In their recent paper, Lyberis and Manby (1993a) argued, possibly following Hanish (1984), that the age of the deformation that affected the West Spitsbergen Orogen (Harland and Horsfield 1974) was Late Cretaceous, a view they have repeated elsewhere (e.g. Lyberis and Manby 1993b). The age of later deformation has generally been regarded as Tertiary (e.g. Orvin 1940;Harland, 1961 Harland, , 1965) ) and more precisely as Late Palaeocene to Eocene (Dallmann et al. 1993 list over 200 relevant references). Late Cretaceous diastrophism had been considered, but only to produce a slight warping (Harland 1969a). About 2500 m of Mesozoic strata (Harland 1973) are cut out from south to north over 250 km, averaging 34 minutes of arc. The new hypothesis is inconsistent with observations that seem to have long been established. The onus is therefore on Lyberis and Manby to justify ignoring conflicting evidence. Even with much supporting evidence any hypothesis can never be certain, but it can be ruled out by only a little contradictory evidence -at least in the form proposed. This discussion identifies three such critical observations (at arrows on Figure 1).
Palaeocene strata include the basal Tertiary Firkanten Formation of the Central Basin and the Ny-Alesund Formation to the north-west. It would therefore be critical to know if these formations were deformed in the West Spitsbergen Orogeny. This has long been taken as established, but was denied by Lyberis and Manby. Figures 2 and3 illustrate the alternative interpretations at only two key localities, as explained in the captions. The author has seen these and other occurrences where the unconformity is not noticeably angular. Lyberis and Manby should give localities where clear angular unconformity can be observed.
The late, or post-tectonic, Tertiary flat-lying strata in the Forlandsundet Graben suggest a later constraint on the timing of the West Spitsbergen Orogeny (Harland 1975). Their age was estimated as late Eocene (Manum and Throndsen 1986). However, the occurrence of the near-vertical indurated Tertiary strata resting against the Early Palaeozoic Grampian Group at the northern tip of Prins Karls Forland (the third locality) shows that the Graben history spanned the main orogeny.
It follows from the proposed Late Cretaceous compressive strain of Lyberis and Manby that Svalbard would then have been north of Greenland. Seafloor spreading suggests (e.g. Srivastava and Tapscott 1986) that if, on the other hand, the deformation was approximately Eocene, then Svalbard would already have travelled by dextral strike-slip to a position off north-east Greenland (Figure 4) where Harland (e.g. 1969b) suggested that the orogeny occurred with combined compression and strike-slip (i.e. transpression; Lowell 1972). Lyberis and Manby argued against this idea by several constructed sections illustrating apparent east-west compression. Whether or not such sections give an accurate direction of transport, as does the strain ellipsoid interpretation of deformed anhydrite spheroids which was to the ENE (Harland et al., 1988), is irrelevant. Unless they can show that there was no partitioning of transpression between compression and transcurrence (as integral in the transpression hypothesis of Harland 1971), the matter remains indeterminate on that evidence alone, as do arguments for the apparent northward directed thrusting south of Kongsfjorden in support of a transpression hypothesis. The positive argument for the