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Field data from recent geological mapping over a major part of the north-central Scandinavian Caledonides combined with published information give a detailed view of early Cambrian basin successions, comprising the Gärdsjön formation (Gf; Jämtland supergroup) in the Lower Allochthon and autochthonous equivalents (Dividal Group). The Gf comprises ten units of sandstone and siltstone or mudstone (Gf I—X, > 300 m thick). Green siltstones with red layers (Gf VI, c. 521 to 519 Ma) and green–grey siltstones at the top (Gf X, c. 516.5 to 513.5 Ma) are regional key horizons. Gf V, VI, VII, IX, and X deposition may be related to eustatic events. Restoration of Caledonian shortening reveals a major "Hornavan-Vattudal basin" (HVB; > 330 km NW–SE, > 400 km NE-SW) between the Grong–Olden culmination in the S and the Akkajaure–Tysfjord culmination in the N. Published zircon ages imply the latter separated the HVB from those shed from the Timan orogen in the N. The eastern basin margin straddles the present Caledonian erosional margin. Basement highs identified here within the Nasafjället, Bångonåive, and Børgefjellet "basement" windows define the western margin. They separate the HVB from the outer shelf towards the Iapetus Ocean in the W. The onset of sedimentation is time-related with E–W extension at c. 544–534 Ma. NNE–SSW-directed extension occurs after c. 518 Ma, perhaps related with Timan late-orogenic extension. The HVB is distinctly younger (c. 535–513.5 Ma) than Rodinia break-up and Iapetus ocean formation (> 550 Ma), comparable with post-rift basins in inner parts of modern passive margins. [ABSTRACT FROM AUTHOR]

Abstract The present work focuses on the comprehension of the growth mechanisms and dimensional properties of the pre-Pliocene Monte Alpi fault network by mean of integrated field and laboratory analyses. After this multidisciplinary approach, detailed throw profiles are computed for each fault belonging to the Monte Alpi network. Subsequently, the dimensional properties of the individual faults are calculated. Data obtained from this work are discussed in terms of fault growth mechanisms and timing of deformation, and reported in a conceptual tectonic evolution model of the Messinian foreland basin system. Data suggest that originally isolated fault segments developed during the earliest stages of foreland basin formation by re-activation of a pre-existing, Early Cretaceous fault set, and formation of an orthogonal one. These two fault sets formed a scale-independent network. Differently, the same fault sets were also active during its subsequent development forming a scale-dependent fault network characterized by T- and Y-shaped fault intersections. This deformation controlled the half-graben depocenters evolution filled by up to ca. 600 meters of terrigenous deposits during the Late Messinian time. Highlights • Both timing and growth processes are deciphered for the pre-Pliocene fault network. • Main dimensional attributes computed for all analyzed faults. • Inferences on the fault-control evolution of the Messinian foreland basin system. [ABSTRACT FROM AUTHOR]

This paper introduces a methodology based on Python libraries and machine learning k-Nearest Neighbors (KNN) algorithms to create an interactive 3D HTML model (3D_Vertical_Sections_Faults_LRD.html) that combines 2D grain-size KNN-prediction vertical maps (vertical sections) from which syn-sedimentary faults and other features in sedimentary porous media can be delineated. The model can be visualized and handled with conventional web browsers. The grain-size physical parameter is measurable, constant over instrumental time, handleable mathematically, and its range can be associated to lithological classes. Grain-size input data comes from a public database of 433 boreholes in the Llobregat River Delta (LRD) in NE Spain. Four lithological classes were defined: Pre-Quaternary basement, and Quaternary gravel, sand, and clay–silt. Using a new KNN-prediction algorithm, seven NW–SE (transversal) and three SW–NE (longitudinal) vertical sections were created following the orientation of faults identified in surface and detected in reflection seismic geophysical surveys. For exploratory K values in the 1–75 range were used. K around 25 provides the general and smoothy shape of the basement top surface, whereas K = 1 is a optimal value to represent the heterogeneity of the LRD at short distance. Using a new KNN-prediction confidence algorithm inspired in the Similarity Ratio algorithm for machine-learning KNN, the vertical sections overall confidence was evaluated as satisfactory. A general decreasing confidence trend according to the decreasing data density with depth and from inland to seaward was found. The vertical sections created with K = 1 show horizontal interruptions (displacements or vertical steps) in the basement continuity and in the Quaternary coarse bodies (gravel and sand) attributable to the action of Quaternary active faults. These faults have been linked or correlated with well-known active faults in the area related in much cases with the Valencia Trough opening. Moreover, several faults detected in surface and other identified in this paper by the first time have been revealed as fault zones made of fault branches with different steps in an echelon-like arrangement. Faulting seems to be more evident in the Pleistocene Lower Detrital Complex and much less active or inactive in the Holocene Upper Detrital Complex. Syn-tectonic gravel channels faulty controlled, progradation of gravel lobes, and lateral migration of channel bars were also observed. At its current development stage, this methodology could also be applied to other geological environments, making the due minor modifications of the code, and is especially suitable to reduce the high (usually unmeasurable) uncertainty associated to the qualitative geological data used in more complex numerical tools aimed at modelling a lot of geological resources (groundwater, minerals, geothermal, petroleum) or different Earth phenomena. • Llobregat River Delta (Barcelona, NE Spain). • Python Libraries. • K-Nearest Neighbors algorithm. • D HTML models. • Syn-sedimentary faults and gravel channels migration. [ABSTRACT FROM AUTHOR]

The controls on basin-fill stratigraphy such as sediment supply, climate, eustasy and tectonics are well understood in many basin types, but there are few examples documented from forearc basins. Traditional evolutionary models for forearc basins emphasise the importance of accretionary processes under a largely contractional tectonic regime. The Talara Basin of northwestern Peru preserves a lower Eocene stratigraphic record of dominantly extensional collapse tectonics punctuated by periods of uplift, driven by variability of the subduction process. The margin is dominated by subduction erosion and only minor accretion processes. In this geodynamic setting, we present for the first time a sedimentological and sequence stratigraphic model for the 350 m-thick fluvio-deltaic succession of the Pariñas Formation. Three depositional sequences are stacked into a highstand sequence set comprising proximal fluvial strata that correlate down dip into marginal marine and marine deposits. Syn-sedimentary normal faulting related to episodes of subduction erosion restricted much of the Pariñas to hanging-wall locations subject to minor-scale transgressions. The succession evolved from shelf-confined clinoforms to later basin margin scale clinoforms, related to long-term sea-level rise. The interaction of eustasy, sediment supply and episodes of subduction erosion are integrated into an evolutionary model that may have application in other non-accretionary forearc basins worldwide. Although the model shares characteristics with extensional models for rift basins, the episodic subduction-driven uplift events add another component of relative sea-level complexity. [ABSTRACT FROM AUTHOR]

Abstract: The transition between extensional and compressional-driven magnetic fabrics in sedimentary rocks is explored in this paper through the study of an example of the Basque–Cantabrian basin. In the area where extensional structures prevail and no superimposed deformation is observed, except for gentle large-scale folds, the magnetic fabric is interpreted as extensional, in consistency with mesostructural (tension gashes) and macrostructural (large-scale faults) data. Compressional tectonic fabrics are unequivocally interpreted in the area with cleavage development related to the buttressing of the syn-rift sequence against faults located near the northern basin margin. In this area, k max is oriented according either to the intersection lineation or the dip direction of cleavage planes. In the area located in-between, where no macroscopic evidence of either compression or extension exist, there is a transitional fabric between compressional (resulting from the modification during inversion of a previous sedimentary or extensional fabric) and extensional (inherited from the extensional stage) magnetic fabrics that correlate with subtle evidences at the microscopic scale (pressure shadows, deformation and re-orientation of nodules). Therefore, the magnetic fabric is revealed as an exceptionally sensitive marker of deformation in sedimentary rocks. This transition in the magnetic fabric occurs within a length of 6.25 km along the cross-section that correlates with a thickness of 200 m of the stratigraphic pile. These results indicate that even in the absence of clear structural markers of compressional deformation, extensional magnetic fabrics can be only interpreted when there is a minimum separation (in the vertical or the horizontal) to the cleavage front. [Copyright &y& Elsevier]

The succession in the Tizra Formation shows an excellent exposure of a small open marine platform where alternating microbial boundstones (buildups) and oolitic/bioclastic grainstone (shoals) and packstone facies tempestites occur repetitively for a sort interval only 0.55 Myr, an scenario unknown in the geological record. The relatively small extent of the platform allows a detailed study of facies and ecological variations, to determine the controlling factors for the growth and evolution of the platform (tectonics, glacioeustatism, terrigenous input), as well as the particular environmental/ecological conditions for the formation of microbial buildups and oolitic shoals (turbidity, energy, nutrients, chemical variations). Although microbial mounds are well-known during the Palaeozoic, the close relationship with ooids, as observed in the studied succession, is unusual, particularly for the frequent ooids embedded in the microbial facies, an ecological parameter used by previous authors to identified shallower stages in the microbial growths. Petrographic analysis of the ooids, as well as their ecological conditioning, suggest that less than 40% of samples yield ooids generated in situ, whereas there is a predominance of transported ooids. Ooids formed in situ, which include large irregular and elongated ooids, were generated in calmer water than the typical rounded and egg-shaped ooids. The occurrence of the predominant types of ooids in shallower-water grainstones with in situ generation, and in the deepest-water microbial facies, suggest their ease of transport. The higher production of ooids occurs during the shallowing phases of the cycles, whereas they were more easily transported during the deepening phases, whereas in the microbial buildups, no features of in situ ooid generation are found. [Display omitted] • Distribution on microbial mounds and ooids are primary controlled by energy and turbidity. • Secondary controls on microbial mound growths are nutrients and Mg/alkalinity. • Overall geometry of the deposits is conditioned by syn -sedimentary faults and glacioeustatic cycles. • Higher productions of ooids occurred during the transgressive phases. [ABSTRACT FROM AUTHOR]