库车坳陷大北地区下白垩统巴什基奇克组储层成因地质分挝   总被引：6，自引：0，他引：6       下载免费PDF全文

张荣虎  张惠良  寿建峰  沈扬  李昌 《地质科学》2008,43(3)

塔里木盆地库车坳陷大北地区白垩系巴什基奇克组储层以细一中粒岩屑砂岩为主夹少量长石岩屑砂岩,杂基为铁泥质和泥质(2%～10%).胶结物以方解石(3%～15%)为主.粘土矿物以伊利石、绿泥石和伊/蒙混层为主,不含高岭石,伊/蒙混层中的蒙皂石含量一般为(15～20)%;主要孔隙组合为残余原生粒问孔-溶蚀孔-微孔隙,占储集空间总量的(50～90)%,其次为构造缝-溶蚀孔,主要的孔隙类型为溶蚀孔和裂缝,总体属于低孔低渗-特低孔特低渗储层.综合分析认为:阶段性的前陆构造逆冲推覆作用对沉积旋回性、水体盐度变化及物源区距离变化的控制至关重要;构造活跃期扇三角洲前缘环境中形成的差分选中-粗砂岩、近源快速堆积造成的高岩屑含量、干旱成湖导致的高碳酸盐胶结和早成岩期相对深埋-后期持续快速深埋压实作用,是特低孔特低渗储层的主要成因;而较优质储层足构造平缓期辫状河三角洲前缘环境中形成的分选好的中-细砂岩、早期表生溶蚀及弱碳酸盐胶结作用、早期构造破裂的复合作用及其叠加效应的结果.  相似文献   

辽宁沿海泥炭堆积与全新世海面变化     

符文侠  王玉广  刘国海 《海洋科学进展》1995,(2)

辽宁沿海分布有丰富的泥炭资源，主要为埋藏泥炭，属于低位型的草本泥炭。按其成因可分为泻湖型、河漫滩型和沟谷型泥炭三种类型。在整个全新世时期均有泥炭形成，可分为早、中、晚全新世三个发育期，中全新世是辽宁沿海泥炭发育的最盛时期；沉积速率为０．２５～１．１ｍｍ／ａ。全新世海侵，约在距今６０００～７０００ａ达到最大范围；近五千年来海面在下降过程中有波动和相对稳定时期。  相似文献   

Paleoenvironmental records of water level and climatic changes from the middle to late Holocene at a Lake Erie coastal wetland, Ontario, Canada   总被引：2，自引：0，他引：2  

Sarah A. Finkelstein  Anthony M. Davis 《Quaternary Research》2006,65(1):33-43

Pollen and diatom assemblages, and peat stratigraphies, from a coastal wetland on the northern shore of Lake Erie were used to analyze water level and climatic changes since the middle Holocene and their effects on wetland plant communities. Peat deposition began 4700 cal yr B.P. during the Nipissing II transgression, which was driven by isostatic rebound. At that time, a diatom-rich wild rice marsh existed at the site. Water level dropped at the end of the Nipissing rise at least 2 m within 200 yr, leading to the development of shallower-water plant communities and an environment too dry for most diatoms to persist. The sharp decline in water level was probably driven primarily by outlet incision, but climate likely played some role. The paleoecological records provide evidence for post-Nipissing century-scale transgressions occurring around 2300, 1160, 700 and 450 cal yr B.P. The chronology for these transgressions correlates with other studies from the region and implies climatic forcing. Peat inception in shallow sloughs across part of the study area around 700 cal yr B.P. coincides with the Little Ice Age. These records, considered alongside others from the region, suggest that the Little Ice Age may have resulted in a wetter climate across the eastern Great Lakes region.  相似文献   

Subsidence due to peat oxidation and impact on drainage infrastructures in a farmland catchment south of the Venice Lagoon   总被引：1，自引：0，他引：1  

G. Gambolati  M. Putti  P. Teatini  G. Gasparetto Stori 《Environmental Geology》2006,49(6):814-820

Large agricultural areas reclaimed in the past century, south of the Venice Lagoon, have experienced significant land subsidence due to oxidation of peat organic soils. This has exposed the region to flood hazard particularly during severe storms and has contributed to increase the marginal management cost of the infrastructures (ditches, levees, pumping stations) designed to operate the drainage system. Direct measurements and indirect evidence from the channel network suggest a land settlement between 1.5 and 2 m over the past 70 years. This paper provides an overview of the problem with important information on its most recent evolution.  相似文献   

Late Pliocene to late Pleistocene environments preserved at the Palisades Site, central Yukon River, Alaska     

Paul Matheus  James BegétOwen Mason  Carol Gelvin-Reymiller 《Quaternary Research》2003,60(1):33-43

The Palisades Site is an extensive silt-loam bluff complex on the central Yukon River preserving a nearly continuous record of the last 2 myr. Volcanic ash deposits present include the Old Crow (OCt; 140,000 yr), Sheep Creek (SCt; 190,000 yr), PA (2.02 myr), EC (ca. 2 myr), and Mining Camp (ca. 2 myr) tephras. Two new tephras, PAL and PAU, are geochemically similar to the PA and EC tephras and appear to be comagmatic. The PA tephra occurs in ice-wedge casts and solifluction deposits, marking the oldest occurrence of permafrost in central Alaska. Three buried forest horizons are present in association with dated tephras. The uppermost forest bed occurs immediately above the OCt; the middle forest horizon occurs below the SCt. The lowest forest bed occurs between the EC and the PA tephras, and correlates with the Dawson Cut Forest Bed. Plant taxa in all three peats are common elements of moist taiga forest found in lowlands of central Alaska today. Large mammal fossils are all from common late Pleistocene taxa. Those recovered in situ came from a single horizon radiocarbon dated to ca. 27,000 ¹⁴C yr B.P. The incongruous small mammal assemblage in that horizon reflects a diverse landscape with both wet and mesic environments.  相似文献   

岩溶浸没－内涝灾害研究   总被引：2，自引：0，他引：2  

光耀华 《地理研究》1996,15(4):24-31

水库周边岩溶浸没-内涝现象是水利水电设计的环境问题之一。80年代以来,已在若干水库发生了此类现象,造成了一定的经济损失,本文以红水河岩滩水电站库区的内涝为例,分析了岩溶浸没内涝的主要原因和形成条件,归纳为降雨、管道、水库三要素。讨论了岩溶浸没-内涝灾害的预测及对策。  相似文献   

Holocene peat and carbon accumulation rates in the southern taiga of western Siberia     

Wiebe Borren  Wladimir Bleuten 《Quaternary Research》2004,61(1):42-51

Although recent studies have recognized peatlands as a sink for atmospheric CO₂, little is known about the role of Siberian peatlands in the global carbon cycle. We have estimated the Holocene peat and carbon accumulation rate in the peatlands of the southern taiga and subtaiga zones of western Siberia. We explain the accumulation rates by calculating the average peat accumulation rate and the long-term apparent rate of carbon accumulation (LORCA) and by using the model of Clymo (1984, Philosophical Transactions of the Royal Society of London Series B 303, 605-654). At three key areas in the southern taiga and subtaiga zones we studied eight sites, at which the dry bulk density, ash content, and carbon content were measured every 10 cm. Age was established by radiocarbon dating. The average peat accumulation rate at the eight sites varied from 0.35 ± 0.03 to 1.13 ± 0.02 mm yr⁻¹ and the LORCA values of bogs and fens varied from 19.0 ± 1.1 to 69.0 ± 4.4 g C m⁻² yr⁻¹. The accumulation rates had different trends especially during the early Holocene, caused by variations in vegetation succession resulting in differences in peat and carbon accumulation rates. The indirect effects of climate change through local hydrology appeared to be more important than direct influences of changes in precipitation and temperature. River valley fens were more drained during wetter periods as a result of deeper river incision, while bogs became wetter. From our dry bulk density results and our age-depth profiles we conclude that compaction is negligible and decay was not a relevant factor for undrained peatlands. These results contribute to our understanding of the influence of peatlands on the global carbon cycle and their potential impact on global change.  相似文献   

Effects of peat on the shapes of alluvial channels: examples from the Cumberland Marshes, Saskatchewan, Canada     

Norman D. Smith  Marta Prez-Arlucea 《Geomorphology》2004,61(3-4):323-335

An avulsion of the lower Saskatchewan River in the 1870s inundated a large segment of peat-covered floodplain that subsequently has become aggraded with a broad (500 km²) belt of alluvium deposited by the redirected flow. Routing of water and sediment discharge through the avulsion-affected area has been accomplished mainly by networks of sandy bedded anastomosed channels that have formed, evolved, and abandoned as the alluvial belt prograded down the floodplain slope. These processes continue today, though at a much-reduced rate. New channels, formed by crevassing and basinward extension of distributaries, are initially small and shallow, with bottom elevations situated within the avulsive alluvium but above the pre-avulsion peat (floodplain) surface. Subsequent enlargement and downcutting of many of these channels eventually uncovers the underlying peat layer whose resistance to erosion exerts significant influence on cross-sectional shape and further channel development. Peat-floored channels tend to have rectangular cross-sections, high ratios of average to maximum depth (D/D_max), and a large range of width-to-depth ratios. If the channel continues to enlarge, the peat layer eventually becomes breached, commonly leading to temporarily irregular cross-sections caused by localized scouring at the breach sites. Eventually, the peat layer is completely eroded from the channel floor by undercutting and slumping, after which channel shape becomes governed mainly by other perimeter characteristics. Channels unaffected by peat, either before the peat layer is encountered during early channel development or after it is entirely removed, tend to have low width/depth ratios and a large range of D/D_max values.  相似文献   

Predicting the future DOC flux from upland peat catchments   总被引：6，自引：0，他引：6  

Fred Worrall  Tim Burt 《Journal of Hydrology》2005,300(1-4):126-139

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How a wet tropical rainforest copes with repeated volcanic destruction     

Leigh C.F. Jago  William E. Boyd 《Quaternary Research》2005,64(3):399-406

The Holocene Period for the province of West New Britain, Papua New Guinea, is characterised by periodic catastrophic volcanism. The region is mantled in dense wet tropical rainforest, and has been occupied by people since the Pleistocene. Analyses of peat from two nearby sites within a lowland rainforest environment provide us with a macro-level landscape account of the periodic destruction and recovery of the coastal forests during seven periods of volcanic activity in the latter part (2900 yr ago to present) of the Holocene. Radiocarbon dating shows the very close correlation of the peat and tephra layers at both sites, yet the pollen analysis reveals different vegetation communities. These initial results allow us to begin identifying the processes of recovery, and to recognise different ecological pressures placed on vegetation at these neighbouring sites. Evidence of hydrological changes are observed beginning with a marine incursion recorded at Garu Site 3 1360 ¹⁴C yr B.P. The distinct differences in the vegetation re-establishment and community regeneration rates suggest the greater level of disturbance at Garu Site 1 could be related to the depth of the ashfall, although the proximity of a known human settlement may also be a contributing factor. Of note, palynologically, we found that the fern spore flora is particularly rich and believe it will be useful for ecological interpretation.  相似文献