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31.
鄂尔多斯西南缘前陆盆地沉降和沉积过程模拟 总被引:17,自引:8,他引:17
本文将东祁东逆冲带与鄂尔多斯西南缘晚三叠世前陆盆地相结合,研究了逆冲带内部变形特征,前陆盆地中层序地层格架特征及其反映的盆缘构造性质和幕式逆作作用。 相似文献
32.
University of Maryland, College Park 相似文献
33.
二郎坪群抱树坪组作为北秦岭早古生代重要的沉积记录,其研究程度较低。本文通过对抱树坪组内火山岩夹层和花岗斑岩脉进行岩石学、地球化学和锆石U- Pb测年研究,旨在进一步确定其沉积时代与构造环境。研究结果表明:豫西夏馆地区抱树坪组火山岩夹层已变质为(黑云)阳起钠长片岩,常与黑云石英片岩呈“互层状”产出;岩石原岩为安山质凝灰岩,具有相对低的SiO2(52. 56%~62. 04%)、较高的Al2O3(10. 70%~18. 55%)、低的MgO(4. 06%~6. 21%)和FeOT/MgO(1. 23~1. 81),富集轻稀土元素和大离子亲石元素Rb、Th、U、K,相对亏损高场强元素Nb、Ta、P、Ti,具镁安山质岩石的特点;结合地球化学特征及前人研究认为,抱树坪组可能形成于活动陆缘弧后盆地。获得黑云阳起钠长片岩原岩的结晶锆石U- Pb年龄为446. 0±1. 7 Ma,以及侵入其中花岗斑岩脉的成岩年龄为430. 0±3. 0 Ma,首次将抱树坪组的形成时代准确地限定为晚奥陶世至早志留世。综合区域研究成果认为,小寨组和抱树坪组在地层层序和地层时代上符合广义二郎坪群的划分方案,但大庙组、火神庙组及由小寨组和抱树坪组构成的整体三者在形成时代上表现为近于同时性,在空间上主体呈现近平行关系,可能主体属时代大体相当的不同沉积环境的产物;在大地构造属性方面,认为二郎坪群是在约470 Ma之前由于商丹洋向北俯冲而形成的火山岛弧,在470~436 Ma转化为弧后盆地,至约430 Ma之前最终完成消减闭合。 相似文献
34.
《Geoforum》2015
This paper examines the importance of national-level institutional arrangements for promoting the EU’s Protected Geographic Indication scheme (PGI). Taking the example of Ireland, for which PGI designations remain comparatively low, it explores whether the approach to providing institutional supports to the PGI scheme is influenced by top-down technocratic governance structures that pertain to food safety and quality certification that encompass the broader operating environment for food production in Ireland. Although the regulation of food safety and quality certification are distinct remits to the administration of the PGI scheme, in the Irish context the same institutional bodies are involved in governance of both. Using a discourse analysis interpretative framework, this paper draws on interviews with Irish producer group members and institutional representatives to examine how governance of the PGI scheme reflects management perspectives and practices more in keeping with a regulatory environment for food safety and quality than with development of place-based food product links. It suggests that incentives to avail of the PGI scheme as a means of realising value-added for producers are not well established because they require the development of more subjective, context-dependent processes and practices linked to geographical place and place identity. These are not easily accommodated under current institutional arrangements that also incorporate food safety and quality remits because these are in turn strongly established through nationally and internationally recognised systems of regulation and benchmarking. The findings point to the benefits to be gained from a more layered governance structure for PGI; devolving operation of the scheme to relevant regional and local development organisations that possess the expertise and relevant local knowledge to (a) incentivise the formation of producer groups, and (b) prioritise mentoring and support for PGI concept development as a clearer reflection of bottom-up rural sustainability policy. 相似文献
35.
A long history of increases in population pressure in Java has caused agricultural land use to expand and intensify. More recent land use changes caused the conversion of prime agricultural land into residential and industrial area. Results of a dynamic, regional-scale, land use change model are presented, defining the spatial distribution of these land use changes. The model is based on multi-scale modelling of the relations between land use and socio-economic and biophysical determinants. Historical validation showed that the model can adequately simulate the pattern of land use change. Future patterns of land use change between 1994 and 2010 are simulated assuming further urbanization. The results suggest that most intensive land use changes will occur in Java's lowland areas. 相似文献
36.
37.
剖析"太阳-气候-水资源"体系作用机制对区域水资源科学管理具有重要科学意义。利用相关分析、主成分分析和小波分析方法,探究太阳黑子运动和厄尔尼诺(ENSO)对日本吉野川流域降雨、地表径流和地下水位影响。研究结果表明:太阳黑子活动和ENSO对研究区域水文过程显著影响分别发生在11 a和2~7 a周期上;太阳黑子运动能量以ENSO为"媒介"作用于流域降水和河川径流,但对地下水位波动影响不明显;太阳黑子活动在不同时频域对研究区域水文过程产生"直接"和"间接"影响,太阳黑子的"直接"影响可能通过调制ENSO外的气候模态来实现,其"间接"作用则通过"ENSO-西太平洋副高-东亚环流-水汽运动"系统作用实现。 相似文献
38.
39.
To begin exploring the underlying mechanisms that couple vegetation to cloud formation processes, we derive the lifting condensation
level (LCL) to estimate cumulus cloud base height. Using a fully coupled land–ocean–atmosphere general circulation model (HadCM3LC),
we investigate Amazonian forest feedbacks on cloud formation over three geological periods; modern-day (a.d. 1970–1990), the last glacial maximum (LGM; 21 kya), and under a future climate scenario (IS92a; a.d. 2070–2090). Results indicate that for both past and future climate scenarios, LCL is higher relative to modern-day. Statistical
analyses indicate that the 800 m increase in LCL during the LGM is related primarily to the drier atmosphere promoted by lower
tropical sea surface temperatures. In contrast, the predicted 1,000 m increase in LCL in the future scenario is the result
of a large increase in surface temperature and reduced vegetation cover. 相似文献
40.