Acoustic facies mapping of the Lomonosov Ridge and adjacent basins, in the Arctic Ocean. Author: Supervisors: Jolien van der Krogt Dr. Catalina Gebhardt Dr. João P. Trabucho Alexandre Thesis for Master in Marine Sciences Utrecht University Conducted at Alfred Wegener Institut, Bremerhaven October 2018 i Abstract The Lomonosov Ridge is a prominent geological feature in the Arctic Ocean and bears evidence of glacial activity during the Quaternary. Subglacial features on the Ridge have been studied thoroughly but their cause is still a debated topic. The main objective of this research is to create a surficial geological map that can help explain the glacial history of the Lomonosov Ridge and with that, the Arctic Basin. The map is part of an international collective to produce a new layer of the International Bathymetric Chart of the Arctic Ocean, to enable the study of, for example, sedimentary, climatic and oceanographic processes within the basin. In order to create this map, a list of seventeen principal acoustic facies types and seven compound facies types is created by Canadian colleagues, based on their occurrence in the Canada basin and adjacent continental shelves. This list is tested for its ability to classify the surficial geology of the Lomonosov Ridge and adjacent basins. The high-resolution acoustic data covers sub- bottom profiles of the top 100 meters of seafloor of the research area. This data is acquired by the German research vessel Polarstern over the last 30 years and stretches about 65.000 kilometers. Consulting multibeam swath bathymetry data, the sub-bottom is categorized according to its acoustic characteristics. First by their bottom echo and after that by the sub- bottom reflectors and shape. The surficial map of the research area is created using ten of the seventeen principal facies and two of the seven compound. One new principal facies type is added, which is the diamicton. It is chosen to distinguish diamicton as new facies type because the optical characteristics differ significantly from the transparent wedge facies type, which is how the Canadians described this facies. Furthermore, the diamicton occurs on structural highs, whereas deposit wedges are present on slopes and in valleys. The distribution of the facies types, that has become apparent after the creation of the surficial geology map, can mainly be explained by waxing and waning of ice, ocean currents and mass movements. The subglacial features found on the sub-bottom data are Mega Scale Glacial Lineations, depositions of reworked sediments and ice-rafted debris, and deposit wedges. These features are analysed and afterwards used to test the theory that states a pan-Arctic ice shelf was present during MIS 6. This theory could not be rejected, because all the areas on the Lomonosov Ridge above 900 meters water depth are eroded. Moreover, the MSGLs on these areas are all in the same direction, west-northwest. These findings might encourage future research to confirm or reject the theory. Key words: Arctic Ocean, Lomonosov Ridge, diamicton, pan-Arctic ice shelf, Mega Scale Glacial Lineations, surficial geology. iii Table of Content 1 Introduction ..................................................................................................................................... 1 2 Glacial features and geology ........................................................................................................... 4 2.1 Glacials and sedimentation ..................................................................................................... 4 2.2 Glacial geology ......................................................................................................................... 6 2.2.1 Surficial features .............................................................................................................. 6 2.2.2 Sub bottom features........................................................................................................ 8 2.2.3 Principal Facies ................................................................................................................ 9 2.2.4 Compound Facies .......................................................................................................... 12 2.2.5 Sedimentation rate ........................................................................................................ 14 3 Research area ................................................................................................................................ 15 3.1 Ocean wide ............................................................................................................................ 15 3.2 Oceanographic settings ......................................................................................................... 17 3.3 Lomonosov Ridge and surroundings ..................................................................................... 18 3.4 Glacial evidence on the Lomonosov Ridge ............................................................................ 19 4 Method .......................................................................................................................................... 21 4.1 Data acquisition ..................................................................................................................... 21 4.2 Data processing ..................................................................................................................... 22 4.3 Categorizing ........................................................................................................................... 23 4.4 Mapping................................................................................................................................. 26 5 Results ........................................................................................................................................... 28 5.1 Description of facies types .................................................................................................... 28 5.1.1 Facies type 1a ................................................................................................................ 28 5.1.2 Facies type 3b ................................................................................................................ 29 5.1.3 Facies type 4a ................................................................................................................ 30 5.1.4 Facies type 5a ................................................................................................................ 31 5.1.5 Facies type 7a ................................................................................................................ 32 5.1.6 Facies type 7b ................................................................................................................ 32 5.1.7 Facies type 7c ................................................................................................................ 33 5.1.8 Facies type 7e ................................................................................................................ 34 5.1.9 Facies type 8a ................................................................................................................ 35 5.1.10 Facies type 9a ................................................................................................................ 36 5.1.11 Facies type 10a .............................................................................................................. 36 5.2 Distribution of and interpretation of facies .......................................................................... 38 5.2.1 Chaotic facies (1a) ......................................................................................................... 38 iv 5.2.2 Large hyperbolic facies (3b) ........................................................................................... 39 5.2.3 Small hyperbolic facies (4a) ........................................................................................... 40 5.2.4 Wedging facies (5a) ....................................................................................................... 41 5.2.5 Undulating laminated facies (7a) .................................................................................. 42 5.2.6 Wavy laminated facies (7b) ........................................................................................... 43 5.2.7 Laminated facies with gas blanking (7c) ........................................................................ 43 5.2.8 Rugose laminated facies (7e) ........................................................................................ 44 5.2.9 Parallel laminated facies (8a) ........................................................................................ 44 5.2.10 Flat laminated facies (9a) .............................................................................................. 44 5.2.11 Subglacial diamicton facies (10a) .................................................................................. 45 5.3 Distribution of facies summarized ......................................................................................... 48 6 Discussion ...................................................................................................................................... 50 6.1 Facies categorization based on the Canada basin. ................................................................ 50 6.2 What caused the presence of