ECHINOID AND CRUSTACEAN BURROWS AND THEIR DIAGENETIC SIGNIFICANCE IN THE MAASTRICHTIAN-DANIAN OF STEVNS KLINT, DENMARK

The increase in species and specimens of fossils in the uppermost part of the Maastrichtian White Chalk is interpreted as a result of reduced depth. The absence of bryozoans, brachiopods, and regular echinoids in the Cerithium Limestone indicates sedimentation in tidal pools. After sedimentation of the Cerithium Limestone, burrowing activity followed. A burrow of Brissopneustes danicus similar to burrows of the recent Echinocardium cordatum is described. Callianassa and its burrows are found in the Upper Danian calcarenite but not in the Lower Danian or Maastrichtian of Denmark. The dominant type of burrows along the Maastrichtian-Danian boundary has presumably been formed by the crustacean Ctenocheles.
The early post-Maastrichtian burrowing activity was succeeded by (1) induration of the bottom sediment and a slight abrasion (2) dissolution of aragonite shells and siliceous sponges, (3) offshore sedimentation and filling of the burrows with Lower Danian chalk mud, bryozoan fragments and other fossil remains, and (4) settling in the deeper part of the soft chalk sediment and precipitation of flint in or around burrows near the surface of the sediment.