基于"湛江群岛"的湛江区域发展格局构建     

张义丰  张伟  张宏业  谭杰  贾大猛  孙瑞峰 《地理研究》2011,30(5):804-813

如何通过区域各类要素资源的有效整合,构建区域发展战略格局,推动区域社会经济的可持续发展一直是学术界研究的热点.本文以社会经济发展较为滞后的湛江市为例,通过实地调研和多方论证,在深入分析湛江市各类资源要素禀赋的基础上,首次提出了"湛江群岛"的概念,阐释了"湛江群岛"理念在推动湛江市区域社会经济发展过程中的重要意义.在此基...  相似文献   

Nearshore to offshore facies and depositional history of the Ordovician Daylesford Limestone New South Wales     

V. Semeniuk 《Australian Journal of Earth Sciences》2013,60(4):449-463

The Daylesford Limestone is the basal formation of the Ordovician Bowan Park Group of central western New South Wales. The formation contains four main limestone types and minor intercalated terrigenous beds. Limestones are: (1) grain‐stone, (2) grey skeletal wackestone and packstone, (3) dark grey burrowed wackestone and packstone, and (4) dark grey burrowed lime mudstone. Grainstone and grey skeletal wackstone and packstone are dominant in eastern sections; they are laterally equivalent to, and interfinger with, dark grey muddy limestones that dominate western sections. Lithoclasts are abundant in the grainstone but are absent from muddy sections to the west except in thin beds above disconformities. The rock types of the Daylesford Limestone also tend to occur sequentially above some disconformities; the full sequence is: grainstone (or grey skeletal wackestone and packstone) grading up into dark grey burrowed wackestone and packstone and thence into dark grey burrowed lime mudstone. Each sequence is probably trans‐gressive and reflects deepening water.

During deposition of the Daylesford Limestone, an area to the east was uplifted, providing lithoclasts to be reworked into the neighbouring depositional basin. Uplift also produced numerous regressions and subaerial disconformities. Facies patterns were essentially similar throughout the history of the formation. Grainstone accumulated in high‐energy nearshore environments adjacent to the uplifted area, and grey skeletal wackestone and packstone in low‐energy nearshore environments. Dark grey lime mudstone formed in offshore low‐energy environments to the west of the uplifted area; and dark grey wackestone and packstone in intermediate environments. In parts, burrowing organisms kept pace with sedimentation and locally mixed interbedded grainstone and muddy limestone.  相似文献   

Metamorphic consequences of Neogene thermal anomaly in the northern Apennines (Radicondoli-Travale area,Larderello geothermal field – Italy)     

Marilisa Carella  Paolo Fulignati  Giovanni Musumeci 《Geodinamica Acta》2013,26(6):345-366

Abstract

In the Radicondoli–Travale area of the Larderello geothermal field (Italy) new structural and petrologic data on some metamorphic units, cored from geothermal wells, reveal the existence of a wide complex of hornfels rocks. The development of the complex is related to the emplacement of Neogene magmatic rocks at a shallow depth within a Permo–Triassic terrigenous metasedimentary sequence of a low metamorphic grade. The sequence was subjected to alpine tectonic-metamorphic events. This reconstruction gives new insights in the tectonic setting of metamorphic units below the Tuscan Nappe, in southern Tuscany. Particularly, the medium and high grade metamorphic rocks seem strictly related to the development of Neogene thermal aureoles and do not represent remnants of a Paleozoic basement. Furthermore, in this sector of the Larderello geothermal system, the presence of deep geothermal reservoir at a depth of 3 000 m is mainly linked to the enhanced permeability caused by fracturing in these hornfels rocks. This fracturing is a consequence of the dehydration reaction occurring in the metapelites due to Neogene thermal metamorphism. This mechanism allowed the development of a long-lived hydrothermal system, shown by the secondary mineralogical assemblages. These testify the presence of at least two hydrothermal stages which are well preserved in the less permeable units. © 2000 Editions scientifiques et médicales Elsevier SAS  相似文献   

造山过程重力塌陷与褶皱作用——面理弯切轴与褶皱轴面数据对比研究          下载免费PDF全文

曹汇 《中国地质》2013,40(6):1818-1828

提要：美国东部阿巴拉契亚造山带北端缅因州Rangeley地区志留—泥盆纪中温低压片岩测得的面理弯切轴与褶皱轴面数据有很好的对应关系。西部科迪勒拉造山带落基山脉南端科罗拉多州阿肯色河地区Texas Creek 以东高温低压前寒武纪堇青石片岩中测得的褶皱轴面方向和片理走向数据与该地区堇青石、斜长石变斑晶内测得的5期面理弯切轴也表现出很好的一致性。而在Rangeley北东200 km的佛蒙特州Chester Dome地区奥陶—泥盆纪中温中压片麻岩中测得的类似褶皱轴面数据却只反映了该地区5期面理弯切轴中较晚的北北西-南南东走向和北北东-南南西走向的两期面理弯切轴,未测得与其余3期面理弯切轴对应的褶皱轴面数据。通过对变质峰期温度相近、压力不同的两个造山带内3个典型变质岩区面理弯切轴、褶皱轴面方向和片理走向数据的对比分析认为,造山作用发生的地壳深度差异是早期褶皱经历多期造山运动后能否保存下来的主要影响因素。重力形成的去褶皱作用使得早期形成的规模较小褶皱经历复杂造山过程后难以保存。区域内早期形成的规模较大褶皱和造山过程晚期形成的褶皱由于受到重力塌陷作用影响较小,所以能够较好保存下来。  相似文献   

Island mass effect in the Juan Fernández Archipelago (33°S), Southeastern Pacific     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

Spatial and temporal variability of the island mass effect (IME; defined as local increases of phytoplankton associated with the presence of islands) at the Juan Fernández Archipelago (JFA) is analyzed using chlorophyll-a (Chl-a) satellite data, altimetry, sea surface temperature, wind, geostrophic currents and net heat flux over a ten year period (2002–2012). The the JFA islands (Robinson Crusoe-Santa Clara (RC-SC) and Alejandro Selkirk (AS)) present wakes with significant Chl-a increases, mainly during spring time. These wakes can reach Chl-a values of one order of magnitude higher (~1 mg m⁻³) than the surrounding oligotrophic waters (<0.1 mg m⁻³). The wakes are similar to von Kármán vortex streets which have been used to explain the impact of IME on Chl-a increases in numerical models. The wakes are formed from a high productivity area in the lee of the island, extending to the oceanic region as high Chl-a patches associated with submesoscale eddies that are detached from the islands and connected by less-productive zones. This pattern coincides with previous models that predict the effects of island-generated flow perturbations on biological production variability. The IME is a recurrent feature of islands that has even been observed in decadal average fields. In such average fields, the Chl-a values in RC-SC and AS islands can exceed values found in a Control Zone (a zone without islands) by ~50% and 30%, respectively. Seasonal and interannual variability reveals that, as a consequence of the IME, the winter Chl-a maximum associated with the development of winter convection and mesoscale eddies that propagate from the continental zone, promote that the Chl-a maximum extends towards spring. The IME has an impact on the island on both a local as well as a more regional scale that affects an area of ~40,000 km² (1°Latitude×4°Longitude) centered on the islands. The transport of high productivity patches associated with submesoscale eddies may be responsible for IME propagation at a regional scale. Around the islands, the presence of a weak oceanic incident flow and strong and recurrent wind-wakes, suggest that the generation of Chl-a wakes result from a combined effect between both forcings.  相似文献   

大别山及邻区若干重要基础地质问题的再认识:再论大别造山带非板块碰撞造山过程   总被引：1，自引：0，他引：1  

汤家富  侯明金 《地学前缘》2016,23(4):1-21

就大别山及邻区若干重要基础地质问题作了较深入阐述,并据前人资料与新近调查成果,进一步明确：(1)北淮阳地区属扬子地块北缘,与华北地块南缘的分界为固始-肥中断裂以北。(2)超高压变质带内新元古代浅变质岩层确系存在,并与榴辉岩及其他超高压岩石,共同经受两期褶皱变形,形成早期为伸展拆离,主期为收缩挤压叠加褶皱变形带,而非外来构造残片,或俯冲过程被铲刮下来的“构造加积楔”。(3)蓝片岩形成于伸展拆离构造带内。榴辉岩为地幔岩,属岩浆成因。其他超高压岩石与“柯石英”可在“地壳异常压力”与“高压釜”机制联合作用下,在地壳较浅层次的伸展拆离构造环境下形成。(4)广泛分布的新元古代火山岩系及侵入岩,代表了晋宁期地壳被强烈拉伸裂解扩张事件,但未形成洋壳盆地。(5)详细描述了大别山及邻区构造变形及拉伸与生长线理特征以及形成机制,认为是由“地幔差速环流”所引发的岩石圈与地壳各分层间伸展拆离滑断剪切过程中形成。大别造山带经历了裂解成盆、伸展拆离、收缩挤压、热隆成山,由多阶段构造运动所完成,而非板块碰撞造山。  相似文献   

西沙群岛造礁石珊瑚主要疾病调查与初步研究   总被引：1，自引：1，他引：0  

朱志雄  周永灿  柯韶文  王世锋  谢珍玉 《海洋学报》2012,34(6):195-204

记录了2010年5-10月及2011年4-8月在西沙群岛海域开展珊瑚疾病调查的结果,发现普哥滨珊瑚(Porites pukoensis)、扁枝滨珊瑚(Porites andrewsi)、蔷薇珊瑚(Montipora spp.)、杯形珊瑚(Pocillopora spp.)、鹿角珊瑚(Acropora spp.) 、菊花珊瑚(Goniastrea spp.)、澄黄滨珊瑚(Porites lutea)和滨珊瑚(Porites spp.)等共14种珊瑚主要出现了白化、白斑病、黑化、黄色炎症样病症、粉红颗粒状综合症等9种不同症状的疾病,目前该海域为珊瑚疾病的频发区。其中,普哥滨珊瑚的黄色炎症样病症和扁枝滨珊瑚的白化最为常见。普哥滨珊瑚黄色炎症样病症主要出现在永兴岛附近海区,患病部位存在大量黄色脓样分泌物,患病部位水螅体生长正常、萎缩或缺失,有时骨骼部分缺失,患病部位面积一般为0.02~12.00 cm2;该疾病由机械损伤或其他原因引起,因机械损伤引起的伤口一般在2~3个月可以恢复,其中小面积伤口的黄色物质可在10~20d内消失、伤口基本恢复正常,而其他原因产生的黄色物质需1~3个月才能消失,有的甚至在观察期内无明显变化。扁枝滨珊瑚的白化出现在七连屿一带的扁枝滨珊瑚分布区,该病存在整枝完全白化、局部大面积白化、散布白色斑点3种情况,白化部位水螅体缺失。本文为我国西沙海域珊瑚疾病的首次报道,可为今后开展西沙珊瑚疾病研究提供参考。  相似文献   

Seasonal surface ocean circulation and dynamics in the Philippine Archipelago region during 2004–2008     

Weiqing Han  Andrew M. Moore  Julia Levin  Bin Zhang  Hernan G. Arango  Enrique Curchitser  Emanuele Di Lorenzo  Arnold L. Gordon  Jialin Lin 《Dynamics of Atmospheres and Oceans》2009,47(1-3):114-137

The dynamics of the seasonal surface circulation in the Philippine Archipelago (117°E–128°E, 0°N–14°N) are investigated using a high-resolution configuration of the Regional Ocean Modeling System (ROMS) for the period of January 2004–March 2008. Three experiments were performed to estimate the relative importance of local, remote and tidal forcing. On the annual mean, the circulation in the Sulu Sea shows inflow from the South China Sea at the Mindoro and Balabac Straits, outflow into the Sulawesi Sea at the Sibutu Passage, and cyclonic circulation in the southern basin. A strong jet with a maximum speed exceeding 100 cm s⁻¹ forms in the northeast Sulu Sea where currents from the Mindoro and Tablas Straits converge. Within the Archipelago, strong westward currents in the Bohol Sea carry the surface water of the western Pacific (WP) from the Surigao Strait into the Sulu Sea via the Dipolog Strait. In the Sibuyan Sea, currents flow westward, which carry the surface water from the WP near the San Bernardino Strait into the Sulu Sea via the Tablas Strait.These surface currents exhibit strong variations or reversals from winter to summer. The cyclonic (anticyclonic) circulation during winter (summer) in the Sulu Sea and seasonally reversing currents within the Archipelago region during the peak of the winter (summer) monsoon result mainly from local wind forcing, while remote forcing dominates the current variations at the Mindoro Strait, western Sulu Sea and Sibutu passage before the monsoons reach their peaks. The temporal variations (with the mean removed), also referred to as anomalies, of volume transports in the upper 40 m at eight major Straits are caused predominantly by remote forcing, although local forcing can be large during sometime of a year. For example, at the Mindoro Strait, the correlation between the time series of transport anomalies due to total forcing (local, remote and tides) and that due only to the remote forcing is 0.81 above 95% significance, comparing to the correlation of 0.64 between the total and local forcing. Similarly, at the Sibutu Passage, the correlation is 0.96 for total versus remote effects, comparing to 0.53 for total versus local forcing. The standard deviations of transports from the total, remote and local effects are 0.59 Sv, 0.50 Sv, and 0.36 Sv, respectively, at the Mindoro Strait; and 1.21 Sv, 1.13 Sv, and 0.59 Sv at the Sibutu Passage. Nonlinear rectification of tides reduces the mean westward transports at the Surigao, San Bernardino and Dipolog Straits, and it also has non-negligible influence on the seasonal circulation in the Sulu Sea.  相似文献   

Highly restricted gene flow between disjunct populations of the skunk clownfish (Amphiprion akallopisos) in the Indian Ocean          下载免费PDF全文

Filip Huyghe  Marc Kochzius 《Marine Ecology》2017,38(1)

The skunk clownfish (Amphiprion akallopisos) has a disjunct distribution, occurring in the Eastern Indian Ocean (EIO) and the Western Indian Ocean (WIO), separated by several thousands of kilometres. Information on connectivity of marine species is very important for the correct spacing of marine protected areas, a powerful instrument for the protection of coral reefs. The population genetic structure of A. akallopisos was analysed in order to investigate connectivity amongst populations and to explain the disjunct distribution of the species. A fragment of the mitochondrial control region was used to investigate the genetic population structure. Fin clips were collected from 263 individuals at 14 sites in the WIO and three sites in the EIO. The obtained DNA sequences were used to calculate genetic diversity, evaluate demographic history and to construct a haplotype network. An analysis of molecular variance (AMOVA) was conducted to evaluate the significance of the observed genetic population structure. None of the identified 69 haplotypes was shared between the WIO and EIO. Haplotype as well as nucleotide diversity was considerably higher in the EIO than in the WIO. Significant genetic population structure was revealed by an AMOVA with an overall φ_st‐value of 0.28 (P < 0.001) in the Indian Ocean. The overall AMOVA (φ_st = ?0.00652) was not significant in the EIO, but was significant in the WIO (φ_st = 0.016; P < 0.01). Demographic analysis indicated population expansion in the EIO and WIO. Population genetic analysis revealed highly restricted gene flow between the EIO and WIO. Genetic diversity was much higher in the EIO than in the WIO, suggesting that the EIO is the geographical origin of the species. Given the large distance between the disjunct populations and the short pelagic larval duration, long‐distance dispersal is rather unlikely. A stepping stone model involving islands in the Central Indian Ocean is a more likely scenario for colonization of the WIO.  相似文献   

长山群岛水环境基本特征与水资源开发研究     

邓伟 《地理科学》1997,17(3):278-284

长山群岛特有的地质，地理环境肽其气候条件决定其水环境容量水，水资源有限。海岛区域开发协调发展的道路，水资源开发不应以损害水环境炒代价，必须走水资源持续利用的开发模式  相似文献