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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
221

Sequence Stratigraphy of Basal Oquirrh Group Caronates (Bashkirian) Thorpe Hills, Lake Mountain, Wasatch Front, Utah

Derenthal, Andrew D. 10 November 2011 (has links) (PDF)
The Early Pennsylvanian (Bashkirian/Morrowan) Bridal Veil Limestone of north-central Utah was deposited in the eastern portion of the rapidly subsiding Oquirrh basin. The 420 meter-thick Bridal Veil Limestone displays distinct cyclicity formed by stacked, meter to decameter scale high-frequency sequences and their constituent parasequences. Though no one ideal cycle may be defined for the Bridal Veil Limestone, each high-frequency sequence and parasequence contains a general shallowing upward trend that ranges from anaerobic to dysaerobic mudstone at the base to skeletal wackestone to mud-dominated packstone, capped by heterozoan grain-rich carbonates or siliciclastic tidalites. Cycles bounded by exposure surfaces, indicated by micro-brecciation, rhizoliths, laminated calcite or silica crusts, rip-up clasts, centimeter-scale teepee structures, and/or pronounced erosional relief are termed high-frequency sequences. Those bounded by marine flooding surfaces are defined as parasequences. Thusly defined, the Bridal Veil Limestone is divided into 25 high-frequency sequences designated BVL-1 through BVL-25. Overall, two distinct sets of high-frequency sequences may be observed in the Bridal Veil Limestone. Sequences comprising the lower half of the formation (BVL-1 through BVL-12) are thicker, muddier, and less sand-prone than sequences in the upper half of the formation (BVL-13 through BVL-25), indicating an overall change in oxygenation, depositional texture, and accommodation upward in the section. Tracing of key beds and surfaces between the Thorpe Hills, Lake Mountain, and the Wasatch Range (spanning a distance greater than 50 miles) reveals that deposition was remarkably uniform across the southeastern part of the Oquirrh basin which we herein designate the Bridal Veil sub-basin and distinct from coeval formations in the southern Oquirrh basin, Ely basin, and Wyoming shelf. Mudstone and wackestone textures comprise a large portion of the formation by volume. Grain-rich carbonates are almost exclusively heterozoan in composition, indicating that the sub-basin was subphotic to aphotic through Early Pennsylvanian time.
222

High-frequency Sequences within the Lower Mississippian Allensville Member, Logan Formation, South-central Ohio

Klopfenstein, Trey 01 October 2018 (has links)
No description available.
223

The Last Stand of the Great American Carbonate Bank: Tectonic Activation of the Upper Ordovician Passive Margin in Eastern North America

Cornell, Sean Richard January 2008 (has links)
No description available.
224

The Role of Cenozoic Oceanic Plateau Collision in the Tectonic Growth of Western North America

Erin Elizabeth Donaghy (18243379) 15 April 2024 (has links)
<p dir="ltr">This dissertation uses a multidisciplinary basin analysis approach to document the sedimentary, structural, and volcanic response to Cenozoic oceanic plateau collision and translation along the northwestern Cordillera. During this time, two fragments of oceanic plateau accreted in the Pacific Northwest (Siletzia terrane) and in southeastern Alaska (Yakutat terrane). My research aims to test if the Siletzia and Yakutat terranes have an early shared history as the same spreading ridge-centered plateau in the Pacific Northwest and constrain timing of breakup and translation of the Yakutat terrane to southeastern Alaska. Chapter 2 focuses on development of a new U-Pb zircon geochronology technique to aid in a more accurate and precise understanding of sediment routing systems. The goal of developing this technique is to utilize it in pinpointing the source regions along the northwestern Cordillera supplying sediment to the basin on the Yakutat terrane as it made its northward journey to southeastern Alaska. Chapter 3 focuses on creating a regional chronostratigraphy for deep-marine Cenozoic sedimentary and volcanic rocks of the peripheral rock sequence on the northern Olympic Peninsula in Washington. These sedimentary rocks directly overlie the Siletzia plateau and record basin evolution before, during, and following its collision to the continental margin. Chapter 4 uses detailed lithofacies mapping and U-Pb geochronology of metasedimentary and volcanic rocks in the Olympic subduction complex to document the structural response to seamount subduction in the Eocene. Seamount subduction began shortly after collision of the Siletzia oceanic plateau to the Pacific Northwest and played a critical role in development of the early forearc region and Ancestral Cascades arc. Chapter 5 compares the lowermost sedimentary and geochronologic basin record on both Siletzia and Yakutat terranes to test if they have an early shared history in the Pacific Northwest.</p>
225

Application of Growth Strata and Detrital-Zircon Geochronology to Stratigraphic Architecture and Kinematic History

Barbeau, David Longfellow Jr. January 2003 (has links)
Growth strata analysis and detrital-zircon geochronology are useful applications of stratigraphy to tectonic problems. Whereas both tools can contribute to kinematic analyses of supracrustal rock bodies, growth strata are also useful for analyzing the influence of tectonics on stratigraphic architecture. This study reports: 1) a conceptual model for growth strata development; 2) stratigraphic and kinematic analyses of growth strata architectures from growth structures in southeastern Utah, the Gulf of Mexico, and northeastern Spain; and 3) the detrital-zircon geochronology of the Salinian block of central coastal California. Kinematic sequence stratigraphy subdivides growth strata into kinematic sequences that are separated by kinematic sequence boundaries. Kinematic sequences can be further partitioned into kinematic domains based on the termination patterns of strata within a kinematic sequence. Salt- related fluvial growth strata from the Gulf of Mexico and southeastern Utah contain stratigraphic architectures that are unique to different kinematic domains. Offlap kinematic domains contain fluvial strata indicative of high slopes, low accommodation rates, and strong structural influence on paleocurrent direction. Onlap kinematic domains contain fluvial strata indicative of moderate slopes, high accommodation rates, and decreased structural influence on paleocurrent direction. The stratigraphic architecture of alluvial -fan thrust -belt growth strata in northeastern Spain does not display a marked correlation with kinematic domain, and is most easily interpreted using existing models for autocyclic alluvial -fan evolution. Detrital- zircon (U -Pb) geochronologic data from basement and cover rocks of Salinia suggest that Salinia originated along the southwestern margin of North America, likely in the vicinity of the Mojave Desert. The presence of Neoproterozoic and Late Archean detrital zircons in Salinian basement rocks also suggest that Salinian sediments were recycled from miogeoclinal sediments of the western margin of North America.
226

Faciès, architecture et diagenèse des carbonates du Jurassique moyen et supérieur dans la chaîne du sud-ouest Gissar (Ouzbékistan) / Facies, architecture and diagenesis of middle to upper Jurassic carbonates in the southwestern Gissar range (Uzbekistan)

Carmeille, Mehdi 09 November 2018 (has links)
Cette étude transdisciplinaire incluant sédimentologie, stratigraphie séquentielle, chimiostratigraphie, et géochimie organique et inorganique, examine la série carbonatée du Jurassique moyen-supérieur dans la chaîne du sud-ouest Gissar. Cette série représente l’affleurement le plus complet de la marge nord du Bassin d’Amu-Darya, une province gazière majeure d’Asie Centrale. La production de carbonates commence au début du Callovien, lors d’un ralentissement de la subsidence tectonique régionale associé à un réchauffement climatique. Un changement majeur dans la production carbonatée et la configuration de la plate-forme est enregistré à la fin du Callovien. Ce changement se caractérise par le passage (i) d’une rampe carbonatée avec un gradient proximal-distal bien contrasté du Callovien à (ii) un lagon à faciès péritidaux probablement protégé par des récifs de grande dimension à l’Oxfordien. La surface stratigraphique séparant ces deux séquences est interprétée comme une surface d'émersion régionale, enregistrant une chute du niveau marin entraînée par la tectonique et le climat. Durant la partie terminale de l’Oxfordien moyen, un ou plusieurs bassins intrashelfs sont localisés au sud-ouest de la plate-forme carbonatée. Des carbonates fins nodulaires ou laminés se déposent dans des eaux stratifiées, légèrement hypersalées et anoxiques à dysoxiques, où des tapis microbiens produisent de la matière organique et des carbonates. Ces faciès enregistrent l’initiation de la restriction du Bassin d’Amu Darya, qui se poursuit avec la progradation d’une sabkha et le dépôt de séries anhydritiques et salifères. La comparaison des séries sédimentaires met en évidence des évènements stratigraphiques communs entre le sud-ouest Gissar et les autres bassins des marges nord téthysienne et sud téthysienne : initiation de la plate-forme carbonatée, excursions isotopiques du carbone, âge et mode de formation des roches mères organiques (etc.), impliquant des contrôles climatiques et/ou tectoniques à grande échelle. L’étude pétrographique et géochimique de la diagenèse des carbonates révèle une paragenèse complexe. Certains faciès sont influencés par la fabrique sédimentaire lors de la diagenèse précoce. La succession des phases diagénétiques est reliée à la stratigraphie et à la subsidence des carbonates. Après leur dépôt, les sédiments de la série du Kugitang ont été enfouis à plus de 2 km de profondeur. Des phases liées à des fluides chauds et possiblement à la réduction thermochimique des sulfates se mettent en place durant la Mésogenèse. Finalement, les données stratigraphiques à haute résolution obtenues sur les affleurements du sud-ouest Gissar sont utilisées pour aider à la prédiction de la répartition des réservoirs d’hydrocarbures en subsurface du Bassin d’Amu-Darya. / This transdisciplinary study including sedimentology, sequence stratigraphy, chemostratigraphy, and organic and inorganic geochemistry examines the Middle-Upper Jurassic carbonates series located in the southwestern Gissar range. These carbonates, also known as the Kugitang series, represent the most complete outcrop of the northern margin of the Amu-Darya Basin, a gas-producing province of Central Asia. Carbonate production begins in the late Early Callovian during a regional slowing of the tectonic subsidence, coeval with a climate warming. A major change in the carbonate production and platform configuration is recorded at the end of the Callovian: (i) a carbonate ramp with a well-contrasted proximal-distal gradient develops during the Lower to Middle or Upper Callovian. It is overlain by (ii) a vast low energy lagoon dominated by peritidal facies, probably protected by large reefs, during the Lower and Middle Oxfordian. The stratigraphic surface separating the two depositional sequences is associated with a hiatus (Upper Callovian-Lower Oxfordian) and interpreted as a regional exposure surface recording a sea-level drop caused by tectonics and/or climate. During the Middle Oxfordian, one or several intrashelf basins develop southwestwards of the studied carbonate platform. Laminated and nodular carbonates rich in organic matter predominate in these basins. They are interpreted to have formed through the mineralization of microbial mats colonizing the stratified, slightly hypersaline, anoxic to dysoxic basin floor. Large scale reefs may have favored the isolation of these basins. These deposits record the initiation of the tectonic isolation of the Amu Darya Basin, which culminates with the progradation of a large-scale sabkha and the deposition of a thick anhydrite and salt series. The comparison of stratigraphic series highlights common events in several basins of the northern Tethyan margin, but also with the Arabian Plate: initiation of the carbonate platform, carbon isotope excursions, age and depositional conditions of organic-matter rich rocks, etc. The petrography and geochemistry of carbonates reveal a complex diagenetic history. Some facies are strongly controlled by the sedimentary fabric. The diagenetic succession is tentatively linked with the stratigraphy and the subsidence history. Following deposition, the Kugitang series was buried at more than 2 km. Some cements are interpreted to have formed through the circulation of hot fluids in the rocks during the mesogenesis and possibly due to thermochemical sulfate reduction, especially in the Callovian Sequence. Finally, the high-resolution stratigraphy established in this study is used to help improving the prediction of carbonate reservoirs in the subsurface Amu Darya Basin.
227

Sequence stratigraphic interpretation methods for low-accommodation, alluvial depositional sequences: applications to reservoir characterization of Cut Bank field, Montana

Ramazanova, Rahila 15 May 2009 (has links)
In South Central Cut Bank Sand Unit (SCCBSU) of Cut Bank field, primary production and waterflood projects have resulted in recovery of only 29 % of the original oil in place from heterogeneous, fluvial sandstone deposits. Using highresolution sequence stratigraphy and geostatistical analysis, I developed a geologic model that may improve the ultimate recovery of oil from this field. In this study, I assessed sequence stratigraphic concepts for continental settings and extended the techniques to analyze low-accommodation alluvial systems of the Cut Bank and Sunburst members of the lower Kootenai formation (Cretaceous) in Cut Bank field. Identification and delineation of five sequences and their bounding surfaces led to a better understanding of the reservoir distribution and variability. Recognition of stacking patterns allowed for the prediction of reservoir rock quality. Within each systems tract, the best quality reservoir rocks are strongly concentrated in the lowstand systems tract. Erosional events associated with falling baselevel resulted in stacked, communicated (multistory) reservoirs. The lowermost Cut Bank sandstone has the highest reservoir quality and is a braided stream parasequence. Average net-to-gross ratio value (0.6) is greater than in other reservoir intervals. Little additional stratigraphically untapped oil is expected in the lowermost Cut Bank sandstone. Over most of the SCCBSU, the Sunburst and the upper Cut Bank strata are valley-fill complexes with interfluves that may laterally compartmentalize reservoir sands. Basal Sunburst sand (Sunburst 1, average net-to-gross ratio ~0.3) has better reservoir quality than other Sunburst or upper Cut Bank sands, but its reservoir quality is significantly less than that of lower Cut Bank sand. Geostatistical analysis provided equiprobable representations of the heterogeneity of reservoirs. Simulated reservoir geometries resulted in an improved description of reservoir distribution and connectivity, as well as occurrences of flow barriers. The models resulting from this study can be used to improve reservoir management and well placement and to predict reservoir performance in Cut Bank field. The technical approaches and tools from this study can be used to improve descriptions of other oil and gas reservoirs in similar depositional systems.
228

Middle-Hauterivian to Lower-Campanian sequence stratigraphy and stable isotope geochemistry of the Comanche platform, south Texas

Phelps, Ryan Matthew, 1982- 11 July 2012 (has links)
Carbonate platforms contain a wealth of information regarding the changing biota, sea level, ocean-chemistry, and climate of the Cretaceous Period. The Comanche platform of the northern Gulf of Mexico represents a vast, long-lived carbonate system that extended from west Texas through the Florida panhandle. In central and south Texas, excellent outcrops and an extensive suite of subsurface data provide an opportunity to document the evolution of this system, from the shoreline to the shelf-margin and slope. This study examines the changing facies, platform morphologies, and shelf-margin architectures of the mixed carbonate-siliciclastic, middle-Hauterivian to lower-Campanian interval. Stratigraphic results are integrated with stable-isotope geochemistry to document the detrimental effects of oceanic anoxic events on the carbonate platform. Seven second-order, transgressive-regressive supersequences of 3-14 Myr duration are defined in south Texas using sequence stratigraphic analysis of shelf-interior facies successions. Second-order supersequences are subdivided into several third-order depositional sequences of 1-3 Myr duration. In these sequences, facies proportions and stratal geometries of the shelf-interior are found to be the result of changing platform morphology and temporal evolution from distally-steepened ramp to rimmed-shelf depositional profiles. Shelf-margin trajectories, stratigraphic architectures, and facies proportions are a function of long-term accommodation trends expressed in second-order supersequences. These characteristics are modified by lateral variability in the underlying structural/tectonic setting and localized syndepositional faulting. The stratigraphic equivalents of oceanic anoxic events 1a, 1b, 1d, 2, and 3 are documented in the Cretaceous section of south Texas. These oceanic anoxic events coincided with maximum flooding zones of supersequences and are linked to carbonate platform drowning events on four separate occasions. The occurrence of oceanic anoxic events is found to be a fundamental driver of carbonate platform morphology, faunal composition, and facies evolution in transgressive-regressive supersequences of the northern Gulf of Mexico. / text
229

Η ιζηματολογική εξέλιξη της λεκάνης της Ιονίου ζώνης από το Τριαδικό έως το Ηώκαινο και η πιθανή σύνδεση τους με πεδία υδρογονανθράκων σε περιοχές του κεντρικού τμήματος της λεκάνης / The sedimentological evolution of the Ionian basin during Triassic to Eocene and the possible existence of hydrocarbon plays in the central part of the basin.

Γκέτσος, Κοσμάς 22 June 2007 (has links)
Η περιοχή μελέτης καλύπτει ένα μέρος των ανθρακικών αποθέσεων της Κεντρικής και Εξωτερικής Ιόνιας ζώνης οι οποίες αποτέθηκαν από το Τριαδικό έως το Ηώκαινο. Γεωγραφικά οριοθετείται, κατά τον άξονα Ανατολή – Δύση, από τον εθνικό δρόμο Άρτας – Ιωαννίνων και το Ιόνιο Πέλαγος, και κατά Βορά – Νότο από νοητούς, παράλληλους προς τον Ισημερινό άξονες που διέρχονται από την Άρτα και την Ηγουμενίτσα. Η περιοχή βρίσκεται ανάμεσα στις συντεταγμένες 20ο 12΄ και 21ο 00΄ Ανατολικά, και 39ο 00΄ με 39ο 30΄ Βόρεια και καλύπτεται από τα ακόλουθα γεωλογικά φύλλα του Ι.Γ.Μ.Ε, κλίμακας 1:50.000: Άρτα, Καναλάκι, Πάργα, Θεσπρωτικό και Παραμυθιά. Από την μικροφασική ανάλυση και την ανάλυση φασικών ζωνών που προηγήθηκε σε συνδυασμό με την βιοχρονολόγηση εξάγεται το συμπέρασμα ότι κατά το Α.Τριαδικό αποτέθηκαν μικριτικοί και κατά θέσεις λιθοκλαστικοί ασβεστόλιθοι σε περιβάλλον υφαλοκρηπίδας περιορισμένης κυκλοφορίας. Από το Α.Τριαδικό και μέχρι το τέλος του Λιασίου αποτίθενται σε όμοιες περιβαλλοντικές συνθήκες grapestones, rudstones, floatstones και grainstones. Από το Λιάσιο και μέχρι το Σαντώνιο αποτίθενται mudstone – wackestone και σπανιότερα packstone σε περιβάλλον πρόσθιας κατωφέρειας έως και υφαλοκρηπίδας ανοιχτής θάλασσας. Από το Καμπάνιο έως το Πριαμπόνιο, όπου τοποθετείται και το τέλος της ανθρακικής ιζηματογένεσης στην Ιόνιο ζώνη, αποτίθενται εναλλαγές από mudstone – wackestone και floatstone – packstone σε περιβάλλον πρόσθιας κατωφέρειας και βαθύτερο όριο υφαλοκρηπίδας. Στρωματογραφικά οι αποθέσεις της περιοχής μελέτης αποτελούνται από τέσσερις συνολικά ακολουθίες 3ης τάξης, δύο χαμηλής στάθμης (LST), μία υψηλής στάθμης (HST) και μια επικλυσιγενής (TST). Ο συνολικός όγκος των μελετηθέντων ιζημάτων ανέρχεται σε 3064,796 χλμ3, καταλαμβάνοντας χρονικό διάστημα από το Ανώτερο Τριαδικό έως το Παλαιογενές, από τα όποια 1398,050 χλμ3 αποτελούνται από τους ασβεστόλιθους του Ιουρασσικού οι οποίοι λόγω της απουσίας το Ammonitico Rosso δεν διαχωρίζονται. Επιπλέον 796,777 χλμ3 αποτελούνται από τους ασβεστόλιθους της Βίγλας οι οποίοι μαζί με τις πελαγικές αποθέσεις του Μέσου – Άνω – Ιουρασσικού απαρτίζουν την πελαγική ακολουθία 2ης τάξης. Τέλος 449,921 χλμ3 και 420,048 χλμ3 ανήκουν στους ασβεστόλιθους το Α.Κρητιδικού και του Παλαιογενούς οι οποίοι απαρτίζουν την δεύτερη ακολουθία 3ης τάξης. Οι αποθέσεις του Τριαδικού λόγω του άγνωστου υποβάθρου τους και τις ευδιάλυτης φύσης τους δεν συμπεριλήφθηκαν στους υπολογισμούς όγκου. Από την μελέτη με ηλεκτρονικό μικροσκόπιο σάρωσης προέκυψε ότι διεργασίες όπως μικριτίωση, ανακρυστάλωση, προσαύξηση και νεομορφισμός του υλικού τσιμεντοποίησης είναι καθολικές για όλα τα δείγματα. Σε κάποια δείγματα παρατηρήθηκαν πυριτικά συσσωματώματα τα οποία συνδέονται με την δράση θειοβακτηριδίων. Επίσης στο σύνολο των δειγμάτων παρατηρήθηκε ασήμαντο από άποψη υδραυλικών χαρακτηριστικών μεσοκρυσταλλικό και μεσοκοκκώδες πορώδες. Το πιο σημαντικό πορώδες παρατηρήθηκε σε δείγματα wackestone του Παλαιογενούς το οποίο συνίσταται από πορώδες διαλυσιγενών καναλιών, βιοδιάτρησης και ενδοκοκκώδες παρουσιάζοντας αυξημένο ενδιαφέρον από άποψη υδροχωριτικότητας και διαπερατότητας. Από την μελέτη των αργιλικών ορυκτών προκύπτει ότι τα ιζήματα το Μέσου Ιουρασσικού βρέθηκαν σε στάδιο Μέσης διαγένεσης και σε θερμοκρασίες που δεν υπερέβησαν τους 100 0C. Τα μεταγενέστερα ιζήματα βρεθήκαν όπως αναμένονταν σε ζώνες ασθενέστερης διαγένεσης με αποκορύφωμα τα ιζήματα του Παλαιογενούς που βρέθηκαν μόνο στο στάδιο της πρώιμης διαγένεσης ή ρηχής ταφής. Οι συνθήκες διαγένεσης κρίνονται ανεπαρκής για την ωρίμανση και γένεση υδρογονανθράκων. Από τη ανάλυση σταθερών ισοτόπων και οργανικού άνθρακα εξάγεται το συμπέρασμα ότι κανένα από τα δείγματα που μελετήθηκαν δεν συνδέεται με κανένα τρόπο με μητρικό πέτρωμα υδρογονανθράκων. Επίσης από ανάλυση μάζας πετρώματος δεν μπορούν να εξαχθούν ασφαλή συμπεράσματα ως προς την θερμοκρασία που επικρατούσε στο περιβάλλον απόθεσης, λόγω των διαγενετικών αλλαγών. Όλα τα δείγματα που εξετάστηκαν έχουν δ τιμές μέσα στο εύρος των κανονικών πελαγικών αποθέσεων. Η υπό αμφισβήτηση παραδοχή ότι από τα παλαιότερα σε νεότερα πετρώματα το περιεχόμενο σταθερών ισοτόπων γίνεται ελαφρύτερο, δεν επιβεβαιώθηκε και επιπρόσθετα από τα αποτελέσματα τεκμηριώνεται η μη ορθότητα της παραδοχής. Το ποσοστό οργανικού άνθρακα καθορίζεται από τις οξειδωτικές ή αναγωγικές συνθήκες που επικρατούσαν και από τη δράση θειοβακτηριδίων και παραμένει εξαιρετικά χαμηλο στο σύνολο των δειγμάτων (<0,05 %). Η Ιόνιος ζώνη αναπτύχθηκε πάνω από ένα παθητικό περιθώριο με υπόβαθρο παλαιοζωικά μεταμορφωμένα πετρώματα τα οποία δεν έχουν επιφανειακές εμφανίσεις. Αρχικά και μετά από ηπειρωτική διάρρηξη αποτέθηκαν εβαποριτικά και ανθρακικά ιζήματα σε περιβάλλον περιορισμένης υφαλοκρηπίδας με εκτεταμένες και διάσπαρτες υπεράλμυρες λίμνες (sabkhas). Μετά από μία σύντομη περίοδο επιφανειακής έκθεσης η στάθμη της θάλασσας αυξήθηκε και αποτέθηκαν κανονικής αλμυρότητας ασβεστόλιθοι υφαλοκρηπίδας σε όλη τη διάρκεια του Λιασίου (Κ.Ιουρασσικό, κυρίως οι λεγόμενοι ασβεστόλιθοι ‘‘Παντοκράτορα’’). Στη συνέχεια και μέχρι το Σαντώνιο (Α.Κρητιδικό) αποτίθενται πελαγικοί ασβεστόλιθοι σε περιβάλλον υφαλοκρηπίδας ανοιχτής κυκλοφορίας με γεωμετρία ράμπας ίσης κλίσης (homoclinal ramp). Το περιβάλλον παραμένει ίδιο, με κάποιες μικρές τροποποιήσεις, όπως μεταβολή της κλίσης σε συνάρτηση με τη απόσταση από την ακτή και μικρή μείωση της στάθμης της θάλασσας, μέχρι το τέλος του Ηωκαίνου (Παλαιογενές) οπότε γίνεται μετάβαση σε κλαστική ιζηματογένεση. Από όλα τα δείγματα που μελετήθηκαν αυτά που δείχνουν να έχουν εκτεθεί σε θερμοκρασίες πάνω από 90-100 0C είναι ηλικίας Ιουρασσικού ή παλαιότερα. Στη περιοχή μελέτης όλα τα δείγματα που μελετήθηκαν έχουν περιεκτικότητα σε οργανικό υλικό μέχρι 0,05 % το οποίο είναι πολύ χαμηλότερο από το ελάχιστο απαιτούμενο 0,7 % για να είναι πιθανή ή γένεση υδρογονανθράκων. Επιπλέον οι τιμές δ του σταθερού ισοτόπου 13C απέχουν πολύ από τις τιμές -18 ‰ έως -27 ‰ οι οποίες χαρακτηρίζουν τα μητρικά πετρώματα υδρογονανθράκων. Για τους παραπάνω λόγους πιθανά μητρικά πετρώματα φαίνεται να είναι οι Τοάρσιας ηλικίας, λεγόμενοι “Κατώτεροι σχιστόλιθοι με Poseidonia”, και οι πλούσιες σε οργανικό υλικό παρενστρώσεις που βρίσκονται μέσα στα Τριαδικής ηλικίας ιζήματα. Σημαντικό είναι ότι καμία από τις παραπάνω αποθέσεις δεν έχουν επιφανειακή εμφάνιση στην περιοχή μελέτης. Ταμιευτήρια πετρώματα μπορεί να είναι είτε οι ημιπελαγικές αποθέσεις του Α.Κρητιδικού και του Παλαιογενούς είτε οι μεταηωκαινικές κλαστικές αποθέσεις. Ολοκληρώνοντας το ρόλο καλυμμάτων μπορούν να παίξουν τόσο οι πελαγικές αποθέσεις από το Μ.Ιουρασσικό έως το Κ.Κρητιδικό όσο και οι μεταηωκαινικές κλαστικές αποθέσεις. / PhD Thesis title is “The sedimentological evolution of the Ionian basin during Triassic to Eocene and the possible existence of hydrocarbon plays in the central part of the basin”. The main target of the study is to reveal, in every detail, the sedimentation pattern during the above mentioned time interval. The study area is located in western Greece (Fig. 1). The sediments of the Ionian basin were studied in fifty outcrops and a number of 300 samples were collected (Fig 2). Thin sections were prepared for all the samples and they were studied under polar microscopy. The samples were classified using Dunham’s (1965) classification chart. Afterwards, SMF and FZ, after Flugel (1972) and Wilson (1975), were determined. In addition, stable isotope analysis; clay mineral analysis, organic carbon analysis and micropaleontological study were contacted. The Triassic rocks crop out sparsely and only in signs due to their stratigraphic position, the oldest rocks, and their soluble nature. The outcrops are consisted of chaotic masses with no preferred orientation and no primary structures, like bedding (Getsos et al., 2004). Often they have suffered extensive dissolution and collapsing giving rise to the formation “Solution Collapse Breccias” (Pomoni-Papaioannou, 1980; Pomoni-Papaioannou, 1985; Karakitsios & Pomoni-Papaioannou 1998). Extensive outcrops characterize lower Jurassic sediments with great thickness, completely absence of bedding or other similar primary structure and abundant fragments and fragmentation effects. Karstification, calichification and pedogenesis are common. The sediments were studied in the following six different outcrops: T45, T5, T6, T30, T33, and T38. Samples were studied under polar microscope and their sedimentological and diagenetical pattern were revealed. The studied Early to Late Cretaceous Vigla’s formation appear as extensive outcrops of thin to medium bedded limestones with an average thickness of 200-400 m. Samples were collected from fifteen outcrops around the study area and they were studied under polar microscope. The results of the sedimentological analysis were further combined with the results of low resolution stable isotope analysis, organic carbon and clay mineral analysis. The Paleogene limestones appear as extensive outcrops consisted of intercalations of thin bedded pelagic limestones and medium to thick bedded coarse bioclastic – lithoclastic limestones. Their thickness varies between 180 and 440 m. Triassic. The studied sediments are contributed to four 3rd order sequences, two low stand systems tracts (LST), one of high stand systems tract (HST) and one transressive systems tract (TST). The total volume of studied sediments amounts in 3000 km3, occupying the Late Triassic – Paleogene time interval. The first LST has a duration of 45 million years and average thickness more than 3000 metres. It is consisted of the Triassic rocks and the Early Jurassic shallow shelf limestones, the so called “Pantokrator Limestones”. The HST is constituted of the Late Jurassic to Late Cretaceous (Santonian) pelagic limestones with an average thickness of 600 metres. The duration of the sequence is almost 80 million years. Between the above mentioned sequences the TST were deposited. The deposition took part during the Middle Jurassic and duration was almost 20 million years with a maximum thickness of no more than 200 metres. Finally the last LST sequence is constituted by the Late Cretaceous (Campanian) to Paleogene (Eocene) limestones with an average thickness of 400 m. and 45 million years duration. The study of samples under SEM has revealed a common diagenetic pattern. It is consisted of early diagenetic micritization and early diagenetic neomorphism and recrystallization. In a small number of samples pyrite was studied. Usually pyrite is the product of sulphate reduction bacteria. The microporosity is mainly intecrystall and it has no importance for reservation and fluid circulation. The most important porosity was observed in samples consisted of wackestones and packstones Paleogene in age and it was consisted of solution channels, borings and intraparticle. Clay mineral analysis have revealed the Middle Jurassic sediments suffered the Middle diagenesis stage and their temperatures did not exceed 100 0C. The newer sediments reached up to the Middle stage as well with only exception the Paleogene sediments which suffered only Early diagenesis or “Shallow burial stage”. The diagenetical conditions are insufficient for the maturation and genesis of hydrocarbons. Oxygen and carbon stable isotopes analysis and organic carbon analysis has revealed that the studied sediments do not constitute oil source rocks or reservoirs. The obtained δ values of the studied sediments are within the -+ 4 ‰ which is the characteristic of the normal pelagic limestones. The organic carbon analysis was contacted with the wet oxidation method. The organic carbon content of the whole sediments is very low and do not exceeds the 0.05% value. The Ionian basin was developed on a Mesozoic passive margin. The basement is studied only in signs in nearby areas (Albania) and it is consisted of metamorphosed Palaeozoic rocks. The first sediments deposited were carbonates and sulfates. The depositional environment was restricted circulation shelf and tidal flats and evaporates on sabkhas – Salinas. During the transgressive phase the environment was deep shelf margin and it was part of a homoclinal ramp system (middle ramp). The homoclinal ramp was covered until the initialization of the deposition of the last LST phase when the environment was transformed into a distally steepened ramp or rimmed shelf. Afterwards the carbonate sedimentation came to an end and the clastic sedimentation was established in a foreland basin. The studied sediments with depositional age after the Middle Jurassic have been exposed in temperature much less than 100 0C and as a consequence they are immature. The older sediments have suffered diagenetical temperature almost 100 0C or more and as consequence they are mature. The organic carbon content, as have already been mentioned, is maximum 0.05 %. This value is much lower than minimum hydrocarbon source rock organic carbon content (0.7%). Furthermore the δ values of the carbon stable isotope are much heavier than the values -18 to -27 ‰ which are the typical values of the source rocks. Taking into account the above facts the possible source rocks of the studied area could be the Toarcian age “Lower Posidonia Shales” and the rich in organic matter clayey intercalation of Triassic age. These possible source rocks do not crop out anywhere in the study are. Potential reservoirs can be the hemipelagic LST sequence of Late Cretaceous – Paleogene age or the clastic post Eocene sediments. Potential seal rocks are the pelagic HST sequence of Middle Jurassic – Late Cretaceous limestone and the fine-grained post Eocene clastic sediments.
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The terraces of the Conway Coast, North Canterbury: Geomorphology, sedimentary facies and sequence stratigraphy

McConnico, Tim January 2012 (has links)
A basin analysis was conducted at the Conway Flat coast (Marlborough Fault Zone, South Island, New Zealand) to investigate the interaction of regional and local structure in a transpressional plate boundary and its control on basin formation. A multi-tiered approach has been employed involving: (i) detailed analysis of sedimentary deposits; (ii) geomorphic mapping of terraces, fault traces and lineaments; (iii) dating of deposits by 14C and OSL and (iv) the integration of data to form a basin-synthesis in a sequence stratigraphy framework. A complex thrust fault zone (the Hawkswood Thrust Fault Zone), originating at the hinge of the thrust-cored Hawkswood anticline, is interpreted to be a result of west-dipping thrust faults joining at depth with the Hundalee Fault and propagating eastwards. The faults uplift and dissect alluvial fans to form terraces along the Conway Flat coast that provide the necessary relief to form the fan deltas. These terrace/fan surfaces are ~9 km long and ~3 km wide, composite features, with their upper parts representing sub-aerial alluvial fans. These grade into delta plains of Quaternary Gilbert-style fan deltas. Uplift and incision have created excellent 3D views of the underlying Gilbert-style fan delta complexes from topsets to prodelta deposits. Erosive contacts between the Medina, Rafa, Ngaroma and modern Conway fan delta deposits, coupled with changes in terrace elevations allow an understanding of the development of multiple inset terraces along the Conway Flat coast. These terraces are divided into five stages of evolution based on variations in sedimentary facies and geomorphic mapping: Stage I involves the uplift of the Hawkswood Range and subsequent increased sedimentation rate such that alluvial fans prograded to the sea to form the Medina fan delta Terrace. Stage II began with a period of incision, from lowering sea level or changes in the uplift and sedimentation rate and continued with the deposition of the Dawn and Upham fan deltas. Stage III starts with the incision of the Rafa Terrace and deposition of aggradational terraces in the upper reaches. Stage IV initiated by a period of incision followed by deposition of estuarine facies at ~8ka and Stage V began with a period of incision and continues today with the infilling of the incised valley by the modern fan delta of the Conway River and its continued progradation. New dates from within the Gilbert-type fan deltas along the Conway Flat coast are presented, using OSL and 14C dating techniques. Faulting at the Conway Flat coast began ~ 94 ka, based on the development of the Medina Terrace fan delta with uplift rates ~1.38~1.42 m/ka. The interplay of tectonics and sea level fluctuations continued as the ~79 ka Rafa Terrace fan deltas were created, with uplift rates calculated at ~1.39 m/ka. Detailed 14C ages from paleoforest (~8.4-~6.4 ka) in the Ngaroma Terrace and from the mouths of smaller streams have established uplift rates during the Holocene ~1-3 m/ka, depending on sea level.

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