The Pleistocene evolution of the East Antarctic Ice Sheet in the Prydz bay region: stable isotopic evidence from ODP Site 1167     

Kevin M. Theissen  Robert B. Dunbar  Alan K. Cooper  David A. Mucciarone  Dirk Hoffmann 《Global and Planetary Change》2003,39(3-4):227-256

Ocean Drilling Program Leg 188, Prydz Bay, East Antarctica is part of a larger initiative to explore the Cenozoic history of the Antarctic Ice Sheet through direct drilling and sampling of the continental margins. In this paper, we present stable isotopic results from Ocean Drilling Program (ODP) Site 1167 located on the Prydz Channel Trough Mouth Fan (TMF), the first Antarctic TMF to be drilled. The foraminifer-based δ¹⁸O record is interpreted along with sedimentary and downhole logging evidence to reconstruct the Quaternary glacial history of Prydz Bay and the adjacent Lambert Glacier Amery Ice Shelf System (LGAISS). We report an electron spin resonance age date of 36.9±3.3 ka at 0.45 m below sea floor and correlate suspected glacial–interglacial cycles with the global isotopic stratigraphy to improve the chronology for Site 1167. The δ¹⁸O record based on planktonic (Neogloboquadrina pachyderma (s.)) and limited benthic results (Globocassidulina crassa), indicates a trend of ice sheet expansion that was interrupted by a period of reduced ice volume and possibly warmer conditions during the early–mid-Pleistocene (0.9–1.38 Ma). An increase in δ¹⁸O values after 900 ka appears to coincide with the mid-Pleistocene climate transition and the expansion of the northern hemisphere ice sheet. The δ¹⁸O record in the upper 50 m of the stratigraphic section indicates as few as three glacial–interglacial cycles, tentatively assigned as marine isotopic stages (MIS) 16–21, are preserved since the Brunhes/Matuyama paleomagnetic reversal (780 ka). This suggests that there is a large unconformity near the top of the section and/or that there may have been few extreme advances of the ice sheet since the mid-Pleistocene climate transition resulting in lowered sedimentation rates on the Prydz Channel TMF. The stable isotopic record from Site 1167 is one of the few available from the area south of the Antarctic Polar Front that has been linked with the global isotopic stratigraphy. Our results suggest the potential for the recovery of useful stable isotopic records in other TMFs.  相似文献   

Evaluation of the relative roles of global versus local sedimentary controls on Middle to Late Pleistocene formation of continental margin strata,Canterbury Basin,New Zealand          下载免费PDF全文

Tania Villaseñor  John M. Jaeger  Kathleen M. Marsaglia  Greg H. Browne 《Sedimentology》2015,62(4):1118-1148

Determining the relative influence of eustasy versus local sedimentary processes on strata formation is a fundamental challenge in the study of continental margin stratigraphy. In this paper, the relative contribution of these factors on continental margin evolution during the Middle to Late Pleistocene is evaluated using samples from Integrated Ocean Drilling Program Expedition 317. Core‐logging, biostratigraphy and quantitative X‐ray diffraction mineralogy are used to delineate continental shelf sedimentary systems. Major lithological unconformities bound stratigraphic sequences that contain recurring compositional patterns and that resemble other examples of Middle to Upper Pleistocene sequences. However, a preliminary chronology suggests that sequence boundary formation cannot be linked ‘one to one’ with eustatic cycles and therefore these sequences can contain multiple ca 100 ka eustatic cycles. Smaller amplitude, higher frequency transitions in sediment composition are interpreted as stratigraphic sequences driven by more rapid perturbations in the interplay of accommodation and sediment supply; their stratigraphy is variable in time and across the shelf, suggesting a strong influence of local sedimentary forcing in their formation. Changes in sediment composition after the Middle Pleistocene Transition indicate that sediment transfer from onshore sources in the glaciated Southern Alps to the middle‐shelf occurred over a single 100 ka glacio‐eustatic cycle, with an additional 100 ka lag before the mineralogical signal was preserved on the outer‐shelf. This phenomenon is coincident with rapid shelf progradation in this basin, suggesting a causal relation between across‐shelf sediment transport and margin progradation. This is one of very few studies that provide insights at the core scale into the processes driving continental margin evolution during the Middle to Late Pleistocene. This work shows that compositional changes in mud‐dominated successions can lead to a sequence stratigraphic interpretation and the identification of high‐frequency sequences, which may not be possible using a conventional stratigraphic approach.  相似文献   

CJF-12型冲击反循环钻机在浅海施工工艺          下载免费PDF全文

张亚东  王玉吉 《山东国土资源》2007,23(2):48-49

在浅海岸边进行钻机作业,由于海平面水位不稳定,采用6BS反循环泵已不合适。在工作实践中,将原施工工艺改进为气举反循环,此方法不仅没有降低原钻机的施工性能,而且快捷、方便,经济效益显著。  相似文献   

用拉格朗日插值法求钻程坐标及其PC—1500程序     

陈昭明 《湖南地质》1989,8(3):71-74

传统方法绘制的钻程线投影图,往往成为较明显的折线。不符合本来是圆滑曲线的钻程线,且其误差也较大,而用拉格朗日插值法可以根据已得到的测斜结果,拟合出一条圆滑的钻程线。本文介绍了用这种方法编制的PC—1500机BASIC程序,使地质人员可用该机计算制图,摆脱繁锁的手工操作,提高工效和成图质量。  相似文献   

Multi-electrode resistivity survey for groundwater exploration in the Harare greenstone belt, Zimbabwe     

R. J. Owen  O. Gwavava  P. Gwaze 《Hydrogeology Journal》2006,14(1-2):244-252

A multi-electrode resistivity survey, carried out over metasedimentary strata and metavolcanics in the Harare greenstone belt in northeastern Zimbabwe as part of a groundwater resources investigation, illustrates the ability of this technique to produce high-resolution images of the subsurface, which are useful for groundwater resources assessment. The resistivity results provide a clear view of the thickness of the weathered regolith and of the distribution of the various lithological units. Using a combination of apparent formation resistivity and inferred depth of weathering, it is possible to characterize the various lithologies on the geophysical profiles. These assigned lithologies show excellent correlation with the mapped geology, and the main lithologies, metabasalt, meta-arenite, granodiorite and banded iron formation can be clearly identified. The banded iron formation is characterized by low resistivity values, while a combination of the depth of weathering and resistivity values are used to distinguish between the meta-arenite on one hand and the metabasalt and granodiorite on the other. The multi-electrode method is successful in identifying potentially favourable zones for obtaining groundwater, such as areas with a maximum depth of weathered regolith, zones of fracturing and faulting, and high porosity and permeability zones associated with lithological contacts.

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Resumen Un estudio de resistividad multi-electrodo que se llevó a cabo en estratos meta sedimentarios y metavolcánicos en el cinturón de rocas verdes de Harare, en la parte noreste de Zimbabwe, como parte de una investigación de recursos de agua subterránea, ilustra la capacidad de esta técnica para producir imágenes de alta resolución de la subsuperficie, las cuales son útiles para la evaluación de los recursos da agua subterránea. Los resultados de resistividad suministran una visión clara el espesor del regolito meteorizado y de la distribución de varias unidades litológicas. Mediante el uso de una combinación de resistividad aparente de formación y de una profundidad inferida de meteorización, es posible caracterizar las diferentes litologías en los perfiles geofísicos. Estas litologías asignadas muestran una excelente correlación con la cartografía geológica y se pueden identificar las litologías predominantes como metabasalto, meta-arenita, granodiorita y formación de hierro bandeado. Esta última se caracteriza por valores bajos de resistividad, mientras que se utiliza una combinación de profundidad de meteorización y valores de resistividad, para distinguir entre meta-arenita por un lado y metabasalto y granodiorita por el otro. El método multi-electrodo es exitoso para identificar zonas potencialmente favorables para captar agua subterránea, las cuales pueden ser áreas con una profundidad máxima de regolito meteorizado, o bien zonas de fracturamiento y fallamiento, o también zonas de porosidad y permeabilidad altas asociadas con contactos litológicos.

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Résumé La prospection électrique par la méthode de multiélectrodes, effectuée pour linvestigation des eaux souterraines cantonnés dans des roches métamorphiques dorigine sédimentaire et volcanique de la ceinture de Harare-Zimbabwe a mis en évidence les possibilités de cette technique de réaliser des images à grande résolution du sous-sol qui sont très utiles pour lévaluation de la ressource en eaux souterraines. Daprès la distribution de la résistance il résulte une image très claire de lépaisseur des regolithes altérés ainsi que de la distribution des différentes unités lithologiques. Daprès les profiles géophysiques on peut caractériser les différents lithologies en utilisant les résistivités apparentes de la formation respective et les informations sur la profondeur de la zone altérée. Les lithologies ainsi déterminées montrent une excellente corrélation avec les cartes géologiques et on peut très bien identifier les lithologies principales comme les metabasaltes et les meta-arenites, les granodiorites et les formations de fer rubanées. Cettes dernières sont caractérisées par des faibles valeurs de la résistivité, tandis que en utilisant les résistivité et la profondeur de la zone altérée on peut distinguer les meta-arenites de granodiorites et des metabasaltes. La méthode des multiélectrodes est donc capable didentifier des formations favorables à laccumulation en eau comme les zones de faille et des fractures, ainsi que les zones à grande porosité et perméabilité, associées aux contactes lithologiques.

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Mediterranean Neogene stratigraphy: development and evolution through the centuries     

MARIA BIANCA CITA 《Sedimentology》2009,56(1):43-62

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Deep root of a continent-continent collision belt: Evidence from the Chinese Continental Scientific Drilling (CCSD) deep borehole in the Sulu ultrahigh-pressure (HP-UHP) metamorphic terrane, China   总被引：2，自引：0，他引：2  

Zhiqin Xu  Shaocheng Ji  Zeming Zhang  Qin Wang 《Tectonophysics》2009,475(2):204-219

The Chinese Continental Scientific Drilling (CCSD) deep borehole, which reached a depth of 5158 m in the Sulu ultrahigh-pressure (UHP) metamorphic terrane, provides a new window into the deep root of a continent-continent collision belt, and the tectonic processes by which supracrustal material is recycled into the mantle by subduction and then uplifted to the surface. Major research themes of the CCSD project were to: (1) determine the three-dimensional composition, structure and geophysical character of the deep root of this orogenic belt; (2) investigate the nature and timing of the UHP metamorphism; (3) investigate the processes of crust-mantle interaction involved in the formation and exhumation of the UHP rocks; (4) study the process of fluid circulation and mineralization during subduction and exhumation; (5) study the rheological properties of the various rocks during subduction and exhumation; (6) develop and refine dynamic models for deep subduction and exhumation of crustal rocks, and (7) establish a long-term, natural laboratory for the study of present-day crustal dynamics (e.g., stress, strain, fluid activity). The CCSD has developed precise oriented profiles of the main borehole in terms of lithology, geochemistry, oxygen isotopes, zircon SHRIMP U-Pb ages, ⁴⁰Ar-³⁹Ar ages, deformation, rheology, mineralization, physical properties of the rocks, petrophysical logs, seismic reflections and underground fluids. The present paper summarizes the integrated research results of this project, especially the new findings concerning the deep root of a continent-continent collision.  相似文献   

Paleomagnetic and rock magnetic results from lower crustal rocks of IODP Site U1309: Implication for thermal and accretion history of the Atlantis Massif     

Xixi Zhao  Masako Tominaga   《Tectonophysics》2009,474(3-4):435-448

Integrated Ocean Drilling Program (IODP) Expeditions 304/305 recovered a total of 1.4 km sequence of lower crustal gabbroic and minor ultramafic rocks from the Atlantis Massif oceanic core complex on the western flank of the Mid Atlantic Ridge (MAR) at 30°N. We conducted an integrated paleomagnetic and rock magnetic study on this sequence to help address the interplay between magmatism and detachment faulting. Detailed thermal and alternating-field demagnetization results demonstrate that stable components of magnetization of mainly reversed polarity with unblocking temperatures below the Curie temperature of magnetite are retained in gabbroic rocks at IODP Site U1309. Several samples also contain multicomponent remanences of both normal and reversed polarities that were acquired over sharply defined blocking temperature intervals, providing evidence for localized reheating of some intervals during both normal and reversed polarity periods. Results from a series of rock magnetic measurements corroborate the demagnetization behavior and show that titanomagnetites are the main magnetic carrier rocks recovered at Site U1309D. The overall magnetic inclination of Hole U1309D is -35°, implying significant (up to ~ 50° counterclockwise, viewed to the north) rotation of the footwall around a horizontal axis parallel to the rift axis (010°) may have occurred. The tectonic rotations inferred by the paleomagnetic data suggest that the original fault orientation dipped relative steeply toward the spreading axis and subsequently rotated to a shallower angle. Coupled with the newly published U–Pb zircon ages for Hole U1309D rocks [Grimes, C.B., John, B.E., Wooden, J.L., 2008. Protracted construction of gabbroic crust at a slow-spreading ridge: Constraints from ²⁰⁶Pb/²³⁸U zircon ages from Atlantis Massif and IODP Hole 1309D, (30°N, MAR). Geochem. Geophys. Geosyst. 9, Q08012. doi:1029/2008GC002063], the new paleomagnetic data provide temporal and thermal constraints on the accretion history of the Atlantis Massif.  相似文献   

Application of Greek lignite as an additive for controlling rheological and filtration properties of water–bentonite suspensions at high temperatures: A review     

Vassilios C. Kelessidis  Cassiani Papanicolaou  Antonios Foscolos 《International Journal of Coal Geology》2009,77(3-4):394-400

This review paper presents the results of an extensive study investigating whether addition of 3% w/w Greek lignite to 6.42% w/w water–bentonite suspensions, after being exposed to high temperatures, can prevent gelation and control filtration characteristics. Two different bentonites and eight lignites from different Greek basins have been used while a commercial lignite product has been used as standard. The lignite-free bentonite suspensions heated to 177 °C for 16 h (thermal aging) thicken considerably, increasing the yield stress and the yield point. Fluid consistency and flow behavior indices also change while no significant change is observed for plastic viscosity. Thermal aging of the suspensions results in unacceptably high fluid loss values.Addition of Greek lignite to water–bentonite suspensions, followed by thermal aging, provided the rheological stability of the suspensions by maintaining the low yield stress/point regardless of the type of bentonite. Some of the lignites performed as well as their commercial counterpart. No specific trends for rheological improvement have been identified with respect to various characteristics of lignites such as contents of humic, fulvic acids, humins and other parameters such as specific surface area and cation exchange capacity.Furthermore, addition of lignite in most cases provided very good filtration control of the water–bentonite suspensions after exposure to 177 °C, with some Greek lignites being superior to the commercial product. The same lignite parameters examined for rheological control, were also examined to determine their effect on fluid loss of these suspensions for both bentonites. The content of humic and fulvic acids of two groups of lignites showed weak inverse correlations with the fluid loss volumes for both bentonites, while all other parameters did not seem to directly correlate with the effectiveness of the lignites.  相似文献   

南黄海中部隆起印支面剥蚀量恢复与演化过程——来自CSDP-2井的证据     

庞玉茂  郭兴伟  张训华  韩作振  朱晓青  侯方辉  蔡来星 《大地构造与成矿学》2019,43(2):235-245

南黄海中部隆起是下扬子地块向海域的延伸,是当前海相盆地海域资源调查的潜力区。中部隆起自印支期以来经历多期构造隆升、挤压及剥蚀作用,显著影响了盆地油气资源的形成和分布。2016年底完钻的大陆架科学钻探CSDP-2井首次在中部隆起钻穿印支不整合面,该不整合面在中部隆起既是新近系-第四系底界,又是下三叠统灰岩的顶界,横向延伸平缓,上、下地层产状差异巨大,下伏地层具有强烈的挤压变形及逆冲推覆,呈现显著的角度不整合接触关系。本次研究基于泥岩声波时差法计算的印支面地层剥蚀量约为1200 m,镜质体反射率法计算的剥蚀量约为1400 m,与地层趋势面估算的剥蚀量基本一致。结合南黄海盆地演化过程分析,认为中部隆起大致于晚三叠世开始隆升,至晚白垩世期间经历快速剥蚀,并可能延续到渐新世末期。在当前南黄海盆地资源调查逐步转向中、古生界海相残留盆地之际,依托实际钻探资料进行印支不整合面研究及剥蚀量恢复对于恢复盆地构造-热演化史及评价油气资源等均具有重要的现实意义。  相似文献