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991.
Rodolfo Carosi Chiara Montomoli Nicola Bertuccelli Maurizio Profeti 《Comptes Rendus Geoscience》2002,334(5):339-346
Structural analysis performed in the southern sector of the Apuan Alps Metamorphic Complex (AAMC) and on the overlaying Tuscan Nappe (TN) pointed out a structural evolution much more complex than that outlined till now. The comparison between the structural evolutions of the two tectonic units could provide new important constraints on the tectonic evolution of the whole belt. The two tectonic units recorded different tectonic evolution during the first stages of compression, while they shared the same deformation history later after the Tuscan Nappe overlapped the AAMC. The coupled tectonic units have been then deformed by two systems of folds, in a compressive tectonic regime. Extensional tectonics affected the units later, at upper crustal levels. To cite this article: R. Carosi et al., C. R. Geoscience 334 (2002) 339–346. 相似文献
992.
韩国和马来西亚建立本国三维地心大地坐标系统的进展 总被引:1,自引:0,他引:1
介绍了韩国大地坐标系统的沿革 ,阐述了近年来韩国建立本国三维地心坐标系的工作和进展。为了对比韩国 ,简约介绍了马来西亚等国在这方面的新进展 相似文献
993.
A coastal environment has been interpreted from 110 cm thick mudstone deposits found at the base of a 10 m immature laterite profile, which forms the modern coastal cliff on Mosqueiro Island in northeastern Pará state, northern Brazil. The late Tertiary sediment deposits of the Barreiras Formation are studied by multi-element geochemistry and pollen analyses. The mineralogical and geochemical results show that the gray, organic-rich deposits are composed of kaolinite, quartz, and illite/muscovite, as well as pyrite and anatase. They are rich in SiO2, Al2O3, and some FeO. The composition is homogenous, indicating that the detritus source area is formed of lateritic soils derived from acid rock composition. Their chemical composition, including trace elements, is somewhat comparable to continental shale, and the values are below the upper continental Earth crust composition. The pollen analytical data document that the mudstone deposits were formed by an ancient mangrove ecosystem. Mineralogical, geochemical, and pollen analytical data obtained from late Tertiary mangrove deposits are compared with modern mangrove deposits from the Bragança Peninsula of the northeastern coast of Pará state. Although the pollen composition of the deposits is very similar to the modern one, the geochemical and mineralogical composition is different. Smectite was only found in the modern deposit; illite/mica occurs in the ancient deposit, along with Mg, K, and Na. The pollen signature and detrital minerals (kaolinite, quartz and anatase) found in both mangrove deposits show that during the Miocene, a humid tropical climate condition prevailed, similar to modern conditions. 相似文献
994.
Fátima Franco-Múgica Mercedes García-Antón Javier Maldonado-Ruiz Carlos Morla-Juaristi Helios Sainz-Ollero 《Quaternary Research》2005,63(1):1-14
We present a new stratigraphic (pollen and nonpollen microfossils and charcoal particle) sequence with five AMS dates, covering about the last 9000 yr, of a core collected from the Spanish northern meseta, one of the territories of the Iberian Peninsula for which little paleobotanical information is available. The results support the hypothesis of the permanence of the pine forests, in more or less pure masses or large timber stands, during the Holocene in some Iberian continental zones. The typical substitution in postglacial dynamics of heliophyllous species, such as pines or Cupressaceae, by broadleaf trees did not occur in this inland region. Presumably, factors linked to the substrate, in this case very deep sand dunes covering vast areas, may have contributed to the scarce local competitiveness of the broadleaf trees, which would account for the hegemony of pines in this region. Based on the dynamics of aquatic plants and nonpollen microfossils, an initial phase previous to 7500 14C yr B.P. of high levels in the lake can be identified by high percentages of hydrophytes. A progressive increase in helophytes and the gradual infilling of the lake over the last 5000 yr appear to indicate a phase of aridification similar to those established for the western Mediterranean. Study of charcoal particles, more abundant in the last 2500 yr, has given rise to certain hypotheses regarding the incidence of recurring fires of a local or regional nature. 相似文献
995.
Detrital zircon provenance evidence for large-scale extrusion along the Altyn Tagh fault 总被引:12,自引:1,他引:12
Yongjun Yue Stephan A. Graham Bradley D. Ritts Joseph L. Wooden 《Tectonophysics》2005,406(3-4):165-178
The question of whether or not the Altyn Tagh fault is a large-scale extrusion boundary is critical for understanding the role of lateral extrusion in accommodating the Indo-Asian convergence and in building the Tibetan Plateau. Oligocene conglomerate clasts in the eastern Xorkol basin are low-grade slate, phyllite, sandstone, dacite and carbonate, and associated paleocurrent indicators evince sediment derivation from the opposing side of the Altyn Tagh fault. Matching these clasts with similar basement rocks in the North Qilian and Tuolainanshan terranes requires post-Oligocene left-lateral offset of 380 ± 60 km on the eastern segment of the Altyn Tagh fault, suggesting large-scale extrusion along the fault in the Cenozoic (Yue, Y.J., Ritts, B.D., Graham, S.A., 2001b. Initiation and long-term slip history of the Altyn Tagh fault. International Geological Review 43, 1087–1094.). In order to further define this piercing point, the detrital zircon pattern of Oligocene sandstone from the Xorkol basin and the zircon ages of basement on the southern side of the fault were established by ion microprobe dating. Characterized by strong peaks between 850 and 950 Ma and the absence of Paleozoic and Mesozoic ages, the detrital zircon age pattern of the Oligocene sandstone matches the age distribution of zircon-bearing rocks of the Tuolainanshan terrane. This match requires 360 ± 40 km of post-Oligocene left-lateral displacement on the eastern segment of the Altyn Tagh fault, supporting as well as refining the previously reported lithology-based cross-fault match. At least one of the following three extrusion scenarios must have existed to accommodate this large offset: (1) northeastward extrusion along the Altyn Tagh–Alxa–East Mongolia fault, (2) eastward extrusion along the Altyn Tagh–North Qilian–Haiyuan fault, and (3) northeastward extrusion of northern Tibet as a Himalaya-scale thrust sheet along the North Qilian–Haiyuan fault. We prefer the first scenario inasmuch as rapidly growing evidence for Cenozoic strike-slip activity on the Alxa–East Mongolia fault and mid-Miocene exhumation of northern Tibet supports it. 相似文献
996.
Origin of the Gabbro-Peridotite Association from the Northern Apennine Ophiolites (Italy) 总被引:4,自引:0,他引:4
TRIBUZIO RICCARDO; THIRLWALL MATTHEW F.; VANNUCCI RICCARDO 《Journal of Petrology》2004,45(6):1109-1124
The Northern Apennine ophiolites are remnants of the MiddleJurassicEarly Cretaceous lithosphere from the LigurianTethys. New trace element and NdSr isotope investigationswere performed on: (1) the rare gabbros associated with thesubcontinental mantle rocks from the External Liguride ophiolites;(2) the gabbroperidotite association from the poorlyknown ophiolitic bodies from Cecina valley (Southern Tuscany).Clinopyroxenes from the External Liguride and Cecina valleygabbros have similar trace element compositions, which are consistentwith formation from normal mid-ocean ridge basalt (N-MORB) magmas.SmNd mineral isochron ages are 179 ± 9 Ma foran External Liguride gabbro and 170 ± 13 Ma and 173·5± 4·8 Ma for two different gabbroic bodies fromthe Cecina valley ophiolites. These ages are interpreted todate the igneous crystallization of the gabbros and are slightlyolder than the oldest pelagic sediments of the Ligurian Tethys.Initial 相似文献
997.
Sallie Yea 《Singapore journal of tropical geography》2004,25(2):180-197
Although the migration of Filipinas to the Republic of Korea has only a short history, some Filipinas have already begun to form incipient communities around the largest United States military bases there. These communities are formed by an increasing number of women who run away from the military camptown clubs where they work as entertainers, to marry or live in cohabitation/de facto relationships with the enlisted American army personnel (or GIs) whom they meet and develop relationships with while working as entertainers in the GI clubs. Drawing on ethnographic research and interviews with the women in one such camptown, this paper documents their experiences and the dynamics of their marriages as they attempt to negotiate their transition from “trafficked entertainers” to “runaway brides”. Their experiences illustrate the daily tribulations of women who wish to improve their prospects, or more ambitiously, transform their identity whilst abroad, by entering into marriages or similar arrangements, but who continue to be encumbered with the stigma attached to being trafficked entertainers. The discussion in this paper aims to contribute to the literature on Filipina migrants' anxieties about identity in the context of transnational migration. 相似文献
998.
999.
1000.
系统分析了山东及朝鲜半岛地区历史地震记载的情况和特点,分析表明,两区的历史与现代地震资料有较强的互补性强震具有同步涨落,遥相呼应的相关性,这种相关性天时间上具有步进次序关系,受高层次地震活动韵所制约;空间上则有相近纬度优势呼应现象。初步认为,这两个地区地震的相关现象与共同受到西太平洋消减带的俯冲推挤作用有关。 相似文献