Thèses sur le sujet « Permian tectonic »

The Alleghanian orogeny was a collision between the Gondwanan and Laurentian continents that produced the Pangean supercontinent. Mechanical and kinematic models of collisional orogens are believed to follow a critical taper geometry, where the tectonic imbrication of continental crust begins nearest to the edge of continental plate and advances toward the craton in a break- forward sequence. Studies of shear zones within the Alleghanian collisional orogen, however, suggest that most of the early deformation was translational. Propagation of craton-directed thrusts into the foreland did not occur until the latest Pennsylvanian in the southern Appalachians, and the middle-late Permian in the central Appalachians. Radiometric sedimentary provenance proxies have been applied to the late Mississippian-early Permian strata within the Appalachian foreland basin to determine the crustal composition and structural evolution of the orogen during the continental collision. U-Pb ages of detrital zircons from the early to middle Pennsylvanian sandstones suggest that most of the detritus within the Appalachian basin was recycled from Mesoproterozoic basement and Paleozoic strata of the Laurentian margin. The presence of Archean and late Paleoproterozoic age detrital zircons is cited as evidence of recycling of the Laurentian syn-rift and passive-margin sandstones. Detrital zircon ages from early-middle Permian-age sandstones of the Dunkard Group do not contain any Archean or Paleoproterozoic detrital-zircon ages, implying a source of sediment with a much more restricted age population, possibly the igneous and metamorphic internides or middle Paleozoic sandstones from the Appalachian basin. The persistance of 360-400 Ma K/Ar ages of detrital white mica suggest that the sediment was supplied from a source that was exhumed during the Devonian Acadian orogeny. Detrital-zircon and detrital-white-mica ages from Pennsylvanian-age sandstones indicate that the late Paleozoic orogen did not incorporate any significant synorogenic juvenile crust. The 87Sr/86Sr ratios of middle Pennsylvanian-early Permian lacustrine limestones within the Appalachian basin show a slight enrichment through time, suggesting that labile 87Sr-rich minerals in the Alleghanian hinterland are being exposed. Stable isotopic data from the lacustrine limestones also corroborates that the Appalachian basin became much more arid through time.

A single interval of red chert-clast conglomerate and associated strata (RCC/CRCC interval) occur within the Earp Formation (pennsylvanian-Permian) at many localities in southeastern Arizona, southwestern New Mexico, and northern Mexico, and record a middle Wolfcampian erosional event in the Pedregosa shelf and northern basin. The RCC and CRCC intervals are respective proximal and distal braidplain deposits, in contrast to the Earp Formation exclusive of the RCC/CRCC interval, which consists of interbedded carbonate and fine-grained siliciclastic strata that were deposited in mostly shallow- and marginalmarine environments. Deposition of stream channel, gravel bar, and interfluvial shale beds of the RCC/CRCC interval occurred on a broad, low-lying surface with negligible local topography. Paleocurrents were generally southward. Biostratigraphic evidence suggests that lower Wolfcampian strata below the RCC/CRCC interval were beveled northward. Much of the chert present- in the RCC/CRCC interval is probably residual material from the beveled strata, as well as from a region just north of the Pedregosa shelf. The evolution of the Pedregosa shelf and northern basin during depoSition of the Earp Formation is illuminated by identification of facies belts for three time intervals: (1) restricted shelf, inner shelf, and open-marine shelf facies belts during Virgilian through early Wolfcampian ttme, (2) proximal and distal braidplain facies belts during middle Wolfcampian time, and (3) restricted shelf, estuarine-marginal marine, and tidal-flat facies belts during middle through late(?) Wolfcampian time . The middle Wolfcampian erosional event caxnpanying the deposition of the RCC/CRCC interval was probably related to the Ouachita orogeny. Stratigraphic evidence suggests that the southern Pedregosa basin in Chihuahua, Mexico, evolved rapidly to a deep foreland basin during early or middle Wolfcarrpian tine because of downflexure under northward overthrusts during the Ouachita orogeny. Flexural subsidence of the Pedregosa foreland basin was accanpanied by peripheral forebulging, causing subaerial exposure of large parts of the Pedregosa shelf and northern basin. Deposition of the FCC/CFfX interval probably occurred on the subaerially exposed forebulge. Flexural mxlels predicting the deflection of the lithosphere under isostatic thrust and secliIrent loads agree satisfactorily with the forebulge concept for the origin of the RCC/CRCC interval.

The stratal architecture of the upper Ely Limestone and Mormon Gap Formation (Pennsylvanian-early Permian) in western Utah reflects the interaction of icehouse sea-level change and tectonic activity in the distal Antler-Sonoma foreland basin. Eighteen physically and biostratigraphically corelated stratigraphic sections provide a database for tracing Permo-Carboniferous boundary strata over a north-south distance of 60 km. These formations comprise 14 unconformity-bounded depositional sequence: three in the upper Ely (UE1-UE3) and 11 in the Mormon Gap Formation (MG1-MG11). Conodont and fusulinid faunas provide precise biostratigraphic information for a number of parasequences in the upper Ely and Mormon Gap formations. This paleontological information clarifies the tectonostratigraphic evolution of the distal foreland basin (study area) and permits correlation with events in the proximal foreland (Nevada) and with depositional sequences in the North American midcontinent. The stratigraphic succession is divided into three depositional intervals (I-III) with distinctive differences in constituent facies and facies stacking patterns, the regional continuity of cycles, the relative abundance of dolomite and limestone, calculated sediment accumulation rates, and the frequency and inferred duration of sequence-bounding hiatuses. These reflect the interaction of high-frequency sea-level change on an intermittently subsiding distal foreland basin. Subsidence is generally continuous during the Bashkirian through middle Moscovian (Interval I) and again during the Artinskian (Interval II). During the late Moscovian through Sakmarian stages (Interval III), subsidence rates dropped and sedimentation occurred mainly in consequence of second-order sea-level rise associated with the highstand of the Lower Absaroka II seas. Strata in the distal foreland are bounded by low-relief disconformities of variable duration in stark contrast to the angular unconformities and intensely deformed tectonostratigraphic domains that characterize the proximal foreland basin in north-central Nevada.

Durante il Permiano Inferiore, l’evoluzione post-Varisica dell’attuale regione Alpina è stata caratterizzata da una importante estensione crostale combinata con intensa attività magmatica, che ha favorito lo sviluppo di bacini estensionali intra-continentali con deposizione di sedimenti vulcanoclastici (e.g. Bacino Orobico). Nel settore centrale delle Alpi Meridionali, l’apertura di questi bacini era controllata da complessi sistemi di faglia, attivi contemporaneamente con l’intrusione di plutoni e l’attività vulcanica in superficie. Il seguente progetto di dottorato si focalizza sullo studio di queste caratteristiche, con l’intento di approfondire i processi geologici attivi durante il Permiano. Diverse faglie di età Permiana sono state indagate nel Bacino Orobico, con particolare enfasi sul riconoscimento dei loro tratti originali, poiché esse sono eccezionalmente sfuggite alla deformazione Alpina. Nel passato, l’architettura dei bacini Permiani era stata descritta con strutture a horst-graben, formatesi in risposta ad una tettonica transtensiva controllata da una zona di taglio che ha portato alla trasformazione da Pangea B a Pangea A. Tuttavia, studi più recenti hanno indicato un diverso setting di faglie che hanno controllato l’apertura dei bacini Permiani: si tratta di una combinazione di faglie normali a basso e alto angolo. Le faglie normali a basso angolo identificate lungo il Bacino Orobico rappresentano il miglior luogo in cui osservare l’interazione tra attività tettonica e magmatismo, poiché i loro nuclei di faglia sono caratterizzati da cataclasiti sigillate da livelli di tormaliniti. Queste ultime testimoniano la circolazione di fluidi arricchiti in boro e incanalati lungo importanti zone di faglia correlate all’apertura del Bacino Orobico. Simili brecce a tormalina affiorano anche in Val Trompia (BS): molti autori hanno suggerito che le tormaliniti delle Alpi Orobie, quelle della Val Trompia unitamente alla mineralizzazione di uranio del distretto di Novazza-Val Vedello potrebbero essere geneticamente correlate. Esse potrebbero essere correlate ad un sistema idrotermale di alta temperatura su ampia scala, coevo con l’attività tettono-magmatica del Permiano Inferiore che è responsabile anche della messa in posto di svariati depositi di minerali metalliferi nelle Alpi Meridionali. Tuttavia, la genesi delle tormaliniti non è mai stata dettagliatamente caratterizzata e la loro connessione con i giacimenti di U finora non è mai stata investigata. Le faglie tormalinizzate sono state riconosciute in molte località del settore centrale delle Alpi Meridionali quando ancora non era nota l’importanza delle faglie normali a basso angolo. In questa tesi di dottorato, vengono caratterizzate tutte le aree con i ritrovamenti di tormaliniti, ricercando la causa dell’idrotermalismo regionale nel contesto di estensione durante il Permiano Inferiore. Inoltre, per via del possibile link con i giacimenti di uranio, lo studio dei borosilicati viene proposto come strumento per meglio caratterizzare la genesi delle mineralizzazioni. Nuove osservazioni di terreno su tormaliniti sono combinate con lo studio della geochimica dei minerali e della roccia totale, insieme alla geocronologia, a studi microstrutturali e analisi isotopiche del B, con lo scopo finale di definire l’origine di questi fluidi arricchiti in boro. I risultati ottenuti da questa ricerca dimostrano che le tormaliniti e il magmatismo Permiano sono in stretta correlazione temporale e genetica. Inoltre, i dati geochimici sugli elementi in tracce forniscono maggiori indizi su una diretta connessione tra tormaliniti e la mineralizzazione a U dell’area di Novazza-Val Vedello. Tutti questi dati, per concludere, sono discussi nel contesto di interazione di processi tettonici, magmatici e di formazione di giacimenti che hanno interessato l’attuale settore centrale delle Alpi Meridionali durante il Permiano Inferiore.
During the Early Permian, the post-Variscan evolution of the present-day Alpine region was characterized by crustal extension combined with strong magmatic activity at different crustal levels, which finally led to the development of intracontinental extensional basins filled with volcanoclastic sediments (e. g. the Orobic Basin, N Italy). In the central Southern Alps (cSA), the opening of these basins was controlled by complex fault system that were active at the same time of plutons intrusion and volcanic activity at the surface. Relationships among magmatism, tectonics and hydrothermal activity related to the formation of ore deposits in the Early Permian so far have been only briefly addressed. This Ph.D. research project focuses on the investigations of the above described features, trying to consider the geological processes active in the Early Permian in an integrated scenario. Several Early Permian faults of the Orobic Basin have been investigated with special emphasis on the recognition of their original features, as they have exceptionally escaped most of the Alpine deformation. In the past, the architecture of Permian basins was described as horst-and-graben structures, formed in response to wrench tectonics developed during the activity of a megashear zone that led to the Pangea B to Pangea A transformation after the collapse of the Variscan orogen. However, thanks recent studies, a different fault architecture has been suggested to had controlled the opening of the Permian basins: a combination of Low-Angle Normal faults and High-Angle Normal Faults. The identified LANFs of the Orobic Basin represent the best site to study the interplay among tectonics and magmatism, as they are characterized by cataclastic bands sealed with cm to dm thick layers of dark, aphanitic tourmalinites. These latter are proof of fluids circulation channelled along higher permeability fault zones related to opening of the Orobic Basin. Such tourmaline breccias also crop out in the Trompia Valley (BS): several authors suggested that tourmalinites from Orobic Alps, tourmalinites from Trompia Valley together with uranium mineralization of Novazza - Vedello Valley are genetically linked. They are seen as products of a large-scale high-temperature hydrothermal system coeval with the Early Permian plutonic-volcanic activity and tectonism, which was also responsible for the emplacement of various types of magmatic-hydrothermal ore deposits in the Southern Alps (Sn-W, U-Mo-Zn, Fe carbonates, sulphides, quartz). However, their genesis has never been fully characterized and the connection between tourmalinites and U ore bodies has also not been deeply investigated so far. The tourmalinized faults were first noted in various sites of the cSA during the 90’s, when the tectonic importance of LANFs was not yet recognized. In this thesis, all the occurrences of tourmalinites are characterized, looking for the cause of the regional hydrothermalism in the context of intracontinental extension during the Early Permian. Furthermore, due to the likely connection with U ore deposits, the borosilicate study is proposed as tool for better understanding the genesis of the mineralizations. New field based structural analysis are combined with mineral and whole-rock geochemistry, geochronology, microstructural studies and boron- isotopic analysis of tourmalinites from different sectors of the study area, in order to evaluate the origin of these fluids. Results coming out from this study demonstrate, together with B isotope ratios, a temporal and genetical relationship between tourmalinites and Early Permian magmatism in the cSA. Furthermore, the geochemical data on trace elements provide more clues on a direct connection between tourmalinites and the U-mineralization. All these results are finally discussed in the frame of the interplay between tectonic, magmatic and ore generation processes that interested the present day cSA area in the Early Permian

The amalgamation of the Central Asian Orogenic Belt in the southwestern Tian Shan in Tajikistan is represented by tectono-magmatic-metamorphic processes that accompanied late Paleozoic ocean closure and collision between the Karakum-Tarim and Kazakh-Kyrgyz terranes. Integrated U-Pb geochronology, thermobarometry, pseudosection modeling, and Hf geochemistry constrain the timing and petro-tectonic nature of these processes. The Gissar batholith and the Garm massif represent an eastward, along-strike increase in paleodepth from upper-batholith (similar to 21-7km) to arc-root (similar to 36-19km) levels of the Andean-syn-collisional Gissar arc, which developed from similar to 323-288Ma in two stages: (i) Andean, I-type granitoid magmatism from similar to 323-306Ma due to northward subduction of the Gissar back-arc ocean basin under the Gissar microcontinent, which was immediately followed by (ii) syn-collisional, I-S-type granitoid magmatism in the Gissar batholith and the Garm massif from similar to 304-288Ma due to northward subduction/underthrusting of Karakum marginal-continental crust under the Gissar microcontinent. A rapid isotopic pull-up from similar to 288-286Ma signals the onset of juvenile, alkaline-syenitic, post-collisional magmatism by similar to 280Ma, which was driven by delamination of the Gissar arclogite root and consequent convective asthenospheric upwelling. Whereas M-HT/LP prograde metamorphism in the Garm massif (650-750 degrees C/6-7kbar) from similar to 310-288Ma was associated with subduction-magma inundation and crustal thickening, HT/LP heating and decompression to peak-metamorphic temperatures (similar to 800-820 degrees C/6-4kbar) at similar to 2886Ma was driven by the transmission of a post-collisional, mantle-derived heat wave through the Garm-massif crust.

The Permian Cutler Group in the northwest part of the Paradox foreland basin of south-eastern Utah and south-western Colorado comprises a succession of conglomerate and sandstone of mixed fluvial and aeolian affinity up to 4000 m thick: the proximal and medial parts of this basin-fill succession are the focus of this study. Fluctuations in climate and sediment flux resulted in growth and recession of penecontemporaneously operating fluvial and aeolian systems. Fluvial sediment was sourced from the Uncompahgre Uplift of the Ancestral Rocky Mountains. Progressive loading and movement of older salt deposits during accumulation of the Cutler Group generated a series of salt-wall-bounded mini-basins, collectively known as the “Salt Anticline Region~, in the eastern part of the study area. Here, the so-called Undifferentiated Cutler Group varies in thickness from zero over some salt highs to -4000 m just a few kilometres away in adjacent mini-basin depocentres. indicating that syn-sedimentary salt movement generated Significant variations in accommodation. In the Salt Anticline Region syn-sedimentary salt movement was the dominant control on the preserved stratigraphy and the distribution of architectural elements, which in turn was closely linked to the rate and style of influx, of sediment derived from the Uncompahgre Uplift. During tectonically quiescent episodes, fluvial systems filled accommodation in mini-basin depocentres before establishing flow pathways over buried salt-wall highs. In the Shafer Basin, in the western part of the study area, subtle salt structures form low-amplitude, long-wavelength anticlines upon which architectural elements thin and pinch out. Aeolian elements are rare in the Salt Anticline Region, but more common in medial parts of the Paradox Basin. Here, styles of aeolian-fluvial interaction occur at three scales: (i) large-scale intertonguing and interbedding of fluvial and aeolian elements; (il) small-scale feathering and reworking of elements and (iii) interactions at the grain-scale. These styles of interaction demonstrate penecontemporaneous aeolian and fluvial activity and large-scale alternations between episodes of aeolian and fluvia1 dominance. The large-scale cycles between aeolian and fluvial elements were likely controlled by a combination of extrinsic climatic forcing and episodic recurrence of Uncompahgre Uplift. resulting in tectonically driven pulses of enhanced rates of sediment delivery. System interactions at smaller scales record the effects of intrinsic (autogenic) controls. whereby localized dominance of fluvial over aeolian processes (and vice versa) occurred.

Die einer unterschiedlichen Genese zuordenbaren tektonischen Strukturen, welche sich im Raum des Thüringer Waldes bündeln, formten in einem gerichteten Entwicklungsablauf das komplizierteste und vielseitigste hochoberkarbonisch-unterpermische Strukturgebäude Mitteleuropas. In dieser Arbeit wird der Versuch einer Synthese der strukturellen und der daran geknüpften vulkanogen-sedimentären Entwicklung innerhalb der permokarbonischen Thüringer Wald-Senke und ihres unmittelbaren mitteleuropäischen Umfeldes unternommen. Sie stützt sich dabei maßgeblich auf die Ergebnisse langfristig durchgeführter Kartierungsarbeiten, die in diskontinuierlichen Bearbeitungsphasen seit 1957 bis in die 90er Jahre des vergangenen Jahrhunderts erfolgten. Einbezogen werden die Ergebnisse von insgesamt 54 Forschungs- und Erkundungsbohrungen, die zu einem Großteil im Kontext dieser Arbeiten geteuft worden sind. 36 Bohrprofile werden hier erstmals vollständig beschrieben und publiziert. Neben einer nochmaligen Überprüfung der gesamten lithostratigraphischen Abfolge in der permokarbonischen Thüringer Wald-Senke besteht die Zielstellung der Arbeit in deren Einbindung in die regionale mitteleuropäische strukturelle Entwicklung während dieser Zeitspanne, beginnend bei den potenziellen variszisch-kollisional angelegten Wurzeln der permokarbonischen Strukturen, über ihre weitere tektono-magmatische Ausgestaltung bis hin zur Ausprägung der postvariszischen Großschollenfelderung Mitteleuropas am Ende des Permokarbons.

Die Sedimente des Halleschen Permokarbonkomplexes gaben schon immer Raum für Spekulationen. Aufgrund ihrer Dominanz an rhyolithischen Geröllen wurden sie über einen langen Zeitraum einheitlich als Postporphyrschutt ausgehalten. Vielfältig wechselnde Faziesbedingungen machten es jedoch notwendig, die Sedimente aufzugliedern. Neuere Erkenntnisse in der Erforschung des Halleschen Permokarbonkomplexes erfordern eine Überprüfung v. a. der nach KUNERT (1995) aufgestellten allgemeinen stratigraphischen Gliederung der Unterrotliegendsedimente in Halle,- Hornburg,- Sennewitz- und Brachwitz-Formation anhand einiger ausgewählter Beispiele. Der ursprüngliche Gedanke der Diplomarbeit bestand darin, eine Fazies- und eine Geröllanalyse der unterpermischen Abtragungsprodukte des Halle-Vulkanitkomplexes anzufertigen. Zur Verfügung standen zwei Kernbohrungen und zwei Aufschlüsse, sowie diverse Unterlagen zu angrenzenden Bohrungen in der Saale-Senke. Die beiden Oberflächenaufschlüsse Riveufer und Teichgrund sollten stratigraphisch aufgenommen werden, so dass eine Fazieszuordnung möglich ist. Die Bohrung Brachwitz 2/62 wurde mit dem Ziel aufgenommen, neuere Theorien über den Ablagerungszeitraum der Rotliegend-Sedimente in Bezug auf den permokarbonen Vulkanismus zu widerlegen oder zu bekräftigen. Die zweite Bohrung (Kb Lochau 7/65) wurde am Rande mit in die Diplomarbeit einbezogen, da sie das immense Spektrum der spätvulkanischen Aktivitäten im Halle Permokarbonkomplex erweitert. Ergebnis ist eine Neugliederung des Rotliegend im Halleschen Permokarbonkomplex, in der nur noch die Halle-Formation mit ihrem ausgeprägten Vulkanismus und die Hornburg-Formation, stellvertretend für alle jüngeren Abtragungsprodukte des Halle Vulkanitkomplexes, unterschieden werden. Mit einem großen Hiatus folgt anschließend die Eisleben-Formation.

In eastern Australia, the New England Fold Belt (NEFB) comprises an ancient convergent margin that was active from the Paleozoic until the late Mesozoic. Considerable effort has been expended in understanding the development of this margin over the past twenty years. However, proposed tectonic models for the orogen have either been too broad, ignoring contradictory local evidence, or too locally specific without paying attention to the 'big picture'. The research presented in this work addresses the issue of appropriate scale and depth of geological detail by studying the NEFB at the terrane-scale. Using one succession, the Silverwood Group of southeast Queensland, this work demonstrates that detailed sedimentological studies and basin analysis at the terrane-scale can help to refine hypotheses regarding the tectonic evolution of the NEFB. The Silverwood Group (Keinjan terrane), located approximately 140 km southwest of Brisbane, Australia, is a succession of arc-related basins that developed within an ancient intraoceanic island-arc during the mid-Cambrian to Late Devonian. From the base of the succession, the group consists of five formations totalling -9700 m. These include the Risdon Stud Formation (2500 m), Connolly Volcanics (2400 m), Bald Hill Formation (2450 m), Ormoral Volcanics (600 m) and the Bromley Hills Formation (1700 m). The Long Mountain Breccia Member (300m) is a separate unit which forms the lower part of the Bromley Hills Formation. The entire succession has been thrust west over the Late Devonian to Early Carboniferous Texas beds. Elsewhere, the Silverwood Group is unconformably overlain by and faulted against Early to Late Permian units including the Rokeby beds, Wallaby beds, Tunnel beds, Fitz Creek beds, Eight Mile Creek beds, Rhyolite Range beds and Condamine beds. Of these Permian units, all but the Condamine beds form part of the Wildash Succession. To the west, southwest and south, the Silverwood Group is intruded by the Late Triassic Herries and Stanthorpe Adamellites. All of these sequences and the two plutonic intrusives are unconformably overlain by the Jurassic sediments of the Marburg Sandstone. The Silverwood Group and Texas beds consist of various lithologies including grey, purple- grey, green and green-grey volcaniclastic conglomerates, sandstones, siltstones or mudstones, massive and laminated chert, polymict or monomict breccias, muddy breccias, muddy sandstones, and volcanic rocks. Volcanic rocks include various tholeiitic metabasites, dolerite, meta-andesites and infrequent metadacite. In the Silverwood Group, these volcanic rocks are often accompanied by mafic pyroclastic rocks (e.g. peperite and hyaloclastite). Facies analyses of these lithologies has led to the recognition of 19 deep-marine turbiditic and volcanic/volcaniclastic facies that were deposited by three main processes: i) gravity-flow processes (e.g. low- and high-density volcaniclastic turbidites and mass-flows), ii) chemical/biological processes (siliceous oozes- chert) and iii) direct initiation by volcanic processes (e.g. flows, hypabyssal intrusions and associated pyroclastic facies). For the Silverwood Group, the defined facies occur in distinct vertical associations that form recognisable 3rd and 4th-order architectural elements such as channel, levee, suprafan lobe, outer-fan, basin plain, mass transport complex, volcanic flows, syn-sedimentary sills and syn-sedimentary emergent cryptodomes. These architectural elements are represented in a series of deep-marine depositional environments including slope, shelf-edge failure, submarine-fan and subaqueous basaltic volcanoes. The Risdon Stud Formation and parts of the Connolly Volcanics were deposited along a 'normal' clastic or mud, mud/sand-rich and/or sand/mud-rich slope. Both upper and lower slope environments are represented and in both formations, the slope is speculated to have faced eastwards and prograded away from an active arc located west. Sediments from both successions accumulated at palaeodepths of 1200 to 2000 m. Although sediments from the upper part of the Bald Hill Formation were also deposited on a slope, these sequences have subsequently collapsed into the depocentre to form extensive slump deposits accompanied by olistoliths of older arc crust. The lower part of the Bald Hill Formation formed by similar processes, although the failure was far more extensive (>20 km along strike). This latter part of the formation is interpreted to be a major shelf-edge failure succession. Upper parts of the Bald Hill Formation also accumulated at palaeodepths of 1200 to 2000 m, but the deposition of these sediments occurred farthest from the shelf and at the greatest depth compared to the Risdon Stud Formation and Connolly Volcanics. Lower parts of the Bald Hill Formation were deposited at palaeodepths of approximately 1700 m. Subaqueous basaltic volcanoes are prominent in the Connolly Volcanics, Bald Hill Formation and Ormoral Volcanics. In the Bald Hill Formation, igneous rocks were emplaced into the shelf-edge failure succession as a series of syn-sedimentary sills and cryptodomes. These high-level hypabyssal rocks occasionally became emergent above the sediment-water interface, whereupon they were partially resedimented. In some parts of the Bald Hill Formation, the hypabyssal intrusions were blanketed by basin plain deposits that are contemporaneous with the slumps and olistoliths in the upper part of the formation. The intrusive rocks were emplaced at 1700 m palaeodepth. Unlike the Bald Hill Formation, the Ormoral Volcanics and lower parts of the Connolly Volcanics form thick accumulations of extrusive volcanic and pyroclastic rocks that built a significant volcanic pile. Volcanic and pyroclastic facies within these successions were deposited proximal to their source (0-10 km of vent). Extrusive rocks within the Ormoral Volcanics are thought to be derived from intrabasinal fissure-vents located at palaeodepths of 1700 to 3100 m. Igneous rocks from the Connolly Volcanics, Bald Hill Formation and Ormoral Volcanics have the petrological and geochemical characteristics of back-arc basin basalts (BAB) that were sourced from undepleted to slightly enriched Fertile MORB Mantle-wedge (FMM). The FMM material was variably enriched in trace elements by fluids derived from the subducting slab prior to emplacement of the igneous rocks. Immediately following emplacement, these rocks were hydrothermally metamorphosed under conditions of low-pressure and transitional low to high-temperature (200-300 °C). By contrast, igneous rocks within the Texas beds lack enrichment in subduction components and are characteristic of N-MORB. The Bromley Hills Formation is a sand-rich point-source submarine fan deposited at palaeodepths of 500 to 2000 m. The fan was initiated by a mass transport complex resulting from subaerial collapse of a basaltic-andesitic stratovolcano. The submarine fan is characterised by two repetitive stages of retrogressive sedimentation during which channel-levee elements (inner-fan channels) are overlain by suprafan lobe elements (mid-fan) and then by outer-fan deposits as sea-level rises within the depocentre. Both inner-fan channels and suprafan lobes show centralised stacking patterns with limited lateral migration that indicate the depocentre was laterally restricted during sedimentation (e.g. submarine ridges). The Bromley Hills Formation exhibits all the characteristics typical of an active margin fan that formed by a combination of tectonic stage initiation followed by eustatically controlled regressive deposition. Volcaniclastic sediments of the Silverwood Group range in composition from lithic to lithic- feldspathic wackes and arenites, although they are mainly lithic or feldspathic-lithic wackes and arenites. Many samples are tuffaceous (25-75% pyroclasts), particularly those from the Connolly Volcanics, Ormoral Volcanics and Bromley Hills Formation. Samples in the Bald Hills Formation and Texas beds can be classified as quartz-rich. The majority of the Silverwood Group was sourced from an undissected intraoceanic island-arc, although sediments within the Bald Hill Formation exhibit a provenance that is characteristic of uplift within the arc (recorded as a 'strike-slip continental arc' model). Epiclastic sediments from the Texas beds were sourced from a transitional to dissected continental arc. Formations of the Silverwood Group were mostly deposited in a series of intra-arc basins within an ancient intra-oceanic island arc, although the lowermost formation developed in a marginal basin (Risdon Stud Formation). All of the basins were located east of the active arc (behind the arc), keeping in mind the present location of the Group relative to the Texas-Coffs Harbour megafold. The entire succession formed during four-phases of arc-related basin development that coincide with major changes in the strain regime of the arc. From the base of the succession, these changes are: I) mid Cambrian to late Silurian marginal basin sedimentation- relative compression within the arc (Risdon Stud Formation), II) late Silurian to Early Devonian intra-arc rifting- relative extension within the arc (Connolly Volcanics), Ill) Early to early Middle Devonian basin collapse followed by intra-arc rifting- relative extension to compression (Bald Hill Formation and Ormoral Volcanics) and IV) early Middle to Late Devonian intra-arc submarine fan sedimentation- relative compression (Bromley Hills Formation). Comparing the Silverwood Group against equivalent terranes of Cambrian to Devonian age within the New England Fold Belt (NEFB) suggests that the Gamilaroi terrane, Calliope Volcanic Assemblage, Willowie Creek beds and Silverwood Group all formed as one intraoceanic island-arc during the Early to Late Devonian. Prior to this, significant differences in the sedimentological evolution of these terranes suggests that they occupied different positions relative to each other within the one arc. It is proposed that the NEFB formed as a result of dual west-directed subduction zones during the Cambrian to Middle Devonian period. During this time, a single intraoceanic island-arc located seaward of the Australian craton developed above a west-directed subduction zone. This arc was separated from the craton by a marginal sea. A second west-directed subduction zone was located beneath a continental arc developed on the Australian craton. Cambrian to Early Devonian terranes within and along the Peel Fault are proposed to form a part of the ancient subduction zone present beneath the intraoceanic island-arc (Weraerai and Djungati terranes). Collision of the intraoceanic island-arc occurred during the Late Devonian, at which point west-directed subduction occurred beneath the Australian craton and the accreted intraoceanic island-arc. Following collision, a new continental volcanic arc was established that was active during the Late Devonian to Early Carboniferous.

The Early Permian strata of the Hongliuhe Group, NW China, experienced a thin-skinned fold-and-thrust belt style of deformation that recorded the final stages of amalgamation of the Beishan orogenic collage, a part of the Central Asian Orogenic Belt. The Hongliuhe Group was syn-orogenically deposited on an undetermined foreland, with the Mazongshan arc terrane acting as the hinterland. In this study results from detailed mapping combined with a regional analysis elucidate involvement of a northward-dipping subduction system with the collision. Well-preserved fold-and-thrust belt style deformation mapped in the upper stratigraphy of the Hongliuhe Group exhibits dominantly south-southeast verging structure, including shear folding, low-angle thrust ramping, imbrication and duplexing. Restoration of a portion of a mapped outcrop-scale cross-section estimates the accommodation of a minimum of 24% shortening. Lower stratigraphy shows discrete, steeper, north-over-south dip-slip ductile shear zones that bound packages of less deformed Hongliuhe Group strata. Fault displacement is considered to have been prolonged enough to juxtapose basal formations in northerly hangingwalls against upper formations in southerly footwalls. Faulting is closely associated with the creation of large-scale brittle-ductile eye-fold structures that are postulated to be sheath folds. The most examined and mapped structure, 16km wide, is a synclinal structure with axes plunging steeply towards its center. The ellipticity of the exposed bedding traces increases towards the center of the eye-fold, implying a structural relationship with metamorphic shear zones. Except for large-scale folding, the bulk of its strata remain relatively undeformed and have preserved primary soft-sediment deformation structures indicating younging towards the center on both limbs of the synclinal structure. Stratigraphic reconstruction of the Hongliuhe Group that considers the significant faulting shows that the Group's basal conglomerates unconformably overlie a Late-Carboniferous volcanic assemblage. The clast lithotypes of the conglomeratic successions change from polymictic metamorphic rocks at the base to monomictic granitoid clasts mid-section, showing the gradual unroofing sequence of the provenance. The stratigraphic reconstruction shows a general fining upward sequence, transitioning from terrestrial to nearshore marine depositional environments that, and in conjunction with the conglomeratic successions, suggests that the tectonic setting for deposition of the Hongliuhe Group is a foreland basin. Considering the deformation styles reported in this study, the Hongliuhe Group is interpreted to be a foreland fold-and-thrust belt. Stratigraphic reconstruction of the Hongliuhe Group that considers the significant faulting shows that the Group’s basal conglomerates unconformably overlie a Late Carboniferous volcanic assemblage. The clast lithotypes of the conglomeratic successions change from polymictic metamorphic rocks at the base to monomictic granitoid mid-section, showing the gradual unroofing sequence of the provenance. The stratigraphic reconstruction shows a general fining upward sequence through nearshore depositional environments that, and in conjunction with the conglomeratic successions, give interpretation that the tectonic setting for deposition of the Hongliuhe Group is a foreland basin. Considering the deformation styles reported in this study the Hongliuhe Group is interpreted to be a foreland fold-and-thrust belt.

The southern and central Appalachian foreland fold-thrust belt comprises a series of orogen -scale curves that extend from Alabama to New York. One of these is the Tennessee salient, a foreland-convex curve that extends from Cartersville, Georgia, to Roanoke, Virginia. Development of a kinematic model for deformation in the salient has been hindered by a paucity of penetrative deformation in this generally low temperature, low volume-loss portion of the orogen. Industry seismic reflection lines provide greater resolution of subsurface geometry of both the basement surface and the overlying fold-thrust belt, confirming some previous interpretations and changing others. A series of cross sections based on the seismic reflection data incorporates the improved understanding of basement geometry, as well as new interpretations of fold-thrust belt structures such as a sub-thrust detachment fold along the western margin of the Valley and Ridge, a smaller detachment fold along the Cumberland Escarpment, and a duplex below the Knoxville sheet in southeastern Tennessee. The cross sections, combined with recently published analyses of calcite twin strain and paleomagnetic data around the salient, provide sufficient data to develop a new palinspastic reconstruction method and to propose a kinematic model for development of the salient. The basis of the reconstruction method is, in areas where the front of the indenter is oriented oblique to transport, the maximum shortening direction and particle displacement paths are also oblique to the bulk transport direction. Cross sections, kinematic indicators, and palinspastic reconstructions suggest that the Tennessee salient is a primary arc formed by a combination of uniform displacement in a single direction and transport-parallel simple shear (plane strain), that most major faults formed initially curved in front of the irregularly shaped Blue Ridge-Inner Piedmont indenter, and that transport in the fold-thrust belt may have occurred by plan view movement on networks of minor faults, which permitted forelandward propagation of the curved faults without significant rotation. Although the technique does not provide a unique solution, the resulting palinspastic restoration is kinematically admissible and geometrically reasonable. So, it may improve palinspastic restorations of facies in basins with no vertical axis rotations and minimal penetrative strain. Attachments are in PDF format and may be opened with Adobe Reader™.

Die Sedimente des Halleschen Permokarbonkomplexes gaben schon immer Raum für Spekulationen. Aufgrund ihrer Dominanz an rhyolithischen Geröllen wurden sie über einen langen Zeitraum einheitlich als Postporphyrschutt ausgehalten. Vielfältig wechselnde Faziesbedingungen machten es jedoch notwendig, die Sedimente aufzugliedern. Neuere Erkenntnisse in der Erforschung des Halleschen Permokarbonkomplexes erfordern eine Überprüfung v. a. der nach KUNERT (1995) aufgestellten allgemeinen stratigraphischen Gliederung der Unterrotliegendsedimente in Halle,- Hornburg,- Sennewitz- und Brachwitz-Formation anhand einiger ausgewählter Beispiele. Der ursprüngliche Gedanke der Diplomarbeit bestand darin, eine Fazies- und eine Geröllanalyse der unterpermischen Abtragungsprodukte des Halle-Vulkanitkomplexes anzufertigen. Zur Verfügung standen zwei Kernbohrungen und zwei Aufschlüsse, sowie diverse Unterlagen zu angrenzenden Bohrungen in der Saale-Senke. Die beiden Oberflächenaufschlüsse Riveufer und Teichgrund sollten stratigraphisch aufgenommen werden, so dass eine Fazieszuordnung möglich ist. Die Bohrung Brachwitz 2/62 wurde mit dem Ziel aufgenommen, neuere Theorien über den Ablagerungszeitraum der Rotliegend-Sedimente in Bezug auf den permokarbonen Vulkanismus zu widerlegen oder zu bekräftigen. Die zweite Bohrung (Kb Lochau 7/65) wurde am Rande mit in die Diplomarbeit einbezogen, da sie das immense Spektrum der spätvulkanischen Aktivitäten im Halle Permokarbonkomplex erweitert. Ergebnis ist eine Neugliederung des Rotliegend im Halleschen Permokarbonkomplex, in der nur noch die Halle-Formation mit ihrem ausgeprägten Vulkanismus und die Hornburg-Formation, stellvertretend für alle jüngeren Abtragungsprodukte des Halle Vulkanitkomplexes, unterschieden werden. Mit einem großen Hiatus folgt anschließend die Eisleben-Formation.:Inhalt Abbildungsverzeichnis Tabellenverzeichnis Abkürzungsverzeichnis 1. Einleitender Teil 1 1.1 Einleitung 1 1.2 Aufgabenstellung und Problematik 1 1.3 Geographischer Überblick über die Bohrungen und Aufschlüsse 2 2. Regionalgeologischer Teil 4 2.1 Aufbau des Halle Vulkanitkomplexes 4 2.2 Beckenentwicklung des Permokarbons im Bereich des Halle- Vulkanitkomplexes 5 2.3 Historischer Rückblick über die Einstufung der Rotliegend-Formationen im Halle Vulkanitkomplex 10 2.4 Neueste Entwicklungen in der Erforschung des Saale-Beckens 15 2.4.1 Die Ablagerungen der Halle-Formation 15 2.4.2 Die Ablagerungen der Sennewitz-Formation 16 2.4.3 Die Ablagerungen der Hornburg-Formation 17 2.4.4 Die Ablagerungen der Brachwitz-Formation 19 2.4.5 Die Ablagerungen der Eisleben-Formation 20 2.4.6 Aktuelle Stratigraphische Gliederung 22 2.5 Die späte Phase des Halle Vulkanitkomplexes und ihr Bezug zur Diplomarbeit 23 3 Arbeitsmethodik 24 3.1 Aufnahme der Bohrungen Brachwitz 2/62 und Lochau 7/65 24 3.2 Aufnahme des Aufschlusses am Teichgrund bei Döblitz 26 3.3 Aufnahme des Aufschlusses am Riveufer im Stadtgebiet von Halle 26 4. Vulkanische und sedimentäre grobklastische Transport- und Ablagerungssysteme 27 4.1 Vulkanische Massentransporte 27 4.1.1 Pyroklastische Ablagerungen 27 4.1.1.1 Pyroklastische Fallablagerungen 28 (1) Aschefallablagerungen 28 (2) Bimsführende Fallablagerungen 29 (3) Scoriaführende Fallablagerungen 29 4.1.1.2 Pyroklastische Stromablagerungen 29 (1) Bimsführende pyroklastische Stromablagerungen oder Ignimbrite 29 (2) Block- und Aschestromablagerungen 31 (3) Scoriaführende pyroklastische Stromablagerungen 32 4.1.1.3 Pyroklastische Surge-Ablagerungen 32 (1) Surgeablagerungen durch Aschewolken 32 (2) Ablagerungen am Boden der pyroklastischen Surge 33 (3) Ablagerungen an der Basis der pyroklastischen Surge 33 4.1.2 Explosive vulkanische Eruptionen 33 (1) Hawaiianische Eruptionen 34 (2) Plinianische Eruptionen 34 (3) Strombolianische Eruptionen 35 (4) Vulkanianische und Surtseyanische Eruptionen 35 4.1.3 Produkte phreatomagmatischer Eruptionen 36 (1) Maare 37 (2) Tuffkegel und Tuffringe 37 4.1.4 Tephraablagerungen 38 4.2 Sedimentäre Massentransporte 39 4.2.1 Alluviale Fächer 40 4.2.2 Schichtfluten 42 4.2.3 Flußsyteme 42 4.2.4 Überflutungsebenen 43 4.2.5 Deltas und Ästuare 44 5. Lithologien und Faziestypen 45 6. Aufschlüsse und Bohrungen 45 6.1 Aufschlußkomplex am Riveufer im Stadtteil Giebichenstein in Halle 48 6.1.1 Allgemeine Aussagen 48 6.1.2 Das Faziesmodell eines verflochtenen Flußsystems 48 (1) Ausbildung von Rinnen 48 (2) Einfallen der Rinnen 50 (3) Prallhänge 50 (4) Seitenanschnitte an beiden Enden des Aufschlusses 51 6.1.3 Ein tuffgefülltes Spaltensystem als syn- bis postsedimentäres Ereignis 52 6.1.4 Interpretation 53 6.2 Aufschluß am Teichgrund bei Döblitz 55 6.2.1 Allgemeine Aussagen 55 6.2.2 Sedimentäre Lithofaziestypen und -assoziationen 56 6.2.3 Dokumentation der einzelnen Aufschlüsse 56 6.2.3.1 Aufschluß T1 56 (1) Detaildarstellung Aufschluß am Teichgrund T1-1 56 6.2.3.2 Aufschluß T2 59 6.2.3.3 Aufschluß T3 59 6.2.4 Fazielle Diskussion 59 6.3 Kernbohrung Brachwitz BrwSk 2/62 südöstlich der Ortschaft Friedrichsschwerz 61 6.3.1 Allgemeine Informationen 61 6.3.2 Erläuterungen zu den Lithofaziestypen 61 (1) SFT-B1 Konglomerat der Eislebenformation 61 (2) SFT-T1 Sedimentäre Brekzie 61 (3) SFT-T4 Mittel- bis Grobsandstein 62 (4) SFT-B2 Schluffstein 62 (5) VFT-T0 Rhyolith, brekziös/ VFT-T1 Porphyrbrekzie, monomikt 63 (6) VFT-B12 Porphyrbrekzie mit Obsidianmatrix 64 (7) VFT-B2 Porphyrbrekzien, oligomikt und polymikt 64 (8) VFT-B3 Mittelsand, vulkanogen 65 (9) VFT-B5 Schluffstein, brekziiert 66 6.3.3 Auswertung 66 6.4 Kernbohrung Lochau 7/65 südöstlich Halle 68 6.4.1 Allgemeines 68 6.4.2 Erläuterungen zu den Vulkanischen Faziestypen 68 (1) VFT-L1 Aschentuff 68 (2) VFT-L2 Surges 69 (3) VFT-L3 Surge oder Explosionsbrekzie 70 (4) VFT-L4 Explosionsbrekzie mit Tuffzwickelfüllung 71 (5) Tuff mit einzelnen Ballistischen Bomben 72 6.4.4 Beispiel Ha-Lo7/17 73 6.4.5 Diskussion 74 7. Zusammenfassung und Ausblick 76 8. Literatur- und Quellenverzeichnis 78 9. Anhang Anlage 1: Allgemeines Anlage 2: Teichgrund bei Döblitz Anlage 3: Riveufer im Stadtzentrum von Halle (Saale) Anlage 4: Kb Brachwitz 2/62 Anlage 5: Kb Lochau 7/65

Die einer unterschiedlichen Genese zuordenbaren tektonischen Strukturen, welche sich im Raum des Thüringer Waldes bündeln, formten in einem gerichteten Entwicklungsablauf das komplizierteste und vielseitigste hochoberkarbonisch-unterpermische Strukturgebäude Mitteleuropas. In dieser Arbeit wird der Versuch einer Synthese der strukturellen und der daran geknüpften vulkanogen-sedimentären Entwicklung innerhalb der permokarbonischen Thüringer Wald-Senke und ihres unmittelbaren mitteleuropäischen Umfeldes unternommen. Sie stützt sich dabei maßgeblich auf die Ergebnisse langfristig durchgeführter Kartierungsarbeiten, die in diskontinuierlichen Bearbeitungsphasen seit 1957 bis in die 90er Jahre des vergangenen Jahrhunderts erfolgten. Einbezogen werden die Ergebnisse von insgesamt 54 Forschungs- und Erkundungsbohrungen, die zu einem Großteil im Kontext dieser Arbeiten geteuft worden sind. 36 Bohrprofile werden hier erstmals vollständig beschrieben und publiziert. Neben einer nochmaligen Überprüfung der gesamten lithostratigraphischen Abfolge in der permokarbonischen Thüringer Wald-Senke besteht die Zielstellung der Arbeit in deren Einbindung in die regionale mitteleuropäische strukturelle Entwicklung während dieser Zeitspanne, beginnend bei den potenziellen variszisch-kollisional angelegten Wurzeln der permokarbonischen Strukturen, über ihre weitere tektono-magmatische Ausgestaltung bis hin zur Ausprägung der postvariszischen Großschollenfelderung Mitteleuropas am Ende des Permokarbons.

Indiana University-Purdue University Indianapolis (IUPUI)
The Antler and Sonoma orogenies occurred along the southwest-trending passive Pacific margin of North America during the Paleozoic concluding with the accretion of the McCloud Arc. A southeast-trending sinistral transform fault truncated the continental margin in the Permian, becoming a locus for initiation of an east-dipping subduction zone creating the Sierran magmatic arc. Constrained in age between two early Triassic tuff layers, the volcanic clasts in the breccia of Frog Lakes represent one of the earliest records of mafic magmatism in the eastern Sierra Nevada. Tholeiitic rock clasts found in the breccia of Frog Lakes in the Saddlebag Lake pendant in the east central Sierra Nevada range in composition from 48% to 63% SiO2. Boninites produced by early volcanism of subduction initiation by spontaneous nucleation at the Izu-Bonin-Mariana arc are more depleted in trace element concentrations than the clasts while andesites from the northern volcanic zone of the Andes produced on crust 50 km thick have similar levels of enrichment and provide a better geochemical modern analogue. Textural analysis of the breccia of Frog Lakes suggest a subaqueous environment of deposition from a mature magmatic arc built on continental crust > 50 km thick during the Triassic. The monzodiorites of Saddlebag and Odell Lakes are temporal intrusive equivalents of the breccia of Frog Lakes and zircon geochemistry indicates a magmatic arc petrogenesis.