of the tidal behavior of the Early Permian epicontinental sea.</p><p> </p><p>References:</p><p>Fritzen, M.R., Cagliari, J., Candido, M., Lavina, E.L., 2019. Tidal bar cyclicity record in the Lower Permian (Rio Bonito Formation of the Paraná Basin). Sedimentary Geology 381, 76-83.</p><p>Lavina, E.L., 1992. Geologia sedimentar e paleogeografia do Neopermiano e Eotriassico (intervalo Kanzaniano - Scythiano) da Bacia do Parana. Ph.D. Thesis, UFRGS University.</p><p>Lavina, E.L., Lopes, R.C., 1987. A Transgressão Marinha do Permiano Inferior e a Evolução Paleogeográfica do Supergrupo Tubarão no Estado do Rio Grande do Sul. Paula-Coutiana 1, 51-103.</p><p>Lopes, R.C., Lavina, E.L., 2001. Estratigrafia de sequências nas Formações Rio Bonito e Palermo (Bacia do Paraná), na região carbonífera do Jacuí, Rio Grande do Sul, in: Severiano Ribeiro, H.J.P. (Ed.), Estratigrafia de sequências: fundamentos e aplicações. Edunisinos, São Leopoldo, pp. 391-419.</p>

Ediacaran (Vendian)-period alluvial and coastal geomorphology applied to development of Verkhnechonskoye and Yaraktinskoye fields, East Siberia, Russian Federation

ABSTRACT Ediacaran-age (635–542 Ma) oil-bearing strata in the Yarakta Horizon at the Verkhnechonskoye and Yaraktinskoye fields, East Siberia, consist of conglomerate, sandstone, dolomitic sandstone, and mudstone overlying and onlapping igneous to metasedimentary highlands of the East Siberia craton. Initial drainage networks formed within structurally defined valleys, and early deposition occurred in localized alluvial to shallow-marine depositional systems. Base-level-controlled depositional cycles aggraded the valleys; thus, as valleys aggraded, they buried interfluves and coalesced forming broad alluvial and coastal plains. Three to seven bedsets of variable net-to-gross content constitute a genetic cycle. Depositional cycles varied locally, as nine and eight cycles separated by decimeter- to multi-meter-thick mudstones are defined at Verknechonskoye and Yaraktinskoye, respectively. Within one genetic cycle, facies associations grade basinward from alluvial (channel-bar, channel-fill, floodplain, playa, and crevasse-splay) to shallow marine (sabkha, tidal-flat, estuarine-channel, and poorly developed shoreface). Coarse-grained lithofacies are typically arranged in decimeter- to meter-scale bedsets with sharp to scoured bases. Bedsets commonly, but not always, show an upward decrease in grain size, bed thickness, and scale of sedimentary structure. Typically, medium-grained sandstones exhibit low-angle cross bedding and are gradationally overlain by fine-grained sandstones exhibiting scour-and-fill, cuspate-ripple lamination, climbing-ripple lamination, and parallel lamination. Clay clasts and small pebbles are accessories. Interbedded mudstones, siltstones, and sandstones show ripple cross bedding, wavy to lenticular bedding, abundant soft-sediment deformation (e.g., shear, fluid-escape, slump features), and slickensides. Thin-bedded sandstones are micaceous and contain granule-size mud chips. Some mudstones exhibit crinkled to parallel laminae indicative of algal growth. Sandstone fills mudcracks. Interbedded green and black mudstones, plus pyrite and siderite cements, indicate alternating redox conditions. Alluvial facies have patchy quartz, anhydrite, and carbonate cements. Marine-influenced facies show early and well-developed quartz cement as well as abundant halite. Gypsum and halite dissolution formed secondary pores. Calculated estimates of fluvial-channel dimensions and sinuosities indicate that despite the lack of vegetation, fluvial channels in the Yarakta Horizon were shallow and relatively narrow, moderately sinuous, and exhibited varying degrees of mud-prone overbank deposition. Recognition and correlation of flooding surfaces and channel diastems bounding genetically related strata identified multiple stratigraphic compartments in each field. Porosity loss at chronostratigraphic boundaries accounts for complex water, oil, and gas contacts. Economic field development is hampered by locally varying reservoir quality and sandstone continuity caused by its channelized and onlapping stratigraphy and diagenesis. Reservoir simulation of varying geostatistical models demonstrate that differing porosity-distribution methods had little effect on estimates of in-place hydrocarbon volumes. Model differences in porosity and permeability distribution and lithofacies connectivity show large variations in recovery factor and productivity/injectivity.