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Answer Set Programming Modulo Acyclicity

Bomanson J., Janhunen T., Schaub T., Gebser M., Kaufmann B.

Fundamenta Informaticae

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2016

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Vol. 147, nr 1

63--91

EN

Acyclicity constraints are prevalent in knowledge representation and applications where acyclic data structures such as DAGs and trees play a role. Recently, such constraints have been considered in the satisfiability modulo theories (SMT) framework, and in this paper we carry out an analogous extension to the answer set programming (ASP) paradigm. The resulting formalism, ASP modulo acyclicity, offers a rich set of primitives to express constraints related to recursive structures. In the technical results of the paper, we relate the new generalization with standard ASP by showing (i) how acyclicity extensions translate into normal rules, (ii) how weight constraint programs can be instrumented by acyclicity extensions to capture stability in analogy to unfounded set checking, and (iii) how the gap between supported and stable models is effectively closed in the presence of such an extension. Moreover, we present an efficient implementation of acyclicity constraints by incorporating a respective propagator into the stateof- the-art ASP solver CLASP. The implementation provides a unique combination of traditional unfounded set checking with acyclicity propagation. In the experimental part, we evaluate the interplay of these orthogonal checks by equipping logic programs with supplementary acyclicity constraints. The performance results show that native support for acyclicity constraints is a worthwhile addition, furnishing a complementary modeling construct in ASP itself as well as effective means for translation-based ASP solving.

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The Steinplatte complex (Late Triassic, Northern Calcareous Alps, Austria) - subsidence-controlled development of a carbonate-platform-to-intrashelfbasin-transition

Kaufmann B.

Acta Geologica Polonica

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2009

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Vol. 59, no. 3

341-357

EN

In Rhaetian (Late Triassic) times, the Hauptdolomit/Dachstein carbonate shelf situated at the passive continental margin of the northwestern Tethys was characterized by an extensional tectonic regime. Rifting and spreading movements fragmented this shelf into a loosely fitted mosaic of fault-bounded blocks characterized by a differential subsidence pattern. This is expressed in significant thickness variations of platform carbonates and in the formation of the intrashelf Kossen Basin. In this study, it can be demonstrated that tectonic subsidence triggered the development of a carbonate platform margin and that the influence of eustatic sea-level changes was negligible. The Steinplatte complex developed at the transition of the Kossen Basin to the Dachstein Carbonate Platform. Small-scale isolated carbonate mounds situated on a smoothly inclined homoclinal ramp characterized the initial phase and acted as nuclei of further carbonate buildup growth. However, only the ideal palaeogeographic position far enough away from the carbonate-suppressive terrigenous influence of the Kossen Beds, combined with vigorous carbonate production stimulated by rapid subsidence-caused sea-level rise, favoured continuous mound growth. Once established, the carbonate buildup was characterized by rapid aggradational growth, developing a palaeogeographic high with a steep slope and a depression with decreased sedimentation behind, several kilometres distant from the Dachstein Carbonate Platform. Contemporaneously, isostatic adjustment caused an accommodation minimum on the nearby margin of the Dachstein Carbonate Platform leading to its westward progradation. Fading out of subsidence caused filling of the former depression in the back of the buildup by prograding shallow-water Dachstein Limestones. Thus, a new platform margin was established in the Steinplatte area, elevated almost 200 m above the adjacent Kossen Basin. At the Triassic-Jurassic boundary, the Steinplatte complex was subjected to subaerial exposure by a sudden tectonic uplift followed by a rapid isostatic drop. Emergence is indicated by levels of karstified limestones directly underlying supposed exposure surfaces. Final drowning of the Steinplatte complex as well as of the whole Dachstein Carbonate Platform is indicated by the cover of Early Jurassic (Sinemurian) deeper water, ammonitebearing limestones (Adnet Formation).

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Devonian / Lower Carboniferous stratigraphy, facies patterns and palaeogeography of Iran Part 1, Southeastern Iran

Wendt J., Kaufmann B., Bełka Z., Farsan N., Bavandpur A. K.

Acta Geologica Polonica

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2002

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Vol. 52, nr 2

129-168

EN

The mountains N of Kerman in southeastern Iran are a key region for Devonian/Lower Carboniferous stratigraphy of a still poorly known segment on the northern margin of Gondwana and display a great diversity of neritic depositional environments. The hitherto applied subdivision into lithostratigraphic formations has been calibrated by means of conodonts and brachiopods allowing good correlations of 36 sections, the majority of them ranging from the top of the Cambrian or the Silurian into the Lower Permian. Upper Cambrian sandstones or Silurian carbonates are unconformably overlain by red siliciclastics of uncertain Early to early Middle Devonian age (Padeha Formation) which in turn pass into skeletal limestones (upper Middle Devonian to Tournaisian Bahram and Sardar Formations). The latter are erosionally capped by Permian platform carbonates (Jamal Formation). Facies patterns during 5 intervals from the Silurian into the Tournaisian show evolution from a carbonate platform and siliciclastic shelf during the Silurian and the Early Devonian into shallow open marine embayments during the late Middle and Late Devonian, and a carbonate platform during the Early Carboniferous. Sharp boundaries between Upper Devonian facies belts appear controlled by synsedimentary epeirogenic movements which may have been active since the Early Palaeozoic.

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Facies, stratigraphy and diagenesis of Middle Devonian reef- and mud-mounds in the Mader (eastern Anti-Atlas, Morocco)

Kaufmann B.

Acta Geologica Polonica

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1998

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Vol. 48, no. 1

43-106

EN

During the Devonian, the eastern Anti-Atlas formed a part of the northwestern continental margin of Gondwana which was a mid-latitudinal (30-40 stopni S), temperate-water carbonate province. In the Mader region, ten carbonate mounds (one reef-mound and nine mud-mounds), distributed over five discrete localities, are intercalated within a 200-400 m thick Middle Devonian succession. The arid climate of the northwestern margin of the Sahara has exhumed these mounds which display perfectly their original morphologies and relations to off-mound lithologies. The carbonate mounds of the Mader area consist of massive, stromatactis-bearing boundstones (wackestones and floatstones in a purely descriptive manner) with the bulk of the mound volume consisting of fine-grained carbonate (microspar). High accumulation rates (0,2-0,8 m/1000 a), purity of mound carbonates (.95% CaCo3) and homogeneous Mg-calcite mineralogy strongly argue for in situ carbonate production by microbial (cyanobacterial/bacterial) communities. In addition, other indications (calcified cyanobacteria in the immediate neighbourhood of stromatactis fabrics, dark crusts surrounding stromatactis fabrics and alignment of stromatactis fabrics parallel to the accretionary mound surfaces) suggest a close relationship between stromatactis formation and carbonate production. Microbial communities probably flourished on the mound surfaces, precipitating fine-grained carbonates and consolidating the steepmound flanks by their mucilages. Once embedded, these communities decayed and were successively replaced by calcite cements, finally resulting in stromatactis fabrics. The facies model proposed for the three most conspicuous mound occurrences (Aferdou el Mrakib, Guelb el Maharch, Jebel el Otfal) is a 40 km wide, tectonically-controlled homoclinal ramp, which developed between an area of uplift (Mader Platform) and another area of strong subsidence (depocentre of the Mader Basin). The bathymetric gradient of this ramp is reflected by a Middle Devonian facies pattern varying from shallow to deeper water environments and by different faunal associations of the carbonate mounds. The Aferdou el Mrakib reef-mound was established at moderate water depth (midramp setting), because it contains abundant frame-builders (stromatoporoids, colonial rugose corals) but lacks indications for euphotic conditions, like calcareous algae and micritic envelopes. The Guelb el Maharch and Jebel el Otfal mud-mounds contain a much more impoverished fauna, dominated by crinoids and tabulate corals (auloporids), indicating a deeper bathymetric position (outer ramp setting) on the ramp. Further, but rather unspectacular mud-mounds (SE' Zireg, Jebel Ou Driss) are situatedapart from the ramp at localities in the southern and the southwestern Mader area respectively. Mound growth was possibly initiated by hydrothermalseepage at the seafloor though no evidences for hydrothermal activity, like mineralizations or depleted delta^13 C values, have been found to date. Slightly elevated temperatures may have stimulated the benthic fauna, especially crinoids, forming flat in situ lenses, which in turn served as substrates for microbial colonization. Termination of mound growth in the Mader Basin is connected with the subsidence-caused drowning of the carbonate ramp. Poorly-fossiliferous, laminated mudstones overlie the mounds and suggest a southward-directed extension of basinal facies onlapping the ramp and its mounds and resulting in poorly oxygenated seafloor conditions. Diagenesis of the Mader Basin carbonate mounds includes early marine, shallow marine burial and deeper burial cementation, recrystallization of the fine-grained mound carbonates, stylolitization and dolomitization. Radiaxial calcites (RC) precipitated in the marine environment and are believed to have preserved a nearly primary marine stable isotopic composition of the Mader Basin seawater with mean values of delta^18 O=-2.6(+-0.2)promili PDB and delta^13C=+2.7(+-0.5)promili PDB. The exceptional high delta^18 O values,compared with other Middle Devonian data derived from North American studies, are interpreted as resulting from the mid-latitudinal, temperate-water settings of the Mader Basin carbonate mounds. The diagenetic history is characterized by progressive burial conditions. Meteoric influences can be ruled out because the progressively deepening bathymetric evolution of the Mader Basin excludes subaerial exposure. All diagenetic events, especially cement zones, are probably diachronous and therefore cannot be correlated within in the Mader Basin and not even within individual mounds. Fault-related dolomitization, postdating Variscan compression was the last diagenetic event which affected the carbonate mounds of the Mader area.