Streamlined ridges and depressions in the glacial sediments of the Arendal Terrace, Norwegian Skagerrak

Abstract

Streamlined ridges and depressions occur on many high-latitude continental shelves and are often regarded as the signature of glacial activity. The Arendal Terrace, Norwegian Skagerrak, is characterized by a series of hills, ridges and depressions (hill–hole topography) produced by glacitectonic activity that has formed a very unusual submarine geomorphology. The Arendal Terrace is a well-developed landform (with finer-scale landforms on top) of about 800 km2 located along the northern flank of the Skagerrak (Fig. 1g) (Longva & Thorsnes 1997; Ottesen et al. 2005; Rise et al. 2008). It is nearly 80 km long, trends SW–NE and reaches a width of 18 km in its central and northeastern parts. The terrace narrows towards the SW to less than 3 km in width. Fig. 1. Multibeam bathymetry and cross-profiles of the Arendal Terrace, Norwegian Skagerrak. ( a ) Sun-illuminated multibeam-bathymetric image showing very irregular topography with numerous hill–hole pairs, ridges and elongate depressions. Note convergent pattern of ridges and depressions towards the SW. Ridges are up to 30 m high and 20 km long, while depressions reach 50 m depth and 5 km length. Acquisition system Kongsberg Simrad EM100. Frequency 95 kHz. Grid-cell size 50 m. ( b , c ) Enlarged parts of …