Provenance of the Lower Triassic Bunter Sandstone Formation: implications for distribution and architecture of aeolian vs. fluvial reservoirs in the North German Basin          下载免费PDF全文

Mette Olivarius  Rikke Weibel  Henrik Friis  Lars O. Boldreel  Nynke Keulen  Tonny B. Thomsen 《Basin Research》2017,29(Z1):113-130

Zircon U–Pb geochronometry, heavy mineral analyses and conventional seismic reflection data were used to interpret the provenance of the Lower Triassic Bunter Sandstone Formation. The succession was sampled in five Danish wells in the northern part of the North German Basin. The results show that sediment supply was mainly derived from the Ringkøbing‐Fyn High situated north of the basin and from the Variscan belt located south of the basin. Seismic reflection data document that the Ringkøbing‐Fyn High was a local barrier for sediment transport during the Early Triassic. Hence, the Fennoscandian Shield did not supply much sediment to the basin as opposed to what was previously believed. Sediment from the Variscan belt was transported by wind activity across the North German Basin when it was dried out during deposition of the aeolian part of the Volpriehausen Member (lower Bunter Sandstone). Fluvial sand was supplied from the Ringkøbing‐Fyn High to the basin during precipitation events which occurred most frequently when the Solling Member was deposited (upper Bunter Sandstone). Late Neoproterozoic to Carboniferous zircon ages predominate in the Volpriehausen Member where the dominant age population with a peak age of 337 Ma corresponds to the culmination of Variscan high‐grade metamorphism, whereas a secondary age population with a peak at 300 Ma matches the timing of volcanism and magmatism at the Carboniferous/Permian boundary in the northern Variscan belt. Parts of the basement in the Ringkøbing‐Fyn High were outcropping during the Early Triassic and zircon ages similar to this Mesoproterozoic basement are present in the Bunter Sandstone. The heavy mineral assemblage of the Solling Member is uniform and has a high garnet content compared to the contemporaneous sediments in the Norwegian‐Danish Basin and in the southern part of the North German Basin. This finding confirms that a local source in the Ringkøbing‐Fyn High supplied most of the fluvial sediment in the northern part of the North German Basin. The northernmost part of the Bunter Sandstone is situated on a platform area that is separated from the basin area by a broad WNW–ESE‐oriented fault zone. The most promising reservoir in the basin area is the aeolian Volpriehausen Member since the sandstone has a wide lateral distribution and a constant thickness. The alluvial to ephemeral fluvial Solling Member may be a good reservoir in the platform area and marginal basin area, but the complex sand‐body architecture makes it difficult to predict the reservoir quality.  相似文献   

On the maximum width of oil stringers under hydrodynamic flow conditions     

R. O. Thomsen  I. Lerche 《Mathematical Geology》1996,28(3):331-339

An analysis is presented of the maximum thickness of a stationary buoyant oil-mass, trapped under an angled incline, when subjected to hydrodynamic, surface tension and buoyancy forces. For high water-flow speeds down the aquifer, with upward buoyancy forces dominantly combating hydrodynamic pressure, it is shown that the maximum oil thickness occurs at about 60% of the length of the oil stringer measured from the upward end. The length of the oil stringer then is roughly proportional to the square root of the oil-mass contained, as is the maximum thickness. For low water-flow speeds, in which buoyancy and surface tension are dominantly balanced (with only lesser contributions from hydrodynamic pressure), the oil length is effectively constant, whereas the maximum thickness grows proportionately to the 3/4 power of the contained oil mass at low oil masses, and proportionately to the oil mass at high mass values. As the water-flow velocity increases, the shaping of the oil stringer shifts from the small bubble form to the long oil stringer form. Analytic formulae are given to provide approximate methods from which to estimate oil and gas accumulations under more complex conditions.  相似文献   

Atlantic surface water inflow to the Nordic seas during the Pleistocene–Holocene transition (mid–late Younger Dryas and Pre‐Boreal periods, 12 450–10 000 a BP)     

Tine L. Rasmussen  Erik Thomsen  Tove Nielsen  Stefan Wastegård 《第四纪科学杂志》2011,26(7):723-733

The inflow of Atlantic Water to the Nordic seas from mid–late Younger Dryas to earliest Holocene (12 450–10 000 a BP) is reconstructed on the basis of a high‐resolution core (LINK14) from 346 m water depth on the east Faroe shelf. We have analysed the distribution of planktic and benthic foraminifera, stable isotopes and ice‐rafted debris (IRD), and calculated absolute temperatures and salinities by transfer functions. During the investigated time period there was almost continuous inflow of Atlantic Water to the Nordic seas. Deposition of IRD during the mid–late Younger Dryas and Pre‐Boreal coolings indicates the presence of melting icebergs and that summer sea surface temperatures were low. The east–west temperature gradient across the Faroe–Shetland Channel was much steeper than today. The cold conditions around the Faroe Islands are attributed to stronger East Greenland and East Icelandic currents than at present. The near‐continuous inflow of Atlantic Water is consistent with published evidence suggesting that deep convection took place in the Nordic seas, although the convection sites probably had shifted to a more easterly position than at present. Around the time of deposition of the Saksunarvatn Tephra c. 10 350 a BP, sea surface temperatures increased to the present level. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Ground Water Remediation Using an Extraction, Treatment, and Recharge System     

Kurt O. Thomsen  Majid A. Chaudhry  Kostas Dovantzis  Ronald R. Riesing 《Ground Water Monitoring & Remediation》1989,9(1):92-99

Ground water remediation of volatile organic compound (VOC) contamination at a site in Michigan was initiated as a result of a consent agreement between the Michigan Department of Natural Resources (MDNR) and the responsible party. Under the direction of the MDNR, the responsible party conducted a remedial investigation/feasibility study using federal guidelines to define the extent of contamination at the site and to select a response action for site remediation. The selected alternative included a combination of ground water extraction, treatment, and recharge, and soil flushing. The extraction system withdraws ground water from various depths in heavily contaminated areas. The ground water is treated using an air stripper. A spray distribution system spreads effluent from the stripper over a recharge basin constructed over the most contaminated areas. Additional contaminant removal is achieved by volatilization from the spray and percolation through the gravel bed. Recharge water moves downward through the contaminated soils, thus flushing residual soil contaminants. The initial operating data demonstrated that the system can effectively remove trichloroethylene (TCE) from ground water (approximately 95 percent overall removal efficiency). The annualized capital and operation and maintenance (O & M) costs of the remedial action were estimated for several operating periods (15, 20, and 30 years).  相似文献