Danian Cool-Water Bryozoan Mounds at Stevns Klint, Denmark--A New Class of Non-Cemented Skeletal Mounds

摘要

A laterally extensive Danian (early Paleogene) bryozoan mound complex is well exposed in 14 km of nearly continuous outcrop in the coastal cliff Stevns Klint in eastern Denmark. A NW–SE oriented seaway covered the Danish Basin in Danian time. It widened towards the NW, where it passed into the deeper North Sea Basin and narrowed towards the SE, where it was connected with the Polish Trough. The exposed mound succession is up to 20 m thick. Individual mounds are oval in plan view, internally asymmetrical, 5–11 m high, 45–110 m long in NNE–SSW oriented dip sections parallel to the direction of mound migration, and 50–300 m in strike sections. The southern flanks are steep and dip 15–30° mainly towards the SSW, whereas northern flanks have gentle dips of 0–15° towards the NNE. Four facies associations are distinguished: (1) the initial mound association, consisting mainly of bryozoan packstone–rudstone; (2) the steep flank-mound crest association, consisting of bryozoan rudstone with subsidiary octocoral and encrusting bryozoan rudstone and bryozoan grainstone; (3) the gentle-flank association, characterized by bryozoan packstone, and incipient to fully developed hardgrounds; and (4) the intermound association, consisting of echinoid rudstone, packstone, and minor occurrences of bioclastic grainstone and argillaceous wackestone–packstone beds and laminae.