Three‐dimensional to two‐dimensional cross‐strata transition in the lower Pleistocene Catanzaro tidal strait transgressive succession (southern Italy)     

Sergio G. Longhitano  Domenico Chiarella  Francesco Muto 《Sedimentology》2014,61(7):2136-2171

Sandstone tidal cross‐strata are the predominant sedimentary feature of strait‐fill stratigraphic successions. However, although widely described in numerous studies, tidal strait‐fill two‐dimensional and three‐dimensional cross‐strata have rarely been reported to occur in discrete intervals which are laterally adjacent or vertically stacked, and the meaning of this stratigraphic architecture has not yet been fully investigated. Understanding of the processes responsible for changes in the internal features of modern and ancient tidal bedforms is essential in order to predict lateral and vertical heterogeneities in analogous reservoir strata. This facies‐based study aims to interpret the three‐dimensional to two‐dimensional cross‐strata transition observed in the lower Pleistocene mixed siliciclastic/bioclastic sandstone filling the Catanzaro Strait, in southern Italy, during a continuous phase of tectonically driven marine transgression. Tidal cross‐strata disappear in the uppermost interval of the studied succession, where mudstone strata prevail. This stratigraphic trend is interpreted as the evidence of an important change in the tidal strait hydrodynamics due to a phase of relative sea‐level rise. At the beginning of the transgression, three‐dimensional tidal dunes migrated throughout the ca 3 to 4 km wide and ca 30 km long, WNW–ESE‐oriented Catanzaro Strait, due to strong tidal currents amplified through the seaway and flowing in semi‐diurnal phase opposition. As the intermediate phase of transgression enlarged the seaway width, the tidal current strength decreased as tidal water exchange occurred over a larger cross‐sectional area. The progressive reduction of the bed shear stress modified three‐dimensional tidal dunes into an extensive two‐dimensional bedform field. At the end of the transgression, the further widening of the Catanzaro Strait into a ca 10 to 12 km wide marine passageway changed the tidally dominated strait into a non‐tidal open shelf. The results of this research suggest the presence of a ‘critical cross‐sectional area’ in the narrowest strait‐centre zone which controls the activation and deactivation of tidal current amplification along a marine seaway.  相似文献   

Propagation history of the Osaka-wan blind thrust,Japan, from trishear modeling     

《Journal of Structural Geology》2014

Mapping the nucleation and 3D fault tip growth of the active Osaka-wan blind thrust provides an opportunity to asses how reactivated thrusts build slip from preexisting faults and the threat they pose as sources of large earthquakes. Analysis of folded growth strata, based on 2D trishear inverse modeling allows a range of best-fit models of the evolution of slip and propagation of the fault to be defined. The depth of the fault tip at 1200 ka varies between ∼1.5–4.5 km, suggesting the fault grew upward from high in the crust, and that it is reactivated. From its onset at ∼1500 ka, the fault grew rapidly along strike in ∼300 ky, and upwards with a P/S ratio of 2.5–3.0, but variable fault slip in space and time. Shallower depths of the fault tip at initiation and thinner basin fill correlates with slower propagation with time, contradicting models that argue for sediments as inhibitors of fault growth. Results also suggest the displacement profile of the currently active thrust is offset from its predecessor, assuming shallower depths to the original fault correlate with greater displacement in its prior history. These results suggest reactivated faults may accrue slip differently than newly developed ones, based on the history of upward fault propagation.  相似文献   

生态系统服务权衡与协同视角下的重点生态功能区保护特征   总被引：1，自引：0，他引：1  

祝汉收  翟俊  侯鹏  王桥  陈妍  金点点  王永财 《地理学报》2022,77(5):1275-1288

重点生态功能区提供着源源不断的生态系统服务,在保障国家生态安全和社会可持续发展方面,有着不可或缺的基础作用。但是,以生态系统服务权衡与协同关系为视角,进而探讨分析重点生态功能区保护特征的研究案例相对较少。本文以秦巴重点生态功能区为评估分析区域,选择自然地理条件相似度极高的秦巴山区为参照单元,以生态系统供给服务与调节服务为核心内容,在定量分析2000—2019年期间的生态空间变化特征基础上,分析评估生态系统服务权衡与协同关系。结果表明：秦巴山区生态状况逐渐变好,重点生态功能区划定之后,生态系统趋于稳定;重点生态功能区服务能力呈逐渐增强的趋势,平均净初级生产力、土壤保持总量和水源涵养总量比重点生态功能区外分别高出了25.95 gC/m²、5.81亿t和24.95亿m³;土壤保持服务和生态系统供给服务的协同关系与生态状况改善呈正相关;由于受到降水的影响,2010年之后的水源涵养服务与生态系统供给服务的协同关系变差。总体来看,秦巴重点生态功能区的划定带动了区域生态空间“量的增长”和生态系统服务“质的提升”,但生态系统服务之间关系的“协调性”仍然不足,甚至从“协同”转为“权衡”关系,这要求未来国家需要制定更有针对性的生态系统保护管理决策,提高生态系统总体效益,支撑区域生态系统服务的可持续供给。  相似文献   

The Formation Model for Marine Potash Deposits within China’s Small Continental Blocks     

LIU Chenglin  WANG Licheng  ZHAO Yanjun  CAO Yangtong  JIAO Pengcheng  SHEN Lijian  ZHANG Hua 《《地质学报》英文版》2014,88(Z1):225-226

正Chinese geologists have always been expecting to find out a large scale of potash deposits in marine basins,but only one small-middle scale industrial solid potash deposit had been found at Mengyejing in Langping-Simao basin  相似文献   

Magnetite Quartzite-Type Iron Ores – China’s Most Important Current Iron Ore Source     

HAO Ziguo  FEI Hongcai  HAO Qingqing  Susan TURNER 《《地质学报》英文版》2014,88(4):1329-1333

正China is abundant in iron-ore resources,with proven ore reserves of 576.62×108 t and proven reserves of 210×108 t,containing an average iron content of 33%.However,the rich iron-ore reserves of 10.85×108 t only account for 1.9%of all proven reserves.China’s iron-ore resources are characterized by many lean ores and a few rich ones.  相似文献   

吉林省白山市木通沟铁矿地质特征与找矿预测     

高明珠  路恩兰  范国友  孙月  路猛 《吉林地质》2014,(4)

木通沟铁矿均赋存于太古界杨家店组上段含铁角闪岩中,处于板石沟复式向斜西部起翘转折端,板石沟所处的区域构造位置决定该矿床矿体产状变化不稳定性,同时也决定了该矿床与板石沟铁矿南北两条成矿带的连续性。转折端出露南北向薄层矿体是受三期褶皱改造叠加变形作用影响,矿区所含矿体呈北东倾没,南东倾斜的多层斜列宽缓向形盲矿体群,东部被F201逆断层破坏,断层倾向北东东,预测深部矿体主要分布在F201断层的下盘,木通沟向斜横跨板石沟复式向斜两翼,与板石沟向斜两翼具备连续性赋矿因素。  相似文献   

岩土工程勘察中的质量控制探讨     

吴茂盛  艾云峰  孟吉泽  张楠  孟凡利 《吉林地质》2014,(1):118-120

本文阐述了岩土工程勘察成果质量的重要性,重点论述了岩土工程勘察工序流程的质量管理要点,这对于岩土工程勘察专业宏观管理到指导具有实际意义。  相似文献   

大厂泥盆纪地层控矿规律及找矿意义     

杨眉 《矿产与地质》2014,(1):35-37,45

大厂矿田主要矿体的产出均受泥盆纪地层限制,通过对泥盆纪地层控矿规律的研究,并综合其他控矿因素,对今后在该区的找矿工作具有重要的指导意义。  相似文献   

基于数值模拟的采动影响下覆岩裂隙演化过程分析   总被引：1，自引：0，他引：1  

陈峰 《中国地质灾害与防治学报》2014,(2):60-64

以平顶山东部矿区为工程背景,利用岩石真实破裂过程分析软件（RFPA2D）,模拟了采动影响下覆岩介质损伤的动态发展过程。数值模拟结果表明,采动裂隙的形成过程是一个复杂的演化过程,在加载初期覆岩介质损伤小,声发射现象不明显,应力和位移基本上无变化,无明显裂隙产生。随着加载步的增加,覆岩内部介质出现破裂,声发射次数、应力值和位移值不断增加,此时裂隙场处于孕育、不断积累并扩大阶段。当声发射次数、应力值、位移值都达到最大值时,裂隙经过萌生、扩展之后形成宏观裂隙,进而导致煤岩体由弹性状态转变为塑性状态,使覆岩大面积垮落。该数值模拟结果对平顶山东部矿区的开采具有巨大指导意义。  相似文献   

安徽省寒武纪地层最新划分方案     

储东如  刘家云  王传堂 《安徽地质》2014,(4):241-246

在对安徽省内寒武纪典型或标准地层剖面测量和总结的基础上,据中国地层表的四分方案,对区内寒武系进行了修订。安徽省寒武系顶底及各统界线也做了相应修定,其底界年龄为541Ma,第一与第二统界线年龄为521Ma,第二与三统界线年龄为507 Ma,第三四统界线年龄为497Ma,顶界年龄为485.4 Ma。  相似文献