末次冰期深切谷的识别及其在生物气勘探中的意义──以钱塘江深切谷为例     

林春明 《浙江国土资源》1996,(2)

本文通过钱塘江深切谷的论述对末次冰期深切谷的恢复主要依据下列证据进行：（1）谷底为侵蚀不整合面，为末次冰期海平面下降，河流侵蚀切割所致；（2）谷内为异常厚的河流沉积物所充填，是冰后期海平面上升时形成，其中河漫滩沉积年代约14000～7500a以前；（3）深切谷之上被海相地层覆盖。超浅层生物气田分布在深切谷内，当今河流及全新世晚期河口湾与末次冰期深切谷既有区别又有继承性，其流域是浅层生物气藏分布的有利地段。  相似文献   

Early and Middle Valdaian glaciations, ice-dammed lakes and periglacial interstadials in northwest Russia: new evidence from the Pyoza River area     

Michael Houmark-Nielsen  Igor Demidov  Svend Funder  Kari Grsfjeld  Kurt H. Kjr  Eiliv Larsen  Nadya Lavrova  Astrid Lys  Jan K. Nielsen 《Global and Planetary Change》2001,31(1-4)

The Pyoza River area in the Arkhangelsk district exposes sedimentary sequences suitable for study of the interaction between consecutive Valdaian ice sheets in Northern Russia. Lithostratigraphic investigations combined with luminescence dating have revealed new evidence on the Late Pleistocene history of the area. Overlying glacigenic deposits of the Moscowian (Saalian) glaciation marine deposits previously confined to three separate transgression phases have all been connected to the Mikulinian (Eemian) interglacial. Early Valdaian (E. Weichselian) proglacial, lacustrine and fluvial deposits indicate glaciation to the east or north and consequently glacier damming and meltwater run-off in the Pyoza area around 90–110 ka BP. Interstadial conditions with forest-steppe tundra vegetation and lacustrine and fluvial deposition prevailed at the end of the Early Valdaian around 75–95 ka BP. A terrestrial-based glaciation from easterly uplands reached the Pyoza area at the Early to Middle Valdaian transition around 65–75 ka BP and deposited glaciofluvial strata and subglacial till (Yolkino Till). During deglaciation, laterally extensive glaciolacustrine sediments were deposited in ice-dammed lakes in the early Middle Valdaian around 55–75 ka BP. The Barents–Kara Sea ice sheet deposited the Viryuga Till on the lower Pyoza from northerly directions. The ice sheet formed the Pyoza marginal moraines, which can be correlated with the Markhida moraines further east, and proglacial lacustrine deposition persisted in the area during the first part of the Middle Valdaian. Glacio-isostatic uplift caused erosion followed by pedogenesis and the formation of a deflation horizon in the Middle Valdaian. Widely dispersed periglacial river plains were formed during the Late Valdaian around 10–20 ka BP. Thus, the evidence of a terrestrial-based ice sheet from easterly uplands in the Pyoza area suggests that local piedmont glaciers situated in highlands such as the Timan Ridge or the Urals could have developed into larger, regionally confined ice sheets. Two phases of ice damming and development of proglacial lakes occurred during the Early and Middle Valdaian. The region did not experience glaciation during the Late Valdaian.  相似文献   

Late Quaternary glaciation of the Tianshan, Central Asia, using cosmogenic Be surface exposure dating     

Ping Kong  David Fink  Chunguang Na  Feixin Huang 《Quaternary Research》2009,72(2):229-233

Glacial deposits are present at the head of the Ürümqi River valley, Tianshan, Central Asia. ¹⁰Be surface exposure ages of 15 boulders from three sites along a 12 km valley transect range from 9 to 21 ka suggesting emplacement by glacial retreat and advance commencing at the global last glacial maximum (LGM) and most likely abating in the early Holocene. Although the age spread for a given locality is not small, perhaps indicating post-depositional reworking, maximum ages per site are either coeval with or are post-LGM and inconsistent with previous pre-LGM electron spin resonance ages.  相似文献   

贵州江口震旦系陡山沱组沉积层序和沉积环境分析   总被引：4，自引：0，他引：4  

喻美艺  何明华  王约  赵元龙 《地质科技情报》2005,24(3):38-42

通过对贵州江口桃映及邻区的坝黄、石竹溪的陡山沱组剖面的沉积序列研究,将陡山沱组划分为2个海侵-海退层序,并根据层序对比认为陡山沱期的生物群均产于陡山沱期第二次海平面开始上升之后形成的沉积中.从晚震旦世陡山沱期的第二次海侵开始是多细胞藻类、后生动物的第一次"爆发".桃映陡山沱组剖面产庙河生物群分子的沉积为局限滞流海盆沉积,进一步证明了庙河生物群型宏体生物的生存、保存环境模式仅限于局限滞流海盆中,为贫氧环境.  相似文献   

Iceberg discharge to the Chukchi shelf during the Younger Dryas     

Jenna C. Hill  Neal W. Driscoll 《Quaternary Research》2010,74(1):57-62

The extent of glaciation in northwestern Alaska, the source of sediment supply to the Chukchi shelf and slope, and the movement of sea ice and icebergs across the shelf during the last glacial maximum (LGM) remain poorly constrained. Here we present geophysical and geological data from the outer Chukchi margin that reveal a regionally extensive, heavily ice-scoured surface ∼ 5-8 m below the modern seafloor. Radiocarbon dating of this discrete event yields age estimates between 10,600 and 11,900 ¹⁴C yr BP, indicating the discharge event occurred during the Younger Dryas. Based on mineralogy of the ice-rafted debris, the icebergs appear to be sourced from the northwestern Alaskan margin, which places important constraints on the ice extent in northern Alaska during the LGM as well as existing circulation models for the region.  相似文献   

Cenozoic uplift of Nuussuaq and Disko, West Greenland—elevated erosion surfaces as uplift markers of a passive margin   总被引：1，自引：0，他引：1  

Johan M. Bonow  Peter Japsen  Karna Lidmar-Bergstrm  James A. Chalmers  Asger Ken Pedersen 《Geomorphology》2006,80(3-4):325-337

Remnants of a high plateau have been identified on Nuussuaq and Disko, central West Greenland. We interpret the plateau as an erosion surface (the summit erosion surface) formed mainly by a fluvial system and graded close to its former base level and subsequently uplifted to its present elevation. It extends over 150 km east–west, being of low relative relief, broken along faults, tilted westwards in the west and eastwards in the east, and having a maximum elevation of ca. 2 km in central Nuussuaq and Disko. The summit erosion surface cuts across Precambrian basement rocks and Paleocene–Eocene lavas, constraining its age to being substantially younger than the last rift event in the Nuussuaq Basin, which took place during the late Maastrichtian and Danian. The geological record shows that the Nuussuaq Basin was subjected to subsidence of several kilometres during Paleocene–Eocene volcanism and was transgressed by the sea later during the Eocene. By comparing with results from apatite fission track analysis and vitrinite reflectance maturity data, it is suggested that formation of the erosion surface was probably triggered by an uplift and erosion event starting between 40 and 30 Ma. Surface formation was completed prior to an uplift event that started between 11 and 10 Ma and caused valley incision. This generation of valleys graded to the new base level and formed a lower erosion surface, at most 1 km below the summit erosion surface, thus indicating the magnitude of its uplift. Formation of this generation of valleys was interrupted by a third uplift event also with a magnitude of 1 km that lifted the landscape to near its present position. Correlation with the fission-track record suggests that this uplift event started between 7 and 2 Ma. Uplift must have been caused initially by tectonism. Isostatic compensation due to erosion and loading and unloading of ice sheets has added to the magnitude of uplift but have not significantly altered the configuration of the surface. It is concluded that the elevations of palaeosurfaces (surfaces not in accordance with present climate or tectonic conditions) on West Greenland's passive margin can be used to define the magnitude and lateral variations of Neogene uplift events. The striking similarity between the landforms in West Greenland and those on many other passive margins is also noted.  相似文献   

Hazard assessment of the Tidal Inlet landslide and potential subsequent tsunami, Glacier Bay National Park, Alaska     

Gerald F. Wieczorek  Eric L. Geist  Roman J. Motyka  Matthias Jakob 《Landslides》2007,4(3):205-215

An unstable rock slump, estimated at 5 to 10 × 10⁶ m³, lies perched above the northern shore of Tidal Inlet in Glacier Bay National Park, Alaska. This landslide mass has the potential to rapidly move into Tidal Inlet and generate large, long-period-impulse tsunami waves. Field and photographic examination revealed that the landslide moved between 1892 and 1919 after the retreat of the Little Ice Age glaciers from Tidal Inlet in 1890. Global positioning system measurements over a 2-year period show that the perched mass is presently moving at 3–4 cm annually indicating the landslide remains unstable. Numerical simulations of landslide-generated waves suggest that in the western arm of Glacier Bay, wave amplitudes would be greatest near the mouth of Tidal Inlet and slightly decrease with water depth according to Green’s law. As a function of time, wave amplitude would be greatest within approximately 40 min of the landslide entering water, with significant wave activity continuing for potentially several hours.  相似文献   

Quaternary glaciation and hydrologic variation in the South American tropics as reconstructed from the Lake Titicaca drilling project     

Sherilyn C. Fritz  Paul A. Baker  Geoffrey O. Seltzer  Ashley Ballantyne  Pedro Tapia  Hai Cheng  R. Lawrence Edwards 《Quaternary Research》2007,68(3):410-420

A 136-m-long drill core of sediments was recovered from tropical high-altitude Lake Titicaca, Bolivia-Peru, enabling a reconstruction of past climate that spans four cycles of regional glacial advance and retreat and that is estimated to extend continuously over the last 370,000 yr. Within the errors of the age model, the periods of regional glacial advance and retreat are concordant respectively with global glacial and interglacial stages. Periods of ice advance in the southern tropical Andes generally were periods of positive water balance, as evidenced by deeper and fresher conditions in Lake Titicaca. Conversely, reduced glaciation occurred during periods of negative water balance and shallow closed-basin conditions in the lake. The apparent coincidence of positive water balance of Lake Titicaca and glacial growth in the adjacent Andes with Northern Hemisphere ice sheet expansion implies that regional water balance and glacial mass balance are strongly influenced by global-scale temperature changes, as well as by precessional forcing of the South American summer monsoon.  相似文献   

Palynological evidence for a latest Carboniferous-Early Permian glaciation in Northern Ethiopia     

Robert Bussert  Eckart Schrank 《Journal of African Earth Sciences》2007,49(4-5):201-210

Palynomorphs extracted from glacigenic sediments in Northern Ethiopia are latest Carboniferous-Early Permian in age. These sediments were hitherto thought to be either of Upper Ordovician or of Late Carboniferous-Early Permian age. The predominantly glaciolacustrine and glaciofluviatile sediments were deposited in glacial troughs and valleys that were eroded into Precambrian basement rocks and into Early Palaeozoic deposits, possibly equivalents of Upper Ordovician sediments in Eritrea. In the latest Carboniferous-Early Permian, glaciated uplands to the north of Ethiopia must have existed in Eritrea and/or in southern or central Saudi Arabia.  相似文献   

Stratigraphic and tectonic settings of Proterozoic glaciogenic rocks and banded iron-formations: relevance to the snowball Earth debate   总被引：1，自引：0，他引：1  

Grant M. Young   《Journal of African Earth Sciences》2002,35(4)

Among Palaeoproterozoic glacial deposits on four continents, the best preserved and documented are in the Huronian on the north shore of Lake Huron, Ontario, where three glaciogenic formations have been recognized. The youngest is the Gowganda Formation. The glacial deposits of the Gowganda Formation were deposited on a newly formed passive margin. To the west, on the south side of Lake Superior, the oldest Palaeoproterozoic succession (Chocolay Group) begins with glaciogenic diamictites that have been correlated with the Gowganda Formation. The >2.2 Ga passive margin succession (Chocolay Group=upper Huronian) is overlain, with profound unconformity, by a >1.88 Ga succession that includes the superior-type banded iron-formations (BIFs). The iron-formations are therefore not genetically associated with Palaeoproterozoic glaciation but were deposited 300 Ma later in a basin that formed as a result of closure of the “Huronian” ocean. In Western Australia, Palaeoproterozoic glaciogenic deposits of the Meteorite Bore Member appear to have formed part of a similar basin fill. The glaciogenic rocks are, however, separated from underlying BIF by a thick siliciclastic succession. In both North America and Western Australia, BIF-deposition took place in compressional (possibly foreland basin) settings but the iron-formations are of greatly different age, suggesting that the most significant control on their formation was not oxygenation of the Earth’s atmosphere but rather, emplacement of Fe-rich waters (uplifted as a result of ocean floor destruction?) in a siliciclastic-starved environment where oxidation (biogenic?) could take place. Some of the Australian BIFs appear to predate the appearance of red beds in North American Palaeoproterozoic successions and are therefore unlikely to be related to oxygenation of the atmosphere.Neoproterozoic glaciogenic deposits are widespread on the world’s continents. Some are associated with iron-formations. Two theories have emerged to explain these enigmatic BIFs. According to the snowball Earth hypothesis (SEH), ice-covered oceans would have permitted buildup of dissolved Fe. Precipitation of Fe-rich sediments would have taken place following reoxygenation of the hydrosphere as the ice cover disappeared. A second theory involves glaciation of Red Sea rift-type basins. Fe-charged brines in such basins would have precipitated on being mixed with “normal” seawater as a result of glacially driven thermal overturn. Both theories provide an explanation of the hydrothermal imprint on the geochemistry of Neoproterozoic BIF but the restricted development of BIF (relative to glacial deposits), evidence of rift activity such as significant facies and thickness changes, and association with volcanic rocks, all favour deposition in a rift environment.Cap carbonates are one of the cornerstones of the SEH. Escape from the snowball condition is said to have resulted from buildup of atmospheric CO₂ while the weathering cycle was stopped. Under such conditions, the first siliciclastic deposits following glaciation, should be extremely weathered, and should be overlain by sedimentary rocks that show a gradual return to more “normal” compositions. Using a chemical index of alteration (CIA) it can be shown that, in the case of the Gowganda Formation, the CIA shows a gradual upward increase, opposite to that predicted by the SEH. The Earth underwent severe climatic perturbations both near the beginning and end of the Proterozoic Eon but whether it attained a totally frozen surface condition (as postulated under the SEH) remains speculative.  相似文献