Riedel, Michael, Gausepohl, Florian, Gazis, Iason-Zois, Hähnel, Line, Kampmeier, Mareike, Urban, Peter and Bialas, Jörg, eds. (2018) RV METEOR Fahrtbericht / Cruise Report M143: SLOGARO: Slope failures and active gas expulsion along the Romanian margin – investigating relations to gas hydrate distribution, Varna (Bulgaria) – Heraklion (Greece), 12.12.-22.12.2017. . GEOMAR Report, N. Ser. 042 . GEOMAR Helmholtz-Zentrum für Ozeanforschung, Kiel, Germany, 35 pp. DOI 10.3289/GEOMAR_REP_NS_42_2018.

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Abstract

Expedition M143 is a replacement for the originally scheduled expedition to the
Marmara Sea to retrieve long term monitoring geodetic equipment. A short proposal to extend
bathymetric mapping and imaging of active gas seepage in the Danube Delta region was
approved and permission to operate in Romanian waters was successfully secured. Based on
the results of mapping completed during the previous expedition M142 and other earlier
missions to the same region, a set of survey lines and imaging targets were defined for M143.
Objectives for expedition M143 were twofold and include the of use a dedicated 38 kHz
single beam echo sounder installed in the moonpool of the research vessel METEOR for gas
emission quantification and to complete bathymetric mapping for the detection of sub marine
slope failures and mass transport deposits in associated with gas seepage and the occurrence
of gas hydrates.
During the active data acquisition phase of expedition M143 (December 12 to
December 17, 2017) three sub-regions for gas flare imaging were visited (Lander Site from
M142, S2 channel eastern flank, and shallow shelf region). A total of 1,189 line kilometers
(642 nautical miles) of data were acquired. Out of these, a total of 238 km were acquired
using the 38 kHz EK80 and EM710 (and partially EM122) multibeam data. Also, a full
calibration of the 38 kHz echo sounder was accomplished and sound velocity data were
recorded at the Lander and shallow shelf region survey sites.
Bathymetric mapping using both EM systems EM122 and EM710 combined with the
PARASOUND sub bottom profiler was completed in two main regions filling in data gaps in
the existing multibeam coverage prior to M143. The first region was visited during the initial
transit to the study region (December 14) around the region of the S2 channel head in water
depths ~120 m. Here, a set of six parallel lines were acquired, totaling 70 km line lengths and
covering an area of 11.5 square kilometers. The second region was in the eastern part of the
Danube delta region, close to the Ukrainian border. In total 805 line kilometers and 472
square kilometers of multibeam data were acquired.

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