NEW INFORMATION ON THE GRAPTOLITE BIOSTRATIGRAPHY OF THE JUTLAND ALLOCHTHON

Identification of additional specimens of Ordovician graptolites from the Jutland Allochthon confirms previous determinations of some of the youngest horizons yet reported. A stratum believed to be a metabentonite horizon has yielded additional specimens correlating to the Glyptograptus teretiusculus Zone of previous authors (Zone 10 of standard correlations), and raises the possibility of obtaining an absolute age determination for that horizon. Although there are a number of faunules in the allochthon that correlate to the Nemagraptus gracilis Zone (Zone 11 of standard correlations), later ages cannot be fully ruled out, even possible overlaps of age with the main body of the Martinsburg Formation.

On-going studies of the Hedgehaven Farm area of the allochthon have provided additional information, but the biostratigraphy of the tract remains vague, with a wide variety of age determinations found within a limited area of structural complexity. Hypotheses of structure and stratigraphy of the Jutland area, almost constantly under review, require further revision in order to account for the close proximity of localities that differ substantially in age within the Ordovician System.