Seismoacoustic Study of the Shallow Gas Transport and ... - E-LIB

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Chapter 3 Seismic Unit 6 belongs to the Upper Miocene section. In Area 1, based on the observation of thickness variations and seismic facies (Fig. 5), slope fan deposits (seismic facies G) are located in the depocenter of seismic Unit 6 in Area 1, which suggest that sediments were probably supplied mainly from NNW and northern direction, probably from Crimean Mountains and the Kerch Peninsula. However, we don’t know the information about the river at that time, which formed the slope fan. Other parts of seismic Unit 6 in Area 1 are dominated by mass transport deposits (seismic facies D). Similar mass transport deposits also developed in Areas 2 and 3. Seismic Unit 5 The surface between seismic Units 5 and 6 is marked by erosional truncation (Fig.s 3b and 12) spanning the transition from Miocene to Pliocene. Seismic Unit 5 dates to the lower Pliocene. In Area 1, slope fan deposits (seismic facies G) probably continued developing, forming an elongated sediment depocenter in the NNW-SSE direction (Fig. 6). Another depocenter in the ENE part may suggest that sediments filled the depression created by the anticline formation. Hemipelagic sediments interbedded with coarser grained sediments during the transgression (Seismic facies E) were observed in the midslope to downslope part, which may suggest an overall sea-level rise in the study area. Mass transport deposits (seismic faceis D) mainly occurred in the upper part of the Unit 5. Seismic Unit 4 Seismic Unit 4 is of middle to late Pliocene age. In Area 1, a shift in depocenter (Fig. 7a) compared to seismic Units 5 and 6 suggest a large input of sediment from a northeasterly direction. The dominant seismic facies is facies B (Fig. 7b), which is interpreted as distal fan deposits. Seismic facies D and E still exist in Unit 4. Concurrently, slumps or channels (seismic facies F) occurred in Areas 2 and 3 without seismic facies B. Local truncation surfaces can be observed at the boundary between seismic Units 4 and 5 in Area 3 (Fig. 12). Seismic Unit 3 Seismic Unit 3 belongs to the early Pleistocene. Seismic facies A (Fig. 8b) started to appear in seismic profiles since the formation of Unit 3. Seismic facies A was interpreted as hemipelagic sediments interbedded with coarse grained sediments. Changes in sea level may have lead to cyclic deposition of finer (highstand) and coarser (lowstand) grained material. Within this unit, the Paleo-Don River fan deposits (seismic facies C) were observed in Area 1 indicating a possible shift of the river mouth. Slumps or channels (seismic facies F) occurred in all the three areas, which probably suggests higher sediment input and/or more intense tectonic movement, e.g. uplift of the Great Caucasus and Crimean Mountains (Brunet, 2003) and the basin subsidence of the Black Sea (Nikishin et al., 2003). In Area 1, two depocenters (Fig. 8a) were formed by seismic facies C and F, respectively. And the trend of the river fan deposits (seismic facies C), slumps or channels (seismic facies F) lines up in NW to SE direction (Fig. 8b), which may be the evidence of the uplift of the Crimean Mountain in the northwest of the study 87
Chapter 3 area or the subsidence of the Black Sea basin in the south, creating a sediment source and according downslope erosive sediment fluxes. Seismic Unit 2 Seismic Unit 2 dates to the middle Pleistocene. It is also characterized by seismic facies A (Fig. 9), and accompanied by seismic facies F in Areas 1 and 2, and in Area 3 by seismic facies B (Fig.s 12 and 13). An unconformity can be observed on the upper slope of Areas 1 and 2, suggesting erosional processes. In Area 3, seismic facies F is less present and an unconformity cannot be observed. Uniform deposits in Area 3 (seismic facies ) were interpreted as hemipelagic sediments or distal fan deposits. In Area 1, the depocenter is also dominated by channel-fills or slumps extending in NW to SE direction. Seismic Unit 1 Seismic Unit 1 covers middle Pleistocene to Holocene times, revealing a distinct similarity to Unit 2. In Areas 1 and 2, slumps or channels (Fig. 10), and river fan deposits (Fig. 11) occurred on the upper slopes, but less of them occurred inside Unit 1. In Area 3 (Fig.s 12 and 13), seismic Unit 1 consists of hemipelagic sediments interbedded with coarse grained sediments (seismic facies A). 3.5.3. Sedimentary evolution of the study area According to the lithological-paleogeographic maps of Paratethys during the late Miocene (Popov et al., 2004), the Kerch Peninsula was covered by sea water, and the study area was likely in a relatively deep water marine environment. Seismic Unit 6 shows that mass transport deposits occurred in the study area, while slope fan deposits started developing in the Area 1. Subsequently, the Black Sea was influenced by the Messinian Salinity Crisis, which was associated with a dramatic fall in sea level with a maximum at the Miocene-Pliocene boundary, and with erosional surfaces on the shelves of the Black Sea (Gillet et al., 2007; Hsü and Giovanoli, 1979; Kojumdgieva, 1983; Popov et al., 2004). Deep water environments existed only in the deepest parts of the Black Sea basins. The Black Sea became an isolated basin, and did not connect to the Mediterranean Sea and the Caspian Sea at this time (Paluska and Degens, 1979). DSDP Leg 42B drill sites indicated a subtropical dry climate, and lithology was mainly composed by laminated carbonates indicating shallow marine or lake environments. Aragonite and gravel appeared at the unconformity between the Miocene and Pliocene near the Bosporus on the basin apron of the Black Sea (DSDP, Site 380, Hsü and Giovanoli 1979). During the Pliocene to Quaternary, the intensity of tectonic movements increased. There was an acceleration of the basin subsidence of the Black Sea with a rate reaching 85 m/Ma (Nikishin et al., 2003), and the most rapid subsidence occurred from the late Pliocene to the Quaternary (Meisner et al., 2011). The reason for the rapid subsidence was illustrated by kinematic and dynamic modeling (Nikishin, 2003) attributing it to compression-induced downward bending of the lithosphere. The unusually rapid 88
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Seismoacoustic Study of the Shallow
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Table of contents Table of contents
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Abstract Abstract In recent years,
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Outline of the Dissertation Outline
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Chapter 1 Chapter 1. Introduction 1
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Chapter 1 reflections, interpreted
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Chapter 1 Submarine gas seeps, pock
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Chapter 1 which have documented act
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Chapter 1 fluid migration related t
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Chapter 1 Evidence of gas seepage
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Chapter 1 The three main different
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Chapter 1 from deeper sources in th
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Chapter 1 numerous countries such a
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Chapter 1 1.5 Geological setting of
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Chapter 1 main sequences consist of
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Chapter 1 craterlike depressions wi
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Chapter 1 Jurassic - Paleogene, Upp
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Chapter 1 respectively, and one wat
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Chapter 1 During the seismic data p
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Chapter 1 1.6.2 The Parasound sedim
Page 42 and 43: Chapter 1 Caress, D.W., and Chayes,
Page 44 and 45: Chapter 1 Hovland, M., Gardner, J.V
Page 46 and 47: Chapter 1 Luo, X.R. and Vasseur, G.
Page 48 and 49: Chapter 1 Schroot, B.M., Klaver, G.
Page 50 and 51: Chapter 2 Chapter 2. Shallow Gas Tr
Page 52 and 53: Chapter 2 times. Seismically imaged
Page 54 and 55: Chapter 2 spike noise were marked a
Page 56 and 57: Chapter 2 The 2D high resolution se
Page 58 and 59: Chapter 2 Figure 4 A close-up of se
Page 60 and 61: Chapter 2 within the upper sediment
Page 62 and 63: Chapter 2 volcanoes between 66 and
Page 64 and 65: Chapter 2 Figure 7 Geo-seismic sect
Page 66 and 67: Chapter 2 In the study area, many b
Page 68 and 69: Chapter 2 volcanism could be calcul
Page 70 and 71: Chapter 2 along the feeder channel
Page 72 and 73: Chapter 2 Evpatoriya). Soviet Geol
Page 74 and 75: Chapter 3 Chapter 3. Sedimentary Ev
Page 76 and 77: Chapter 3 South (Fig. 2). The water
Page 78 and 79: Chapter 3 Figure 3 (a) Uninterprete
Page 80 and 81: Chapter 3 Seven seismic facies type
Page 82 and 83: Chapter 3 Seismic Unit 5 ranges in
Page 84 and 85: Chapter 3 3.4.3.5. Seismic Unit 2 A
Page 86 and 87: Chapter 3 Figure 11 (a) Uninterpret
Page 88 and 89: Chapter 3 Figure 13 (a) Uninterpret
Page 90 and 91: Chapter 3 boundary between the Plio
Page 94 and 95: Chapter 3 subsidence was coincident
Page 96 and 97: Chapter 3 Acknowledgements We thank
Page 98 and 99: Chapter 3 Tugolesov, D.A., Gorshkov
Page 100 and 101: Chapter 4 study area at ~900 m wate
Page 102 and 103: Chapter 4 Figure 2 Bathymetry of th
Page 104 and 105: Chapter 4 University of Bremen). At
Page 106 and 107: Chapter 4 and Ridge R2 (GeoB07-139)
Page 108 and 109: Chapter 4 flares location. Anticlin
Page 110 and 111: Chapter 4 GeoB07-145. Green arrows
Page 112 and 113: Chapter 4 4.4.3.2.3. Other anomalou
Page 114 and 115: Chapter 4 Slope fan deposits with f
Page 116 and 117: Chapter 4 Figure 12 Possible locati
Page 118 and 119: Chapter 4 bulk hydrate or even high
Page 120 and 121: Chapter 4 may add to gas accumulati
Page 122 and 123: Chapter 4 The narrow-beam Parasound
Page 124 and 125: Chapter 4 River fan deposits. Being
Page 126 and 127: Chapter 4 Klaucke, I., Sahling, H.,
Page 128 and 129: Chapter 4 Wagner-Friedrichs, M., 20
Page 130 and 131: Chapter 5 deposited; during lowstan
Page 132 and 133: Chapter 5 accumulations. An acousti
Page 134 and 135: Acknowledgements Acknowledgements I
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