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51.
泌阳断陷下第三系核三上亚段层序地层学研究 总被引:4,自引:0,他引:4
根据陆相层序在地震剖面及电测曲线上的识别标志和在岩石矿物学方面的旋回性特征,采用沉积旋回分析技术及Fischer图解法,将泌阳断陷双河—赵凹地区下第三系核三段上亚段划分为3个陆相层序,其沉积体系呈现冲积扇—扇三角洲—湖相空间配置关系。在这3个陆相层序中共发育小层序组13个,其中可识别的小层序达50余个。针对研究区目的层段所划3个陆相层序发育的共同特点,在连井剖面层序地层对比的基础上,编制了研究区目的层段的陆相层序地层等时框架模式。 相似文献
52.
Molecular biomarker record of paleooceanographic environment in the East China Sea during the last 35000 years 总被引:2,自引:0,他引:2
By reference of the δ18O and δ13C isotopic compositions of G.sacculifer and accelerator mass spectrometry (AMS)14C dates, the U
K
37
, ∑C
–
21
/∑C
+-
22
and Pr/Pn in core DGKS9603 have been used to characterize the changes of paleooceanographic environment occurring in the
East China Sea (ECS) during the last 35000 years. The stratigraphic records of these proxies have shown that during the last
35 ka the Okinawa Trough has gone through 7 stronger cold-climate events (C1–C7) and 9 terrigenous matter-decreasing events (e2–e9), of which, the C1 corresponds to the cold episode occurring in the middle late Holocene, C2–C4 and C7 correspond to the H1–H4 events, respectively. e1 and e3–e8 correspond to the decrease of sea surface temperature (SST), respectively. The terrigenous inputs increased when Heinrich
events occurred. Climate colding resulted in the decrease of terrigenous matter transported by rivers, and the increase of
that transported by winter monsoon. Heinrich events are closely related to East Asia monsoon. During the Last Glacial Maximum
(LGM, 15.5–25.8 Cal ka BP), reduction environment fluctuated strongly, bringing forth three stronger reduction events (R1–R3) and one weaker reduction event (O), of which, R1–R3 correspond to the decrease of SST and increase of terrigenous nutrient and O corresponds to the decrease of terrigenous nutrient.
The fluctuation of reduction condition must be related to the change of sea surface productivity. 相似文献
53.
Geochemistry of Peruvian near-surface sediments 总被引:6,自引:0,他引:6
Philipp Böning Michael E. Böttcher Cornelia Kriete Sven Lars Borchers 《Geochimica et cosmochimica acta》2004,68(21):4429-4451
Sixteen short sediment cores were recovered from the upper edge (UEO), within (WO) and below (BO) the oxygen minimum zone (OMZ) off Peru during cruise 147 of R/V Sonne. Solids were analyzed for major/trace elements, total organic carbon, total inorganic carbon, total sulfur, the stable sulfur isotope composition (δ34S) of pyrite, and sulfate reduction rates (SRR). Pore waters were analyzed for dissolved sulfate/sulfide and δ34S of sulfate. In all cores highest SRR were observed in the top 5 cm where pore water sulfate concentrations varied little due to resupply of sulfate by sulfide oxidation and/or diffusion of sulfate from bottom water. δ34S of dissolved sulfate showed only minor downcore increases. Strong 32S enrichments in sedimentary pyrite (to −48‰ vs. V-CDT) are due to processes in the oxidative part of the sulfur cycle in addition to sulfate reduction. Manganese and Co are significantly depleted in Peruvian upwelling sediments most likely due to mobilization from particles settling through the OMZ, whereas release of both elements from reducing sediments only seems to occur in near-coastal sites. Cadmium, Mo and Re are exceptionally enriched in WO sediments (<600 m water depth). High Re and moderate Cd and Mo enrichments are seen in BO sediments (>600 m water depth). Re/Mo ratios indicate anoxic and suboxic conditions for WO and BO sediments, respectively. Cadmium and Mo downcore profiles suggest considerable contribution to UEO/WO sediments by a biodetrital phase, whereas Re presumably accumulates via diffusion across the sediment-water interface to precipitation depth. Uranium is distinctly enriched in WO sediments (due to sulfidic conditions) and in some BO sediments (due to phosphorites). Silver transfer to suboxic BO sediments is likely governed by diatomaceous matter input, whereas in anoxic WO sediments Ag is presumably trapped due to sulfide precipitation. Cadmium, Cu, Zn, Ni, Cr, Ag, and T1 predominantly accumulate via biogenic pre-concentration in plankton remains. Rhenium, Sb, As, V, U and Mo are enriched in accordance with seawater TE availability. Lead and Bi enrichment in UEO surface sediments is likely contributed by anthropogenic activity (mining). Accumulation rates of TOC, Cd, Mo, U, and V from Peruvian and Namibian sediments exceed those from the Oman Margin and Gulf of California due to enhanced preservation off Peru and Namibia. 相似文献
54.
The distributions of free 4-desmethyl sterols in sediments from the Peru coastal zone at 15°S have been determined. Major free sterols in the surface sediments include cholesterol, which is mainly derived from zooplankton, and two C28 sterols: 24-methylcholesta-5,24(28)-dien-3β-ol and 24-methylcholesta-5,22E-dien-3β-ol both of which are derived fro diatoms. Their concentrations decrease by almost an order of magnitude in the top 20 cm of sediment depth, indicating that free sterols are rapidly degraded in this sedimentary environment. Lipids from higher plants were also detected: long chain fatty acids and alcohols and various triterpenoid alcohols, including taraxerol, lupeol and α- and β-amyrin. The concentrations of most terrigenous lipids varied by less than a factor of 3 over the same depth, and these changes were not correlated with changes in the concentrations of total organic carbon. Below 3 cm, lipids from higher plants predominated in the extractable lipid distributions due to the more rapid degradation of marine lipids. We postulate that there are significant marine sources of the higher plant sterols 24-ethylcholesterol, 24-ethylcholesta-5,22E-dien-3β-ol and 24-methylcholesterol in these sediments. A high proportion of many of the terrigenous lipids in these sediments are probably transported into the coastal zone by rivers, rather than from the atmosphere, and then redistributed by bottom currents. 相似文献
55.
Since their first occurrence in the late Cretaceous, seagrasses have played a major role in carbonate production and sedimentation across shallow-water and nearshore environments, sustaining a prolific carbonate factory and contributing to sediment accumulation through the combination of baffling and trapping effects. Most reported Palaeogene seagrass occurrences developed in oligo?mesotrophic shallow warm-water habitats and are characterized by distinct associations of small and larger benthic foraminifers adapted to low terrigenous influence. This study describes a number of seagrass episodes interbedded in the Bartonian (middle Eocene) of San Fausto–Lazkua area (Navarra region, North Spain), within a nearshore to inner-ramp succession that, in spite of being deposited under general transgressive conditions, was highly influenced by terrigenous supply from the adjacent land. Up to twelve different seagrass bed intervals occur interbedded in a cyclical manner with high-energy nearshore siliciclastics and inner ramp bioclastic carbonates rich in mesophotic?oligophotic foraminifers and heterozoan biota (red algae, echinoderms, bryozoans). Seagrass deposits exhibit typical unsorted textures, abundant bioturbation and moderate to high terrigenous content, and comprise a characteristic skeletal association of epiphytic foraminifers, red algae and, most particularly, of abundant encrusting acervulinids, commonly with distinct hooked and tubular growth forms. This abundance of suspension-feeders relative to autotrophs and mixotrophs may be indicative of temperate waters, although the taxonomic diversity of the foraminiferal assemblages in both seagrass and non-seagrass embedding deposits supports the interpretation of shallow, warm-water conditions. The studied seagrass deposits provide evidence that high siliciclastic supply and associated nutrient input may determine the occurrence of temperate-like seagrass deposits in warm-water settings, analogous to extensive heterozoan carbonate production in modern shallow-tropical environments. Thus, the identification and correct interpretation of past seagrass-vegetated environments are crucial for reconstructing palaeoecological conditions in ancient shallow-marine environments. Therefore, in comparison with carbonate-dominated environments, the mixed terrigenous?carbonate seagrass deposits are volumetrically less important, presenting a more irregular, patchy distribution, and a skeletal assemblage dominated by heterotrophs, regardless of the water temperature. 相似文献
56.
南海中沙群岛以北至陆坡表层沉积物碳酸钙含量的分布 总被引:2,自引:0,他引:2
对南海北部(16°―20°N、114°―116°E)区域、285~4 175 m水深范围内78个表层样进行了碳酸钙含量分析。表层样碳酸钙含量变化范围是1.3%~87.8%,平均约25.6%;碳酸钙含量具有随水深增大而减小的趋势,在北部陆坡和中沙北海岭,碳酸钙含量突然变小的界面分别位于水深约3 000 m、3 250 m处。中沙北海岭碳酸钙含量40%等值线水深变化介于2 500~3 900 m之间,北部陆坡碳酸钙含量20%等值线水深范围约为2 180~3 515 m;碳酸钙含量10%等值线水深变化相对较小,在16°~17.5°N和17.5°~20°N范围内平均水深分别约4 009 m、3 551 m。研究区碳酸钙溶跃面可能位于水深约3 000 m处。18°N以北区域比18°N以南区域的陆源物质稀释作用强,且二者间陆源物质稀释作用强度的差异随水深从2 000 m增至3 000 m而逐渐减小,在水深超过3 000 m后基本保持不变。 相似文献
57.
58.
59.
文章围绕陆相碎屑岩成岩作用系统这一议题,概述了成岩作用系统研究的发展历程,总结近年来国内外成岩作用系统的研究进展,提出了未来的研究趋势。认为当前陆相碎屑岩成岩作用系统研究取得的进展包括5个方面:(1)原始沉积环境对成岩作用系统的影响,(2)成岩流体对成岩作用系统的影响,(3)构造作用对成岩作用系统的影响,(4)成岩系统的封闭性与成岩作用的关系,(5)层序控制下的成岩响应。未来成岩作用系统研究的趋势:各种实验手段的革新和综合利用、成岩系统过程恢复、成岩作用定量化研究及多学科交叉融合等方面将是未来成岩作用系统研究的主要方向,必将推动成岩作用系统研究进入新的阶段。 相似文献
60.
目前,绘图软件所绘制的岩性剖面图中,将所有岩性框架均用矩形来表示。对于陆源碎屑岩来说,这样既不能表示出其粒度变化情况,又不能反映出它形成时的沉积动力学特征。为了弥补绘图软件的这些不足,提出用曲边矩形代替矩形来绘制陆源碎屑岩岩性框架,并以表示正粒序陆源碎屑岩岩性框架的曲边矩形为例,详细推导了其曲边的函数表达式,为绘图软件的二次开发提供了陆源碎屑岩岩性框架绘制的一种数学模型。 相似文献