caa a22 4500 46321630X CHVBK 20180405153157.0 cr unu---uuuuu 170326e20070601xx s 000 0 eng 10.1007/s00367-007-0066-2 doi (NATIONALLICENCE)springer-10.1007/s00367-007-0066-2 Shallow gas depth-contour map of the Skagerrak-western Baltic Sea region [Elektronische Daten] [Troels Laier, Jørn Jensen] A shallow gas depth-contour map covering the Skagerrak-western Baltic Sea region has been constructed using a relatively dense grid of existing shallow seismic lines. The digital map is stored as an ESRI® shape file in order to facilitate comparison with other data from the region. Free gas usually occurs in mud and sandy mud but is observed only when sediment thickness exceeds a certain threshold value, depending on the water depth of the area in question. Gassy sediments exist at all water depths from approx. 20m in the coastal waters of the Kattegat to 360m in the Skagerrak. In spite of the large difference in water depths, the depth of free gas below seabed varies only little within the region, indicating a relatively fast movement of methane in the gas phase towards the seabed compared to the rate of diffusion of dissolved methane. Seeps of old microbial methane occur in the northern Kattegat where a relatively thin cover of sandy sediments exists over shallow, glacially deformed Pleistocene marine sediments. Previous estimates of total methane escape from the area may be correct but the extrapolation of local methane seepage rate data to much larger areas on the continental shelf is probably not justified. Preliminary data on porewater chemistry were compared with the free gas depth contours in the Aarhus Bay area, which occasionally suffers from oxygen deficiency, in order to examine if acoustic gas mapping may be used for monitoring the condition of the bay. Springer-Verlag, 2007 Laier Troels Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, 1350, Copenhagen, Denmark aut Jensen Jørn Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, 1350, Copenhagen, Denmark aut Geo-Marine Letters Springer-Verlag 27/2-4(2007-06-01), 127-141 0276-0460 27:2-4<127 2007 27 367 https://doi.org/10.1007/s00367-007-0066-2 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00367-007-0066-2 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Laier Troels Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, 1350, Copenhagen, Denmark aut NATIONALLICENCE 700 1- Jensen Jørn Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, 1350, Copenhagen, Denmark aut NATIONALLICENCE 773 0- Geo-Marine Letters Springer-Verlag 27/2-4(2007-06-01), 127-141 0276-0460 27:2-4<127 2007 27 367 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer