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11.
J.T. Andrews A. Aksu M. Kelly R. Klassen G.H. Miller W.N. Mode P. Mudie 《Quaternary Science Reviews》1985,4(4):333-355
Evidence from terrestrial sections, ice cores, and marine cores are reviewed and used to develop a scenario for environmental change in the area of the extreme northwest North Atlantic during marine isotope stages 5 and 4. The critical physical link between the landbased glacial chronology and marine events in Baffin Bay is the presence of carbonate rich drift along the Baffin Bay coast of Bylot Island and a detrital carbonate facies (Facies B) in Baffin Bay sediments. Cores from Baffin Bay/Labrador Sea can be dated by means of oxygen isotope variations and by peaks in the abundance of volcanic glass shards. One occurrence of Facies B is dated between late stage 5 and stage 4 and we correlate this event with the Eclipse Glaciation of Bylot Island and the Ayr Lake stade of the Foxe Glaciation of Baffin Island (= Kogalu aminozone). In contrast on West Greenland, amino acid racemization evidence suggests that the Greenland Ice Sheet developed throughout stage 4 and reached a maximum in stage 3 (Svartenhuk advance >40 ka). The oxygen isotope record in the Devon Island Ice Cap (northwest Baffin Bay) indicates that Baffin Bay was largely open during marine isotope stage 5. Analyses of shallow water molluscan and foraminiferal assemblages, deep-water foraminifera, pollen from Iand sections and deep-sea cores, and dinoflagellates from marine cores indicate that interglacial conditions prevailed during much of the stage
glaciation. 相似文献
12.
Güven Aksu 《地震工程与结构动力学》1984,12(5):709-714
The energy approach using the variational procedure in conjunction with the finite difference technique has been applied for the Mindlin theory dynamic analysis of rectangular plates with cutouts in which account is taken of the effects of both transverse shear deformation and rotary inertia. This study has clearly demonstrated that the discrepancy with the thin plate theory solutions increases with increasing values of thickness ratio β and the error due to the thin plate assumptions increases particularly for the higher modes. It is also concluded that the effect of a cutout becomes more pronounced as the thickness of the plate approaches the size of cutout. 相似文献
13.
A.E. Aksu 《Marine Geology》1983,53(4):331-348
Calcium-carbonate dissolution has been studied in several grab samples and piston cores from Baffin Bay and Davis Strait ranging in water depth from 200 to 2300 m. The intensity of dissolution was determined from examining: (1) the ratio of arenaceous to calcareous benthonic foraminifera; (2) the ratio of benthonic to planktonic foraminifera; (3) the relationships between the dissolution-susceptible and dissolution-resistant foraminifera; (4) the degree of foraminiferal test fragmentation; and (5) the relationships between plankton tows and the fauna in the surface sediments. All core tops and grab samples from Baffin Bay surface sediments below 600–900 m water depth demonstrated intense dissolution of calcium carbonate. Sediments below 900 m were biogenic carbonate free, indicating 100% foraminiferal loss due to dissolution. Possible causes of substantial undersaturation in calcium carbonate of Baffin Bay Bottom Water are very low temperatures, and higher concentrations of carbon dioxide. All cores also demonstrated intense dissolution during interglacial or interstadial isotope stages 1, 3, 5, 7 and 9. Similarities in planktonic foraminiferal assemblages suggested the presence of similar bottom-water masses during these periods. The preservation state of biogenic carbonate debris in glacial isotope stages 2, 4, 6, 8 and 10 is similar to the assemblage found in the water at present. 相似文献
14.
Geologic evidence across orogenic plateau margins enables the discrimination of the relative contributions of orogenic, epeirogenic and/or climatic processes that lead to growth and maintenance of those plateaus and their margins. Here, we discuss the mode of formation of the southern margin of the Central Anatolian Plateau (SCAP) and evaluate its time of formation using fieldwork in the onshore and seismic reflection data in the offshore. In the onshore, uplifted Miocene rocks in a dip‐slope topography show monocline flexure over >100 km, km‐scale asymmetric folds verging south, and outcrop‐scale syn‐sedimentary reverse faults. On the Turkish shelf, vertical faults transect the basal latest Messinian of a 10 km fold where on‐structure syntectonic wedges and synsedimentary unconformities indicate pre‐Pliocene uplift and erosion, followed by Pliocene and younger deformation. Collectively, Miocene rocks delineate a flexural monocline at plateau margin scale that is expressed along our on‐offshore sections as a kink‐band fold with a steep flank 20–25 km long. In these reconstructed sections, we estimate a relative vertical displacement of 3.8 km at rates of ca. 0.5 mm/y, and horizontal shortening values <1 %. We use this evidence together with our observations of shortening at outcrop, basin, plateau‐margin and forearc‐system scales to infer that the SCAP forms as a monoclinal flexure to accommodate deep‐seated thickening and shortening since >5 Ma, and to contextualize the plateau margin as the forearc high of the Cyprus subduction system. 相似文献
15.
Some earthquakes in the Eastern Mediterranean are tsunamigenic and some of their tsunamis affected the coastal area of the
Gulf of Fethiye, SW Turkey. Recent trenching surveys on the low-lying coastal areas of Dalaman delta beach across the Rhodes
Pass revealed three probable tsunami impacts as a result of the historical earthquakes of 1303, 1481 and 1741. Yet, there
have been relatively few studies of the processes associated with tsunami sediment transport, their deposition and nature
in geological record. In addition to the interpretation of sedimentary features, accurate paleoenvironmental assessments might
be possible by distinctive biogeochemical researches on marine-sourced organic matters, geochemical properties, quantitative
amounts of marine-sourced biomarkers and deterministic ratios. The identification of major lipid biomarkers (fatty acids and
sterols) in the samples recovered from the sidewalls of the studied trench, for example, indicated biogenic contributions
due to the presence of phytoplankton, zooplankton, dinoflagellates and bacteria. Quantitative estimation of biomarkers and
deterministic ratios also indicated some evidences for marine-sourced organic matters, implying that biomarkers can be used
to answer the open questions in tsunami and paleotsunami researches. 相似文献
16.
A. E. Aksu 《Geo-Marine Letters》1984,4(2):83-90
Thin-bedded debris flow deposits are an important constituent of the marine Quaternary, sequence in NW Baffin Bay, covering about 30,000 km2 of sea floor. Individual debris flows traveled over a slope as low as 0.4° and a distance of several hundred kilometers. Some debris flows have generated turbidity currents. Debris flow deposits observed in the cores displayed distinctive downslope trends in grain size, bed thickness, and sorting, and showed variations in structures and sequences of sedimentary structures with poorly to moderately well-developed gravel fabric, showing the long axes of clasts aligned nearly parallel to the bedding plane. 相似文献
17.
Aksu Hakan Cetin Mahmut Aksoy Hafzullah Yaldiz Sait Genar Yildirim Isilsu Keklik Gulsah 《Natural Hazards》2022,111(3):2379-2405
Natural Hazards - This study characterises the spatial and temporal behaviours of maximum precipitation over the Black Sea Region in northern Turkey. Maximum precipitation data of 14 standard... 相似文献
18.
Side-scan data from the epicentral area of the 1929 Grand Banks earthquake and cores from the resulting turbidite are used to determine a sediment budget for the event. The 1929 turbidite has a volume of about 185 cubic km, which is mostly sand. Features indicating failure on the continental slope are observed only in muddy sediment. A major source of sand in the heads of the fan valleys of the Laurentian Fan is postulated to balance the sediment budget. This sand accumulated proglacially during the Wisconsinan glaciation and probably failed through liquefaction in the 1929 earthquake. 相似文献