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Stratigraphic Sections (stratigraphic + section)
Selected AbstractsDEVONIAN CARBONATES OF THE NIGEL PEAK AREA, ROCKY MOUNTAINS, CANADA: A FOSSIL PETROLEUM SYSTEM?JOURNAL OF PETROLEUM GEOLOGY, Issue 3 2008J. Köster In this study we report on Devonian (Frasnian , Famennian) limestones and dolostones exposed near Nigel Peak in the Main Ranges of the Canadian Rocky Mountains. These carbonates are a proximal facies of the Southesk-Cairn Carbonate Complex. The investigated strata are stratigraphically equivalent to the oil- and gas bearing Nisku Formation in the subsurface of the Western Canada Sedimentary Basin, about 300 km to the east. The rocks were investigated by polarisation and cathodoluminescence microscopy, total organic carbon analysis, Rock-Eval pyrolysis, solid bitumen reflectance measurements, gas chromatography and fluid inclusion analysis. Thin section analyses showed that silt-grade quartz and saddle dolomite increase upward from the base of the stratigraphic section, and that porosities are generally low. This is due to reduction of pore space due to early cementation and extensive dolomitization. Cathodoluminescence identified up to four generations of calcite cements. TOC values ranged from 0.2 to 2.4 %. Rock-Eval pyrolysis of carbonate samples resulted in measurable S1 peaks but not S2 peaks, indicating that there was no residual petroleum generation potential. Organic petrographic analyses identified dispersed kerogen and migrabitumen, and calculated vitrinite reflectance values were around 4 % on average which implies peak temperatures of 234,262 °C (due to deep burial) or 309,352 °C (due to short term hydrothermal heating). Fluid inclusion data indicates at least one pulse of hot fluids with elevated homogenization temperatures of > 300 °C, and this may explain the high thermal maturity of the studied rocks. [source] Propagation of orographic barriers along an active range front: insights from sandstone petrography and detrital apatite fission-track thermochronology in the intramontane Angastaco basin, NW ArgentinaBASIN RESEARCH, Issue 1 2006Isabelle Coutand ABSTRACT The arid Puna plateau of the southern Central Andes is characterized by Cenozoic distributed shortening forming intramontane basins that are disconnected from the humid foreland because of the defeat of orogen-traversing channels. Thick Tertiary and Quaternary sedimentary fills in Puna basins have reduced topographic contrasts between the compressional basins and ranges, leading to a typical low-relief plateau morphology. Structurally identical basins that are still externally drained straddle the eastern border of the Puna and document the eastward propagation of orographic barriers and ensuing aridification. One of them, the Angastaco basin, is transitional between the highly compartmentalized Puna highlands and the undeformed Andean foreland. Sandstone petrography, structural and stratigraphic analysis, combined with detrital apatite fission-track thermochronology from a ,6200-m-thick Miocene to Pliocene stratigraphic section in the Angastaco basin, document the late Eocene to late Pliocene exhumation history of source regions along the eastern border of the Puna (Eastern Cordillera (EC)) as well as the construction of orographic barriers along the southeastern flank of the Central Andes. Onset of exhumation of a source in the EC in late Eocene time as well as a rapid exhumation of the Sierra de Luracatao (in the EC) at about 20 Ma are recorded in the detrital sediments of the Angastaco basin. Sediment accumulation in the basin began ,15 Ma, a time at which the EC had already built sufficient topography to prevent Puna sourced detritus from reaching the basin. After ,13 Ma, shortening shifted eastward, exhuming ranges that preserve an apatite fission-track partial annealing zone recording cooling during the late Cretaceous rifting event. Facies changes and fossil content suggest that after 9 Ma, the EC constituted an effective orographic barrier that prevented moisture penetration into the plateau. Between 3.4 and 2.4 Ma, another orographic barrier was uplifted to the east, leading to further aridification and pronounced precipitation gradients along the mountain front. This study emphasizes the important role of tectonics in the evolution of climate in this part of the Andes. [source] Pendleian (early Serpukhovian) marine carbonates from SW Spain: sedimentology, biostratigraphy and depositional modelGEOLOGICAL JOURNAL, Issue 1 2004P. Cózar Abstract The San Antonio,La Juliana tectono-sedimentary unit contains the only Namurian marine carbonates in the southwestern part of the Iberian Peninsula. The analysis of this unit is fundamental in understanding the sedimentary evolution and tectonic movements which operated during the Namurian in this area. Using foraminifera the succession has been assigned to two biozones (Zones 17 and 18), both occurring in the Pendleian (early Namurian). Seven stratigraphic sections have been analysed: San Antonio, Burjadillo, Lavadero de la Mina, Cornuda, Lozana, Caridad and Via Crucis. The stratigraphic succession of the San Antonio,La Juliana Unit consists of olistolites in the basal part, with common debris-flow deposits (mainly of carbonates, with minor siliciclastic rocks), and turbidites, all of them embedded in shales. These rocks, interpeted as slope deposits, pass up into shallow-water platform facies, with sediments characteristic of the inner platform and tidal flats. Above these rocks, terrigenous deltaic deposits occur. Thus, the stratigraphic sections show an overall shallowing-upward trend. The isolation of some outcrops, and the duplication and absence of some parts of the stratigraphic succession are explained by tectonic movements. Overall, tectonic factors seem to be the main control rather than glacio-eustatic or autocyclic processes, and sedimentation took place in a strike-slip regime. Copyright © 2004 John Wiley & Sons, Ltd. [source] Palaeomagnetism, rock magnetism and geochemistry of Jurassic dykes and correlative redbeds, Massachusetts, USAGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2000Suzanne A. McEnroe Jurassic diabase dykes, sills and sedimentary rocks in central Massachusetts were sampled for palaeomagnetic analysis. The intrusions fall into three of the chemical types for eastern North American diabases: high TiO2 quartz-normative (Holden); low TiO2 quartz-normative (Ware); and high Fe2O3 quartz-normative (Pelham,Loudville). The characteristic magnetizations in the majority of intrusive samples unblock between 550 °C and 580 °C, with Curie temperatures in a discrete interval between 556 °C and 580 °C. The dominant remanence in the diabases is carried by C1 to C3 oxidation-exsolved titanomagnetite occurring as euhedral grains, as fine needles or dust in the matrix, as devitrifed glass, and as fine magnetite-ilmenite-silicate symplectite. In some dykes, titanomagnetite was further modified by deuteric oxidation during post-magmatic cooling, creating titanomaghematite and/or a granulation of the magnetite. Palaeopoles for the three diabase groups are: Holden, 60.1°N, 80.5°E, A95 = 4.1°; Ware, 73.5°N, 85.8°E, A95 = 3.9°; and Pelham,Loudville, 65.3°N, 95.6°E, A95 = 4.1°. These data are combined with samples from two stratigraphic sections through the Early Jurassic part of the Sugarloaf Formation in the Deerfield Basin representing both fine-grained mudstones and coarser arkoses. These haematite-dominated rocks reveal several components of magnetization, a steep recent field direction, an intermediate secondary diagenetic overprint direction in both mudstones and arkoses, and a high-temperature shallow primary direction found only in the mudstones. Palaeopoles for the Sugarloaf Formation are: mudstones, 57.7°N, 81.3°E, A95 = 9.1°; and arkoses, 75.1°N, 131.6°E, A95 = 5.9°. Based on the new palaeomagnetic data reported here, the North American plate in the Middle Jurassic was at higher palaeolatitudes than indicated by the present North American apparent polar wander path. [source] Miocene to Recent exhumation of the central Himalaya determined from combined detrital zircon fission-track and U/Pb analysis of Siwalik sediments, western NepalBASIN RESEARCH, Issue 4 2006Matthias Bernet ABSTRACT Fission-track (FT) analysis of detrital zircon from synorogenic sediment is a well-established tool to examine the cooling and exhumation history of convergent mountain belts, but has so far not been used to determine the long-term evolution of the central Himalaya. This study presents FT analysis of detrital zircon from 22 sandstone and modern sediment samples that were collected along three stratigraphic sections within the Miocene to Pliocene Siwalik Group, and from modern rivers, in western and central Nepal. The results provide evidence for widespread cooling in the Nepalese Himalaya at about 16.0±1.4 Ma, and continuous exhumation at a rate of about 1.4±0.2 km Myr,1 thereafter. The ,16 Ma cooling is likely related to a combination of tectonic and erosional activity, including movement on the Main Central thrust and Southern Tibetan Detachment system, as well as emplacement of the Ramgarh thrust on Lesser Himalayan sedimentary and meta-sedimentary units. The continuous exhumation signal following the ,16 Ma cooling event is seen in connection with ongoing tectonic uplift, river incision and erosion of lower Lesser Himalayan rocks exposed below the MCT and Higher Himalayan rocks in the hanging wall of the MCT, controlled by orographic precipitation and crustal extrusion. Provenance analysis, to distinguish between Higher Himalayan and Lesser Himalayan zircon sources, is based on double dating of individual zircons with the FT and U/Pb methods. Zircons with pre-Himalayan FT cooling ages may be derived from either nonmetamorphic parts of the Tethyan sedimentary succession or Higher Himalayan protolith that formerly covered the Dadeldhura and Ramgarh thrust sheets, but that have been removed by erosion. Both the Higher and Lesser Himalaya appear to be sources for the zircons that record either ,16 Ma cooling or the continuous exhumation afterwards. [source] Gastropods Associated with Fossil Traces from Yacoraite Formation (Maastrichtian-Danian), and its Paleoenvironmental Significance, Jujuy, Northwestern ArgentinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2009Carlos A. CÓNSOLE GONELLA Abstract: We present results tending to characterize the new records of invertebrates from the Yacoraite Formation (Maastrichtian-Danian). The fossils reported come from two stratigraphic sections exposed in the surroundings of Maimará and Jueya, province of Jujuy, northwestern Argentina. The selection was based on geological and paleontological evidence. The recovered fossils include gastropods and invertebrate fossil traces, including Planolites, Skolithos and Gastrochanoelites ichnogenus. As result of our review, we discussed the possibility of assigning the analyzed gastropods to the family Zygopleuridae (gene. et. sp. indet.), as an approximation to the taxonomic resolution of this fossil fauna. The trace fossils were assigned to the archetypical Glossifungites ichnofacies. The study of the fossil assemblage allowed us to define a shallow depositional environment, characteristic of a marine context with high-energy conditions. [source] Cenozoic Exhumation and Thrusting in the Northern Qilian Shan, Northeastern Margin of the Tibetan Plateau: Constraints from Sedimentological and Apatite Fission-Track DataACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2009Zhaojie GUO Abstract: The Qilian Shan lies along the northeastern edge of the Tibetan Plateau. To constrain its deformation history, we conducted integrated research on Mesozoic,Cenozoic stratigraphic sections in the Jiuxi Basin immediately north of the mountain range. Paleocurrent measurements, sandstone compositional data, and facies analysis of Cenozoic stratigraphic sections suggest that the Jiuxi Basin received sediments from the Altyn Tagh Range in the northwest, initially in the Oligocene (,33 Ma), depositing the Huoshaogou Formation in the northern part of the basin. Later, the source area of the Jiuxi Basin changed to the Qilian Shan in the south during Late Oligocene (,27 Ma), which led to the deposition of the Baiyanghe Formation. We suggest that uplift of the northern Qilian Shan induced by thrusting began no later than the Late Oligocene. Fission-track analysis of apatite from the Qilian Shan yields further information about the deformation history of the northern Qilain Shan and the Jiuxi Basin. It shows that a period of rapid cooling, interpreted as exhumation, initiated in the Oligocene. We suggest that this exhumation marked the initial uplift of the Qilian Shan resulting from the India,Asia collision. [source] | ||||||||||