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Figure 4. A comparison of seismic time slices (140 ms) from the Dogger Bank imaged in different ways. (a) A simple seismic amplitude time slice revealing some Holocene depositional features (channels). (b) Opacity rendering of the same seismic amplitude time slice. Note that the manipulation of the opacity and the careful choice of colour allows improved channel definition. (c) Seismic coherence (semblance) time slice at the same level as panels a and b. Note that coherence provides some additional detail of the channels.

Figure 4 A comparison of seismic time slices (140 ms) from the Dogger Bank imaged in different ways. (a) A simple seismic amplitude time slice revealing some Holocene depositional features (channels). (b) Opacity rendering of the same seismic amplitude time slice. Note that the manipulation of the opacity and the careful choice of colour allows improved channel definition. (c) Seismic coherence (semblance) time slice at the same level as panels a and b. Note that coherence provides some additional detail of the channels.

Related Figures (8)

Figure 1. Map illustrating emergent parts of the continental shelves (red) in Europe during the last glacial maximum. The figure assumes a glacial eustatic lowstand of 120 m below present sea level (Fairbanks, 1989) and does not take into account glacially induced flexural uplift in high-latitude regions adjacent to large ice sheets or neotectonic (Holocene) uplift or subsidence.
Figure 1. Map illustrating emergent parts of the continental shelves (red) in Europe during the last glacial maximum. The figure assumes a glacial eustatic lowstand of 120 m below present sea level (Fairbanks, 1989) and does not take into account glacially induced flexural uplift in high-latitude regions adjacent to large ice sheets or neotectonic (Holocene) uplift or subsidence.
Figure 2. Map of the North Sea with Holocene shorelines and the study area indicated. This paper will use 3D seismic data from the Dogger Bank, Southern North Sea (Fig. 2), in order to demonstrate how the use of 3D seismic data, and the techniques developed by the petroleum industry for its analysis, can provide an efficient way of generating regional models for the Late Pleistocene and Holocene. The results of the pilot project described in this paper demonstrate that such an approach provides a detailed temporal and spatial frame- work for the future integration of shallow borehole, environmental and shallow geophysical data. This in turn will provide a valuable resource that may have diverse applications within Pleistocene and Holocene geology, marine engineering (seabed structure and stability) as well
Figure 2. Map of the North Sea with Holocene shorelines and the study area indicated. This paper will use 3D seismic data from the Dogger Bank, Southern North Sea (Fig. 2), in order to demonstrate how the use of 3D seismic data, and the techniques developed by the petroleum industry for its analysis, can provide an efficient way of generating regional models for the Late Pleistocene and Holocene. The results of the pilot project described in this paper demonstrate that such an approach provides a detailed temporal and spatial frame- work for the future integration of shallow borehole, environmental and shallow geophysical data. This in turn will provide a valuable resource that may have diverse applications within Pleistocene and Holocene geology, marine engineering (seabed structure and stability) as well
Figure 3. Simplified cross-section (not to scale) of stratigraphy of the Pleistocene and Holocene of the Dogger Bank region, North Sea. Adapted from Laraminie (1989a,b).
Figure 3. Simplified cross-section (not to scale) of stratigraphy of the Pleistocene and Holocene of the Dogger Bank region, North Sea. Adapted from Laraminie (1989a,b).
Figure 5. Seismic amplitude volume containing a tunnel valley of probable Weichselian age. Incised tunnel valley systems, ranging in age from the Elsterian to the Weichselian, have previously been identi using 3D seismic data from the Sou fied hern North Sea (Praeg, 1996; Lonergan et al., 2003). Within the study area a tunnel valley was located beneath the maximum width of 2.4 km and a Dogger Bank wit na ength of 23 km being observed as it traverses across the study area (Fig. 5). With a U-shaped cross-section and a gradient to the northeast ( 5) the valley is comparable with d Fig. escriptions of classical
Figure 5. Seismic amplitude volume containing a tunnel valley of probable Weichselian age. Incised tunnel valley systems, ranging in age from the Elsterian to the Weichselian, have previously been identi using 3D seismic data from the Sou fied hern North Sea (Praeg, 1996; Lonergan et al., 2003). Within the study area a tunnel valley was located beneath the maximum width of 2.4 km and a Dogger Bank wit na ength of 23 km being observed as it traverses across the study area (Fig. 5). With a U-shaped cross-section and a gradient to the northeast ( 5) the valley is comparable with d Fig. escriptions of classical
Figure 6. Holocene fluvial features of the Dogger Bank. (a) Seismic time slice (114 ms) containing a major meandering river channel with its associated smaller channels, lakes as well as a later dendritic channel network. (b) Expanded view showing the relationships between the major meandering channel, the minor channels and lakes. (c) Close-up view of part of the major fluvial channel. Note the homogeneous infill of the channel/channel belt. (d) Seismic section across the main fluvial channel showing an infill of accreted point bars deposits. (e) Seismic amplitude volume demonstrating that the dendritic channel network is associated with a higher stratigraphic level than the meandering fluvial channel.
Figure 6. Holocene fluvial features of the Dogger Bank. (a) Seismic time slice (114 ms) containing a major meandering river channel with its associated smaller channels, lakes as well as a later dendritic channel network. (b) Expanded view showing the relationships between the major meandering channel, the minor channels and lakes. (c) Close-up view of part of the major fluvial channel. Note the homogeneous infill of the channel/channel belt. (d) Seismic section across the main fluvial channel showing an infill of accreted point bars deposits. (e) Seismic amplitude volume demonstrating that the dendritic channel network is associated with a higher stratigraphic level than the meandering fluvial channel.
Figure 7. Seismic amplitude volume overlain by a seismic coherence volume. The figure demonstrates that the probable Weichselian tunnel valley pre-dates the meandering river system which is consequently of Holocene age.
Figure 7. Seismic amplitude volume overlain by a seismic coherence volume. The figure demonstrates that the probable Weichselian tunnel valley pre-dates the meandering river system which is consequently of Holocene age.
Figure 8. Initial palaeogeographic maps for the study area. Seismic time slices on the left and interpretation right.
Figure 8. Initial palaeogeographic maps for the study area. Seismic time slices on the left and interpretation right.
Figure 9. Seismic amplitude time slice (see Fig. 6a) draped on the current seabed topography. Note that the major fluvial channel, and its tributaries, is no related to the current bathymetry with the channels cross local highs. This highlights the inadequacies of using bathymetry to predict the locations of majo geomorphic features on the Holocene landscape. Although such surveys are optimised to resolve features with burial depths in the kilometre range they are capable of producing detailed images within the top few tens of metres of the sedimentary column. Consequently, as previous reconstructions of the Holocene landscape have relied on the use of bathymetry data (e.g., Coles, 1998) they must now be regarded as obsolete and potentially Although 3D seismic has been shown to provide the best method for mapping Late Pleistocene and Holocene depositional systems in detail, and with relative speed and spatial completeness, this study has also demonstrated the disadvantages of using 3D seismic in isolation. The ambiguities in the interpretation of the fluvial channel systems are primarily the result of the absence detailed lithological and chronological data on the sediments being imaged. Consequently, 3D seismic data need to be integrated with existing or new shallow core and geo- physical data in order to develop a complete model. As the use of 3D seismic data provides the most efficient method of generating a spatially complete model it will allow the
Figure 9. Seismic amplitude time slice (see Fig. 6a) draped on the current seabed topography. Note that the major fluvial channel, and its tributaries, is no related to the current bathymetry with the channels cross local highs. This highlights the inadequacies of using bathymetry to predict the locations of majo geomorphic features on the Holocene landscape. Although such surveys are optimised to resolve features with burial depths in the kilometre range they are capable of producing detailed images within the top few tens of metres of the sedimentary column. Consequently, as previous reconstructions of the Holocene landscape have relied on the use of bathymetry data (e.g., Coles, 1998) they must now be regarded as obsolete and potentially Although 3D seismic has been shown to provide the best method for mapping Late Pleistocene and Holocene depositional systems in detail, and with relative speed and spatial completeness, this study has also demonstrated the disadvantages of using 3D seismic in isolation. The ambiguities in the interpretation of the fluvial channel systems are primarily the result of the absence detailed lithological and chronological data on the sediments being imaged. Consequently, 3D seismic data need to be integrated with existing or new shallow core and geo- physical data in order to develop a complete model. As the use of 3D seismic data provides the most efficient method of generating a spatially complete model it will allow the
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