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1.
Jo De Waele Ilenia M. D'Angeli Tomaso Bontognali Paola Tuccimei Denis Scholz Klaus Peter Jochum Andrea Columbu Stefano M. Bernasconi Joan J. Fornós Esteban R. Grau González Nicola Tisato 《地球表面变化过程与地形》2018,43(11):2313-2326
A flight of marine terraces along the Cuban coast records Quaternary sea‐level highstands and a general slowly uplifting trend during the Pleistocene. U/Th dating of these limestone terraces is difficult because fossil reef corals have been affected by open system conditions. Terrace ages are thus often based on geological and geomorphological observations. In contrast, the minimum age of the terraces can be constrained by dating speleothems from coastal mixing (flank margin) caves formed during past sea‐level highstands and carving the marine limestones. Speleothems in Santa Catalina Cave have ages >360 ka and show various cycles of subaerial–subaqueous corrosion and speleothem growth. This suggests that the cave was carved during the MIS 11 sea‐level highstand or earlier. Some stalagmites grew during MIS 11 through MIS 8 and were submerged twice, once at the end of MIS 11 and then during MIS 9. Phreatic overgrowths (POS) covering the speleothems suggest anchialine conditions in the cave during MIS 5e. Their altitude at 16 m above present sea level indicates a late Pleistocene uplift rate of <0.1 mm/ka, but modelling also shows uplift to have been insignificant over a long timespan during the middle Pleistocene since the cave was carved. Our study shows that some flank margin caves in the region of Matanzas are older than commonly believed (i.e. MIS 11 rather than MIS 5). These caves not only can be preserved but are good markers of interglacial sea‐level highstands, more reliable than marine abrasion surfaces. Copyright © 2018 John Wiley & Sons, Ltd. 相似文献
2.
A major carbonate reef which drowned 13 ka is now submerged 150 m below sea level on the west coast of the island of Hawaii. A 25-km span of this reef was investigated using the submersibleMakali'i. The reef occurs on the flanks of two active volcanoes, Mauna Loa and Hualalai, and the lavas from both volcanoes both underlie and overlie the submerged reef. Most of the basaltic lava flows that crossed the reef did so when the water was much shallower, and when they had to flow a shorter distance from shoreline to reef face. Lava flows on top of the reef have protected it from erosion and solution and now occur at seaward-projecting salients on the reef face. These relations suggest that the reef has retreated shoreward as much as 50 m since it formed. A 7-km-wide shadow zone occurs where no Hualalai lava flows cross the reef south of Kailua. These lava flows were probably diverted around a large summit cone complex. A similar shadow zone on the flank of Mauna Loa volcano in the Kealakekua Bay region is downslope from the present Mauna Loa caldera, which ponds Mauna Loa lava and prevents it from reaching the coastline. South of the Mauna Loa shadow zone the - 150 m reef has been totally covered and obscured by Mauna Loa lava. The boundary between Hualalai and Mauna Loa lava on land occurs over a 6-km-wide zone, whereas flows crossing the - 150 m reef show a sharper boundary offshore from the north side of the subaerial transition zone. This indicates that since the formation of the reef, Hualalai lava has migrated south, mantling Mauna Loa lava. More recently, Mauna Loa lava is again encroaching north on Hualalai lava. 相似文献
3.
Keiichi Sasaki Akio Omura Tetsuo Miwa Yoshihiro Tsuji Hiroki Matsuda Toru Nakamori Yasufumi Iryu Tsutomu Yamada Yuri Sato Hiroshi Nakagawa 《Island Arc》2006,15(4):455-467
Abstract High-resolution seismic reflection profiles delineated the distribution of mound-shaped reflections, which were interpreted as reefs, beneath the insular shelf western off Irabu Island, Ryukyus, southwestern Japan. A sediment core through one of the mounded structures was recovered from the sea floor at a depth of −118.2 m by offshore drilling and was dated by radiometric methods. The lithology and coral fauna of the core indicate that the mounded structure was composed of coral–algal boundstone suggesting a small-scaled coral reef. High-precision α-spectrometric 230 Th/234 U dating coupled with calibrated accelerator mass spectrometric 14 C ages of corals obtained reliable ages of this reef ranging from 22.18 ± 0.63 to 30.47 ± 0.98 ka. This proves that such a submerged reef was formed during the lowstand stage of marine oxygen isotope stages 3–2. The existence of low-Mg calcite in the aragonitic coral skeleton of 22.18 ± 0.63 ka provides evidence that the reef had once been exposed by lowering of the relative sealevel to at least −126 m during the last glacial maximum in the study area. There is no room for doubt that a coral reef grew during the last glacial period on the shelf off Irabu Island of Ryukyus in the subtropical region of western Pacific. 相似文献
4.
The submarine Mahukona Volcano, west of the island of Hawaii, is located on the Loa loci line between Kahoolawe and Hualalai Volcanoes. The west rift zone ridge of the volcano extends across a drowned coral reef at about-1150 m and a major slope break at about-1340 m, both of which represent former shoreines. The summit of the volcano apparently reached to about 250 m above sea level (now at-1100 m depth) did was surmounted by a roughly circular caldera. A econd rift zone probably extended toward the east or sutheast, but is completely covered by younger lavas from the adjacent subaerial volcanoes. Samples were vecovered from nine dredges and four submersible lives. Using subsidence rates and the compositions of flows which drape the dated shoreline terraces, we infer that the voluminous phase of tholeiitic shield growth ended about 470 ka, but tholeiitic eruptions continued until at least 435 ka. Basalt, transitional between tholeiitic and alkalic basalt, erupted at the end of tholeiitic volcanism, but no postshield-alkalic stage volcanism occurred. The summit of the volcano apparently subcided below sea level between 435 and 365 ka. The tholeiitic lavas recovered are compositionally diverse. 相似文献
5.
在阿尔金构造系中,阿尔金走滑断裂具有逆冲分量。文中将阿尔金构造系的逆冲活动分为西、中、东3段描述。西段从阿依耐克至车尔臣河河口,阿尔金南缘断裂具有逆冲活动迹象,在山前发育了规模较小的逆冲断层,有较新的地貌面被错动;中段从车尔臣河河口至拉配泉一带,在阿尔金山北缘发育大规模的逆冲断层,有较新的地貌面被错动;东段从拉配泉至宽滩山,逆冲断层有2种形式,此段阿尔金北缘断裂有逆冲分量,同时在阿尔金山北缘及山前冲洪积扇上发育逆冲断裂。自晚更新世中晚期以来,中段及东段逆冲速率<2mm/a。中段西部江尕拉萨依地区自16kaBP以来逆冲速率约为0.33mm/a,中部米兰桥一带自32kaBP以来的逆冲速率约为1.42mm/a。东段最大的逆冲速率在近中部的团结乡,自约5.31kaBP以来达到约1.81mm/a,向东西两端有减小的趋势,在西部柳城子自约72.36kaBP以来的逆冲速率为0.57mm/a,而东端的红柳沟自约8.99kaBP以来仅为0.05mm/a。团结乡地区约自19kaBP以来,逆冲活动有增强的趋势 相似文献
6.
Raised marine terraces and submerged insular shelves are used through an integrated approach as markers of relative sea level changes along the flanks of the Salina volcanic island (Aeolian Arc, southern Italy) for the purpose of evaluating its crustal vertical deformation pattern through time. Paleo sea level positions are estimated for the terrace inner margins exposed subaerially at different elevations and the erosive shelf edges recognized offshore at different depths. Compared with the eustatic sea levels at the main highstands (for the terraces) and lowstands (for the shelf edges) derived from the literature, these paleo sea level markers allowed us to reconstruct the interplay among different processes shaping the flanks of the island and, in particular, to quantify the pattern, magnitudes and rates of vertical movements affecting the different sectors of Salina since the time of their formation. A uniform uplift process at rates of 0.35 m ka−1 during the Last Interglacial is estimated for Salina (extended to most of the Aeolian Arc) as evidence of a regional (tectonic) vertical deformation affecting the sub-volcanic basement in a subduction-related geodynamic context. Before that, a dominant subsidence at rates of 0.39–0.56 m ka−1 is instead suggested for the time interval between 465 ka (MIS 12) and the onset of the Last Interglacial (MIS 5.5, 124 ka). By matching the insular shelf edges with the main lowstands of the sea level curve, a relative age attribution is provided for the (mostly) submerged volcanic centres on which the deepest (and oldest) insular shelves were carved, with insights on the chronological development of the older stages of Salina and the early emergence of the island. The shift from subsidence to uplift at the Last Interglacial suggests a major geodynamic change and variation of the stress regime acting on the Aeolian sub-volcanic basement. © 2019 John Wiley & Sons, Ltd. 相似文献
7.
Alix Lombard Anny Cazenave Pierre Yves Le Traon Stephanie Guinehut Cécile Cabanes 《Ocean Dynamics》2006,56(5-6):445-451
In this paper, we first discuss the controversial result of the work by Cabanes et al. (Science 294:840–842, 2001), who suggested that the rate of past century sea level rise may have been overestimated, considering the limited and heterogeneous
location of historical tide gauges and the high regional variability of thermal expansion which was supposed to dominate the
observed sea level. If correct, this conclusion would have solved the problem raised by the IPCC third assessment report [Church
et al, Cambridge University Press, Cambridge, pp 881, 2001], namely, the factor two difference between the 20th century observed sea level rise and the computed climatic contributions.
However, recent investigations based on new ocean temperature data sets indicate that thermal expansion only explains part
(about 0.4 mm/year) of the 1.8 mm/year observed sea level rise of the past few decades. In fact, the Cabanes et al.’s conclusion
was incorrect due to a contamination of abnormally high ocean temperature data in the Gulf Stream area that led to an overestimate
of thermal expansion in this region. In this paper, we also estimate thermal expansion over the last decade (1993–2003), using
a new ocean temperature and salinity database. We compare our result with three other estimates, two being based on global
gridded data sets, and one based on an approach similar to that developed here. It is found that the mean rate of thermosteric
sea level rise over the past decade is 1.5±0.3 mm/year, i.e. 50% of the observed 3 mm/year by satellite altimetry. For both
time spans, past few decades and last decade, a contribution of 1.4 mm/year is not explained by thermal expansion, thus needs
to be of water mass origin. Direct estimates of land ice melt for the recent years account for about 1 mm/year sea level rise.
Thus, at least for the last decade, we have moved closer to explaining the observed rate of sea level rise than the IPCC third
assessment report. 相似文献
8.
The TOPEX/POSEIDON (T/P) satellite altimeter mission has provided estimates of global mean sea level since late 1992 with a precision of approximately 4 mm. Over the first 3.5 years of the mission, T/P has observed a mean sea level rise of +0.5 mm/year when on-board estimates of the instrument drift are employed (and after correcting for a recently discovered software error), and +2.8 mm/year when an additional external tide gauge-based calibration estimate is used. A preliminary estimate of the error in the latter estimate is 1.3 mm/year, however this issue requires more research. Characterization of the observed sea level variations using Empirical Orthogonal Functions (EOFs) indicates that most of the mean sea level rise can be described by a single mode of the EOF expansion. The spatial characteristics of this mode suggests it is related to the El Nino Southern Oscillation (ENSO) phenomena. EOF analysis of sea level variations from the Semtner/Chervin ocean circulation model reveal a nearly identical mode, although its effect on mean sea level is unknown due to a constant volume constraint used in the model. EOF analysis of measured sea surface temperature (SST) variations also show a mode with similar temporal and spatial structure. However, the concentration of the observed sea level rise in this mode does not preclude the possibility that multiple phenomena have contributed to this mode, thus a link between the observed sea level rise and the ENSO phenomena is only weakly suggested. The absolute value of the observed mean sea level rise will depend on refinements currently being made in the instrument calibration techniques. In addition, the possibility of interannual and decadal variations of global mean sea level requires that a much longer time series of satellite altimetry be collected before variations caused by climate change can be unambiguously detected. 相似文献
9.
Quantitative analyses of microfossils and stable isotopic analysis were carried out for Core SCS-12 in the southwestern slope
of the South China Sea (SCS). A high-resolution paleoceanographic record for the last 13 ka was revealed with the AMS14C dates. The southern SCS has experienced stepwise paleoceanographic changes since the last deglaciation. The oxygen isotopic
stage 1/2 boundary around 12.05 ka B. P. and the end of the last deglaciation around 7.70 ka B.P. are two rapid change periods
(corresponding to the terminationIa and terminationIb, respectively), in between is a slow change period. The authors infer that the sea level stood at - 110 m before the terminationIa, roughly the same as today after the termination IB, and about - 50 m in between. Subsequently, the average winter sea surface temperature and salinity obviously increased while
paleo-productivity decreased since 12.05 ka B.P. The early Holocene CaCO3 preservation spike, coupled with a high abundance of pteropoda and CaCO3 content, occurred around 7.70 ka B. P.
Project supported by the National Natural Science Foundation of China (Grant Nos. 49576286 and 49732086). 相似文献
10.
位于帕米尔前缘逆冲推覆体(Pamir Front Thrust,PFT)东端的木什滑脱背斜,是帕米尔弧形推覆构造带最前缘和最新的变形带。对地形横剖面、纵剖面和水系发育特征的分析表明,木什背斜总体上具有由西向东扩展生长的特征。在背斜核部及北翼发育数级开阔平坦的沿轴向展布的河流阶地,阶地可划分为4期。利用阶地堆积细颗粒石英光释光测年获得阶地面T2a、T3和T4的形成年龄分别为(15.8±2.40)ka、(55.1±10.3)ka、(131.4±23.9)ka。伴随背斜的生长扩展,河流阶地面发生了横向和纵向掀斜,并形成断层陡坎和褶皱陡坎。木什背斜晚第四纪的缩短和隆升主要是通过褶皱翼旋转机制进行的,估算其最小缩短速率为(1.6±0.3)mm/a,最小隆升速率为(1.9±0.3)mm/a。与此同时,沿轴向背斜发生了向东的侧向迁移和旋转。根据背斜垂直隆升与侧向扩展之间的关系,估算背斜在131～16ka期间向东的侧向迁移扩展速率较快,为 (14.6±3.6)mm/a; 自16ka至今,侧向迁移扩展速率迅速减小至(1.7±0.3)mm/a,背斜向东的迁移扩展可能已基本停止,而以侧向旋转为主。 相似文献
11.
Relationship between subsidence and volcanic load,Hawaii 总被引：1，自引：0，他引：1
J. G. Moore 《Bulletin of Volcanology》1970,34(2):562-576
A computer analysis of tide-gage records in the northeast Pacific indicates that the active volcanic islands of eastern Hawaii are subsiding at a rate considerably faster than the eustatic rise of sea level. The rate of absolute subsidence increases progressively toward the center of current activity on the Island of Hawaii. Honolulu, Oahu, appears to be stable; Kahului, Maui, is subsiding at 1.7 mm per year; and Hilo, Hawaii, is subsiding at 4.8 mm per year. This subsidence is apparently related to downbowing of the crust throughout a zone 400 km in diameter by the weight of volcanic material added to the crust by active volcanoes, principally Mauna Loa and Kilauea on the Island of Hawaii. The Hawaiian Arch encircles the subsiding zone and may be uplifted by material moving down and outward from the zone of subsidence. The annual volume of subsidence is about 270×106 m3, whereas the average annual volume of erupted basalt on the Island of Hawaii (based on historic records back to about 1820) is about 50×106 m3. The great excess of subsidence over volcanic addition cannot be reconciled by isostatic models, and is apparently the result of other processes operating in the volcano and its basement thet are poorly understood. Probably the more important of these processes are intrusions and submarine volcanism, both of which are providing additional unseen load on the volcanoes. Furthermore, the rate of eruption may be uplifted by material moving down and outward from the zone of subsidence may be overestimated due to localized downslope movement of the margins of the islands. 相似文献
12.
Late Pleistocene and Holocene slip rate of the Northern Wadi Araba fault, Dead Sea Transform, Jordan
Tina M. Niemi Hongwei Zhang Mohammad Atallah J. Bruce J. Harrison 《Journal of Seismology》2001,5(3):449-474
The Wadi Araba Valley is a morphotectonic depression along part of theDead Sea Transform (DST) plate boundary that separates the Arabian plateon the east from the Sinai subplate on the west. The Wadi Araba fault(WAF) is the main strike-slip faults one of between the Gulf of Aqaba and the E-Wtrending Khunayzira (Amatzayahu) fault that bounds the southern end ofthe Dead Sea. Just south of the Dead Sea, the WAF cuts across severalgenerations of alluvial fans that formed on tributaries to the Wadi Dahalafter the regression of Late Pleistocene Lake Lisan ca. 15 ka. Geomorphicand stratigraphic evidence of active faulting, including left-laterally offsetstream channels and alluvial-fan surfaces, yielded fault slip-rate data for thenorthern segment of WAF. Typical cumulative displacements of 54 m,39 m, and 22.5 m of stream channels and alluvial-fan surfaces acrossthe fault were measured from detailed geologic and topographic mapping.The 54 m offset of the oldest alluvial-fan surface (Q
f1
) occurredafter the final lowering of Lake Lisan (16–15 ka) and before 11 ka yieldinga slip-rate range of 3.4 mm/yr to 4.9 mm/yr. Based on radiocarbonages of charcoal and landsnail shell samples from the buried Q
f2
alluvial-fan deposits exposed in trenches excavated across the fault, the39 m and 22.5 m offsets occurred after 9 ka and 5.8 ka, respectively. These data yield a slip-rate range between 3.9 mm/yr and 6.0 mm/yr.The small variability in these slip-rate estimates for different time periodssuggests that the northern Wadi Araba fault has maintained a relativelyconstant slip rate in the past 15 ka. We calculate an average slip rate of 4.7± 1.3 mm/yr since 15 ka based on the three separate displacementsand age estimates. Five separate offsets of 3 m were measured from gullybends and the offset of small fault-scarp alluvial fans. These displacementdata suggest a coseismic slip of 3 m in the last earthquake, or acumulative slip of 3 m in the past few earthquakes. A maximum slip of3 m correspond to a Mw 7 earthquake that ruptures about 49 km offault length. Using an average slip rate of 4.7 ± 1.3 mm/yr togetherwith a 3-m slip-per-event suggests a maximum earthquake recurrence intervalof this fault segment of 500 to 885 years. 相似文献
13.
2 Conclusion Fenghuangshan-Tianshui fault is a Holocene active fault. It laterally slips at the average rate of 1.1 mm/a during 6.4 ka
and vertically slips at the average rate of 0.37 mm/a and 0.16 mm/a since the time 16.6 ka and 6.4 ka before respectively.
Diaogoumeng-Dongjiawan segment has occurred an abrupt event in the period of 6.4 ka BP, which is assumed to be related to
the 734 Tianshui M=7 earthquake, but further work is still necessary.
Foundation item: Chinese Joint Seismological Science Foundation (198023). 相似文献
14.
Because of the significance to the formation and evolution of the Tibetan plateau, the displacement and slip rate of the Altyn Tagh fault have been topics full of disputation. Scientists who hold different opinions on the evolution of Tibet insist on different slip rates and displacements of the fault zone. In the article, study is focused on the late Quaternary slip rate of the Altyn Tagh fault west of the Cherchen River (between 85°E and 85°45'E). On the basis of high resolution SPOT images of the region, three sites, namely Koramlik, Aqqan pasture and Dalakuansay, were chosen for field investigation. To calculate the slip rate of the fault, displacement of terraces was measured on SPOT satellite images or in situ during fieldwork and thermo-luminescence (TL) dating method was used. To get the ages of terraces, samples of sand were collected from the uppermost sand beds that lie just under loess. The method for calculating slip rate of fault is to divide the displacement of terrace risers by the age of its neighboring lower terrace. The displacement of rivers is not considered in this article because of its uncertainties. At Koramlik, the slip rate of the Altyn Tagh fault is 11.6±2.6mm/a since 6.02±0.47ka B.P and 9.6±2.6mm/a since 15.76±1.19ka B.P. At Aqqan pasture, about 30km west of Koramlik, the slip rate is 12.1±1.9mm/a since 2.06±0.16 ka B.P. At Dalakuansayi, the slip rate of the fault is 12.2±3.0mm/a since 4.91±0.39ka B.P. Hence, we get the average slip rate of 11.4±2.5mm/a for the western part of the Altyn Tagh Fault since Holocene. This result is close to the latest results from GPS research. 相似文献
15.
焉耆盆地是塔里木盆地东北缘天山山间的重要坳陷区,盆地北缘发育的和静逆断裂-褶皱带是一条现今活动强烈的逆断裂-褶皱带,对其第四纪以来缩短量和隆升量的计算有利于分析该区域的构造活动情况,对缩短速率和隆升速率的估计可以与天山造山带其他区域的活动速率进行横向对比,从而反映出焉耆盆地在天山晚新生代构造变形的作用。在深部资料不足的情况下,对背斜形态完整、构造样式简单的和静逆断裂-褶皱带,利用地表可获得的地层和断层产状,通过恢复褶皱几何形态,计算褶皱的缩短量、隆升量和断层滑动量,得到逆断裂-褶皱带早更新世晚期(1.8Ma)、中更新世(780ka)和晚更新世中期(80ka)以来的缩短量分别为1.79km、0.88km和26m,初步估计的缩短速率分别为0.99mm/a、1.13mm/a和0.33mm/a。显示和静逆断裂-褶皱带自开始形成以来构造活动强度并不一致。与地壳形变观测结果对比,作为南天山东段最主要的坳陷区,焉耆盆地吸收了这一区域(86°～88°E)的大部分地壳缩短,且主要表现为盆地北缘新生逆断裂-褶皱带的强烈变形。 相似文献
16.
五台山北麓断裂位于山西地堑系北部。本文以五台山北麓断裂繁峙段的地质地貌为研究对象,分别在繁峙县的大峪村和岗里村两地断裂沿线进行了无人机测量。利用三维结构的运动重建技术(Structure from Motion,SfM)进行影像数据处理,得到高精度点云数据,并通过进一步处理获得了分辨率达0.5m的高清断错地貌正射影像(DOM)和数字高程模型(DEM)。通过对典型地区的详细野外调查和挖掘探槽等手段对该段晚第四纪的活动性进行研究,发现断层晚第四纪以来的活动主要是以正倾滑运动为主。同时在五台山北麓断裂沿线的大峪村、岗里村等地进行了断错地貌分析和晚第四纪滑动速率计算,得到约20ka以来的断层垂向滑动速率为0.4—0.6mm/a,近18ka以来该段发生过至少两次古地震事件。古地震事件和滑动速率分析表明,五台山北麓断裂晚第四纪,尤其是全新世以来活动强烈,且不同段落存在明显的活动性差异。 相似文献
17.
宁金抗沙西麓断裂位于亚东-谷露裂谷系南部.本文利用15 m分辨率的ETM 遥感影像和20 m分辨率的数字高程模型,结合野外地质考察,重点研究了该断裂的详细结构和晚第四纪以来的活动习性.依据与热隆盆地的关系,该断裂主要分为三段,热隆盆地以北为北段,热隆盆地边界断裂为中段,热隆盆地以南为南段.该断裂在强烈正断的同时兼具有左旋走滑运动,自中更新世以来,主要有三期活动,活动开始时间分别为384 ka1、08 ka和34 ka,累积水平活动速率分别为4.8 mm/a5、.5 mm/a和6.4 mm/a.断裂自中更新中期以来的垂直断错速率为1 mm/a. 相似文献
18.
The main break-in-slope on the northern submarine flank of Molokai at −1500 to −1250 m is a shoreline feature that has been only modestly modified by the Wailau landslide. Submarine canyons above the break-in-slope, including one meandering stream, were subaerially carved. Where such canyons cross the break-in-slope, plunge pools may form by erosion from bedload sediment carried down the canyons. West Molokai Volcano continued infrequent volcanic activity that formed a series of small coastal sea cliffs, now submerged, as the island subsided. Lavas exposed at the break-in-slope are subaerially erupted and emplaced tholeiitic shield lavas. Submarine rejuvenated-stage volcanic cones formed after the landslide took place and following at least 400–500 m of subsidence after the main break-in-slope had formed. The sea cliff on east Molokai is not the headwall of the landslide, nor did it form entirely by erosion. It may mark the location of a listric fault similar to the Hilina faults on present-day Kilauea Volcano. The Wailau landslide occurred about 1.5 Ma and the Kalaupapa Peninsula most likely formed 330±5 ka. Molokai is presently stable relative to sea level and has subsided no more than 30 m in the last 330 ka. At their peak, West and East Molokai stood 1.6 and 3 km above sea level. High rainfall causes high surface runoff and formation of canyons, and increases groundwater pressure that during dike intrusions may lead to flank failure. Active shield or postshield volcanism (with dikes injected along rift zones) and high rainfall appear to be two components needed to trigger the deep-seated giant Hawaiian landslides. 相似文献
19.
文中采用钻探技术对南口-孙河断裂带进行了试验探测研究,并通过层序地层学、岩性岩相分析、磁化率分析与年代测定等方法建立了钻孔联合剖面,进而研究了断层距今60ka以来的多期活动特征,得出断裂带的3个活跃期是60～47kaBP、36～28kaBP与16kaBP以来,其余时段为相对平静期。断裂带的平均垂直位错速率,距今60～37ka之间约为0.35mm/a,37～32ka之间为0mm/a,32～12ka之间为0.78mm/a,12ka以来为0.35mm/a。研究认为,与传统的岩性、沉积相分析方法相比,层序地层学方法在钻孔地层对比与隐伏断层活动分期研究中有一定的优势 相似文献
20.
Geomorphic study on Wjiahe segment of Serteng piedmont fault,Inner Mongolia is made.Throuth analysis of the available data in combination with the results of predecessors‘studies it can be obtained that average vertical displacement rate is 0.48-0.75mm/a along the Wujiahe segment since the late Pleistocene(14.450-22.340ka BP)and 0.56-0.88mm/s since the early-middle Holocene(5.570-8.830ka BP).Analyzing paleoseismic phenomena revealed in the excavated 5trenches in combination with the results of predecessors‘studies of paleoearthquakes on the fault,we determine five paleoseismic events on the Wujiahe segment of Serteng piedmont fault since 27.0ka BP and the recurrence interval to be about 4.300-4.400ka,A cluster of paleoearthquakes occurred probably during 8.000-9.000ka BP and two paleoeismic events in 10.000-20.000ka BP may be missed.A comparison between height of fault scarps and sum of displacement caused by paleoseismic events revealed in trenches,and recurrence interval of paleoseismic events obtained from average displacement rate along the fault and the disloca-tion by one event suggest that three paleoseismic events are absent in Alagaitu trench.Two paleoseismic events may be absent on the whole active fault segment. 相似文献