Abstract
The aims of this study were to assess the depositional and ecological developments of Drammensfjorden, SE Norway, under pre-anthropogenic influence and attempt to define recent conditions within the fjord, which may have altered over the last two decades due to the time gap between today and the most recent studies. Bathymetric images as well as seismic profiles were compiled for establishing the fjord’s developmental history as well as geomorphological feature analysis.
Two sediment cores approximately 260 and 280cm long were collected from Drammensfjorden for sedimentological and micropaleontological analyses. While no direct dating methods were used within the cores, sedimentation rates calculated from seismic profiles suggest ages of several hundred years. The analyses of the cores included: facies analysis, measurements of water content, undrained shear strength and strength ratio, bulk density, magnetic susceptibility, and Total Organic Carbon content (TOC), as well as benthic foraminifer assemblages, which were extracted from the sediment and counted.
Seismic images of the fjord’s subsurface revealed several infilling sequences, which were identified as Younger-Dryas and Holocene sedimentations. Large landslide debris deposits are also identified within the Holocene strata, and speculated to have been initiated through the actions of climate change, such as acute temperature rise and isostatic uplift. A shift from anoxic to dysoxic waters within the basin is indicated by large populations of opportunistic species and the rise of TOC content, which may coincide with anthropogenic activity within the area.
Authigenic calcite formations are also identified on the outer walls of several E. excavatum forma alba tests, which suggest that some degassing of carbon dioxide occurred within the fjord’s history.