Seabed Sediments - Genesis

Sediments classified by genesis. Classification according to SOSI (Statens kartvek 2006). The list contains only the types of sediments that have been mapped and interpreted in Norwegian waters.

Symbol Sediment genesis Definition/description Code
Suspension deposit Fine grained sediments (mainly clay and silt) transported by and deposited from suspension. 200
Glaciomarine deposit Mostly fine grained sediments (clay and silt) deposited in the ocean from suspension in the vicinity of glaciers. Can be influenced by bottom currents. Occur in great thickness on the continental shelf, along the coastline and in fjords. 202
Beach deposit Deposits reworked by waves and currents in the beach zone. The material is often well rounded and sorted. Grain size varies from sand to boulders, but sand and gravel are most common. Mapped where thicker than 0.5 m. 42
Tidal deposit Deposit formed in coastal area by tidal transport. The sediments are sandy to clayey with typical structures such as sand dunes, ripples, cross-bedding, flaser and lenticular bedding. 207
Shallow marine deposit Sediment deposited in turbulent shallow marine environment. Consists of sand, gravel and cobbles. 210
Bedload (traction) deposit Sediment transported by and deposited from bottom currents. Consists of sand and gravel. Bedload deposits may occur in submarine channels and shallow marine areas, and has often characteristic cross-bedding and lenticular bedding. 201
Contourite Sediment body deposited by a permanent ocean current (contour current) along the continental margin. Consists of fine grained, well sorted material (mainly clay and silt, but also sand). 211
Channel deposit Sediments deposited in a channel. Consist usually of coarse grained particles (sand, gravel). 215
Submarine fan deposit A conical or fan-shaped deposit located seaward of large rivers and submarine. Consists primarily of fine sediments (clay, silt). The fan has a finely laid inner structure with layers which slope slightly toward the deep ocean. 214
Fluvial delta deposit Sediments deposited at the mouth of a river into a fjord, lake or the sea. Grain size is often in sand fraction near the outlet and more fine-grained in deeper water. Typically layered sediments with dip in the direction of the current. 206
Glaciofluvial deposit Sediment transported and deposited by glacial meltwater streams. The sediment consists of sorted, often inclined beds of grain sizes varying from fine sand to cobbles and boulders. 20
Glaciofluvial delta deposit Sediments transported by glacial streams and deposited in the sea, in lakes or glacial lakes. Grain size is often in sand fraction near the outlet and more fine-grained in deeper water. 205
Till, unspecified Unsorted glacial sediment consisting of material ranging in size from clay to boulders. 10
Till, continuous cover Unsorted glacial sediment consisting of material ranging in size from clay to boulders. Locally of great thickness and with sporadic patches of lag. 11
Till, discontinuous or thin cover over the bedrock Unsorted glacial sediment consisting of material ranging in size from clay to boulders. Areas with sparse cover of till and frequent bare patches of bedrock. 12
Till with a thin cover of glacimarine sedimentsTill with a thin cover (less than 1-2 m) of glacimarine sediments. 230
Till with a thin cover of fine-grained sedimentsTill with a thin cover (less than 1-2 m) of fine-grained sediments (glacimarine sediments/suspension deposits/bedload deposits). 231
Terminal moraine Linear or slightly curved ridge of unconsolidated and unsorted debris deposited at the front or the sides of a glacier. Locally, sorted glacio-fluvial deposits may occur. 15
Ice contact deposit Sediments deposited in contact with ice. May consist of moraine, glacio-fluvial material, or a mixture of glacially deposited sediments. 203
Colluvium, unspecified Sediments deposited by rockfalls and snow avalanches on steep valley slopes. Unspecified thickness. 80
Colluvium, continuous and/or thick Sediments deposited by rockfalls and snow avalanches on steep valley slopes. Locally of great thickness. 81
Colluvium, discontinuous and/or thin Thin and/or discontinuous cover of sediments deposited by rockfalls and snow avalanches on steep valley slopes. 82
Mass movement deposit, covered by younger sediments Mass movement deposit, covered by younger sediments. 240
Mass movement deposit, locally covered by younger sediments Mass movement deposit, locally covered by younger sediments. 241
Mass movement deposits and hemipelagic sediments Alternating mass movement deposits and hemipelagic deposits. Hemipelagic deposits comprise mainly fine grained sediments, partly locally derived from the water masses, and partly transported into the area by currents. 242
Debris flow deposit Sediment deposited by a fast moving, liquefied landslide of unconsolidated, saturated debris. Consists of material ranging in size from clay to boulders. 213
Laminated sediments underlain by debris flow deposits Laminated sediments (>1m) underlaid by debris flow deposits. 219
Turbidity deposit A sediment deposited from a turbidity current. It is characterized by graded bedding, moderate sorting, and well developed primary structures in the sequence. 212
Bioclastic sediment Sediment consisting mostly of small particles og biogenic origin (shell, coral). Grain size can vary from sand to whole shells and coral reefs. 217
Marine gyttja Fine sediment formed from the partial decay of vegetable and animals rests, deposited in quiet bays. 45
Carbonate crust Occurrences of carbonate cemented sediments that form crusts on the seafloor, typically several decimeters thick. 220
Compacted sediments or sedimentary rocks Compacted sediments or sedimentary rocks. 150
Lag deposit Sediments consisting of sand, gravel and mineral fragments after the fine fractions have been washed away by waves and current. Makes up a lag with varying grain size covering tills or other sediments. 204
Exposed bedrock Areas without sediment cover. 130
Thin or discontinuous sediment cover on the bedrock Lateral variation of small basins with sediments, exposed bedrock and/or bedrock with thin/discontinuous sediment cover. Sediments in small basins may have varying grain size. 140
Anthropogenic material Masses accumulated or heavily impacted by human activity. 120
Unspecified marin deposit Marine deposit of unknown origin. 250
Last updated 28.09.2023

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