Devonian sediments of East Greenland VI Review of results

Abstract

Seventy generalised stratigraphical columns, and alphabetical and hierarchical indexes of the lithostratigraphical units, are used to summarise stratigraphical relationships. The total aggregate thickness is 10 400 m, adding the maximum thicknesses of each of the five major units. Vertebrate fossils indicate an age range from Upper Middle Devonian (Givetian) to highest Devonian or lowest Carboniferous (Famennian or Tournaisian). A palynological survey has yielded two good micro-floral assemblages, one of Middle to Upper Givetian age, and the other of late Frasnian or early Famennian age, and both of these are consistent with the vertebrate evidence. Conglomerate, sandstone, siltstone and volcanic rock lithological associations are reviewed, and provide detailed evidence of local processes and environments. Some of the most original information concerns the three-dimensional patterns of major sedimentary rock bodies, representing different environmental situations.

Folds, faults and unconformities in the Devonian rocks are reviewed, and define a sequence of (i) early movements, (ii) Kap Franklin Deformation, (iii) Hudson Land Deformation, and (iv) Ymer Ø phase. The structural and sedimentary data are assembled onto ten "unit" maps, representing different time episodes. Most of the major events in the sequence of these episodes appear to be tectonically controlled, but both the major sedimentary basins (Vilddal and Gauss) show gross fining-upwards trends that may have been climatically controlled.

The tectonic controls may have been the activity of a number of northerly trending major fracture zones. These were zones of differential vertical and horizontal (strike-slip) movement, volcanism and granite emplacement. Major zones of this sort appear to have been characteristic of the continent-continent collision that occurred in Devonian times in many parts of the Caledonides.